import std._int;
import std._str;
import std._uint;
import std._vec;
import std._str.rustrt.sbuf;
import std._vec.rustrt.vbuf;
import std.map;
import std.map.hashmap;
import std.option;
import std.option.some;
import std.option.none;

import front.ast;
import front.creader;
import pretty.pprust;
import driver.session;
import middle.ty;
import back.x86;
import back.abi;

import pretty.pprust;

import middle.ty.pat_ty;

import util.common;
import util.common.istr;
import util.common.new_def_hash;
import util.common.new_str_hash;

import lib.llvm.llvm;
import lib.llvm.builder;
import lib.llvm.target_data;
import lib.llvm.type_handle;
import lib.llvm.type_names;
import lib.llvm.mk_pass_manager;
import lib.llvm.mk_target_data;
import lib.llvm.mk_type_handle;
import lib.llvm.mk_type_names;
import lib.llvm.llvm.ModuleRef;
import lib.llvm.llvm.ValueRef;
import lib.llvm.llvm.TypeRef;
import lib.llvm.llvm.TypeHandleRef;
import lib.llvm.llvm.BuilderRef;
import lib.llvm.llvm.BasicBlockRef;

import lib.llvm.False;
import lib.llvm.True;

state obj namegen(mutable int i) {
    fn next(str prefix) -> str {
        i += 1;
        ret prefix + istr(i);
    }
}

type glue_fns = rec(ValueRef activate_glue,
                    ValueRef yield_glue,
                    ValueRef exit_task_glue,
                    vec[ValueRef] native_glues_rust,
                    vec[ValueRef] native_glues_cdecl,
                    ValueRef no_op_type_glue,
                    ValueRef memcpy_glue,
                    ValueRef bzero_glue,
                    ValueRef vec_append_glue);

type tydesc_info = rec(ValueRef tydesc,
                       ValueRef take_glue,
                       ValueRef drop_glue,
                       ValueRef cmp_glue);

/*
 * A note on nomenclature of linking: "upcall", "extern" and "native".
 *
 * An "extern" is an LLVM symbol we wind up emitting an undefined external
 * reference to. This means "we don't have the thing in this compilation unit,
 * please make sure you link it in at runtime". This could be a reference to
 * C code found in a C library, or rust code found in a rust crate.
 *
 * A "native" is a combination of an extern that references C code, plus a
 * glue-code stub that "looks like" a rust function, emitted here, plus a
 * generic N-ary bit of asm glue (found over in back/x86.rs) that performs a
 * control transfer into C from rust. Natives may be normal C library code.
 *
 * An upcall is a native call generated by the compiler (not corresponding to
 * any user-written call in the code) into librustrt, to perform some helper
 * task such as bringing a task to life, allocating memory, etc.
 *
 */

state type crate_ctxt = rec(session.session sess,
                            ModuleRef llmod,
                            target_data td,
                            type_names tn,
                            ValueRef crate_ptr,
                            hashmap[str, ValueRef] externs,
                            hashmap[str, ValueRef] intrinsics,
                            hashmap[ast.def_id, ValueRef] item_ids,
                            hashmap[ast.def_id, @ast.item] items,
                            hashmap[ast.def_id,
                                    @ast.native_item] native_items,
                            ty.type_cache type_cache,
                            hashmap[ast.def_id, str] item_symbols,
                            // TODO: hashmap[tup(tag_id,subtys), @tag_info]
                            hashmap[ty.t, uint] tag_sizes,
                            hashmap[ast.def_id, ValueRef] discrims,
                            hashmap[ast.def_id, str] discrim_symbols,
                            hashmap[ast.def_id, ValueRef] fn_pairs,
                            hashmap[ast.def_id, ValueRef] consts,
                            hashmap[ast.def_id,()] obj_methods,
                            hashmap[ty.t, @tydesc_info] tydescs,
                            hashmap[str, ValueRef] module_data,
                            hashmap[ty.t, TypeRef] lltypes,
                            @glue_fns glues,
                            namegen names,
                            std.sha1.sha1 sha,
                            hashmap[ty.t, str] type_sha1s,
                            hashmap[ty.t, metadata.ty_abbrev] type_abbrevs,
                            ty.ctxt tcx);

type local_ctxt = rec(vec[str] path,
                      vec[str] module_path,
                      vec[ast.ty_param] obj_typarams,
                      vec[ast.obj_field] obj_fields,
                      @crate_ctxt ccx);


type self_vt = rec(ValueRef v, ty.t t);

state type fn_ctxt = rec(ValueRef llfn,
                         ValueRef lltaskptr,
                         ValueRef llenv,
                         ValueRef llretptr,
                         mutable BasicBlockRef llallocas,
                         mutable option.t[self_vt] llself,
                         mutable option.t[ValueRef] lliterbody,
                         hashmap[ast.def_id, ValueRef] llargs,
                         hashmap[ast.def_id, ValueRef] llobjfields,
                         hashmap[ast.def_id, ValueRef] lllocals,
                         hashmap[ast.def_id, ValueRef] llupvars,
                         mutable vec[ValueRef] lltydescs,
                         @local_ctxt lcx);

tag cleanup {
    clean(fn(@block_ctxt cx) -> result);
}


tag block_kind {
    SCOPE_BLOCK;
    LOOP_SCOPE_BLOCK(option.t[@block_ctxt], @block_ctxt);
    NON_SCOPE_BLOCK;
}

state type block_ctxt = rec(BasicBlockRef llbb,
                            builder build,
                            block_parent parent,
                            block_kind kind,
                            mutable vec[cleanup] cleanups,
                            @fn_ctxt fcx);

// FIXME: we should be able to use option.t[@block_parent] here but
// the infinite-tag check in rustboot gets upset.

tag block_parent {
    parent_none;
    parent_some(@block_ctxt);
}


state type result = rec(mutable @block_ctxt bcx,
                        mutable ValueRef val);

fn sep() -> str {
    ret "_";
}

fn extend_path(@local_ctxt cx, str name) -> @local_ctxt {
  ret @rec(path = cx.path + vec(name) with *cx);
}

fn path_name(vec[str] path) -> str {
    ret _str.connect(path, sep());
}


fn mangle_name_by_type(@crate_ctxt ccx, vec[str] path, ty.t t) -> str {
    auto hash = "";
    alt (ccx.type_sha1s.find(t)) {
        case (some[str](?h)) { hash = h; }
        case (none[str]) {
            ccx.sha.reset();
            auto f = metadata.def_to_str;
            // NB: do *not* use abbrevs here as we want the symbol names
            // to be independent of one another in the crate.
            auto cx = @rec(ds=f, tcx=ccx.tcx,
                           use_abbrevs=false, abbrevs=ccx.type_abbrevs);
            ccx.sha.input_str(metadata.Encode.ty_str(cx, t));
            hash = _str.substr(ccx.sha.result_str(), 0u, 16u);
            ccx.type_sha1s.insert(t, hash);
        }
    }
    ret sep() + "rust" + sep() + hash + sep() + path_name(path);
}

fn mangle_name_by_seq(@crate_ctxt ccx, vec[str] path, str flav) -> str {
    ret sep() + "rust" + sep()
        + ccx.names.next(flav) + sep()
        + path_name(path);
}

fn res(@block_ctxt bcx, ValueRef val) -> result {
    ret rec(mutable bcx = bcx,
            mutable val = val);
}

fn ty_str(type_names tn, TypeRef t) -> str {
    ret lib.llvm.type_to_str(tn, t);
}

fn val_ty(ValueRef v) -> TypeRef {
    ret llvm.LLVMTypeOf(v);
}

fn val_str(type_names tn, ValueRef v) -> str {
    ret ty_str(tn, val_ty(v));
}


// LLVM type constructors.

fn T_void() -> TypeRef {
    // Note: For the time being llvm is kinda busted here, it has the notion
    // of a 'void' type that can only occur as part of the signature of a
    // function, but no general unit type of 0-sized value. This is, afaict,
    // vestigial from its C heritage, and we'll be attempting to submit a
    // patch upstream to fix it. In the mean time we only model function
    // outputs (Rust functions and C functions) using T_void, and model the
    // Rust general purpose nil type you can construct as 1-bit (always
    // zero). This makes the result incorrect for now -- things like a tuple
    // of 10 nil values will have 10-bit size -- but it doesn't seem like we
    // have any other options until it's fixed upstream.
    ret llvm.LLVMVoidType();
}

fn T_nil() -> TypeRef {
    // NB: See above in T_void().
    ret llvm.LLVMInt1Type();
}

fn T_i1() -> TypeRef {
    ret llvm.LLVMInt1Type();
}

fn T_i8() -> TypeRef {
    ret llvm.LLVMInt8Type();
}

fn T_i16() -> TypeRef {
    ret llvm.LLVMInt16Type();
}

fn T_i32() -> TypeRef {
    ret llvm.LLVMInt32Type();
}

fn T_i64() -> TypeRef {
    ret llvm.LLVMInt64Type();
}

fn T_f32() -> TypeRef {
    ret llvm.LLVMFloatType();
}

fn T_f64() -> TypeRef {
    ret llvm.LLVMDoubleType();
}

fn T_bool() -> TypeRef {
    ret T_i1();
}

fn T_int() -> TypeRef {
    // FIXME: switch on target type.
    ret T_i32();
}

fn T_float() -> TypeRef {
    // FIXME: switch on target type.
    ret T_f64();
}

fn T_char() -> TypeRef {
    ret T_i32();
}

fn T_fn(vec[TypeRef] inputs, TypeRef output) -> TypeRef {
    ret llvm.LLVMFunctionType(output,
                              _vec.buf[TypeRef](inputs),
                              _vec.len[TypeRef](inputs),
                              False);
}

fn T_fn_pair(type_names tn, TypeRef tfn) -> TypeRef {
    ret T_struct(vec(T_ptr(tfn),
                     T_opaque_closure_ptr(tn)));
}

fn T_ptr(TypeRef t) -> TypeRef {
    ret llvm.LLVMPointerType(t, 0u);
}

fn T_struct(vec[TypeRef] elts) -> TypeRef {
    ret llvm.LLVMStructType(_vec.buf[TypeRef](elts),
                            _vec.len[TypeRef](elts),
                            False);
}

fn T_opaque() -> TypeRef {
    ret llvm.LLVMOpaqueType();
}

fn T_task(type_names tn) -> TypeRef {
    auto s = "task";
    if (tn.name_has_type(s)) {
        ret tn.get_type(s);
    }

    auto t = T_struct(vec(T_int(),      // Refcount
                          T_int(),      // Delegate pointer
                          T_int(),      // Stack segment pointer
                          T_int(),      // Runtime SP
                          T_int(),      // Rust SP
                          T_int(),      // GC chain
                          T_int(),      // Domain pointer
                          T_int()       // Crate cache pointer
                          ));
    tn.associate(s, t);
    ret t;
}

fn T_tydesc_field(type_names tn, int field) -> TypeRef {
    // Bit of a kludge: pick the fn typeref out of the tydesc..
    let vec[TypeRef] tydesc_elts =
        _vec.init_elt[TypeRef](T_nil(), abi.n_tydesc_fields as uint);
    llvm.LLVMGetStructElementTypes(T_tydesc(tn),
                                   _vec.buf[TypeRef](tydesc_elts));
    auto t = llvm.LLVMGetElementType(tydesc_elts.(field));
    ret t;
}

fn T_glue_fn(type_names tn) -> TypeRef {
    auto s = "glue_fn";
    if (tn.name_has_type(s)) {
        ret tn.get_type(s);
    }

    auto t = T_tydesc_field(tn, abi.tydesc_field_drop_glue);
    tn.associate(s, t);
    ret t;
}

fn T_cmp_glue_fn(type_names tn) -> TypeRef {
    auto s = "cmp_glue_fn";
    if (tn.name_has_type(s)) {
        ret tn.get_type(s);
    }

    auto t = T_tydesc_field(tn, abi.tydesc_field_cmp_glue);
    tn.associate(s, t);
    ret t;
}

fn T_tydesc(type_names tn) -> TypeRef {

    auto s = "tydesc";
    if (tn.name_has_type(s)) {
        ret tn.get_type(s);
    }

    auto th = mk_type_handle();
    auto abs_tydesc = llvm.LLVMResolveTypeHandle(th.llth);
    auto tydescpp = T_ptr(T_ptr(abs_tydesc));
    auto pvoid = T_ptr(T_i8());
    auto glue_fn_ty = T_ptr(T_fn(vec(T_ptr(T_nil()),
                                     T_taskptr(tn),
                                     T_ptr(T_nil()),
                                     tydescpp,
                                     pvoid), T_void()));
    auto cmp_glue_fn_ty = T_ptr(T_fn(vec(T_ptr(T_i1()),
                                         T_taskptr(tn),
                                         T_ptr(T_nil()),
                                         tydescpp,
                                         pvoid,
                                         pvoid,
                                         T_i8()), T_void()));
    auto tydesc = T_struct(vec(tydescpp,          // first_param
                               T_int(),           // size
                               T_int(),           // align
                               glue_fn_ty,        // take_glue
                               glue_fn_ty,        // drop_glue
                               glue_fn_ty,        // free_glue
                               glue_fn_ty,        // sever_glue
                               glue_fn_ty,        // mark_glue
                               glue_fn_ty,        // obj_drop_glue
                               glue_fn_ty,        // is_stateful
                               cmp_glue_fn_ty));  // cmp_glue

    llvm.LLVMRefineType(abs_tydesc, tydesc);
    auto t = llvm.LLVMResolveTypeHandle(th.llth);
    tn.associate(s, t);
    ret t;
}

fn T_array(TypeRef t, uint n) -> TypeRef {
    ret llvm.LLVMArrayType(t, n);
}

fn T_vec(TypeRef t) -> TypeRef {
    ret T_struct(vec(T_int(),       // Refcount
                     T_int(),       // Alloc
                     T_int(),       // Fill
                     T_int(),       // Pad
                     T_array(t, 0u) // Body elements
                     ));
}

fn T_opaque_vec_ptr() -> TypeRef {
    ret T_ptr(T_vec(T_int()));
}

fn T_str() -> TypeRef {
    ret T_vec(T_i8());
}

fn T_box(TypeRef t) -> TypeRef {
    ret T_struct(vec(T_int(), t));
}

fn T_port(TypeRef t) -> TypeRef {
    ret T_struct(vec(T_int())); // Refcount
}

fn T_chan(TypeRef t) -> TypeRef {
    ret T_struct(vec(T_int())); // Refcount
}

fn T_crate(type_names tn) -> TypeRef {
    auto s = "crate";
    if (tn.name_has_type(s)) {
        ret tn.get_type(s);
    }

    auto t = T_struct(vec(T_int(),      // ptrdiff_t image_base_off
                          T_int(),      // uintptr_t self_addr
                          T_int(),      // ptrdiff_t debug_abbrev_off
                          T_int(),      // size_t debug_abbrev_sz
                          T_int(),      // ptrdiff_t debug_info_off
                          T_int(),      // size_t debug_info_sz
                          T_int(),      // size_t activate_glue
                          T_int(),      // size_t yield_glue
                          T_int(),      // size_t unwind_glue
                          T_int(),      // size_t gc_glue
                          T_int(),      // size_t main_exit_task_glue
                          T_int(),      // int n_rust_syms
                          T_int(),      // int n_c_syms
                          T_int(),      // int n_libs
                          T_int()       // uintptr_t abi_tag
                          ));
    tn.associate(s, t);
    ret t;
}

fn T_taskptr(type_names tn) -> TypeRef {
    ret T_ptr(T_task(tn));
}

// This type must never be used directly; it must always be cast away.
fn T_typaram(type_names tn) -> TypeRef {
    auto s = "typaram";
    if (tn.name_has_type(s)) {
        ret tn.get_type(s);
    }

    auto t = T_i8();
    tn.associate(s, t);
    ret t;
}

fn T_typaram_ptr(type_names tn) -> TypeRef {
    ret T_ptr(T_typaram(tn));
}

fn T_closure_ptr(type_names tn,
                 TypeRef lltarget_ty,
                 TypeRef llbindings_ty,
                 uint n_ty_params) -> TypeRef {

    // NB: keep this in sync with code in trans_bind; we're making
    // an LLVM typeref structure that has the same "shape" as the ty.t
    // it constructs.
    ret T_ptr(T_box(T_struct(vec(T_ptr(T_tydesc(tn)),
                                 lltarget_ty,
                                 llbindings_ty,
                                 T_captured_tydescs(tn, n_ty_params))
                             )));
}

fn T_opaque_closure_ptr(type_names tn) -> TypeRef {
    auto s = "*closure";
    if (tn.name_has_type(s)) {
        ret tn.get_type(s);
    }
    auto t = T_closure_ptr(tn, T_struct(vec(T_ptr(T_nil()),
                                            T_ptr(T_nil()))),
                           T_nil(),
                           0u);
    tn.associate(s, t);
    ret t;
}

fn T_tag(type_names tn, uint size) -> TypeRef {
    auto s = "tag_" + _uint.to_str(size, 10u);
    if (tn.name_has_type(s)) {
        ret tn.get_type(s);
    }
    auto t = T_struct(vec(T_int(), T_array(T_i8(), size)));
    tn.associate(s, t);
    ret t;
}

fn T_opaque_tag(type_names tn) -> TypeRef {
    auto s = "opaque_tag";
    if (tn.name_has_type(s)) {
        ret tn.get_type(s);
    }
    auto t = T_struct(vec(T_int(), T_i8()));
    tn.associate(s, t);
    ret t;
}

fn T_opaque_tag_ptr(type_names tn) -> TypeRef {
    ret T_ptr(T_opaque_tag(tn));
}

fn T_captured_tydescs(type_names tn, uint n) -> TypeRef {
    ret T_struct(_vec.init_elt[TypeRef](T_ptr(T_tydesc(tn)), n));
}

fn T_obj_ptr(type_names tn, uint n_captured_tydescs) -> TypeRef {
    // This function is not publicly exposed because it returns an incomplete
    // type. The dynamically-sized fields follow the captured tydescs.
    fn T_obj(type_names tn, uint n_captured_tydescs) -> TypeRef {
        ret T_struct(vec(T_ptr(T_tydesc(tn)),
                         T_captured_tydescs(tn, n_captured_tydescs)));
    }

    ret T_ptr(T_box(T_obj(tn, n_captured_tydescs)));
}

fn T_opaque_obj_ptr(type_names tn) -> TypeRef {
    ret T_obj_ptr(tn, 0u);
}


// This function now fails if called on a type with dynamic size (as its
// return value was always meaningless in that case anyhow). Beware!
//
// TODO: Enforce via a predicate.
fn type_of(@crate_ctxt cx, ty.t t) -> TypeRef {
    if (ty.type_has_dynamic_size(cx.tcx, t)) {
        log_err "type_of() called on a type with dynamic size: " +
            ty.ty_to_str(cx.tcx, t);
        fail;
    }

    ret type_of_inner(cx, t);
}

fn type_of_explicit_args(@crate_ctxt cx, vec[ty.arg] inputs) -> vec[TypeRef] {
    let vec[TypeRef] atys = vec();
    for (ty.arg arg in inputs) {
        if (ty.type_has_dynamic_size(cx.tcx, arg.ty)) {
            check (arg.mode == ast.alias);
            atys += vec(T_typaram_ptr(cx.tn));
        } else {
            let TypeRef t;
            alt (arg.mode) {
                case (ast.alias) {
                    t = T_ptr(type_of_inner(cx, arg.ty));
                }
                case (_) {
                    t = type_of_inner(cx, arg.ty);
                }
            }
            atys += vec(t);
        }
    }
    ret atys;
}

// NB: must keep 4 fns in sync:
//
//  - type_of_fn_full
//  - create_llargs_for_fn_args.
//  - new_fn_ctxt
//  - trans_args

fn type_of_fn_full(@crate_ctxt cx,
                   ast.proto proto,
                   option.t[TypeRef] obj_self,
                   vec[ty.arg] inputs,
                   ty.t output,
                   uint ty_param_count) -> TypeRef {
    let vec[TypeRef] atys = vec();

    // Arg 0: Output pointer.
    if (ty.type_has_dynamic_size(cx.tcx, output)) {
        atys += vec(T_typaram_ptr(cx.tn));
    } else {
        atys += vec(T_ptr(type_of_inner(cx, output)));
    }

    // Arg 1: Task pointer.
    atys += vec(T_taskptr(cx.tn));

    // Arg 2: Env (closure-bindings / self-obj)
    alt (obj_self) {
        case (some[TypeRef](?t)) {
            check (t as int != 0);
            atys += vec(t);
        }
        case (_) {
            atys += vec(T_opaque_closure_ptr(cx.tn));
        }
    }

    // Args >3: ty params, if not acquired via capture...
    if (obj_self == none[TypeRef]) {
        auto i = 0u;
        while (i < ty_param_count) {
            atys += vec(T_ptr(T_tydesc(cx.tn)));
            i += 1u;
        }
    }

    if (proto == ast.proto_iter) {
        // If it's an iter, the 'output' type of the iter is actually the
        // *input* type of the function we're given as our iter-block
        // argument.
        atys +=
            vec(T_fn_pair(cx.tn,
                          type_of_fn_full(cx, ast.proto_fn, none[TypeRef],
                                          vec(rec(mode=ast.alias, ty=output)),
                                          ty.mk_nil(cx.tcx), 0u)));
    }

    // ... then explicit args.
    atys += type_of_explicit_args(cx, inputs);

    ret T_fn(atys, llvm.LLVMVoidType());
}

fn type_of_fn(@crate_ctxt cx,
              ast.proto proto,
              vec[ty.arg] inputs,
              ty.t output,
              uint ty_param_count) -> TypeRef {
    ret type_of_fn_full(cx, proto, none[TypeRef], inputs, output,
                        ty_param_count);
}

fn type_of_native_fn(@crate_ctxt cx, ast.native_abi abi,
                     vec[ty.arg] inputs,
                     ty.t output,
                     uint ty_param_count) -> TypeRef {
    let vec[TypeRef] atys = vec();
    if (abi == ast.native_abi_rust) {
        atys += vec(T_taskptr(cx.tn));
        auto t = ty.ty_native_fn(abi, inputs, output);
        auto i = 0u;
        while (i < ty_param_count) {
            atys += vec(T_ptr(T_tydesc(cx.tn)));
            i += 1u;
        }
    }
    atys += type_of_explicit_args(cx, inputs);
    ret T_fn(atys, type_of_inner(cx, output));
}

fn type_of_inner(@crate_ctxt cx, ty.t t) -> TypeRef {
    // Check the cache.
    if (cx.lltypes.contains_key(t)) {
        ret cx.lltypes.get(t);
    }

    let TypeRef llty = 0 as TypeRef;

    alt (ty.struct(cx.tcx, t)) {
        case (ty.ty_native) { llty = T_ptr(T_i8()); }
        case (ty.ty_nil) { llty = T_nil(); }
        case (ty.ty_bool) { llty = T_bool(); }
        case (ty.ty_int) { llty = T_int(); }
        case (ty.ty_float) { llty = T_float(); }
        case (ty.ty_uint) { llty = T_int(); }
        case (ty.ty_machine(?tm)) {
            alt (tm) {
                case (common.ty_i8) { llty = T_i8(); }
                case (common.ty_u8) { llty = T_i8(); }
                case (common.ty_i16) { llty = T_i16(); }
                case (common.ty_u16) { llty = T_i16(); }
                case (common.ty_i32) { llty = T_i32(); }
                case (common.ty_u32) { llty = T_i32(); }
                case (common.ty_i64) { llty = T_i64(); }
                case (common.ty_u64) { llty = T_i64(); }
                case (common.ty_f32) { llty = T_f32(); }
                case (common.ty_f64) { llty = T_f64(); }
            }
        }
        case (ty.ty_char) { llty = T_char(); }
        case (ty.ty_str) { llty = T_ptr(T_str()); }
        case (ty.ty_tag(_, _)) {
            if (ty.type_has_dynamic_size(cx.tcx, t)) {
                llty = T_opaque_tag(cx.tn);
            } else {
                auto size = static_size_of_tag(cx, t);
                llty = T_tag(cx.tn, size);
            }
        }
        case (ty.ty_box(?mt)) {
            llty = T_ptr(T_box(type_of_inner(cx, mt.ty)));
        }
        case (ty.ty_vec(?mt)) {
            llty = T_ptr(T_vec(type_of_inner(cx, mt.ty)));
        }
        case (ty.ty_port(?t)) {
            llty = T_ptr(T_port(type_of_inner(cx, t)));
        }
        case (ty.ty_chan(?t)) {
            llty = T_ptr(T_chan(type_of_inner(cx, t)));
        }
        case (ty.ty_tup(?elts)) {
            let vec[TypeRef] tys = vec();
            for (ty.mt elt in elts) {
                tys += vec(type_of_inner(cx, elt.ty));
            }
            llty = T_struct(tys);
        }
        case (ty.ty_rec(?fields)) {
            let vec[TypeRef] tys = vec();
            for (ty.field f in fields) {
                tys += vec(type_of_inner(cx, f.mt.ty));
            }
            llty = T_struct(tys);
        }
        case (ty.ty_fn(?proto, ?args, ?out)) {
            llty = T_fn_pair(cx.tn, type_of_fn(cx, proto, args, out, 0u));
        }
        case (ty.ty_native_fn(?abi, ?args, ?out)) {
            auto nft = native_fn_wrapper_type(cx, 0u, t);
            llty = T_fn_pair(cx.tn, nft);
        }
        case (ty.ty_obj(?meths)) {
            auto th = mk_type_handle();
            auto self_ty = llvm.LLVMResolveTypeHandle(th.llth);

            let vec[TypeRef] mtys = vec();
            for (ty.method m in meths) {
                let TypeRef mty =
                    type_of_fn_full(cx, m.proto,
                                    some[TypeRef](self_ty),
                                    m.inputs, m.output, 0u);
                mtys += vec(T_ptr(mty));
            }
            let TypeRef vtbl = T_struct(mtys);
            let TypeRef pair = T_struct(vec(T_ptr(vtbl),
                                            T_opaque_obj_ptr(cx.tn)));

            auto abs_pair = llvm.LLVMResolveTypeHandle(th.llth);
            llvm.LLVMRefineType(abs_pair, pair);
            abs_pair = llvm.LLVMResolveTypeHandle(th.llth);
            llty = abs_pair;
        }
        case (ty.ty_var(_)) {
            log_err "ty_var in trans.type_of";
            fail;
        }
        case (ty.ty_param(_)) {
            llty = T_i8();
        }
        case (ty.ty_bound_param(_)) {
            log_err "ty_bound_param in trans.type_of";
            fail;
        }
        case (ty.ty_type) { llty = T_ptr(T_tydesc(cx.tn)); }
    }

    check (llty as int != 0);
    llvm.LLVMAddTypeName(cx.llmod,
                         _str.buf(ty.ty_to_short_str(cx.tcx,
                                                     cx.type_abbrevs, t)),
                         llty);
    cx.lltypes.insert(t, llty);
    ret llty;
}

fn type_of_arg(@local_ctxt cx, &ty.arg arg) -> TypeRef {
    alt (ty.struct(cx.ccx.tcx, arg.ty)) {
        case (ty.ty_param(_)) {
            if (arg.mode == ast.alias) {
                ret T_typaram_ptr(cx.ccx.tn);
            }
        }
        case (_) {
            // fall through
        }
    }

    auto typ;
    if (arg.mode == ast.alias) {
        typ = T_ptr(type_of_inner(cx.ccx, arg.ty));
    } else {
        typ = type_of_inner(cx.ccx, arg.ty);
    }
    ret typ;
}

fn type_of_ty_param_count_and_ty(@local_ctxt lcx,
                                 ty.ty_param_count_and_ty tpt) -> TypeRef {
    alt (ty.struct(lcx.ccx.tcx, tpt._1)) {
        case (ty.ty_fn(?proto, ?inputs, ?output)) {
            auto llfnty = type_of_fn(lcx.ccx, proto, inputs, output, tpt._0);
            ret T_fn_pair(lcx.ccx.tn, llfnty);
        }
        case (_) {
            // fall through
        }
    }
    ret type_of(lcx.ccx, tpt._1);
}


// Name sanitation. LLVM will happily accept identifiers with weird names, but
// gas doesn't!

fn sanitize(str s) -> str {
    auto result = "";
    for (u8 c in s) {
        if (c == ('@' as u8)) {
            result += "boxed_";
        } else {
            if (c == (',' as u8)) {
                result += "_";
            } else {
                if (c == ('{' as u8) || c == ('(' as u8)) {
                    result += "_of_";
                } else {
                    if (c != 10u8 && c != ('}' as u8) && c != (')' as u8) &&
                        c != (' ' as u8) && c != ('\t' as u8) &&
                        c != (';' as u8)) {
                        auto v = vec(c);
                        result += _str.from_bytes(v);
                    }
                }
            }
        }
    }
    ret result;
}

// LLVM constant constructors.

fn C_null(TypeRef t) -> ValueRef {
    ret llvm.LLVMConstNull(t);
}

fn C_integral(int i, TypeRef t) -> ValueRef {
    // FIXME. We can't use LLVM.ULongLong with our existing minimal native
    // API, which only knows word-sized args.  Lucky for us LLVM has a "take a
    // string encoding" version.  Hilarious. Please fix to handle:
    //
    // ret llvm.LLVMConstInt(T_int(), t as LLVM.ULongLong, False);
    //
    ret llvm.LLVMConstIntOfString(t, _str.buf(istr(i)), 10);
}

fn C_float(str s) -> ValueRef {
    ret llvm.LLVMConstRealOfString(T_float(), _str.buf(s));
}

fn C_floating(str s, TypeRef t) -> ValueRef {
    ret llvm.LLVMConstRealOfString(t, _str.buf(s));
}

fn C_nil() -> ValueRef {
    // NB: See comment above in T_void().
    ret C_integral(0, T_i1());
}

fn C_bool(bool b) -> ValueRef {
    if (b) {
        ret C_integral(1, T_bool());
    } else {
        ret C_integral(0, T_bool());
    }
}

fn C_int(int i) -> ValueRef {
    ret C_integral(i, T_int());
}

fn C_i8(uint i) -> ValueRef {
    ret C_integral(i as int, T_i8());
}

// This is a 'c-like' raw string, which differs from
// our boxed-and-length-annotated strings.
fn C_cstr(@crate_ctxt cx, str s) -> ValueRef {
    auto sc = llvm.LLVMConstString(_str.buf(s), _str.byte_len(s), False);
    auto g = llvm.LLVMAddGlobal(cx.llmod, val_ty(sc),
                                _str.buf(cx.names.next("str")));
    llvm.LLVMSetInitializer(g, sc);
    llvm.LLVMSetGlobalConstant(g, True);
    llvm.LLVMSetLinkage(g, lib.llvm.LLVMInternalLinkage
                        as llvm.Linkage);
    ret g;
}

// A rust boxed-and-length-annotated string.
fn C_str(@crate_ctxt cx, str s) -> ValueRef {
    auto len = _str.byte_len(s);
    auto box = C_struct(vec(C_int(abi.const_refcount as int),
                            C_int(len + 1u as int), // 'alloc'
                            C_int(len + 1u as int), // 'fill'
                            C_int(0),               // 'pad'
                            llvm.LLVMConstString(_str.buf(s),
                                                 len, False)));
    auto g = llvm.LLVMAddGlobal(cx.llmod, val_ty(box),
                                _str.buf(cx.names.next("str")));
    llvm.LLVMSetInitializer(g, box);
    llvm.LLVMSetGlobalConstant(g, True);
    llvm.LLVMSetLinkage(g, lib.llvm.LLVMInternalLinkage
                        as llvm.Linkage);
    ret llvm.LLVMConstPointerCast(g, T_ptr(T_str()));
}

fn C_zero_byte_arr(uint size) -> ValueRef {
    auto i = 0u;
    let vec[ValueRef] elts = vec();
    while (i < size) {
        elts += vec(C_integral(0, T_i8()));
        i += 1u;
    }
    ret llvm.LLVMConstArray(T_i8(), _vec.buf[ValueRef](elts),
                            _vec.len[ValueRef](elts));
}

fn C_struct(vec[ValueRef] elts) -> ValueRef {
    ret llvm.LLVMConstStruct(_vec.buf[ValueRef](elts),
                             _vec.len[ValueRef](elts),
                             False);
}

fn C_array(TypeRef ty, vec[ValueRef] elts) -> ValueRef {
    ret llvm.LLVMConstArray(ty, _vec.buf[ValueRef](elts),
                            _vec.len[ValueRef](elts));
}

fn decl_fn(ModuleRef llmod, str name, uint cc, TypeRef llty) -> ValueRef {
    let ValueRef llfn =
        llvm.LLVMAddFunction(llmod, _str.buf(name), llty);
    llvm.LLVMSetFunctionCallConv(llfn, cc);
    ret llfn;
}

fn decl_cdecl_fn(ModuleRef llmod, str name, TypeRef llty) -> ValueRef {
    ret decl_fn(llmod, name, lib.llvm.LLVMCCallConv, llty);
}

fn decl_fastcall_fn(ModuleRef llmod, str name, TypeRef llty) -> ValueRef {
    ret decl_fn(llmod, name, lib.llvm.LLVMFastCallConv, llty);
}

fn decl_internal_fastcall_fn(ModuleRef llmod,
                            str name, TypeRef llty) -> ValueRef {
    auto llfn = decl_fn(llmod, name, lib.llvm.LLVMFastCallConv, llty);
    llvm.LLVMSetLinkage(llfn, lib.llvm.LLVMInternalLinkage as llvm.Linkage);
    ret llfn;
}

fn decl_glue(ModuleRef llmod, type_names tn, str s) -> ValueRef {
    ret decl_cdecl_fn(llmod, s, T_fn(vec(T_taskptr(tn)), T_void()));
}

fn decl_native_glue(ModuleRef llmod, type_names tn,
                    bool pass_task, uint _n) -> ValueRef {
    // It doesn't actually matter what type we come up with here, at the
    // moment, as we cast the native function pointers to int before passing
    // them to the indirect native-invocation glue.  But eventually we'd like
    // to call them directly, once we have a calling convention worked out.
    let int n = _n as int;
    let str s = abi.native_glue_name(n, pass_task);
    let vec[TypeRef] args = vec(T_int()); // callee
    if (!pass_task) {
        args += vec(T_int()); // taskptr, will not be passed
    }
    args += _vec.init_elt[TypeRef](T_int(), n as uint);

    ret decl_fastcall_fn(llmod, s, T_fn(args, T_int()));
}

fn get_extern_fn(&hashmap[str, ValueRef] externs,
                 ModuleRef llmod, str name,
                 uint cc, TypeRef ty) -> ValueRef {
    if (externs.contains_key(name)) {
        ret externs.get(name);
    }
    auto f = decl_fn(llmod, name, cc, ty);
    externs.insert(name, f);
    ret f;
}

fn get_extern_const(&hashmap[str, ValueRef] externs,
                    ModuleRef llmod, str name, TypeRef ty) -> ValueRef {
    if (externs.contains_key(name)) {
        ret externs.get(name);
    }
    auto c = llvm.LLVMAddGlobal(llmod, ty, _str.buf(name));
    externs.insert(name, c);
    ret c;
}

fn get_simple_extern_fn(&hashmap[str, ValueRef] externs,
                     ModuleRef llmod, str name, int n_args) -> ValueRef {
    auto inputs = _vec.init_elt[TypeRef](T_int(), n_args as uint);
    auto output = T_int();
    auto t = T_fn(inputs, output);
    ret get_extern_fn(externs, llmod, name, lib.llvm.LLVMCCallConv, t);
}

fn trans_upcall(@block_ctxt cx, str name, vec[ValueRef] args) -> result {
    auto cxx = cx.fcx.lcx.ccx;
    auto lltaskptr = cx.build.PtrToInt(cx.fcx.lltaskptr, T_int());
    auto args2 = vec(lltaskptr) + args;
    auto t = trans_native_call(cx.build, cxx.glues, lltaskptr,
                               cxx.externs, cxx.tn, cxx.llmod, name,
                               true, args2);
    ret res(cx, t);
}

fn trans_native_call(builder b, @glue_fns glues, ValueRef lltaskptr,
                     &hashmap[str, ValueRef] externs,
                     type_names tn, ModuleRef llmod, str name,
                     bool pass_task, vec[ValueRef] args) -> ValueRef {
    let int n = (_vec.len[ValueRef](args) as int);
    let ValueRef llnative = get_simple_extern_fn(externs, llmod, name, n);
    llnative = llvm.LLVMConstPointerCast(llnative, T_int());

    let ValueRef llglue;
    if (pass_task) {
        llglue = glues.native_glues_rust.(n);
    } else {
        llglue = glues.native_glues_cdecl.(n);
    }
    let vec[ValueRef] call_args = vec(llnative);

    if (!pass_task) {
        call_args += vec(lltaskptr);
    }

    for (ValueRef a in args) {
        call_args += vec(b.ZExtOrBitCast(a, T_int()));
    }

    ret b.FastCall(llglue, call_args);
}

fn trans_non_gc_free(@block_ctxt cx, ValueRef v) -> result {
    ret trans_upcall(cx, "upcall_free", vec(vp2i(cx, v),
                                            C_int(0)));
}

fn find_scope_cx(@block_ctxt cx) -> @block_ctxt {
    if (cx.kind != NON_SCOPE_BLOCK) {
        ret cx;
    }
    alt (cx.parent) {
        case (parent_some(?b)) {
            be find_scope_cx(b);
        }
        case (parent_none) {
            fail;
        }
    }
}

fn find_outer_scope_cx(@block_ctxt cx) -> @block_ctxt {
    auto scope_cx = find_scope_cx(cx);
    alt (cx.parent) {
        case (parent_some(?b)) {
            be find_scope_cx(b);
        }
        case (parent_none) {
            fail;
        }
    }
}

fn umax(@block_ctxt cx, ValueRef a, ValueRef b) -> ValueRef {
    auto cond = cx.build.ICmp(lib.llvm.LLVMIntULT, a, b);
    ret cx.build.Select(cond, b, a);
}

fn umin(@block_ctxt cx, ValueRef a, ValueRef b) -> ValueRef {
    auto cond = cx.build.ICmp(lib.llvm.LLVMIntULT, a, b);
    ret cx.build.Select(cond, a, b);
}

fn align_to(@block_ctxt cx, ValueRef off, ValueRef align) -> ValueRef {
    auto mask = cx.build.Sub(align, C_int(1));
    auto bumped = cx.build.Add(off, mask);
    ret cx.build.And(bumped, cx.build.Not(mask));
}

// Returns the real size of the given type for the current target.
fn llsize_of_real(@crate_ctxt cx, TypeRef t) -> uint {
    ret llvm.LLVMStoreSizeOfType(cx.td.lltd, t);
}

fn llsize_of(TypeRef t) -> ValueRef {
    ret llvm.LLVMConstIntCast(lib.llvm.llvm.LLVMSizeOf(t), T_int(), False);
}

fn llalign_of(TypeRef t) -> ValueRef {
    ret llvm.LLVMConstIntCast(lib.llvm.llvm.LLVMAlignOf(t), T_int(), False);
}

fn size_of(@block_ctxt cx, ty.t t) -> result {
    if (!ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, t)) {
        ret res(cx, llsize_of(type_of(cx.fcx.lcx.ccx, t)));
    }
    ret dynamic_size_of(cx, t);
}

fn align_of(@block_ctxt cx, ty.t t) -> result {
    if (!ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, t)) {
        ret res(cx, llalign_of(type_of(cx.fcx.lcx.ccx, t)));
    }
    ret dynamic_align_of(cx, t);
}

fn alloca(@block_ctxt cx, TypeRef t) -> ValueRef {
    ret new_builder(cx.fcx.llallocas).Alloca(t);
}

fn array_alloca(@block_ctxt cx, TypeRef t, ValueRef n) -> ValueRef {
    ret new_builder(cx.fcx.llallocas).ArrayAlloca(t, n);
}


// Creates a simpler, size-equivalent type. The resulting type is guaranteed
// to have (a) the same size as the type that was passed in; (b) to be non-
// recursive. This is done by replacing all boxes in a type with boxed unit
// types.
fn simplify_type(@crate_ctxt ccx, ty.t typ) -> ty.t {
    fn simplifier(@crate_ctxt ccx, ty.t typ) -> ty.t {
        alt (ty.struct(ccx.tcx, typ)) {
            case (ty.ty_box(_)) {
                ret ty.mk_imm_box(ccx.tcx, ty.mk_nil(ccx.tcx));
            }
            case (_) { ret typ; }
        }
    }
    auto f = bind simplifier(ccx, _);
    ret ty.fold_ty(ccx.tcx, f, typ);
}

// Computes the size of the data part of a non-dynamically-sized tag.
fn static_size_of_tag(@crate_ctxt cx, ty.t t) -> uint {
    if (ty.type_has_dynamic_size(cx.tcx, t)) {
        log_err "dynamically sized type passed to static_size_of_tag()";
        fail;
    }

    if (cx.tag_sizes.contains_key(t)) {
        ret cx.tag_sizes.get(t);
    }

    auto tid;
    let vec[ty.t] subtys;
    alt (ty.struct(cx.tcx, t)) {
        case (ty.ty_tag(?tid_, ?subtys_)) {
            tid = tid_;
            subtys = subtys_;
        }
        case (_) {
            log_err "non-tag passed to static_size_of_tag()";
            fail;
        }
    }

    // Compute max(variant sizes).
    auto max_size = 0u;
    auto variants = tag_variants(cx, tid);
    for (variant_info variant in variants) {
        auto tup_ty = simplify_type(cx, ty.mk_imm_tup(cx.tcx, variant.args));

        // Perform any type parameter substitutions.
        tup_ty = ty.bind_params_in_type(cx.tcx, tup_ty);
        tup_ty = ty.substitute_type_params(cx.tcx, subtys, tup_ty);

        // Here we possibly do a recursive call.
        auto this_size = llsize_of_real(cx, type_of(cx, tup_ty));

        if (max_size < this_size) {
            max_size = this_size;
        }
    }

    cx.tag_sizes.insert(t, max_size);
    ret max_size;
}

fn dynamic_size_of(@block_ctxt cx, ty.t t) -> result {
    fn align_elements(@block_ctxt cx, vec[ty.t] elts) -> result {
        //
        // C padding rules:
        //
        //
        //   - Pad after each element so that next element is aligned.
        //   - Pad after final structure member so that whole structure
        //     is aligned to max alignment of interior.
        //
        auto off = C_int(0);
        auto max_align = C_int(1);
        auto bcx = cx;
        for (ty.t e in elts) {
            auto elt_align = align_of(bcx, e);
            bcx = elt_align.bcx;
            auto elt_size = size_of(bcx, e);
            bcx = elt_size.bcx;
            auto aligned_off = align_to(bcx, off, elt_align.val);
            off = bcx.build.Add(aligned_off, elt_size.val);
            max_align = umax(bcx, max_align, elt_align.val);
        }
        off = align_to(bcx, off, max_align);
        ret res(bcx, off);
    }

    alt (ty.struct(cx.fcx.lcx.ccx.tcx, t)) {
        case (ty.ty_param(?p)) {
            auto szptr = field_of_tydesc(cx, t, abi.tydesc_field_size);
            ret res(szptr.bcx, szptr.bcx.build.Load(szptr.val));
        }
        case (ty.ty_tup(?elts)) {
            let vec[ty.t] tys = vec();
            for (ty.mt mt in elts) {
                tys += vec(mt.ty);
            }
            ret align_elements(cx, tys);
        }
        case (ty.ty_rec(?flds)) {
            let vec[ty.t] tys = vec();
            for (ty.field f in flds) {
                tys += vec(f.mt.ty);
            }
            ret align_elements(cx, tys);
        }
        case (ty.ty_tag(?tid, ?tps)) {
            auto bcx = cx;

            // Compute max(variant sizes).
            let ValueRef max_size = alloca(bcx, T_int());
            bcx.build.Store(C_int(0), max_size);

            auto variants = tag_variants(bcx.fcx.lcx.ccx, tid);
            for (variant_info variant in variants) {
                // Perform type substitution on the raw argument types.
                let vec[ty.t] raw_tys = variant.args;
                let vec[ty.t] tys = vec();
                for (ty.t raw_ty in raw_tys) {
                    auto t = ty.bind_params_in_type(cx.fcx.lcx.ccx.tcx,
                                                    raw_ty);
                    t = ty.substitute_type_params(cx.fcx.lcx.ccx.tcx, tps, t);
                    tys += vec(t);
                }

                auto rslt = align_elements(bcx, tys);
                bcx = rslt.bcx;

                auto this_size = rslt.val;
                auto old_max_size = bcx.build.Load(max_size);
                bcx.build.Store(umax(bcx, this_size, old_max_size), max_size);
            }

            auto max_size_val = bcx.build.Load(max_size);
            auto total_size = bcx.build.Add(max_size_val, llsize_of(T_int()));
            ret res(bcx, total_size);
        }
    }
}

fn dynamic_align_of(@block_ctxt cx, ty.t t) -> result {
    alt (ty.struct(cx.fcx.lcx.ccx.tcx, t)) {
        case (ty.ty_param(?p)) {
            auto aptr = field_of_tydesc(cx, t, abi.tydesc_field_align);
            ret res(aptr.bcx, aptr.bcx.build.Load(aptr.val));
        }
        case (ty.ty_tup(?elts)) {
            auto a = C_int(1);
            auto bcx = cx;
            for (ty.mt e in elts) {
                auto align = align_of(bcx, e.ty);
                bcx = align.bcx;
                a = umax(bcx, a, align.val);
            }
            ret res(bcx, a);
        }
        case (ty.ty_rec(?flds)) {
            auto a = C_int(1);
            auto bcx = cx;
            for (ty.field f in flds) {
                auto align = align_of(bcx, f.mt.ty);
                bcx = align.bcx;
                a = umax(bcx, a, align.val);
            }
            ret res(bcx, a);
        }
        case (ty.ty_tag(_, _)) {
            ret res(cx, C_int(1)); // FIXME: stub
        }
    }
}

// Replacement for the LLVM 'GEP' instruction when field-indexing into a
// tuple-like structure (tup, rec) with a static index. This one is driven off
// ty.struct and knows what to do when it runs into a ty_param stuck in the
// middle of the thing it's GEP'ing into. Much like size_of and align_of,
// above.

fn GEP_tup_like(@block_ctxt cx, ty.t t,
                ValueRef base, vec[int] ixs) -> result {

    check (ty.type_is_tup_like(cx.fcx.lcx.ccx.tcx, t));

    // It might be a static-known type. Handle this.

    if (! ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, t)) {
        let vec[ValueRef] v = vec();
        for (int i in ixs) {
            v += vec(C_int(i));
        }
        ret res(cx, cx.build.GEP(base, v));
    }

    // It is a dynamic-containing type that, if we convert directly to an LLVM
    // TypeRef, will be all wrong; there's no proper LLVM type to represent
    // it, and the lowering function will stick in i8* values for each
    // ty_param, which is not right; the ty_params are all of some dynamic
    // size.
    //
    // What we must do instead is sadder. We must look through the indices
    // manually and split the input type into a prefix and a target. We then
    // measure the prefix size, bump the input pointer by that amount, and
    // cast to a pointer-to-target type.


    // Given a type, an index vector and an element number N in that vector,
    // calculate index X and the type that results by taking the first X-1
    // elements of the type and splitting the Xth off. Return the prefix as
    // well as the innermost Xth type.

    fn split_type(@crate_ctxt ccx, ty.t t, vec[int] ixs, uint n)
        -> rec(vec[ty.t] prefix, ty.t target) {

        let uint len = _vec.len[int](ixs);

        // We don't support 0-index or 1-index GEPs. The former is nonsense
        // and the latter would only be meaningful if we supported non-0
        // values for the 0th index (we don't).

        check (len > 1u);

        if (n == 0u) {
            // Since we're starting from a value that's a pointer to a
            // *single* structure, the first index (in GEP-ese) should just be
            // 0, to yield the pointee.
            check (ixs.(n) == 0);
            ret split_type(ccx, t, ixs, n+1u);
        }

        check (n < len);

        let int ix = ixs.(n);
        let vec[ty.t] prefix = vec();
        let int i = 0;
        while (i < ix) {
            _vec.push[ty.t](prefix,
                            ty.get_element_type(ccx.tcx, t, i as uint));
            i += 1 ;
        }

        auto selected = ty.get_element_type(ccx.tcx, t, i as uint);

        if (n == len-1u) {
            // We are at the innermost index.
            ret rec(prefix=prefix, target=selected);

        } else {
            // Not the innermost index; call self recursively to dig deeper.
            // Once we get an inner result, append it current prefix and
            // return to caller.
            auto inner = split_type(ccx, selected, ixs, n+1u);
            prefix += inner.prefix;
            ret rec(prefix=prefix with inner);
        }
    }

    // We make a fake prefix tuple-type here; luckily for measuring sizes
    // the tuple parens are associative so it doesn't matter that we've
    // flattened the incoming structure.

    auto s = split_type(cx.fcx.lcx.ccx, t, ixs, 0u);
    auto prefix_ty = ty.mk_imm_tup(cx.fcx.lcx.ccx.tcx, s.prefix);
    auto bcx = cx;
    auto sz = size_of(bcx, prefix_ty);
    bcx = sz.bcx;
    auto raw = bcx.build.PointerCast(base, T_ptr(T_i8()));
    auto bumped = bcx.build.GEP(raw, vec(sz.val));

    if (ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, s.target)) {
        ret res(bcx, bumped);
    }

    auto typ = T_ptr(type_of(bcx.fcx.lcx.ccx, s.target));
    ret res(bcx, bcx.build.PointerCast(bumped, typ));
}

// Replacement for the LLVM 'GEP' instruction when field indexing into a tag.
// This function uses GEP_tup_like() above and automatically performs casts as
// appropriate. @llblobptr is the data part of a tag value; its actual type is
// meaningless, as it will be cast away.
fn GEP_tag(@block_ctxt cx,
           ValueRef llblobptr,
           &ast.def_id tag_id,
           &ast.def_id variant_id,
           vec[ty.t] ty_substs,
           int ix)
        -> result {
    auto variant = tag_variant_with_id(cx.fcx.lcx.ccx, tag_id, variant_id);

    // Synthesize a tuple type so that GEP_tup_like() can work its magic.
    // Separately, store the type of the element we're interested in.
    auto arg_tys = variant.args;
    auto elem_ty = ty.mk_nil(cx.fcx.lcx.ccx.tcx); // typestate infelicity
    auto i = 0;
    let vec[ty.t] true_arg_tys = vec();
    for (ty.t aty in arg_tys) {
        auto arg_ty = ty.bind_params_in_type(cx.fcx.lcx.ccx.tcx, aty);
        arg_ty = ty.substitute_type_params(cx.fcx.lcx.ccx.tcx, ty_substs,
                                           arg_ty);
        true_arg_tys += vec(arg_ty);
        if (i == ix) {
            elem_ty = arg_ty;
        }

        i += 1;
    }

    auto tup_ty = ty.mk_imm_tup(cx.fcx.lcx.ccx.tcx, true_arg_tys);

    // Cast the blob pointer to the appropriate type, if we need to (i.e. if
    // the blob pointer isn't dynamically sized).
    let ValueRef llunionptr;
    if (!ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, tup_ty)) {
        auto llty = type_of(cx.fcx.lcx.ccx, tup_ty);
        llunionptr = cx.build.TruncOrBitCast(llblobptr, T_ptr(llty));
    } else {
        llunionptr = llblobptr;
    }

    // Do the GEP_tup_like().
    auto rslt = GEP_tup_like(cx, tup_ty, llunionptr, vec(0, ix));

    // Cast the result to the appropriate type, if necessary.
    auto val;
    if (!ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, elem_ty)) {
        auto llelemty = type_of(rslt.bcx.fcx.lcx.ccx, elem_ty);
        val = rslt.bcx.build.PointerCast(rslt.val, T_ptr(llelemty));
    } else {
        val = rslt.val;
    }

    ret res(rslt.bcx, val);
}


fn trans_raw_malloc(@block_ctxt cx, TypeRef llptr_ty, ValueRef llsize)
        -> result {
    // FIXME: need a table to collect tydesc globals.
    auto tydesc = C_int(0);
    auto rslt = trans_upcall(cx, "upcall_malloc", vec(llsize, tydesc));
    rslt = res(rslt.bcx, vi2p(rslt.bcx, rslt.val, llptr_ty));
    ret rslt;
}

fn trans_malloc_boxed(@block_ctxt cx, ty.t t) -> result {
    // Synthesize a fake box type structurally so we have something
    // to measure the size of.
    auto boxed_body = ty.mk_imm_tup(cx.fcx.lcx.ccx.tcx,
                                    vec(ty.mk_int(cx.fcx.lcx.ccx.tcx), t));
    auto box_ptr = ty.mk_imm_box(cx.fcx.lcx.ccx.tcx, t);
    auto sz = size_of(cx, boxed_body);
    auto llty = type_of(cx.fcx.lcx.ccx, box_ptr);
    ret trans_raw_malloc(sz.bcx, llty, sz.val);
}


// Type descriptor and type glue stuff

// Given a type and a field index into its corresponding type descriptor,
// returns an LLVM ValueRef of that field from the tydesc, generating the
// tydesc if necessary.
fn field_of_tydesc(@block_ctxt cx, ty.t t, int field) -> result {
    auto tydesc = get_tydesc(cx, t);
    ret res(tydesc.bcx,
            tydesc.bcx.build.GEP(tydesc.val, vec(C_int(0), C_int(field))));
}

// Given a type containing ty params, build a vector containing a ValueRef for
// each of the ty params it uses (from the current frame) and a vector of the
// indices of the ty params present in the type. This is used solely for
// constructing derived tydescs.
fn linearize_ty_params(@block_ctxt cx, ty.t t) ->
        tup(vec[uint], vec[ValueRef]) {
    let vec[ValueRef] param_vals = vec();
    let vec[uint] param_defs = vec();
    type rr = rec(@block_ctxt cx,
                  mutable vec[ValueRef] vals,
                  mutable vec[uint] defs);

    fn linearizer(@rr r, ty.t t) {
        alt(ty.struct(r.cx.fcx.lcx.ccx.tcx, t)) {
            case (ty.ty_param(?pid)) {
                let bool seen = false;
                for (uint d in r.defs) {
                    if (d == pid) {
                        seen = true;
                    }
                }
                if (!seen) {
                    r.vals += vec(r.cx.fcx.lltydescs.(pid));
                    r.defs += vec(pid);
                }
            }
            case (_) { }
        }
    }


    auto x = @rec(cx = cx,
                  mutable vals = param_vals,
                  mutable defs = param_defs);

    auto f = bind linearizer(x, _);
    ty.walk_ty(cx.fcx.lcx.ccx.tcx, f, t);

    ret tup(x.defs, x.vals);
}

fn get_tydesc(&@block_ctxt cx, ty.t t) -> result {
    // Is the supplied type a type param? If so, return the passed-in tydesc.
    alt (ty.type_param(cx.fcx.lcx.ccx.tcx, t)) {
        case (some[uint](?id)) { ret res(cx, cx.fcx.lltydescs.(id)); }
        case (none[uint])      { /* fall through */ }
    }

    // Does it contain a type param? If so, generate a derived tydesc.

    if (ty.type_contains_params(cx.fcx.lcx.ccx.tcx, t)) {

        let uint n_params = ty.count_ty_params(cx.fcx.lcx.ccx.tcx, t);
        auto tys = linearize_ty_params(cx, t);

        check (n_params == _vec.len[uint](tys._0));
        check (n_params == _vec.len[ValueRef](tys._1));

        auto root = get_static_tydesc(cx, t, tys._0).tydesc;

        auto tydescs = alloca(cx, T_array(T_ptr(T_tydesc(cx.fcx.lcx.ccx.tn)),
                                          1u /* for root*/ + n_params));

        auto i = 0;
        auto tdp = cx.build.GEP(tydescs, vec(C_int(0), C_int(i)));
        cx.build.Store(root, tdp);
        i += 1;
        for (ValueRef td in tys._1) {
            auto tdp = cx.build.GEP(tydescs, vec(C_int(0), C_int(i)));
            cx.build.Store(td, tdp);
            i += 1;
        }

        auto bcx = cx;
        auto sz = size_of(bcx, t);
        bcx = sz.bcx;
        auto align = align_of(bcx, t);
        bcx = align.bcx;

        auto v = trans_upcall(bcx, "upcall_get_type_desc",
                              vec(p2i(bcx.fcx.lcx.ccx.crate_ptr),
                                  sz.val,
                                  align.val,
                                  C_int((1u + n_params) as int),
                                  vp2i(bcx, tydescs)));

        ret res(v.bcx, vi2p(v.bcx, v.val,
                            T_ptr(T_tydesc(cx.fcx.lcx.ccx.tn))));
    }

    // Otherwise, generate a tydesc if necessary, and return it.
    let vec[uint] tps = vec();
    ret res(cx, get_static_tydesc(cx, t, tps).tydesc);
}

fn get_static_tydesc(&@block_ctxt cx,
                     ty.t t, vec[uint] ty_params) -> @tydesc_info {
    alt (cx.fcx.lcx.ccx.tydescs.find(t)) {
        case (some[@tydesc_info](?info)) {
            ret info;
        }
        case (none[@tydesc_info]) {

            // FIXME: Use of a simplified tydesc (w/o names) removes a lot of
            // generated glue, but the compile time goes way down due to
            // greatly increasing the miss rate on the type_of cache elsewhere
            // in this file. Experiment with other approaches to this.

            /*
            fn simplifier(ty.t typ) -> ty.t {
                ret @rec(cname=none[str] with *typ);
            }
            auto f = simplifier;
            auto t_simplified = ty.fold_ty(cx.fcx.lcx.ccx.tcx, f, t);
            auto info = declare_tydesc(cx.fcx.lcx, t_simplified);
            cx.fcx.lcx.ccx.tydescs.insert(t_simplified, info);
            */

            auto info = declare_tydesc(cx.fcx.lcx, t);
            cx.fcx.lcx.ccx.tydescs.insert(t, info);
            define_tydesc(cx.fcx.lcx, t, ty_params);
            ret info;
        }
    }
}

// Generates the declaration for (but doesn't fill in) a type descriptor. This
// needs to be separate from make_tydesc() below, because sometimes type glue
// functions needs to refer to their own type descriptors.
fn declare_tydesc(@local_ctxt cx, ty.t t) -> @tydesc_info {
    auto take_glue = declare_generic_glue(cx, t, T_glue_fn(cx.ccx.tn),
                                          "take");
    auto drop_glue = declare_generic_glue(cx, t, T_glue_fn(cx.ccx.tn),
                                          "drop");
    auto cmp_glue = declare_generic_glue(cx, t, T_cmp_glue_fn(cx.ccx.tn),
                                         "cmp");
    auto ccx = cx.ccx;

    auto llsize;
    auto llalign;
    if (!ty.type_has_dynamic_size(ccx.tcx, t)) {
        auto llty = type_of(ccx, t);
        llsize = llsize_of(llty);
        llalign = llalign_of(llty);
    } else {
        // These will be overwritten as the derived tydesc is generated, so
        // we create placeholder values.
        llsize = C_int(0);
        llalign = C_int(0);
    }

    auto glue_fn_ty = T_ptr(T_glue_fn(ccx.tn));

    auto name = mangle_name_by_seq(ccx, cx.path, "tydesc");
    auto gvar = llvm.LLVMAddGlobal(ccx.llmod, T_tydesc(ccx.tn),
                                   _str.buf(name));
    auto tydesc = C_struct(vec(C_null(T_ptr(T_ptr(T_tydesc(ccx.tn)))),
                               llsize,
                               llalign,
                               take_glue,             // take_glue
                               drop_glue,             // drop_glue
                               C_null(glue_fn_ty),    // free_glue
                               C_null(glue_fn_ty),    // sever_glue
                               C_null(glue_fn_ty),    // mark_glue
                               C_null(glue_fn_ty),    // obj_drop_glue
                               C_null(glue_fn_ty),    // is_stateful
                               cmp_glue));            // cmp_glue

    llvm.LLVMSetInitializer(gvar, tydesc);
    llvm.LLVMSetGlobalConstant(gvar, True);
    llvm.LLVMSetLinkage(gvar, lib.llvm.LLVMInternalLinkage
                        as llvm.Linkage);

    auto info = @rec(
        tydesc=gvar,
        take_glue=take_glue,
        drop_glue=drop_glue,
        cmp_glue=cmp_glue
    );

    ret info;
}

tag make_generic_glue_helper_fn {
    mgghf_single(fn(@block_ctxt cx, ValueRef v, ty.t t));
    mgghf_cmp;
}

// declare_tydesc() above must have been called first.
fn define_tydesc(@local_ctxt cx, ty.t t, vec[uint] ty_params) {
    auto info = cx.ccx.tydescs.get(t);
    auto gvar = info.tydesc;

    auto tg = make_take_glue;
    make_generic_glue(cx, t, info.take_glue, mgghf_single(tg), ty_params);
    auto dg = make_drop_glue;
    make_generic_glue(cx, t, info.drop_glue, mgghf_single(dg), ty_params);
    make_generic_glue(cx, t, info.cmp_glue, mgghf_cmp, ty_params);
}

fn declare_generic_glue(@local_ctxt cx,
                        ty.t t,
                        TypeRef llfnty,
                        str name) -> ValueRef {
    auto gcx = @rec(path=vec("glue", name) with *cx);
    auto fn_nm = mangle_name_by_seq(cx.ccx, cx.path, "glue");
    fn_nm = sanitize(fn_nm);
    auto llfn = decl_internal_fastcall_fn(cx.ccx.llmod, fn_nm, llfnty);
    ret llfn;
}

fn make_generic_glue(@local_ctxt cx,
                     ty.t t,
                     ValueRef llfn,
                     make_generic_glue_helper_fn helper,
                     vec[uint] ty_params) -> ValueRef {
    auto fcx = new_fn_ctxt(cx, llfn);
    auto bcx = new_top_block_ctxt(fcx);
    auto lltop = bcx.llbb;

    // Any nontrivial glue is with values passed *by alias*; this is a
    // requirement since in many contexts glue is invoked indirectly and
    // the caller has no idea if it's dealing with something that can be
    // passed by value.

    auto llty;
    if (ty.type_has_dynamic_size(cx.ccx.tcx, t)) {
        llty = T_ptr(T_i8());
    } else {
        llty = T_ptr(type_of(cx.ccx, t));
    }

    auto ty_param_count = _vec.len[uint](ty_params);

    auto lltyparams = llvm.LLVMGetParam(llfn, 3u);

    auto lltydescs = _vec.empty_mut[ValueRef]();
    auto p = 0u;
    while (p < ty_param_count) {
        auto llparam = bcx.build.GEP(lltyparams, vec(C_int(p as int)));
        llparam = bcx.build.Load(llparam);
        _vec.grow_set[ValueRef](lltydescs, ty_params.(p), 0 as ValueRef,
                                llparam);
        p += 1u;
    }
    bcx.fcx.lltydescs = _vec.freeze[ValueRef](lltydescs);

    auto llrawptr0 = llvm.LLVMGetParam(llfn, 4u);
    auto llval0 = bcx.build.BitCast(llrawptr0, llty);

    alt (helper) {
        case (mgghf_single(?single_fn)) {
            single_fn(bcx, llval0, t);
        }
        case (mgghf_cmp) {
            auto llrawptr1 = llvm.LLVMGetParam(llfn, 5u);
            auto llval1 = bcx.build.BitCast(llrawptr1, llty);

            auto llcmpval = llvm.LLVMGetParam(llfn, 6u);

            make_cmp_glue(bcx, llval0, llval1, t, llcmpval);
        }
    }

    // Tie up the llallocas -> lltop edge.
    new_builder(fcx.llallocas).Br(lltop);

    ret llfn;
}

fn make_take_glue(@block_ctxt cx, ValueRef v, ty.t t) {
    // NB: v is an *alias* of type t here, not a direct value.
    auto bcx;
    if (ty.type_is_boxed(cx.fcx.lcx.ccx.tcx, t)) {
        bcx = incr_refcnt_of_boxed(cx, cx.build.Load(v)).bcx;

    } else if (ty.type_is_structural(cx.fcx.lcx.ccx.tcx, t)) {
        bcx = iter_structural_ty(cx, v, t,
                                 bind take_ty(_, _, _)).bcx;
    } else {
        bcx = cx;
    }
    bcx.build.RetVoid();
}

fn incr_refcnt_of_boxed(@block_ctxt cx, ValueRef box_ptr) -> result {
    auto rc_ptr = cx.build.GEP(box_ptr, vec(C_int(0),
                                            C_int(abi.box_rc_field_refcnt)));
    auto rc = cx.build.Load(rc_ptr);

    auto rc_adj_cx = new_sub_block_ctxt(cx, "rc++");
    auto next_cx = new_sub_block_ctxt(cx, "next");

    auto const_test = cx.build.ICmp(lib.llvm.LLVMIntEQ,
                                    C_int(abi.const_refcount as int), rc);
    cx.build.CondBr(const_test, next_cx.llbb, rc_adj_cx.llbb);

    rc = rc_adj_cx.build.Add(rc, C_int(1));
    rc_adj_cx.build.Store(rc, rc_ptr);
    rc_adj_cx.build.Br(next_cx.llbb);

    ret res(next_cx, C_nil());
}

fn make_drop_glue(@block_ctxt cx, ValueRef v0, ty.t t) {
    // NB: v0 is an *alias* of type t here, not a direct value.
    auto rslt;
    alt (ty.struct(cx.fcx.lcx.ccx.tcx, t)) {
        case (ty.ty_str) {
            auto v = cx.build.Load(v0);
            rslt = decr_refcnt_and_if_zero
                (cx, v, bind trans_non_gc_free(_, v),
                 "free string",
                 T_int(), C_int(0));
        }

        case (ty.ty_vec(_)) {
            fn hit_zero(@block_ctxt cx, ValueRef v,
                        ty.t t) -> result {
                auto res = iter_sequence(cx, v, t,
                                         bind drop_ty(_,_,_));
                // FIXME: switch gc/non-gc on layer of the type.
                ret trans_non_gc_free(res.bcx, v);
            }
            auto v = cx.build.Load(v0);
            rslt = decr_refcnt_and_if_zero(cx, v,
                                          bind hit_zero(_, v, t),
                                          "free vector",
                                          T_int(), C_int(0));
        }

        case (ty.ty_box(?body_mt)) {
            fn hit_zero(@block_ctxt cx, ValueRef v,
                        ty.t body_ty) -> result {
                auto body = cx.build.GEP(v,
                                         vec(C_int(0),
                                             C_int(abi.box_rc_field_body)));

                auto body_val = load_if_immediate(cx, body, body_ty);
                auto res = drop_ty(cx, body_val, body_ty);
                // FIXME: switch gc/non-gc on layer of the type.
                ret trans_non_gc_free(res.bcx, v);
            }
            auto v = cx.build.Load(v0);
            rslt = decr_refcnt_and_if_zero(cx, v,
                                           bind hit_zero(_, v, body_mt.ty),
                                           "free box",
                                           T_int(), C_int(0));
        }

        case (ty.ty_port(_)) {
            fn hit_zero(@block_ctxt cx, ValueRef v) -> result {
                ret trans_upcall(cx, "upcall_del_port",
                                 vec(vp2i(cx, v)));
            }
            auto v = cx.build.Load(v0);
            rslt = decr_refcnt_and_if_zero(cx, v,
                                           bind hit_zero(_, v),
                                           "free port",
                                           T_int(), C_int(0));
        }

        case (ty.ty_chan(_)) {
            fn hit_zero(@block_ctxt cx, ValueRef v) -> result {
                ret trans_upcall(cx, "upcall_del_chan",
                                 vec(vp2i(cx, v)));
            }
            auto v = cx.build.Load(v0);
            rslt = decr_refcnt_and_if_zero(cx, v,
                                           bind hit_zero(_, v),
                                           "free chan",
                                           T_int(), C_int(0));
        }

        case (ty.ty_obj(_)) {
            fn hit_zero(@block_ctxt cx, ValueRef v) -> result {

                // Call through the obj's own fields-drop glue first.
                auto body =
                    cx.build.GEP(v,
                                 vec(C_int(0),
                                     C_int(abi.box_rc_field_body)));

                auto tydescptr =
                    cx.build.GEP(body,
                                 vec(C_int(0),
                                     C_int(abi.obj_body_elt_tydesc)));

                call_tydesc_glue_full(cx, body, cx.build.Load(tydescptr),
                                      abi.tydesc_field_drop_glue);

                // Then free the body.
                // FIXME: switch gc/non-gc on layer of the type.
                ret trans_non_gc_free(cx, v);
            }
            auto box_cell =
                cx.build.GEP(v0,
                             vec(C_int(0),
                                 C_int(abi.obj_field_box)));

            auto boxptr = cx.build.Load(box_cell);

            rslt = decr_refcnt_and_if_zero(cx, boxptr,
                                           bind hit_zero(_, boxptr),
                                           "free obj",
                                           T_int(), C_int(0));
        }

        case (ty.ty_fn(_,_,_)) {
            fn hit_zero(@block_ctxt cx, ValueRef v) -> result {

                // Call through the closure's own fields-drop glue first.
                auto body =
                    cx.build.GEP(v,
                                 vec(C_int(0),
                                     C_int(abi.box_rc_field_body)));
                auto bindings =
                    cx.build.GEP(body,
                                 vec(C_int(0),
                                     C_int(abi.closure_elt_bindings)));

                auto tydescptr =
                    cx.build.GEP(body,
                                 vec(C_int(0),
                                     C_int(abi.closure_elt_tydesc)));

                call_tydesc_glue_full(cx, bindings, cx.build.Load(tydescptr),
                                      abi.tydesc_field_drop_glue);


                // Then free the body.
                // FIXME: switch gc/non-gc on layer of the type.
                ret trans_non_gc_free(cx, v);
            }
            auto box_cell =
                cx.build.GEP(v0,
                             vec(C_int(0),
                                 C_int(abi.fn_field_box)));

            auto boxptr = cx.build.Load(box_cell);

            rslt = decr_refcnt_and_if_zero(cx, boxptr,
                                           bind hit_zero(_, boxptr),
                                           "free fn",
                                           T_int(), C_int(0));
        }

        case (_) {
            if (ty.type_is_structural(cx.fcx.lcx.ccx.tcx, t)) {
                rslt = iter_structural_ty(cx, v0, t,
                                          bind drop_ty(_, _, _));

            } else if (ty.type_is_scalar(cx.fcx.lcx.ccx.tcx, t) ||
                       ty.type_is_native(cx.fcx.lcx.ccx.tcx, t) ||
                       ty.type_is_nil(cx.fcx.lcx.ccx.tcx, t)) {
                rslt = res(cx, C_nil());
            } else {
                rslt = res(cx, C_nil());
            }
        }
    }

    rslt.bcx.build.RetVoid();
}

fn decr_refcnt_and_if_zero(@block_ctxt cx,
                           ValueRef box_ptr,
                           fn(@block_ctxt cx) -> result inner,
                           str inner_name,
                           TypeRef t_else, ValueRef v_else) -> result {

    auto load_rc_cx = new_sub_block_ctxt(cx, "load rc");
    auto rc_adj_cx = new_sub_block_ctxt(cx, "rc--");
    auto inner_cx = new_sub_block_ctxt(cx, inner_name);
    auto next_cx = new_sub_block_ctxt(cx, "next");

    auto null_test = cx.build.IsNull(box_ptr);
    cx.build.CondBr(null_test, next_cx.llbb, load_rc_cx.llbb);


    auto rc_ptr = load_rc_cx.build.GEP(box_ptr,
                                       vec(C_int(0),
                                           C_int(abi.box_rc_field_refcnt)));

    auto rc = load_rc_cx.build.Load(rc_ptr);
    auto const_test =
        load_rc_cx.build.ICmp(lib.llvm.LLVMIntEQ,
                              C_int(abi.const_refcount as int), rc);
    load_rc_cx.build.CondBr(const_test, next_cx.llbb, rc_adj_cx.llbb);

    rc = rc_adj_cx.build.Sub(rc, C_int(1));
    rc_adj_cx.build.Store(rc, rc_ptr);
    auto zero_test = rc_adj_cx.build.ICmp(lib.llvm.LLVMIntEQ, C_int(0), rc);
    rc_adj_cx.build.CondBr(zero_test, inner_cx.llbb, next_cx.llbb);

    auto inner_res = inner(inner_cx);
    inner_res.bcx.build.Br(next_cx.llbb);

    auto phi = next_cx.build.Phi(t_else,
                                 vec(v_else, v_else, v_else, inner_res.val),
                                 vec(cx.llbb,
                                     load_rc_cx.llbb,
                                     rc_adj_cx.llbb,
                                     inner_res.bcx.llbb));

    ret res(next_cx, phi);
}

// Structural comparison: a rather involved form of glue.

fn make_cmp_glue(@block_ctxt cx,
                 ValueRef lhs0,
                 ValueRef rhs0,
                 ty.t t,
                 ValueRef llop) {
    auto lhs = load_if_immediate(cx, lhs0, t);
    auto rhs = load_if_immediate(cx, rhs0, t);

    if (ty.type_is_scalar(cx.fcx.lcx.ccx.tcx, t)) {
        make_scalar_cmp_glue(cx, lhs, rhs, t, llop);

    } else if (ty.type_is_box(cx.fcx.lcx.ccx.tcx, t)) {
        lhs = cx.build.GEP(lhs, vec(C_int(0), C_int(abi.box_rc_field_body)));
        rhs = cx.build.GEP(rhs, vec(C_int(0), C_int(abi.box_rc_field_body)));
        auto rslt = call_cmp_glue(cx, lhs, rhs, t, llop);

        rslt.bcx.build.Store(rslt.val, cx.fcx.llretptr);
        rslt.bcx.build.RetVoid();

    } else if (ty.type_is_structural(cx.fcx.lcx.ccx.tcx, t)
               || ty.type_is_sequence(cx.fcx.lcx.ccx.tcx, t)) {

        auto scx = new_sub_block_ctxt(cx, "structural compare start");
        auto next = new_sub_block_ctxt(cx, "structural compare end");
        cx.build.Br(scx.llbb);

        /*
         * We're doing lexicographic comparison here. We start with the
         * assumption that the two input elements are equal. Depending on
         * operator, this means that the result is either true or false;
         * equality produces 'true' for ==, <= and >=. It produces 'false' for
         * !=, < and >.
         *
         * We then move one element at a time through the structure checking
         * for pairwise element equality. If we have equality, our assumption
         * about overall sequence equality is not modified, so we have to move
         * to the next element.
         *
         * If we do not have pairwise element equality, we have reached an
         * element that 'decides' the lexicographic comparison. So we exit the
         * loop with a flag that indicates the true/false sense of that
         * decision, by testing the element again with the operator we're
         * interested in.
         *
         * When we're lucky, LLVM should be able to fold some of these two
         * tests together (as they're applied to the same operands and in some
         * cases are sometimes redundant). But we don't bother trying to
         * optimize combinations like that, at this level.
         */

        auto flag = alloca(scx, T_i1());
        llvm.LLVMSetValueName(flag, _str.buf("flag"));

        auto r;
        if (ty.type_is_sequence(cx.fcx.lcx.ccx.tcx, t)) {

            // If we hit == all the way through the minimum-shared-length
            // section, default to judging the relative sequence lengths.
            r = compare_integral_values(scx,
                                        vec_fill(scx, lhs),
                                        vec_fill(scx, rhs),
                                        false,
                                        llop);
            r.bcx.build.Store(r.val, flag);

        } else {
            // == and <= default to true if they find == all the way. <
            // defaults to false if it finds == all the way.
            auto result_if_equal = scx.build.ICmp(lib.llvm.LLVMIntNE, llop,
                                                  C_i8(abi.cmp_glue_op_lt));
            scx.build.Store(result_if_equal, flag);
            r = res(scx, C_nil());
        }

        fn inner(@block_ctxt last_cx,
                 bool load_inner,
                 ValueRef flag,
                 ValueRef llop,
                 @block_ctxt cx,
                 ValueRef av0,
                 ValueRef bv0,
                 ty.t t) -> result {

            auto cnt_cx = new_sub_block_ctxt(cx, "continue_comparison");
            auto stop_cx = new_sub_block_ctxt(cx, "stop_comparison");

            auto av = av0;
            auto bv = bv0;
            if (load_inner) {
                // If `load_inner` is true, then the pointer type will always
                // be i8, because the data part of a vector always has type
                // i8[]. So we need to cast it to the proper type.

                if (!ty.type_has_dynamic_size(last_cx.fcx.lcx.ccx.tcx, t)) {
                    auto llelemty = T_ptr(type_of(last_cx.fcx.lcx.ccx, t));
                    av = cx.build.PointerCast(av, llelemty);
                    bv = cx.build.PointerCast(bv, llelemty);
                }

                av = load_if_immediate(cx, av, t);
                bv = load_if_immediate(cx, bv, t);
            }

            // First 'eq' comparison: if so, continue to next elts.
            auto eq_r = call_cmp_glue(cx, av, bv, t,
                                      C_i8(abi.cmp_glue_op_eq));
            eq_r.bcx.build.CondBr(eq_r.val, cnt_cx.llbb, stop_cx.llbb);

            // Second 'op' comparison: find out how this elt-pair decides.
            auto stop_r = call_cmp_glue(stop_cx, av, bv, t, llop);
            stop_r.bcx.build.Store(stop_r.val, flag);
            stop_r.bcx.build.Br(last_cx.llbb);
            ret res(cnt_cx, C_nil());
        }

        if (ty.type_is_structural(cx.fcx.lcx.ccx.tcx, t)) {
            r = iter_structural_ty_full(r.bcx, lhs, rhs, t,
                                        bind inner(next, false, flag, llop,
                                                   _, _, _, _));
        } else {
            auto lhs_p0 = vec_p0(r.bcx, lhs);
            auto rhs_p0 = vec_p0(r.bcx, rhs);
            auto min_len = umin(r.bcx, vec_fill(r.bcx, lhs),
                                vec_fill(r.bcx, rhs));
            auto rhs_lim = r.bcx.build.GEP(rhs_p0, vec(min_len));
            auto elt_ty = ty.sequence_element_type(cx.fcx.lcx.ccx.tcx, t);
            r = size_of(r.bcx, elt_ty);
            r = iter_sequence_raw(r.bcx, lhs_p0, rhs_p0, rhs_lim, r.val,
                                  bind inner(next, true, flag, llop,
                                             _, _, _, elt_ty));
        }

        r.bcx.build.Br(next.llbb);
        auto v = next.build.Load(flag);

        next.build.Store(v, cx.fcx.llretptr);
        next.build.RetVoid();


    } else {
        // FIXME: compare obj, fn by pointer?
        trans_fail(cx, none[common.span],
                   "attempt to compare values of type " +
                   ty.ty_to_str(cx.fcx.lcx.ccx.tcx, t));
    }
}

// A helper function to create scalar comparison glue.
fn make_scalar_cmp_glue(@block_ctxt cx, ValueRef lhs, ValueRef rhs, ty.t t,
                        ValueRef llop) {
    if (ty.type_is_fp(cx.fcx.lcx.ccx.tcx, t)) {
        make_fp_cmp_glue(cx, lhs, rhs, t, llop);
        ret;
    }

    if (ty.type_is_integral(cx.fcx.lcx.ccx.tcx, t) ||
            ty.type_is_bool(cx.fcx.lcx.ccx.tcx, t)) {
        make_integral_cmp_glue(cx, lhs, rhs, t, llop);
        ret;
    }

    if (ty.type_is_nil(cx.fcx.lcx.ccx.tcx, t)) {
        cx.build.Store(C_bool(true), cx.fcx.llretptr);
        cx.build.RetVoid();
        ret;
    }

    trans_fail(cx, none[common.span],
               "attempt to compare values of type " +
               ty.ty_to_str(cx.fcx.lcx.ccx.tcx, t));
}

// A helper function to create floating point comparison glue.
fn make_fp_cmp_glue(@block_ctxt cx, ValueRef lhs, ValueRef rhs, ty.t fptype,
                    ValueRef llop) {
    auto last_cx = new_sub_block_ctxt(cx, "last");

    auto eq_cx = new_sub_block_ctxt(cx, "eq");
    auto eq_result = eq_cx.build.FCmp(lib.llvm.LLVMRealUEQ, lhs, rhs);
    eq_cx.build.Br(last_cx.llbb);

    auto lt_cx = new_sub_block_ctxt(cx, "lt");
    auto lt_result = lt_cx.build.FCmp(lib.llvm.LLVMRealULT, lhs, rhs);
    lt_cx.build.Br(last_cx.llbb);

    auto le_cx = new_sub_block_ctxt(cx, "le");
    auto le_result = le_cx.build.FCmp(lib.llvm.LLVMRealULE, lhs, rhs);
    le_cx.build.Br(last_cx.llbb);

    auto unreach_cx = new_sub_block_ctxt(cx, "unreach");
    unreach_cx.build.Unreachable();

    auto llswitch = cx.build.Switch(llop, unreach_cx.llbb, 3u);
    llvm.LLVMAddCase(llswitch, C_i8(abi.cmp_glue_op_eq), eq_cx.llbb);
    llvm.LLVMAddCase(llswitch, C_i8(abi.cmp_glue_op_lt), lt_cx.llbb);
    llvm.LLVMAddCase(llswitch, C_i8(abi.cmp_glue_op_le), le_cx.llbb);

    auto last_result =
        last_cx.build.Phi(T_i1(), vec(eq_result, lt_result, le_result),
                          vec(eq_cx.llbb, lt_cx.llbb, le_cx.llbb));
    last_cx.build.Store(last_result, cx.fcx.llretptr);
    last_cx.build.RetVoid();
}

// A helper function to compare integral values. This is used by both
// `make_integral_cmp_glue` and `make_cmp_glue`.
fn compare_integral_values(@block_ctxt cx, ValueRef lhs, ValueRef rhs,
                           bool signed, ValueRef llop) -> result {
    auto lt_cmp; auto le_cmp;
    if (signed) {
        lt_cmp = lib.llvm.LLVMIntSLT;
        le_cmp = lib.llvm.LLVMIntSLE;
    } else {
        lt_cmp = lib.llvm.LLVMIntULT;
        le_cmp = lib.llvm.LLVMIntULE;
    }

    auto last_cx = new_sub_block_ctxt(cx, "last");

    auto eq_cx = new_sub_block_ctxt(cx, "eq");
    auto eq_result = eq_cx.build.ICmp(lib.llvm.LLVMIntEQ, lhs, rhs);
    eq_cx.build.Br(last_cx.llbb);

    auto lt_cx = new_sub_block_ctxt(cx, "lt");
    auto lt_result = lt_cx.build.ICmp(lt_cmp, lhs, rhs);
    lt_cx.build.Br(last_cx.llbb);

    auto le_cx = new_sub_block_ctxt(cx, "le");
    auto le_result = le_cx.build.ICmp(le_cmp, lhs, rhs);
    le_cx.build.Br(last_cx.llbb);

    auto unreach_cx = new_sub_block_ctxt(cx, "unreach");
    unreach_cx.build.Unreachable();

    auto llswitch = cx.build.Switch(llop, unreach_cx.llbb, 3u);
    llvm.LLVMAddCase(llswitch, C_i8(abi.cmp_glue_op_eq), eq_cx.llbb);
    llvm.LLVMAddCase(llswitch, C_i8(abi.cmp_glue_op_lt), lt_cx.llbb);
    llvm.LLVMAddCase(llswitch, C_i8(abi.cmp_glue_op_le), le_cx.llbb);

    auto last_result =
        last_cx.build.Phi(T_i1(), vec(eq_result, lt_result, le_result),
                          vec(eq_cx.llbb, lt_cx.llbb, le_cx.llbb));
    ret res(last_cx, last_result);
}

// A helper function to create integral comparison glue.
fn make_integral_cmp_glue(@block_ctxt cx, ValueRef lhs, ValueRef rhs,
                          ty.t intype, ValueRef llop) {
    auto r = compare_integral_values(cx, lhs, rhs,
        ty.type_is_signed(cx.fcx.lcx.ccx.tcx, intype), llop);
    r.bcx.build.Store(r.val, r.bcx.fcx.llretptr);
    r.bcx.build.RetVoid();
}


// Tag information

type variant_info = rec(vec[ty.t] args, ty.t ctor_ty, ast.def_id id);

// Returns information about the variants in a tag.
fn tag_variants(@crate_ctxt cx, ast.def_id id) -> vec[variant_info] {
    if (cx.sess.get_targ_crate_num() != id._0) {
        ret creader.get_tag_variants(cx.sess, cx.tcx, id);
    }

    check (cx.items.contains_key(id));
    alt (cx.items.get(id).node) {
        case (ast.item_tag(_, ?variants, _, _, _)) {
            let vec[variant_info] result = vec();
            for (ast.variant variant in variants) {
                auto ctor_ty = node_ann_type(cx, variant.node.ann);
                let vec[ty.t] arg_tys = vec();
                if (_vec.len[ast.variant_arg](variant.node.args) > 0u) {
                    for (ty.arg a in ty.ty_fn_args(cx.tcx, ctor_ty)) {
                        arg_tys += vec(a.ty);
                    }
                }
                auto did = variant.node.id;
                result += vec(rec(args=arg_tys, ctor_ty=ctor_ty, id=did));
            }
            ret result;
        }
    }
    fail;   // not reached
}

// Returns information about the tag variant with the given ID.
fn tag_variant_with_id(@crate_ctxt cx,
                       &ast.def_id tag_id,
                       &ast.def_id variant_id) -> variant_info {
    auto variants = tag_variants(cx, tag_id);

    auto i = 0u;
    while (i < _vec.len[variant_info](variants)) {
        auto variant = variants.(i);
        if (common.def_eq(variant.id, variant_id)) {
            ret variant;
        }
        i += 1u;
    }

    log_err "tag_variant_with_id(): no variant exists with that ID";
    fail;
}


type val_pair_fn = fn(@block_ctxt cx, ValueRef dst, ValueRef src) -> result;

type val_and_ty_fn = fn(@block_ctxt cx, ValueRef v, ty.t t) -> result;

type val_pair_and_ty_fn =
    fn(@block_ctxt cx, ValueRef av, ValueRef bv, ty.t t) -> result;

// Iterates through the elements of a structural type.
fn iter_structural_ty(@block_ctxt cx,
                      ValueRef v,
                      ty.t t,
                      val_and_ty_fn f)
    -> result {
    fn adaptor_fn(val_and_ty_fn f,
                  @block_ctxt cx,
                  ValueRef av,
                  ValueRef bv,
                  ty.t t) -> result {
        ret f(cx, av, t);
    }
    be iter_structural_ty_full(cx, v, v, t,
                               bind adaptor_fn(f, _, _, _, _));
}


fn iter_structural_ty_full(@block_ctxt cx,
                           ValueRef av,
                           ValueRef bv,
                           ty.t t,
                           val_pair_and_ty_fn f)
    -> result {
    let result r = res(cx, C_nil());

    fn iter_boxpp(@block_ctxt cx,
                  ValueRef box_a_cell,
                  ValueRef box_b_cell,
                  val_pair_and_ty_fn f) -> result {
        auto box_a_ptr = cx.build.Load(box_a_cell);
        auto box_b_ptr = cx.build.Load(box_b_cell);
        auto tnil = ty.mk_nil(cx.fcx.lcx.ccx.tcx);
        auto tbox = ty.mk_imm_box(cx.fcx.lcx.ccx.tcx, tnil);

        auto inner_cx = new_sub_block_ctxt(cx, "iter box");
        auto next_cx = new_sub_block_ctxt(cx, "next");
        auto null_test = cx.build.IsNull(box_a_ptr);
        cx.build.CondBr(null_test, next_cx.llbb, inner_cx.llbb);

        auto r = f(inner_cx, box_a_ptr, box_b_ptr, tbox);
        r.bcx.build.Br(next_cx.llbb);
        ret res(next_cx, C_nil());
    }

    alt (ty.struct(cx.fcx.lcx.ccx.tcx, t)) {
        case (ty.ty_tup(?args)) {
            let int i = 0;
            for (ty.mt arg in args) {
                r = GEP_tup_like(r.bcx, t, av, vec(0, i));
                auto elt_a = r.val;
                r = GEP_tup_like(r.bcx, t, bv, vec(0, i));
                auto elt_b = r.val;
                r = f(r.bcx,
                      load_if_immediate(r.bcx, elt_a, arg.ty),
                      load_if_immediate(r.bcx, elt_b, arg.ty),
                      arg.ty);
                i += 1;
            }
        }
        case (ty.ty_rec(?fields)) {
            let int i = 0;
            for (ty.field fld in fields) {
                r = GEP_tup_like(r.bcx, t, av, vec(0, i));
                auto llfld_a = r.val;
                r = GEP_tup_like(r.bcx, t, bv, vec(0, i));
                auto llfld_b = r.val;
                r = f(r.bcx,
                      load_if_immediate(r.bcx, llfld_a, fld.mt.ty),
                      load_if_immediate(r.bcx, llfld_b, fld.mt.ty),
                      fld.mt.ty);
                i += 1;
            }
        }
        case (ty.ty_tag(?tid, ?tps)) {
            auto variants = tag_variants(cx.fcx.lcx.ccx, tid);
            auto n_variants = _vec.len[variant_info](variants);

            // Cast the tags to types we can GEP into.
            auto lltagty = T_opaque_tag_ptr(cx.fcx.lcx.ccx.tn);
            auto av_tag = cx.build.PointerCast(av, lltagty);
            auto bv_tag = cx.build.PointerCast(bv, lltagty);

            auto lldiscrim_a_ptr = cx.build.GEP(av_tag,
                                                vec(C_int(0), C_int(0)));
            auto llunion_a_ptr = cx.build.GEP(av_tag,
                                              vec(C_int(0), C_int(1)));
            auto lldiscrim_a = cx.build.Load(lldiscrim_a_ptr);

            auto lldiscrim_b_ptr = cx.build.GEP(bv_tag,
                                                vec(C_int(0), C_int(0)));
            auto llunion_b_ptr = cx.build.GEP(bv_tag,
                                              vec(C_int(0), C_int(1)));
            auto lldiscrim_b = cx.build.Load(lldiscrim_b_ptr);

            // NB: we must hit the discriminant first so that structural
            // comparison know not to proceed when the discriminants differ.
            auto bcx = cx;
            bcx = f(bcx, lldiscrim_a, lldiscrim_b,
                    ty.mk_int(cx.fcx.lcx.ccx.tcx)).bcx;

            auto unr_cx = new_sub_block_ctxt(bcx, "tag-iter-unr");
            unr_cx.build.Unreachable();

            auto llswitch = bcx.build.Switch(lldiscrim_a, unr_cx.llbb,
                                             n_variants);

            auto next_cx = new_sub_block_ctxt(bcx, "tag-iter-next");

            auto i = 0u;
            for (variant_info variant in variants) {
                auto variant_cx = new_sub_block_ctxt(bcx,
                                                     "tag-iter-variant-" +
                                                     _uint.to_str(i, 10u));
                llvm.LLVMAddCase(llswitch, C_int(i as int), variant_cx.llbb);

                if (_vec.len[ty.t](variant.args) > 0u) {
                    // N-ary variant.
                    auto fn_ty = variant.ctor_ty;
                    alt (ty.struct(bcx.fcx.lcx.ccx.tcx, fn_ty)) {
                        case (ty.ty_fn(_, ?args, _)) {
                            auto j = 0;
                            for (ty.arg a in args) {
                                auto v = vec(C_int(0), C_int(j as int));

                                auto rslt = GEP_tag(variant_cx, llunion_a_ptr,
                                    tid, variant.id, tps, j);
                                auto llfldp_a = rslt.val;
                                variant_cx = rslt.bcx;

                                rslt = GEP_tag(variant_cx, llunion_b_ptr, tid,
                                    variant.id, tps, j);
                                auto llfldp_b = rslt.val;
                                variant_cx = rslt.bcx;

                                auto ty_subst = ty.bind_params_in_type(
                                    cx.fcx.lcx.ccx.tcx, a.ty);
                                ty_subst = ty.substitute_type_params(
                                    cx.fcx.lcx.ccx.tcx, tps, ty_subst);

                                auto llfld_a =
                                    load_if_immediate(variant_cx,
                                                         llfldp_a,
                                                         ty_subst);

                                auto llfld_b =
                                    load_if_immediate(variant_cx,
                                                         llfldp_b,
                                                         ty_subst);

                                auto res = f(variant_cx,
                                             llfld_a, llfld_b, ty_subst);
                                variant_cx = res.bcx;
                                j += 1;
                            }
                        }
                        case (_) { fail; }
                    }

                    variant_cx.build.Br(next_cx.llbb);
                } else {
                    // Nullary variant; nothing to do.
                    variant_cx.build.Br(next_cx.llbb);
                }

                i += 1u;
            }

            ret res(next_cx, C_nil());
        }
        case (ty.ty_fn(_,_,_)) {
            auto box_cell_a =
                cx.build.GEP(av,
                             vec(C_int(0),
                                 C_int(abi.fn_field_box)));
            auto box_cell_b =
                cx.build.GEP(bv,
                             vec(C_int(0),
                                 C_int(abi.fn_field_box)));
            ret iter_boxpp(cx, box_cell_a, box_cell_b, f);
        }
        case (ty.ty_obj(_)) {
            auto box_cell_a =
                cx.build.GEP(av,
                             vec(C_int(0),
                                 C_int(abi.obj_field_box)));
            auto box_cell_b =
                cx.build.GEP(bv,
                             vec(C_int(0),
                                 C_int(abi.obj_field_box)));
            ret iter_boxpp(cx, box_cell_a, box_cell_b, f);
        }
        case (_) {
            cx.fcx.lcx.ccx.sess.unimpl("type in iter_structural_ty_full");
        }
    }
    ret r;
}

// Iterates through a pointer range, until the src* hits the src_lim*.
fn iter_sequence_raw(@block_ctxt cx,
                     ValueRef dst,     // elt*
                     ValueRef src,     // elt*
                     ValueRef src_lim, // elt*
                     ValueRef elt_sz,
                     val_pair_fn f) -> result {

    auto bcx = cx;

    let ValueRef dst_int = vp2i(bcx, dst);
    let ValueRef src_int = vp2i(bcx, src);
    let ValueRef src_lim_int = vp2i(bcx, src_lim);

    auto cond_cx = new_scope_block_ctxt(cx, "sequence-iter cond");
    auto body_cx = new_scope_block_ctxt(cx, "sequence-iter body");
    auto next_cx = new_sub_block_ctxt(cx, "next");

    bcx.build.Br(cond_cx.llbb);

    let ValueRef dst_curr = cond_cx.build.Phi(T_int(),
                                              vec(dst_int), vec(bcx.llbb));
    let ValueRef src_curr = cond_cx.build.Phi(T_int(),
                                              vec(src_int), vec(bcx.llbb));

    auto end_test = cond_cx.build.ICmp(lib.llvm.LLVMIntULT,
                                       src_curr, src_lim_int);

    cond_cx.build.CondBr(end_test, body_cx.llbb, next_cx.llbb);

    auto dst_curr_ptr = vi2p(body_cx, dst_curr, T_ptr(T_i8()));
    auto src_curr_ptr = vi2p(body_cx, src_curr, T_ptr(T_i8()));

    auto body_res = f(body_cx, dst_curr_ptr, src_curr_ptr);
    body_cx = body_res.bcx;

    auto dst_next = body_cx.build.Add(dst_curr, elt_sz);
    auto src_next = body_cx.build.Add(src_curr, elt_sz);
    body_cx.build.Br(cond_cx.llbb);

    cond_cx.build.AddIncomingToPhi(dst_curr, vec(dst_next),
                                   vec(body_cx.llbb));
    cond_cx.build.AddIncomingToPhi(src_curr, vec(src_next),
                                   vec(body_cx.llbb));

    ret res(next_cx, C_nil());
}


fn iter_sequence_inner(@block_ctxt cx,
                       ValueRef src,     // elt*
                       ValueRef src_lim, // elt*
                       ty.t elt_ty,
                       val_and_ty_fn f) -> result {
    fn adaptor_fn(val_and_ty_fn f,
                  ty.t elt_ty,
                  @block_ctxt cx,
                  ValueRef dst,
                  ValueRef src) -> result {
        auto llptrty;
        if (!ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, elt_ty)) {
            auto llty = type_of(cx.fcx.lcx.ccx, elt_ty);
            llptrty = T_ptr(llty);
        } else {
            llptrty = T_ptr(T_ptr(T_i8()));
        }

        auto p = cx.build.PointerCast(src, llptrty);
        ret f(cx, load_if_immediate(cx, p, elt_ty), elt_ty);
    }

    auto elt_sz = size_of(cx, elt_ty);
    be iter_sequence_raw(elt_sz.bcx, src, src, src_lim, elt_sz.val,
                         bind adaptor_fn(f, elt_ty, _, _, _));
}


// Iterates through the elements of a vec or str.
fn iter_sequence(@block_ctxt cx,
                 ValueRef v,
                 ty.t t,
                 val_and_ty_fn f) -> result {

    fn iter_sequence_body(@block_ctxt cx,
                          ValueRef v,
                          ty.t elt_ty,
                          val_and_ty_fn f,
                          bool trailing_null) -> result {

        auto p0 = cx.build.GEP(v, vec(C_int(0),
                                      C_int(abi.vec_elt_data)));
        auto lenptr = cx.build.GEP(v, vec(C_int(0),
                                          C_int(abi.vec_elt_fill)));

        auto llunit_ty;
        if (ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, elt_ty)) {
            llunit_ty = T_i8();
        } else {
            llunit_ty = type_of(cx.fcx.lcx.ccx, elt_ty);
        }

        auto bcx = cx;

        auto len = bcx.build.Load(lenptr);
        if (trailing_null) {
            auto unit_sz = size_of(bcx, elt_ty);
            bcx = unit_sz.bcx;
            len = bcx.build.Sub(len, unit_sz.val);
        }

        auto p1 = vi2p(bcx, bcx.build.Add(vp2i(bcx, p0), len),
                       T_ptr(llunit_ty));

        ret iter_sequence_inner(bcx, p0, p1, elt_ty, f);
    }

    alt (ty.struct(cx.fcx.lcx.ccx.tcx, t)) {
        case (ty.ty_vec(?elt)) {
            ret iter_sequence_body(cx, v, elt.ty, f, false);
        }
        case (ty.ty_str) {
            auto et = ty.mk_mach(cx.fcx.lcx.ccx.tcx, common.ty_u8);
            ret iter_sequence_body(cx, v, et, f, true);
        }
        case (_) { fail; }
    }
    cx.fcx.lcx.ccx.sess.bug("bad type in trans.iter_sequence");
    fail;
}

fn call_tydesc_glue_full(@block_ctxt cx, ValueRef v,
                         ValueRef tydesc, int field) {
    auto llrawptr = cx.build.BitCast(v, T_ptr(T_i8()));
    auto lltydescs = cx.build.GEP(tydesc,
                                  vec(C_int(0),
                                      C_int(abi.tydesc_field_first_param)));
    lltydescs = cx.build.Load(lltydescs);
    auto llfnptr = cx.build.GEP(tydesc, vec(C_int(0), C_int(field)));
    auto llfn = cx.build.Load(llfnptr);

    cx.build.FastCall(llfn, vec(C_null(T_ptr(T_nil())),
                                cx.fcx.lltaskptr,
                                C_null(T_ptr(T_nil())),
                                lltydescs,
                                llrawptr));
}

fn call_tydesc_glue(@block_ctxt cx, ValueRef v,
                    ty.t t, int field) -> result {
    auto td = get_tydesc(cx, t);
    call_tydesc_glue_full(td.bcx,
                          spill_if_immediate(td.bcx, v, t),
                          td.val, field);
    ret res(td.bcx, C_nil());
}

fn call_cmp_glue(@block_ctxt cx, ValueRef lhs, ValueRef rhs, ty.t t,
                 ValueRef llop) -> result {
    // We can't use call_tydesc_glue_full() and friends here because compare
    // glue has a special signature.

    auto lllhs = spill_if_immediate(cx, lhs, t);
    auto llrhs = spill_if_immediate(cx, rhs, t);

    auto llrawlhsptr = cx.build.BitCast(lllhs, T_ptr(T_i8()));
    auto llrawrhsptr = cx.build.BitCast(llrhs, T_ptr(T_i8()));

    auto r = get_tydesc(cx, t);
    auto lltydescs =
        r.bcx.build.GEP(r.val, vec(C_int(0),
                                   C_int(abi.tydesc_field_first_param)));
    lltydescs = r.bcx.build.Load(lltydescs);
    auto llfnptr =
        r.bcx.build.GEP(r.val, vec(C_int(0),
                                   C_int(abi.tydesc_field_cmp_glue)));
    auto llfn = r.bcx.build.Load(llfnptr);

    auto llcmpresultptr = r.bcx.build.Alloca(T_i1());

    let vec[ValueRef] llargs = vec(llcmpresultptr,
                                   r.bcx.fcx.lltaskptr,
                                   C_null(T_ptr(T_nil())),
                                   lltydescs,
                                   llrawlhsptr,
                                   llrawrhsptr,
                                   llop);

    r.bcx.build.FastCall(llfn, llargs);

    ret res(r.bcx, r.bcx.build.Load(llcmpresultptr));
}

fn take_ty(@block_ctxt cx, ValueRef v, ty.t t) -> result {
    if (!ty.type_is_scalar(cx.fcx.lcx.ccx.tcx, t)) {
        ret call_tydesc_glue(cx, v, t, abi.tydesc_field_take_glue);
    }
    ret res(cx, C_nil());
}

fn drop_slot(@block_ctxt cx,
             ValueRef slot,
             ty.t t) -> result {
    auto llptr = load_if_immediate(cx, slot, t);
    auto re = drop_ty(cx, llptr, t);

    auto llty = val_ty(slot);
    auto llelemty = lib.llvm.llvm.LLVMGetElementType(llty);
    re.bcx.build.Store(C_null(llelemty), slot);
    ret re;
}

fn drop_ty(@block_ctxt cx,
           ValueRef v,
           ty.t t) -> result {

    if (!ty.type_is_scalar(cx.fcx.lcx.ccx.tcx, t)) {
        ret call_tydesc_glue(cx, v, t, abi.tydesc_field_drop_glue);
    }
    ret res(cx, C_nil());
}

fn call_memcpy(@block_ctxt cx,
               ValueRef dst,
               ValueRef src,
               ValueRef n_bytes) -> result {
    auto src_ptr = cx.build.PointerCast(src, T_ptr(T_i8()));
    auto dst_ptr = cx.build.PointerCast(dst, T_ptr(T_i8()));
    auto size = cx.build.IntCast(n_bytes, T_int());
    ret res(cx, cx.build.FastCall(cx.fcx.lcx.ccx.glues.memcpy_glue,
                                  vec(dst_ptr, src_ptr, size)));
}

fn call_bzero(@block_ctxt cx,
              ValueRef dst,
              ValueRef n_bytes) -> result {
    auto dst_ptr = cx.build.PointerCast(dst, T_ptr(T_i8()));
    auto size = cx.build.IntCast(n_bytes, T_int());
    ret res(cx, cx.build.FastCall(cx.fcx.lcx.ccx.glues.bzero_glue,
                                  vec(dst_ptr, size)));
}

fn memcpy_ty(@block_ctxt cx,
             ValueRef dst,
             ValueRef src,
             ty.t t) -> result {
    if (ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, t)) {
        auto llszptr = field_of_tydesc(cx, t, abi.tydesc_field_size);
        auto llsz = llszptr.bcx.build.Load(llszptr.val);
        ret call_memcpy(llszptr.bcx, dst, src, llsz);

    } else {
        ret res(cx, cx.build.Store(cx.build.Load(src), dst));
    }
}

tag copy_action {
    INIT;
    DROP_EXISTING;
}

fn copy_ty(@block_ctxt cx,
           copy_action action,
           ValueRef dst,
           ValueRef src,
           ty.t t) -> result {
    if (ty.type_is_scalar(cx.fcx.lcx.ccx.tcx, t) ||
            ty.type_is_native(cx.fcx.lcx.ccx.tcx, t)) {
        ret res(cx, cx.build.Store(src, dst));

    } else if (ty.type_is_nil(cx.fcx.lcx.ccx.tcx, t)) {
        ret res(cx, C_nil());

    } else if (ty.type_is_boxed(cx.fcx.lcx.ccx.tcx, t)) {
        auto r = take_ty(cx, src, t);
        if (action == DROP_EXISTING) {
            r = drop_ty(r.bcx, r.bcx.build.Load(dst), t);
        }
        ret res(r.bcx, r.bcx.build.Store(src, dst));

    } else if (ty.type_is_structural(cx.fcx.lcx.ccx.tcx, t) ||
               ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, t)) {
        auto r = take_ty(cx, src, t);
        if (action == DROP_EXISTING) {
            r = drop_ty(r.bcx, dst, t);
        }
        ret memcpy_ty(r.bcx, dst, src, t);
    }

    cx.fcx.lcx.ccx.sess.bug("unexpected type in trans.copy_ty: " +
                        ty.ty_to_str(cx.fcx.lcx.ccx.tcx, t));
    fail;
}

fn trans_lit(@crate_ctxt cx, &ast.lit lit, &ast.ann ann) -> ValueRef {
    alt (lit.node) {
        case (ast.lit_int(?i)) {
            ret C_int(i);
        }
        case (ast.lit_uint(?u)) {
            ret C_int(u as int);
        }
        case (ast.lit_mach_int(?tm, ?i)) {
            // FIXME: the entire handling of mach types falls apart
            // if target int width is larger than host, at the moment;
            // re-do the mach-int types using 'big' when that works.
            auto t = T_int();
            alt (tm) {
                case (common.ty_u8) { t = T_i8(); }
                case (common.ty_u16) { t = T_i16(); }
                case (common.ty_u32) { t = T_i32(); }
                case (common.ty_u64) { t = T_i64(); }

                case (common.ty_i8) { t = T_i8(); }
                case (common.ty_i16) { t = T_i16(); }
                case (common.ty_i32) { t = T_i32(); }
                case (common.ty_i64) { t = T_i64(); }
            }
            ret C_integral(i, t);
        }
        case(ast.lit_float(?fs)) {
            ret C_float(fs);
        }
        case(ast.lit_mach_float(?tm, ?s)) {
            auto t = T_float();
            alt(tm) {
                case(common.ty_f32) { t = T_f32(); }
                case(common.ty_f64) { t = T_f64(); }
            }
            ret C_floating(s, t);
        }
        case (ast.lit_char(?c)) {
            ret C_integral(c as int, T_char());
        }
        case (ast.lit_bool(?b)) {
            ret C_bool(b);
        }
        case (ast.lit_nil) {
            ret C_nil();
        }
        case (ast.lit_str(?s)) {
            ret C_str(cx, s);
        }
    }
}

fn target_type(@crate_ctxt cx, ty.t t) -> ty.t {
    alt (ty.struct(cx.tcx, t)) {
        case (ty.ty_int) {
            auto struct_ty = ty.mk_mach(cx.tcx,
                                        cx.sess.get_targ_cfg().int_type);
            ret ty.copy_cname(cx.tcx, struct_ty, t);
        }
        case (ty.ty_uint) {
            auto struct_ty = ty.mk_mach(cx.tcx,
                                        cx.sess.get_targ_cfg().uint_type);
            ret ty.copy_cname(cx.tcx, struct_ty, t);
        }
        case (_) { /* fall through */ }
    }
    ret t;
}


// Converts an annotation to a type
fn node_ann_type(@crate_ctxt cx, &ast.ann a) -> ty.t {
    ret target_type(cx, ty.ann_to_monotype(cx.tcx, a));
}

fn node_ann_ty_params(&ast.ann a) -> vec[ty.t] {
    alt (a) {
        case (ast.ann_none) {
            log_err "missing type annotation";
            fail;
        }
        case (ast.ann_type(_, ?tps_opt, _)) {
            alt (tps_opt) {
                case (none[vec[ty.t]]) {
                    log_err "type annotation has no ty params";
                    fail;
                }
                case (some[vec[ty.t]](?tps)) { ret tps; }
            }
        }
    }
}

fn node_type(@crate_ctxt cx, &ast.ann a) -> TypeRef {
    ret type_of(cx, node_ann_type(cx, a));
}

fn trans_unary(@block_ctxt cx, ast.unop op,
               @ast.expr e, &ast.ann a) -> result {

    auto sub = trans_expr(cx, e);
    auto e_ty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, e);

    alt (op) {
        case (ast.bitnot) {
            sub = autoderef(sub.bcx, sub.val,
                            ty.expr_ty(cx.fcx.lcx.ccx.tcx, e));
            ret res(sub.bcx, sub.bcx.build.Not(sub.val));
        }
        case (ast.not) {
            sub = autoderef(sub.bcx, sub.val,
                            ty.expr_ty(cx.fcx.lcx.ccx.tcx, e));
            ret res(sub.bcx, sub.bcx.build.Not(sub.val));
        }
        case (ast.neg) {
            sub = autoderef(sub.bcx, sub.val,
                            ty.expr_ty(cx.fcx.lcx.ccx.tcx, e));
            if(ty.struct(cx.fcx.lcx.ccx.tcx, e_ty) == ty.ty_float) {
                ret res(sub.bcx, sub.bcx.build.FNeg(sub.val));
            }
            else {
                ret res(sub.bcx, sub.bcx.build.Neg(sub.val));
            }
        }
        case (ast.box(_)) {
            auto e_ty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, e);
            auto e_val = sub.val;
            auto box_ty = node_ann_type(sub.bcx.fcx.lcx.ccx, a);
            sub = trans_malloc_boxed(sub.bcx, e_ty);
            find_scope_cx(cx).cleanups +=
                vec(clean(bind drop_ty(_, sub.val, box_ty)));

            auto box = sub.val;
            auto rc = sub.bcx.build.GEP(box,
                                        vec(C_int(0),
                                            C_int(abi.box_rc_field_refcnt)));
            auto body = sub.bcx.build.GEP(box,
                                          vec(C_int(0),
                                              C_int(abi.box_rc_field_body)));
            sub.bcx.build.Store(C_int(1), rc);

            // Cast the body type to the type of the value. This is needed to
            // make tags work, since tags have a different LLVM type depending
            // on whether they're boxed or not.
            if (!ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, e_ty)) {
                auto llety = T_ptr(type_of(sub.bcx.fcx.lcx.ccx, e_ty));
                body = sub.bcx.build.PointerCast(body, llety);
            }

            sub = copy_ty(sub.bcx, INIT, body, e_val, e_ty);
            ret res(sub.bcx, box);
        }
        case (ast.deref) {
            log_err "deref expressions should have been translated using " +
                "trans_lval(), not trans_unary()";
            fail;
        }
    }
    fail;
}

fn trans_compare(@block_ctxt cx0, ast.binop op, ty.t t0,
                 ValueRef lhs0, ValueRef rhs0) -> result {
    // Autoderef both sides.
    auto cx = cx0;

    auto lhs_r = autoderef(cx, lhs0, t0);
    auto lhs = lhs_r.val;
    cx = lhs_r.bcx;

    auto rhs_r = autoderef(cx, rhs0, t0);
    auto rhs = rhs_r.val;
    cx = rhs_r.bcx;

    auto t = autoderefed_ty(cx.fcx.lcx.ccx, t0);

    // Determine the operation we need.
    // FIXME: Use or-patterns when we have them.
    auto llop;
    alt (op) {
        case (ast.eq) { llop = C_i8(abi.cmp_glue_op_eq); }
        case (ast.lt) { llop = C_i8(abi.cmp_glue_op_lt); }
        case (ast.le) { llop = C_i8(abi.cmp_glue_op_le); }
        case (ast.ne) { llop = C_i8(abi.cmp_glue_op_eq); }
        case (ast.ge) { llop = C_i8(abi.cmp_glue_op_lt); }
        case (ast.gt) { llop = C_i8(abi.cmp_glue_op_le); }
    }

    auto rslt = call_cmp_glue(cx, lhs, rhs, t, llop);

    // Invert the result if necessary.
    // FIXME: Use or-patterns when we have them.
    alt (op) {
        case (ast.eq) { ret res(rslt.bcx, rslt.val);                     }
        case (ast.lt) { ret res(rslt.bcx, rslt.val);                     }
        case (ast.le) { ret res(rslt.bcx, rslt.val);                     }
        case (ast.ne) { ret res(rslt.bcx, rslt.bcx.build.Not(rslt.val)); }
        case (ast.ge) { ret res(rslt.bcx, rslt.bcx.build.Not(rslt.val)); }
        case (ast.gt) { ret res(rslt.bcx, rslt.bcx.build.Not(rslt.val)); }
    }
}

fn trans_vec_append(@block_ctxt cx, ty.t t,
                    ValueRef lhs, ValueRef rhs) -> result {

    auto elt_ty = ty.sequence_element_type(cx.fcx.lcx.ccx.tcx, t);

    auto skip_null = C_bool(false);
    alt (ty.struct(cx.fcx.lcx.ccx.tcx, t)) {
        case (ty.ty_str) { skip_null = C_bool(true); }
        case (_) { }
    }

    auto bcx = cx;

    auto llvec_tydesc = get_tydesc(bcx, t);
    bcx = llvec_tydesc.bcx;

    auto llelt_tydesc = get_tydesc(bcx, elt_ty);
    bcx = llelt_tydesc.bcx;

    auto dst = bcx.build.PointerCast(lhs, T_ptr(T_opaque_vec_ptr()));
    auto src = bcx.build.PointerCast(rhs, T_opaque_vec_ptr());

    ret res(bcx, bcx.build.FastCall(cx.fcx.lcx.ccx.glues.vec_append_glue,
                                    vec(cx.fcx.lltaskptr,
                                        llvec_tydesc.val,
                                        llelt_tydesc.val,
                                        dst, src, skip_null)));
}

fn trans_vec_add(@block_ctxt cx, ty.t t,
                 ValueRef lhs, ValueRef rhs) -> result {
    auto r = alloc_ty(cx, t);
    auto tmp = r.val;
    r = copy_ty(r.bcx, INIT, tmp, lhs, t);
    auto bcx = trans_vec_append(r.bcx, t, tmp, rhs).bcx;
    tmp = load_if_immediate(bcx, tmp, t);
    find_scope_cx(cx).cleanups +=
        vec(clean(bind drop_ty(_, tmp, t)));
    ret res(bcx, tmp);
}


fn trans_eager_binop(@block_ctxt cx, ast.binop op, ty.t intype,
                     ValueRef lhs, ValueRef rhs) -> result {

    auto is_float = false;
    alt (ty.struct(cx.fcx.lcx.ccx.tcx, intype)) {
        case (ty.ty_float) {
            is_float = true;
        }
        case (_) {
            is_float = false;
        }
    }

    alt (op) {
        case (ast.add) {
            if (ty.type_is_sequence(cx.fcx.lcx.ccx.tcx, intype)) {
                ret trans_vec_add(cx, intype, lhs, rhs);
            }
            if (is_float) {
                ret res(cx, cx.build.FAdd(lhs, rhs));
            }
            else {
                ret res(cx, cx.build.Add(lhs, rhs));
            }
        }
        case (ast.sub) {
            if (is_float) {
                ret res(cx, cx.build.FSub(lhs, rhs));
            }
            else {
                ret res(cx, cx.build.Sub(lhs, rhs));
            }
        }

        case (ast.mul) {
            if (is_float) {
                ret res(cx, cx.build.FMul(lhs, rhs));
            }
            else {
                ret res(cx, cx.build.Mul(lhs, rhs));
            }
        }

        case (ast.div) {
            if (is_float) {
                ret res(cx, cx.build.FDiv(lhs, rhs));
            }
            if (ty.type_is_signed(cx.fcx.lcx.ccx.tcx, intype)) {
                ret res(cx, cx.build.SDiv(lhs, rhs));
            } else {
                ret res(cx, cx.build.UDiv(lhs, rhs));
            }
        }
        case (ast.rem) {
            if (is_float) {
                ret res(cx, cx.build.FRem(lhs, rhs));
            }
            if (ty.type_is_signed(cx.fcx.lcx.ccx.tcx, intype)) {
                ret res(cx, cx.build.SRem(lhs, rhs));
            } else {
                ret res(cx, cx.build.URem(lhs, rhs));
            }
        }

        case (ast.bitor) { ret res(cx, cx.build.Or(lhs, rhs)); }
        case (ast.bitand) { ret res(cx, cx.build.And(lhs, rhs)); }
        case (ast.bitxor) { ret res(cx, cx.build.Xor(lhs, rhs)); }
        case (ast.lsl) { ret res(cx, cx.build.Shl(lhs, rhs)); }
        case (ast.lsr) { ret res(cx, cx.build.LShr(lhs, rhs)); }
        case (ast.asr) { ret res(cx, cx.build.AShr(lhs, rhs)); }
        case (_) {
            ret trans_compare(cx, op, intype, lhs, rhs);
        }
    }
    fail;
}

fn autoderef(@block_ctxt cx, ValueRef v, ty.t t) -> result {
    let ValueRef v1 = v;
    let ty.t t1 = t;

    while (true) {
        alt (ty.struct(cx.fcx.lcx.ccx.tcx, t1)) {
            case (ty.ty_box(?mt)) {
                auto body = cx.build.GEP(v1,
                                         vec(C_int(0),
                                             C_int(abi.box_rc_field_body)));
                t1 = mt.ty;

                // Since we're changing levels of box indirection, we may have
                // to cast this pointer, since statically-sized tag types have
                // different types depending on whether they're behind a box
                // or not.
                if (!ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, mt.ty)) {
                    auto llty = type_of(cx.fcx.lcx.ccx, mt.ty);
                    v1 = cx.build.PointerCast(body, T_ptr(llty));
                } else {
                    v1 = body;
                }

                v1 = load_if_immediate(cx, v1, t1);
            }
            case (_) {
                ret res(cx, v1);
            }
        }
    }
}

fn autoderefed_ty(@crate_ctxt ccx, ty.t t) -> ty.t {
    let ty.t t1 = t;

    while (true) {
        alt (ty.struct(ccx.tcx, t1)) {
            case (ty.ty_box(?mt)) {
                t1 = mt.ty;
            }
            case (_) {
                ret t1;
            }
        }
    }
}

fn trans_binary(@block_ctxt cx, ast.binop op,
                @ast.expr a, @ast.expr b) -> result {

    // First couple cases are lazy:

    alt (op) {
        case (ast.and) {
            // Lazy-eval and
            auto lhs_res = trans_expr(cx, a);
            lhs_res = autoderef(lhs_res.bcx, lhs_res.val,
                                ty.expr_ty(cx.fcx.lcx.ccx.tcx, a));

            auto rhs_cx = new_scope_block_ctxt(cx, "rhs");
            auto rhs_res = trans_expr(rhs_cx, b);
            rhs_res = autoderef(rhs_res.bcx, rhs_res.val,
                                ty.expr_ty(cx.fcx.lcx.ccx.tcx, b));

            auto lhs_false_cx = new_scope_block_ctxt(cx, "lhs false");
            auto lhs_false_res = res(lhs_false_cx, C_bool(false));

            lhs_res.bcx.build.CondBr(lhs_res.val,
                                     rhs_cx.llbb,
                                     lhs_false_cx.llbb);

            ret join_results(cx, T_bool(),
                             vec(lhs_false_res, rhs_res));
        }

        case (ast.or) {
            // Lazy-eval or
            auto lhs_res = trans_expr(cx, a);
            lhs_res = autoderef(lhs_res.bcx, lhs_res.val,
                                ty.expr_ty(cx.fcx.lcx.ccx.tcx, a));

            auto rhs_cx = new_scope_block_ctxt(cx, "rhs");
            auto rhs_res = trans_expr(rhs_cx, b);
            rhs_res = autoderef(rhs_res.bcx, rhs_res.val,
                                ty.expr_ty(cx.fcx.lcx.ccx.tcx, b));

            auto lhs_true_cx = new_scope_block_ctxt(cx, "lhs true");
            auto lhs_true_res = res(lhs_true_cx, C_bool(true));

            lhs_res.bcx.build.CondBr(lhs_res.val,
                                     lhs_true_cx.llbb,
                                     rhs_cx.llbb);

            ret join_results(cx, T_bool(),
                             vec(lhs_true_res, rhs_res));
        }

        case (_) {
            // Remaining cases are eager:
            auto lhs = trans_expr(cx, a);
            auto lhty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, a);
            lhs = autoderef(lhs.bcx, lhs.val, lhty);
            auto rhs = trans_expr(lhs.bcx, b);
            auto rhty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, b);
            rhs = autoderef(rhs.bcx, rhs.val, rhty);
            ret trans_eager_binop(rhs.bcx, op,
                autoderefed_ty(cx.fcx.lcx.ccx, lhty), lhs.val, rhs.val);
        }
    }
    fail;
}

fn join_results(@block_ctxt parent_cx,
                TypeRef t,
                vec[result] ins)
    -> result {

    let vec[result] live = vec();
    let vec[ValueRef] vals = vec();
    let vec[BasicBlockRef] bbs = vec();

    for (result r in ins) {
        if (! is_terminated(r.bcx)) {
            live += vec(r);
            vals += vec(r.val);
            bbs += vec(r.bcx.llbb);
        }
    }

    alt (_vec.len[result](live)) {
        case (0u) {
            // No incoming edges are live, so we're in dead-code-land.
            // Arbitrarily pick the first dead edge, since the caller
            // is just going to propagate it outward.
            check (_vec.len[result](ins) >= 1u);
            ret ins.(0);
        }

        case (_) { /* fall through */ }
    }

    // We have >1 incoming edges. Make a join block and br+phi them into it.
    auto join_cx = new_sub_block_ctxt(parent_cx, "join");
    for (result r in live) {
        r.bcx.build.Br(join_cx.llbb);
    }
    auto phi = join_cx.build.Phi(t, vals, bbs);
    ret res(join_cx, phi);
}

fn trans_if(@block_ctxt cx, @ast.expr cond,
            &ast.block thn, &option.t[@ast.expr] els) -> result {

    auto cond_res = trans_expr(cx, cond);

    auto then_cx = new_scope_block_ctxt(cx, "then");
    auto then_res = trans_block(then_cx, thn);

    auto else_cx = new_scope_block_ctxt(cx, "else");

    auto else_res;
    auto expr_llty;
    alt (els) {
        case (some[@ast.expr](?elexpr)) {
            alt (elexpr.node) {
                case (ast.expr_if(_, _, _, _)) {
                    else_res = trans_expr(else_cx, elexpr);
                }
                case (ast.expr_block(?blk, _)) {
                    // Calling trans_block directly instead of trans_expr
                    // because trans_expr will create another scope block
                    // context for the block, but we've already got the
                    // 'else' context
                    else_res = trans_block(else_cx, blk);
                }
            }

            // If we have an else expression, then the entire
            // if expression can have a non-nil type.
            // FIXME: This isn't quite right, particularly re: dynamic types
            auto expr_ty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, elexpr);
            if (ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, expr_ty)) {
                expr_llty = T_typaram_ptr(cx.fcx.lcx.ccx.tn);
            } else {
                expr_llty = type_of(else_res.bcx.fcx.lcx.ccx, expr_ty);
                if (ty.type_is_structural(cx.fcx.lcx.ccx.tcx, expr_ty)) {
                    expr_llty = T_ptr(expr_llty);
                }
            }
        }
        case (_) {
            else_res = res(else_cx, C_nil());
            expr_llty = T_nil();
        }
    }

    cond_res.bcx.build.CondBr(cond_res.val,
                              then_cx.llbb,
                              else_cx.llbb);

    ret join_results(cx, expr_llty,
                     vec(then_res, else_res));
}

fn trans_for(@block_ctxt cx,
             @ast.decl decl,
             @ast.expr seq,
             &ast.block body) -> result {
    fn inner(@block_ctxt cx,
             @ast.local local, ValueRef curr,
             ty.t t, ast.block body,
             @block_ctxt outer_next_cx) -> result {

        auto next_cx = new_sub_block_ctxt(cx, "next");
        auto scope_cx =
            new_loop_scope_block_ctxt(cx, option.some[@block_ctxt](next_cx),
                                      outer_next_cx, "for loop scope");

        cx.build.Br(scope_cx.llbb);
        auto local_res = alloc_local(scope_cx, local);
        auto bcx = copy_ty(local_res.bcx, INIT, local_res.val, curr, t).bcx;
        scope_cx.cleanups +=
            vec(clean(bind drop_slot(_, local_res.val, t)));
        bcx = trans_block(bcx, body).bcx;
        bcx.build.Br(next_cx.llbb);
        ret res(next_cx, C_nil());
    }


    let @ast.local local;
    alt (decl.node) {
        case (ast.decl_local(?loc)) {
            local = loc;
        }
    }

    auto next_cx = new_sub_block_ctxt(cx, "next");
    auto seq_ty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, seq);
    auto seq_res = trans_expr(cx, seq);
    auto it = iter_sequence(seq_res.bcx, seq_res.val, seq_ty,
                            bind inner(_, local, _, _, body, next_cx));
    it.bcx.build.Br(next_cx.llbb);
    ret res(next_cx, it.val);
}


// Iterator translation

// Searches through a block for all references to locals or upvars in this
// frame and returns the list of definition IDs thus found.
fn collect_upvars(@block_ctxt cx, &ast.block bloc, &ast.def_id initial_decl)
        -> vec[ast.def_id] {
    type env = @rec(
        mutable vec[ast.def_id] refs,
        hashmap[ast.def_id,()] decls
    );

    fn walk_expr(env e, @ast.expr expr) {
        alt (expr.node) {
            case (ast.expr_path(?path, ?d, _)) {
                alt (option.get[ast.def](d)) {
                    case (ast.def_arg(?did)) {
                        _vec.push[ast.def_id](e.refs, did);
                    }
                    case (ast.def_local(?did)) {
                        _vec.push[ast.def_id](e.refs, did);
                    }
                    case (ast.def_upvar(?did)) {
                        _vec.push[ast.def_id](e.refs, did);
                    }
                    case (_) {}
                }
            }
            case (_) {}
        }
    }

    fn walk_decl(env e, @ast.decl decl) {
        alt (decl.node) {
            case (ast.decl_local(?local)) {
                e.decls.insert(local.id, ());
            }
            case (_) {}
        }
    }

    let vec[ast.def_id] refs = vec();
    let hashmap[ast.def_id,()] decls = new_def_hash[()]();
    decls.insert(initial_decl, ());
    let env e = @rec(mutable refs=refs, decls=decls);

    auto visitor = @rec(visit_decl_pre = bind walk_decl(e, _),
                        visit_expr_pre = bind walk_expr(e, _)
                        with walk.default_visitor());
    walk.walk_block(*visitor, bloc);

    // Calculate (refs - decls). This is the set of captured upvars.
    let vec[ast.def_id] result = vec();
    for (ast.def_id ref_id in e.refs) {
        if (!decls.contains_key(ref_id)) {
            result += vec(ref_id);
        }
    }

    ret result;
}

fn trans_for_each(@block_ctxt cx,
                  @ast.decl decl,
                  @ast.expr seq,
                  &ast.block body) -> result {
    /*
     * The translation is a little .. complex here. Code like:
     *
     *    let ty1 p = ...;
     *
     *    let ty1 q = ...;
     *
     *    foreach (ty v in foo(a,b)) { body(p,q,v) }
     *
     *
     * Turns into a something like so (C/Rust mishmash):
     *
     *    type env = { *ty1 p, *ty2 q, ... };
     *
     *    let env e = { &p, &q, ... };
     *
     *    fn foreach123_body(env* e, ty v) { body(*(e->p),*(e->q),v) }
     *
     *    foo([foreach123_body, env*], a, b);
     *
     */

    // Step 1: walk body and figure out which references it makes
    // escape. This could be determined upstream, and probably ought
    // to be so, eventualy. For first cut, skip this. Null env.

    auto lcx = cx.fcx.lcx;
    // FIXME: possibly support alias-mode here?
    auto decl_ty = ty.mk_nil(lcx.ccx.tcx);
    auto decl_id;
    alt (decl.node) {
        case (ast.decl_local(?local)) {
            decl_ty = node_ann_type(lcx.ccx, local.ann);
            decl_id = local.id;
        }
    }

    auto upvars = collect_upvars(cx, body, decl_id);
    auto upvar_count = _vec.len[ast.def_id](upvars);

    auto llbindingsptr;
    if (upvar_count > 0u) {
        // Gather up the upvars.
        let vec[ValueRef] llbindings = vec();
        let vec[TypeRef] llbindingtys = vec();
        for (ast.def_id did in upvars) {
            auto llbinding;
            alt (cx.fcx.lllocals.find(did)) {
                case (none[ValueRef]) {
                    alt (cx.fcx.llupvars.find(did)) {
                        case (none[ValueRef]) {
                            llbinding = cx.fcx.llargs.get(did);
                        }
                        case (some[ValueRef](?llval)) { llbinding = llval; }
                    }
                }
                case (some[ValueRef](?llval)) { llbinding = llval; }
            }
            llbindings += vec(llbinding);
            llbindingtys += vec(val_ty(llbinding));
        }

        // Create an array of bindings and copy in aliases to the upvars.
        llbindingsptr = alloca(cx, T_struct(llbindingtys));
        auto i = 0u;
        while (i < upvar_count) {
            auto llbindingptr = cx.build.GEP(llbindingsptr,
                                             vec(C_int(0), C_int(i as int)));
            cx.build.Store(llbindings.(i), llbindingptr);
            i += 1u;
        }
    } else {
        // Null bindings.
        llbindingsptr = C_null(T_ptr(T_i8()));
    }

    // Create an environment and populate it with the bindings.
    auto tydesc_count = _vec.len[ValueRef](cx.fcx.lltydescs);
    auto llenvptrty = T_closure_ptr(lcx.ccx.tn, T_ptr(T_nil()),
                                    val_ty(llbindingsptr), tydesc_count);
    auto llenvptr = alloca(cx, llvm.LLVMGetElementType(llenvptrty));

    auto llbindingsptrptr = cx.build.GEP(llenvptr,
                                         vec(C_int(0),
                                             C_int(abi.box_rc_field_body),
                                             C_int(2)));
    cx.build.Store(llbindingsptr, llbindingsptrptr);

    // Copy in our type descriptors, in case the iterator body needs to refer
    // to them.
    auto lltydescsptr = cx.build.GEP(llenvptr,
                                     vec(C_int(0),
                                         C_int(abi.box_rc_field_body),
                                         C_int(abi.closure_elt_ty_params)));
    auto i = 0u;
    while (i < tydesc_count) {
        auto lltydescptr = cx.build.GEP(lltydescsptr,
                                        vec(C_int(0), C_int(i as int)));
        cx.build.Store(cx.fcx.lltydescs.(i), lltydescptr);
        i += 1u;
    }

    // Step 2: Declare foreach body function.

    let str s = mangle_name_by_seq(lcx.ccx, lcx.path, "foreach");

    // The 'env' arg entering the body function is a fake env member (as in
    // the env-part of the normal rust calling convention) that actually
    // points to a stack allocated env in this frame. We bundle that env
    // pointer along with the foreach-body-fn pointer into a 'normal' fn pair
    // and pass it in as a first class fn-arg to the iterator.

    auto iter_body_llty =
        type_of_fn_full(lcx.ccx, ast.proto_fn,
                        none[TypeRef],
                        vec(rec(mode=ast.alias, ty=decl_ty)),
                        ty.mk_nil(lcx.ccx.tcx), 0u);

    let ValueRef lliterbody = decl_internal_fastcall_fn(lcx.ccx.llmod,
                                                       s, iter_body_llty);

    auto fcx = new_fn_ctxt(lcx, lliterbody);
    auto bcx = new_top_block_ctxt(fcx);
    auto lltop = bcx.llbb;

    // Populate the upvars from the environment.
    auto llremoteenvptr = bcx.build.PointerCast(fcx.llenv, llenvptrty);
    auto llremotebindingsptrptr =
        bcx.build.GEP(llremoteenvptr, vec(C_int(0),
                                          C_int(abi.box_rc_field_body),
                                          C_int(abi.closure_elt_bindings)));
    auto llremotebindingsptr = bcx.build.Load(llremotebindingsptrptr);

    i = 0u;
    while (i < upvar_count) {
        auto upvar_id = upvars.(i);
        auto llupvarptrptr = bcx.build.GEP(llremotebindingsptr,
                                           vec(C_int(0), C_int(i as int)));
        auto llupvarptr = bcx.build.Load(llupvarptrptr);
        fcx.llupvars.insert(upvar_id, llupvarptr);

        i += 1u;
    }

    // Populate the type parameters from the environment.
    auto llremotetydescsptr =
        bcx.build.GEP(llremoteenvptr,
                      vec(C_int(0),
                          C_int(abi.box_rc_field_body),
                          C_int(abi.closure_elt_ty_params)));

    i = 0u;
    while (i < tydesc_count) {
        auto llremotetydescptr = bcx.build.GEP(llremotetydescsptr,
                                               vec(C_int(0),
                                                   C_int(i as int)));
        auto llremotetydesc = bcx.build.Load(llremotetydescptr);
        fcx.lltydescs += vec(llremotetydesc);
        i += 1u;
    }

    // Add an upvar for the loop variable alias.
    fcx.llupvars.insert(decl_id, llvm.LLVMGetParam(fcx.llfn, 3u));

    auto r = trans_block(bcx, body);

    // Tie up the llallocas -> lltop edge.
    new_builder(fcx.llallocas).Br(lltop);

    r.bcx.build.RetVoid();


    // Step 3: Call iter passing [lliterbody, llenv], plus other args.

    alt (seq.node) {

        case (ast.expr_call(?f, ?args, ?ann)) {

            auto pair = alloca(cx, T_fn_pair(lcx.ccx.tn,
                                             iter_body_llty));
            auto code_cell = cx.build.GEP(pair,
                                          vec(C_int(0),
                                              C_int(abi.fn_field_code)));
            cx.build.Store(lliterbody, code_cell);

            auto env_cell = cx.build.GEP(pair, vec(C_int(0),
                                                   C_int(abi.fn_field_box)));
            auto llenvblobptr = cx.build.PointerCast(llenvptr,
                T_opaque_closure_ptr(lcx.ccx.tn));
            cx.build.Store(llenvblobptr, env_cell);

            // log "lliterbody: " + val_str(lcx.ccx.tn, lliterbody);
            r = trans_call(cx, f,
                           some[ValueRef](cx.build.Load(pair)),
                           args,
                           ann);
            ret res(r.bcx, C_nil());
        }
    }
    fail;
}


fn trans_while(@block_ctxt cx, @ast.expr cond,
               &ast.block body) -> result {

    auto cond_cx = new_scope_block_ctxt(cx, "while cond");
    auto next_cx = new_sub_block_ctxt(cx, "next");
    auto body_cx = new_loop_scope_block_ctxt(cx, option.none[@block_ctxt],
                                             next_cx, "while loop body");

    auto body_res = trans_block(body_cx, body);
    auto cond_res = trans_expr(cond_cx, cond);

    body_res.bcx.build.Br(cond_cx.llbb);

    auto cond_bcx = trans_block_cleanups(cond_res.bcx, cond_cx);
    cond_bcx.build.CondBr(cond_res.val, body_cx.llbb, next_cx.llbb);

    cx.build.Br(cond_cx.llbb);
    ret res(next_cx, C_nil());
}

fn trans_do_while(@block_ctxt cx, &ast.block body,
                  @ast.expr cond) -> result {

    auto next_cx = new_sub_block_ctxt(cx, "next");
    auto body_cx = new_loop_scope_block_ctxt(cx, option.none[@block_ctxt],
                                             next_cx, "do-while loop body");

    auto body_res = trans_block(body_cx, body);
    auto cond_res = trans_expr(body_res.bcx, cond);

    cond_res.bcx.build.CondBr(cond_res.val,
                              body_cx.llbb,
                              next_cx.llbb);
    cx.build.Br(body_cx.llbb);
    ret res(next_cx, body_res.val);
}

// Pattern matching translation

fn trans_pat_match(@block_ctxt cx, @ast.pat pat, ValueRef llval,
                   @block_ctxt next_cx) -> result {
    alt (pat.node) {
        case (ast.pat_wild(_)) { ret res(cx, llval); }
        case (ast.pat_bind(_, _, _)) { ret res(cx, llval); }

        case (ast.pat_lit(?lt, ?ann)) {
            auto lllit = trans_lit(cx.fcx.lcx.ccx, *lt, ann);
            auto lltype = ty.ann_to_type(ann);
            auto lleq = trans_compare(cx, ast.eq, lltype, llval, lllit);

            auto matched_cx = new_sub_block_ctxt(lleq.bcx, "matched_cx");
            lleq.bcx.build.CondBr(lleq.val, matched_cx.llbb, next_cx.llbb);
            ret res(matched_cx, llval);
        }

        case (ast.pat_tag(?id, ?subpats, ?vdef_opt, ?ann)) {
            auto lltagptr = cx.build.PointerCast(llval,
                T_opaque_tag_ptr(cx.fcx.lcx.ccx.tn));

            auto lldiscrimptr = cx.build.GEP(lltagptr,
                                             vec(C_int(0), C_int(0)));
            auto lldiscrim = cx.build.Load(lldiscrimptr);

            auto vdef = option.get[ast.variant_def](vdef_opt);
            auto variant_id = vdef._1;
            auto variant_tag = 0;

            auto variants = tag_variants(cx.fcx.lcx.ccx, vdef._0);
            auto i = 0;
            for (variant_info v in variants) {
                auto this_variant_id = v.id;
                if (variant_id._0 == this_variant_id._0 &&
                    variant_id._1 == this_variant_id._1) {
                    variant_tag = i;
                }
                i += 1;
            }

            auto matched_cx = new_sub_block_ctxt(cx, "matched_cx");

            auto lleq = cx.build.ICmp(lib.llvm.LLVMIntEQ, lldiscrim,
                                      C_int(variant_tag));
            cx.build.CondBr(lleq, matched_cx.llbb, next_cx.llbb);

            auto ty_params = node_ann_ty_params(ann);

            if (_vec.len[@ast.pat](subpats) > 0u) {
                auto llblobptr = matched_cx.build.GEP(lltagptr,
                    vec(C_int(0), C_int(1)));
                auto i = 0;
                for (@ast.pat subpat in subpats) {
                    auto rslt = GEP_tag(matched_cx, llblobptr, vdef._0,
                                        vdef._1, ty_params, i);
                    auto llsubvalptr = rslt.val;
                    matched_cx = rslt.bcx;

                    auto llsubval = load_if_immediate(matched_cx,
                        llsubvalptr, pat_ty(cx.fcx.lcx.ccx.tcx, subpat));
                    auto subpat_res = trans_pat_match(matched_cx, subpat,
                                                      llsubval, next_cx);
                    matched_cx = subpat_res.bcx;

                    i += 1;
                }
            }

            ret res(matched_cx, llval);
        }
    }

    fail;
}

fn trans_pat_binding(@block_ctxt cx, @ast.pat pat,
                     ValueRef llval, bool bind_alias)
    -> result {
    alt (pat.node) {
        case (ast.pat_wild(_)) { ret res(cx, llval); }
        case (ast.pat_lit(_, _)) { ret res(cx, llval); }
        case (ast.pat_bind(?id, ?def_id, ?ann)) {
            if (bind_alias) {
                cx.fcx.lllocals.insert(def_id, llval);
                ret res(cx, llval);
            } else {
                auto t = node_ann_type(cx.fcx.lcx.ccx, ann);
                auto rslt = alloc_ty(cx, t);
                auto dst = rslt.val;
                auto bcx = rslt.bcx;
                llvm.LLVMSetValueName(dst, _str.buf(id));
                bcx.fcx.lllocals.insert(def_id, dst);
                bcx.cleanups +=
                    vec(clean(bind drop_slot(_, dst, t)));
                ret copy_ty(bcx, INIT, dst, llval, t);
            }
        }
        case (ast.pat_tag(_, ?subpats, ?vdef_opt, ?ann)) {
            if (_vec.len[@ast.pat](subpats) == 0u) { ret res(cx, llval); }

            // Get the appropriate variant for this tag.
            auto vdef = option.get[ast.variant_def](vdef_opt);

            auto lltagptr = cx.build.PointerCast(llval,
                T_opaque_tag_ptr(cx.fcx.lcx.ccx.tn));
            auto llblobptr = cx.build.GEP(lltagptr, vec(C_int(0), C_int(1)));

            auto ty_param_substs = node_ann_ty_params(ann);

            auto this_cx = cx;
            auto i = 0;
            for (@ast.pat subpat in subpats) {
                auto rslt = GEP_tag(this_cx, llblobptr, vdef._0, vdef._1,
                                    ty_param_substs, i);
                this_cx = rslt.bcx;
                auto subpat_res = trans_pat_binding(this_cx, subpat,
                                                    rslt.val, true);
                this_cx = subpat_res.bcx;
                i += 1;
            }

            ret res(this_cx, llval);
        }
    }
}

fn trans_alt(@block_ctxt cx, @ast.expr expr,
             vec[ast.arm] arms, ast.ann ann) -> result {
    auto expr_res = trans_expr(cx, expr);

    auto this_cx = expr_res.bcx;
    let vec[result] arm_results = vec();
    for (ast.arm arm in arms) {
        auto next_cx = new_sub_block_ctxt(expr_res.bcx, "next");
        auto match_res = trans_pat_match(this_cx, arm.pat, expr_res.val,
                                         next_cx);

        auto binding_cx = new_scope_block_ctxt(match_res.bcx, "binding");
        match_res.bcx.build.Br(binding_cx.llbb);

        auto binding_res = trans_pat_binding(binding_cx, arm.pat,
                                             expr_res.val, false);

        auto block_res = trans_block(binding_res.bcx, arm.block);
        arm_results += vec(block_res);

        this_cx = next_cx;
    }

    auto default_cx = this_cx;
    auto default_res = trans_fail(default_cx, some[common.span](expr.span),
                                  "non-exhaustive match failure");

    // FIXME: This isn't quite right, particularly re: dynamic types
    auto expr_ty = ty.ann_to_type(ann);
    auto expr_llty;
    if (ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, expr_ty)) {
        expr_llty = T_typaram_ptr(cx.fcx.lcx.ccx.tn);
    } else {
        expr_llty = type_of(cx.fcx.lcx.ccx, expr_ty);
        if (ty.type_is_structural(cx.fcx.lcx.ccx.tcx, expr_ty)) {
            expr_llty = T_ptr(expr_llty);
        }
    }

    ret join_results(cx, expr_llty, arm_results);
}

type generic_info = rec(ty.t item_type,
                        vec[ValueRef] tydescs);

type lval_result = rec(result res,
                       bool is_mem,
                       option.t[generic_info] generic,
                       option.t[ValueRef] llobj,
                       option.t[ty.t] method_ty);

fn lval_mem(@block_ctxt cx, ValueRef val) -> lval_result {
    ret rec(res=res(cx, val),
            is_mem=true,
            generic=none[generic_info],
            llobj=none[ValueRef],
            method_ty=none[ty.t]);
}

fn lval_val(@block_ctxt cx, ValueRef val) -> lval_result {
    ret rec(res=res(cx, val),
            is_mem=false,
            generic=none[generic_info],
            llobj=none[ValueRef],
            method_ty=none[ty.t]);
}

fn trans_external_path(@block_ctxt cx, ast.def_id did,
                       ty.ty_param_count_and_ty tpt) -> lval_result {
    auto lcx = cx.fcx.lcx;
    auto name = creader.get_symbol(lcx.ccx.sess, did);
    auto v = get_extern_const(lcx.ccx.externs, lcx.ccx.llmod,
                              name, type_of_ty_param_count_and_ty(lcx, tpt));
    ret lval_val(cx, v);
}

fn lval_generic_fn(@block_ctxt cx,
                   ty.ty_param_count_and_ty tpt,
                   ast.def_id fn_id,
                   &ast.ann ann)
        -> lval_result {
    auto lv;
    if (cx.fcx.lcx.ccx.sess.get_targ_crate_num() == fn_id._0) {
        // Internal reference.
        check (cx.fcx.lcx.ccx.fn_pairs.contains_key(fn_id));
        lv = lval_val(cx, cx.fcx.lcx.ccx.fn_pairs.get(fn_id));
    } else {
        // External reference.
        lv = trans_external_path(cx, fn_id, tpt);
    }

    auto monoty;
    let vec[ty.t] tys;
    alt (ann) {
        case (ast.ann_none) {
            cx.fcx.lcx.ccx.sess.bug("no type annotation for path!");
            fail;
        }
        case (ast.ann_type(?monoty_, ?tps, _)) {
            monoty = monoty_;
            tys = option.get[vec[ty.t]](tps);
        }
    }

    if (_vec.len[ty.t](tys) != 0u) {
        auto bcx = lv.res.bcx;
        let vec[ValueRef] tydescs = vec();
        for (ty.t t in tys) {
            auto td = get_tydesc(bcx, t);
            bcx = td.bcx;
            _vec.push[ValueRef](tydescs, td.val);
        }
        auto gen = rec( item_type = tpt._1,
                        tydescs = tydescs );
        lv = rec(res = res(bcx, lv.res.val),
                 generic = some[generic_info](gen)
                 with lv);
    }
    ret lv;
}

fn lookup_discriminant(@local_ctxt lcx, ast.def_id tid, ast.def_id vid)
        -> ValueRef {
    alt (lcx.ccx.discrims.find(vid)) {
        case (none[ValueRef]) {
            // It's an external discriminant that we haven't seen yet.
            check (lcx.ccx.sess.get_targ_crate_num() != vid._0);
            auto sym = creader.get_symbol(lcx.ccx.sess, vid);
            auto gvar = llvm.LLVMAddGlobal(lcx.ccx.llmod, T_int(),
                                           _str.buf(sym));
            llvm.LLVMSetLinkage(gvar,
                                lib.llvm.LLVMExternalLinkage as llvm.Linkage);
            llvm.LLVMSetGlobalConstant(gvar, True);
            lcx.ccx.discrims.insert(vid, gvar);
            ret gvar;
        }
        case (some[ValueRef](?llval)) { ret llval; }
    }
}

fn trans_path(@block_ctxt cx, &ast.path p, &option.t[ast.def] dopt,
              &ast.ann ann) -> lval_result {
    alt (dopt) {
        case (some[ast.def](?def)) {
            alt (def) {
                case (ast.def_arg(?did)) {
                    alt (cx.fcx.llargs.find(did)) {
                        case (none[ValueRef]) {
                            check (cx.fcx.llupvars.contains_key(did));
                            ret lval_mem(cx, cx.fcx.llupvars.get(did));
                        }
                        case (some[ValueRef](?llval)) {
                            ret lval_mem(cx, llval);
                        }
                    }
                }
                case (ast.def_local(?did)) {
                    alt (cx.fcx.lllocals.find(did)) {
                        case (none[ValueRef]) {
                            check (cx.fcx.llupvars.contains_key(did));
                            ret lval_mem(cx, cx.fcx.llupvars.get(did));
                        }
                        case (some[ValueRef](?llval)) {
                            ret lval_mem(cx, llval);
                        }
                    }
                }
                case (ast.def_binding(?did)) {
                    check (cx.fcx.lllocals.contains_key(did));
                    ret lval_mem(cx, cx.fcx.lllocals.get(did));
                }
                case (ast.def_obj_field(?did)) {
                    check (cx.fcx.llobjfields.contains_key(did));
                    ret lval_mem(cx, cx.fcx.llobjfields.get(did));
                }
                case (ast.def_fn(?did)) {
                    auto tyt = ty.lookup_item_type(cx.fcx.lcx.ccx.sess,
                        cx.fcx.lcx.ccx.tcx, cx.fcx.lcx.ccx.type_cache, did);
                    ret lval_generic_fn(cx, tyt, did, ann);
                }
                case (ast.def_obj(?did)) {
                    auto tyt = ty.lookup_item_type(cx.fcx.lcx.ccx.sess,
                        cx.fcx.lcx.ccx.tcx, cx.fcx.lcx.ccx.type_cache, did);
                    ret lval_generic_fn(cx, tyt, did, ann);
                }
                case (ast.def_variant(?tid, ?vid)) {
                    auto v_tyt = ty.lookup_item_type(cx.fcx.lcx.ccx.sess,
                        cx.fcx.lcx.ccx.tcx, cx.fcx.lcx.ccx.type_cache, vid);
                    alt (ty.struct(cx.fcx.lcx.ccx.tcx, v_tyt._1)) {
                        case (ty.ty_fn(_, _, _)) {
                            // N-ary variant.
                            ret lval_generic_fn(cx, v_tyt, vid, ann);
                        }
                        case (_) {
                            // Nullary variant.
                            auto tag_ty = node_ann_type(cx.fcx.lcx.ccx, ann);
                            auto lldiscrim_gv =
                                lookup_discriminant(cx.fcx.lcx, tid, vid);
                            auto lldiscrim = cx.build.Load(lldiscrim_gv);

                            auto alloc_result = alloc_ty(cx, tag_ty);
                            auto lltagblob = alloc_result.val;

                            auto lltagty;
                            if (ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx,
                                                         tag_ty)) {
                                lltagty = T_opaque_tag(cx.fcx.lcx.ccx.tn);
                            } else {
                                lltagty = type_of(cx.fcx.lcx.ccx, tag_ty);
                            }
                            auto lltagptr = alloc_result.bcx.build.
                                PointerCast(lltagblob, T_ptr(lltagty));

                            auto lldiscrimptr = alloc_result.bcx.build.GEP(
                                lltagptr, vec(C_int(0), C_int(0)));
                            alloc_result.bcx.build.Store(lldiscrim,
                                                         lldiscrimptr);

                            ret lval_val(alloc_result.bcx, lltagptr);
                        }
                    }
                }
                case (ast.def_const(?did)) {
                    // TODO: externals
                    check (cx.fcx.lcx.ccx.consts.contains_key(did));
                    ret lval_mem(cx, cx.fcx.lcx.ccx.consts.get(did));
                }
                case (ast.def_native_fn(?did)) {
                    auto tyt = ty.lookup_item_type(cx.fcx.lcx.ccx.sess,
                        cx.fcx.lcx.ccx.tcx,
                        cx.fcx.lcx.ccx.type_cache, did);
                    ret lval_generic_fn(cx, tyt, did, ann);
                }
                case (_) {
                    cx.fcx.lcx.ccx.sess.unimpl("def variant in trans");
                }
            }
        }
        case (none[ast.def]) {
            cx.fcx.lcx.ccx.sess.err("unresolved expr_path in trans");
        }
    }
    fail;
}

fn trans_field(@block_ctxt cx, &ast.span sp, ValueRef v, ty.t t0,
               &ast.ident field, &ast.ann ann) -> lval_result {

    auto r = autoderef(cx, v, t0);
    auto t = autoderefed_ty(cx.fcx.lcx.ccx, t0);

    alt (ty.struct(cx.fcx.lcx.ccx.tcx, t)) {
        case (ty.ty_tup(_)) {
            let uint ix = ty.field_num(cx.fcx.lcx.ccx.sess, sp, field);
            auto v = GEP_tup_like(r.bcx, t, r.val, vec(0, ix as int));
            ret lval_mem(v.bcx, v.val);
        }
        case (ty.ty_rec(?fields)) {
            let uint ix = ty.field_idx(cx.fcx.lcx.ccx.sess, sp, field,
                                       fields);
            auto v = GEP_tup_like(r.bcx, t, r.val, vec(0, ix as int));
            ret lval_mem(v.bcx, v.val);
        }
        case (ty.ty_obj(?methods)) {
            let uint ix = ty.method_idx(cx.fcx.lcx.ccx.sess, sp, field,
                                        methods);
            auto vtbl = r.bcx.build.GEP(r.val,
                                        vec(C_int(0),
                                            C_int(abi.obj_field_vtbl)));
            vtbl = r.bcx.build.Load(vtbl);
            auto v =  r.bcx.build.GEP(vtbl, vec(C_int(0),
                                                C_int(ix as int)));

            auto lvo = lval_mem(r.bcx, v);
            let ty.t fn_ty = ty.method_ty_to_fn_ty(cx.fcx.lcx.ccx.tcx,
                                                    methods.(ix));
            ret rec(llobj = some[ValueRef](r.val),
                    method_ty = some[ty.t](fn_ty)
                    with lvo);
        }
        case (_) {cx.fcx.lcx.ccx.sess.unimpl("field variant in trans_field");}
    }
    fail;
}

fn trans_index(@block_ctxt cx, &ast.span sp, @ast.expr base,
               @ast.expr idx, &ast.ann ann) -> lval_result {

    auto lv = trans_expr(cx, base);
    lv = autoderef(lv.bcx, lv.val, ty.expr_ty(cx.fcx.lcx.ccx.tcx, base));
    auto ix = trans_expr(lv.bcx, idx);
    auto v = lv.val;
    auto bcx = ix.bcx;

    // Cast to an LLVM integer. Rust is less strict than LLVM in this regard.
    auto ix_val;
    auto ix_size = llsize_of_real(cx.fcx.lcx.ccx, val_ty(ix.val));
    auto int_size = llsize_of_real(cx.fcx.lcx.ccx, T_int());
    if (ix_size < int_size) {
        ix_val = bcx.build.ZExt(ix.val, T_int());
    } else if (ix_size > int_size) {
        ix_val = bcx.build.Trunc(ix.val, T_int());
    } else {
        ix_val = ix.val;
    }

    auto unit_ty = node_ann_type(cx.fcx.lcx.ccx, ann);
    auto unit_sz = size_of(bcx, unit_ty);
    bcx = unit_sz.bcx;
    llvm.LLVMSetValueName(unit_sz.val, _str.buf("unit_sz"));

    auto scaled_ix = bcx.build.Mul(ix_val, unit_sz.val);
    llvm.LLVMSetValueName(scaled_ix, _str.buf("scaled_ix"));

    auto lim = bcx.build.GEP(v, vec(C_int(0), C_int(abi.vec_elt_fill)));
    lim = bcx.build.Load(lim);

    auto bounds_check = bcx.build.ICmp(lib.llvm.LLVMIntULT,
                                       scaled_ix, lim);

    auto fail_cx = new_sub_block_ctxt(bcx, "fail");
    auto next_cx = new_sub_block_ctxt(bcx, "next");
    bcx.build.CondBr(bounds_check, next_cx.llbb, fail_cx.llbb);

    // fail: bad bounds check.
    auto fail_res = trans_fail(fail_cx, some[common.span](sp),
                               "bounds check");

    auto body = next_cx.build.GEP(v, vec(C_int(0), C_int(abi.vec_elt_data)));
    auto elt;
    if (ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, unit_ty)) {
        body = next_cx.build.PointerCast(body, T_ptr(T_array(T_i8(), 0u)));
        elt = next_cx.build.GEP(body, vec(C_int(0), scaled_ix));
    } else {
        elt = next_cx.build.GEP(body, vec(C_int(0), ix_val));

        // We're crossing a box boundary here, so we may need to pointer cast.
        auto llunitty = type_of(next_cx.fcx.lcx.ccx, unit_ty);
        elt = next_cx.build.PointerCast(elt, T_ptr(llunitty));
    }

    ret lval_mem(next_cx, elt);
}

// The additional bool returned indicates whether it's mem (that is
// represented as an alloca or heap, hence needs a 'load' to be used as an
// immediate).

fn trans_lval(@block_ctxt cx, @ast.expr e) -> lval_result {
    alt (e.node) {
        case (ast.expr_path(?p, ?dopt, ?ann)) {
            ret trans_path(cx, p, dopt, ann);
        }
        case (ast.expr_field(?base, ?ident, ?ann)) {
            auto r = trans_expr(cx, base);
            auto t = ty.expr_ty(cx.fcx.lcx.ccx.tcx, base);
            ret trans_field(r.bcx, e.span, r.val, t, ident, ann);
        }
        case (ast.expr_index(?base, ?idx, ?ann)) {
            ret trans_index(cx, e.span, base, idx, ann);
        }
        case (ast.expr_unary(?unop, ?base, ?ann)) {
            check (unop == ast.deref);

            auto sub = trans_expr(cx, base);
            auto val = sub.bcx.build.GEP(sub.val,
                                         vec(C_int(0),
                                             C_int(abi.box_rc_field_body)));
            ret lval_mem(sub.bcx, val);
        }
        case (ast.expr_self_method(?ident, ?ann)) {
            alt (cx.fcx.llself) {
                case (some[self_vt](?s_vt)) {
                    auto r =  s_vt.v;
                    auto t =  s_vt.t;
                    ret trans_field(cx, e.span, r, t, ident, ann);
                }
                case (_) {
                    // Shouldn't happen.
                    fail;
                }

            }
        }
        case (_) {
            cx.fcx.lcx.ccx.sess.span_unimpl(e.span,
                                            "expr variant in trans_lval");
        }
    }
    fail;
}

fn trans_cast(@block_ctxt cx, @ast.expr e, &ast.ann ann) -> result {
    auto e_res = trans_expr(cx, e);
    auto llsrctype = val_ty(e_res.val);
    auto t = node_ann_type(cx.fcx.lcx.ccx, ann);
    auto lldsttype = type_of(cx.fcx.lcx.ccx, t);
    if (!ty.type_is_fp(cx.fcx.lcx.ccx.tcx, t)) {
        // TODO: native-to-native casts
        if (ty.type_is_native(cx.fcx.lcx.ccx.tcx,
                              ty.expr_ty(cx.fcx.lcx.ccx.tcx, e))) {
            e_res.val = e_res.bcx.build.PtrToInt(e_res.val, lldsttype);
        } else if (ty.type_is_native(cx.fcx.lcx.ccx.tcx, t)) {
            e_res.val = e_res.bcx.build.IntToPtr(e_res.val, lldsttype);
        } else if (llvm.LLVMGetIntTypeWidth(lldsttype) >
            llvm.LLVMGetIntTypeWidth(llsrctype)) {
            if (ty.type_is_signed(cx.fcx.lcx.ccx.tcx, t)) {
                // Widening signed cast.
                e_res.val =
                    e_res.bcx.build.SExtOrBitCast(e_res.val,
                                                  lldsttype);
            } else {
                // Widening unsigned cast.
                e_res.val =
                    e_res.bcx.build.ZExtOrBitCast(e_res.val,
                                                  lldsttype);
            }
        } else {
            // Narrowing cast.
            e_res.val =
                e_res.bcx.build.TruncOrBitCast(e_res.val,
                                               lldsttype);
        }
    } else {
        cx.fcx.lcx.ccx.sess.unimpl("fp cast");
    }
    ret e_res;
}

fn trans_bind_thunk(@local_ctxt cx,
                    ty.t incoming_fty,
                    ty.t outgoing_fty,
                    vec[option.t[@ast.expr]] args,
                    ty.t closure_ty,
                    vec[ty.t] bound_tys,
                    uint ty_param_count) -> ValueRef {
    // Construct a thunk-call with signature incoming_fty, and that copies
    // args forward into a call to outgoing_fty.

    let str s = mangle_name_by_seq(cx.ccx, cx.path, "thunk");
    let TypeRef llthunk_ty = get_pair_fn_ty(type_of(cx.ccx, incoming_fty));
    let ValueRef llthunk = decl_internal_fastcall_fn(cx.ccx.llmod,
                                                     s, llthunk_ty);

    auto fcx = new_fn_ctxt(cx, llthunk);
    auto bcx = new_top_block_ctxt(fcx);
    auto lltop = bcx.llbb;

    auto llclosure_ptr_ty =
        type_of(cx.ccx, ty.mk_imm_box(cx.ccx.tcx, closure_ty));
    auto llclosure = bcx.build.PointerCast(fcx.llenv, llclosure_ptr_ty);

    auto lltarget = GEP_tup_like(bcx, closure_ty, llclosure,
                                 vec(0,
                                     abi.box_rc_field_body,
                                     abi.closure_elt_target));
    bcx = lltarget.bcx;
    auto lltargetclosure = bcx.build.GEP(lltarget.val,
                                         vec(C_int(0),
                                             C_int(abi.fn_field_box)));
    lltargetclosure = bcx.build.Load(lltargetclosure);

    auto outgoing_ret_ty = ty.ty_fn_ret(cx.ccx.tcx, outgoing_fty);
    auto outgoing_args = ty.ty_fn_args(cx.ccx.tcx, outgoing_fty);

    auto llretptr = fcx.llretptr;
    if (ty.type_has_dynamic_size(cx.ccx.tcx, outgoing_ret_ty)) {
        llretptr = bcx.build.PointerCast(llretptr, T_typaram_ptr(cx.ccx.tn));
    }

    let vec[ValueRef] llargs = vec(llretptr,
                                   fcx.lltaskptr,
                                   lltargetclosure);

    // Copy in the type parameters.
    let uint i = 0u;
    while (i < ty_param_count) {
        auto lltyparam_ptr =
            GEP_tup_like(bcx, closure_ty, llclosure,
                         vec(0,
                             abi.box_rc_field_body,
                             abi.closure_elt_ty_params,
                             (i as int)));
        bcx = lltyparam_ptr.bcx;
        auto td = bcx.build.Load(lltyparam_ptr.val);
        llargs += vec(td);
        fcx.lltydescs += vec(td);
        i += 1u;
    }

    let uint a = 3u;    // retptr, task ptr, env come first
    let int b = 0;
    let uint outgoing_arg_index = 0u;
    let vec[TypeRef] llout_arg_tys =
        type_of_explicit_args(cx.ccx, outgoing_args);

    for (option.t[@ast.expr] arg in args) {

        auto out_arg = outgoing_args.(outgoing_arg_index);
        auto llout_arg_ty = llout_arg_tys.(outgoing_arg_index);

        alt (arg) {

            // Arg provided at binding time; thunk copies it from closure.
            case (some[@ast.expr](?e)) {
                auto e_ty = ty.expr_ty(cx.ccx.tcx, e);
                auto bound_arg =
                    GEP_tup_like(bcx, closure_ty, llclosure,
                                 vec(0,
                                     abi.box_rc_field_body,
                                     abi.closure_elt_bindings,
                                     b));

                bcx = bound_arg.bcx;
                auto val = bound_arg.val;

                if (out_arg.mode == ast.val) {
                    if (type_is_immediate(cx.ccx, e_ty)) {
                        val = bcx.build.Load(val);
                        bcx = take_ty(bcx, val, e_ty).bcx;
                    } else {
                        bcx = take_ty(bcx, val, e_ty).bcx;
                        val = bcx.build.Load(val);
                    }
                } else if (ty.type_contains_params(cx.ccx.tcx,
                                                   out_arg.ty)) {
                    check (out_arg.mode == ast.alias);
                    val = bcx.build.PointerCast(val, llout_arg_ty);
                }

                llargs += vec(val);
                b += 1;
            }

            // Arg will be provided when the thunk is invoked.
            case (none[@ast.expr]) {
                let ValueRef passed_arg = llvm.LLVMGetParam(llthunk, a);

                if (ty.type_contains_params(cx.ccx.tcx, out_arg.ty)) {
                    check (out_arg.mode == ast.alias);
                    passed_arg = bcx.build.PointerCast(passed_arg,
                                                       llout_arg_ty);
                }

                llargs += vec(passed_arg);
                a += 1u;
            }
        }

        outgoing_arg_index += 1u;
    }

    // FIXME: turn this call + ret into a tail call.
    auto lltargetfn = bcx.build.GEP(lltarget.val,
                                    vec(C_int(0),
                                        C_int(abi.fn_field_code)));

    // Cast the outgoing function to the appropriate type (see the comments in
    // trans_bind below for why this is necessary).
    auto lltargetty = type_of_fn(bcx.fcx.lcx.ccx,
                                 ty.ty_fn_proto(bcx.fcx.lcx.ccx.tcx,
                                                outgoing_fty),
                                 outgoing_args,
                                 outgoing_ret_ty,
                                 ty_param_count);
    lltargetfn = bcx.build.PointerCast(lltargetfn, T_ptr(T_ptr(lltargetty)));

    lltargetfn = bcx.build.Load(lltargetfn);

    auto r = bcx.build.FastCall(lltargetfn, llargs);
    bcx.build.RetVoid();

    // Tie up the llallocas -> lltop edge.
    new_builder(fcx.llallocas).Br(lltop);

    ret llthunk;
}

fn trans_bind(@block_ctxt cx, @ast.expr f,
              vec[option.t[@ast.expr]] args,
              &ast.ann ann) -> result {
    auto f_res = trans_lval(cx, f);
    if (f_res.is_mem) {
        cx.fcx.lcx.ccx.sess.unimpl("re-binding existing function");
    } else {
        let vec[@ast.expr] bound = vec();

        for (option.t[@ast.expr] argopt in args) {
            alt (argopt) {
                case (none[@ast.expr]) {
                }
                case (some[@ast.expr](?e)) {
                    _vec.push[@ast.expr](bound, e);
                }
            }
        }

        // Figure out which tydescs we need to pass, if any.
        let ty.t outgoing_fty;
        let vec[ValueRef] lltydescs;
        alt (f_res.generic) {
            case (none[generic_info]) {
                outgoing_fty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, f);
                lltydescs = vec();
            }
            case (some[generic_info](?ginfo)) {
                outgoing_fty = ginfo.item_type;
                lltydescs = ginfo.tydescs;
            }
        }
        auto ty_param_count = _vec.len[ValueRef](lltydescs);

        if (_vec.len[@ast.expr](bound) == 0u && ty_param_count == 0u) {
            // Trivial 'binding': just return the static pair-ptr.
            ret f_res.res;
        } else {
            auto bcx = f_res.res.bcx;
            auto pair_t = node_type(cx.fcx.lcx.ccx, ann);
            auto pair_v = alloca(bcx, pair_t);

            // Translate the bound expressions.
            let vec[ty.t] bound_tys = vec();
            let vec[ValueRef] bound_vals = vec();
            auto i = 0u;
            for (@ast.expr e in bound) {
                auto arg = trans_expr(bcx, e);
                bcx = arg.bcx;

                _vec.push[ValueRef](bound_vals, arg.val);
                _vec.push[ty.t](bound_tys,
                                 ty.expr_ty(cx.fcx.lcx.ccx.tcx, e));

                i += 1u;
            }

            // Synthesize a closure type.
            let ty.t bindings_ty = ty.mk_imm_tup(cx.fcx.lcx.ccx.tcx,
                                                  bound_tys);

            // NB: keep this in sync with T_closure_ptr; we're making
            // a ty.t structure that has the same "shape" as the LLVM type
            // it constructs.
            let ty.t tydesc_ty = ty.mk_type(cx.fcx.lcx.ccx.tcx);

            let vec[ty.t] captured_tys =
                _vec.init_elt[ty.t](tydesc_ty, ty_param_count);

            let vec[ty.t] closure_tys =
                vec(tydesc_ty,
                    outgoing_fty,
                    bindings_ty,
                    ty.mk_imm_tup(cx.fcx.lcx.ccx.tcx, captured_tys));

            let ty.t closure_ty = ty.mk_imm_tup(cx.fcx.lcx.ccx.tcx,
                                                 closure_tys);

            auto r = trans_malloc_boxed(bcx, closure_ty);
            auto box = r.val;
            bcx = r.bcx;
            auto rc = bcx.build.GEP(box,
                                    vec(C_int(0),
                                        C_int(abi.box_rc_field_refcnt)));
            auto closure =
                bcx.build.GEP(box,
                              vec(C_int(0),
                                  C_int(abi.box_rc_field_body)));
            bcx.build.Store(C_int(1), rc);

            // Store bindings tydesc.
            auto bound_tydesc =
                bcx.build.GEP(closure,
                              vec(C_int(0),
                                  C_int(abi.closure_elt_tydesc)));
            auto bindings_tydesc = get_tydesc(bcx, bindings_ty);
            bcx = bindings_tydesc.bcx;
            bcx.build.Store(bindings_tydesc.val, bound_tydesc);

            // Determine the LLVM type for the outgoing function type. This
            // may be different from the type returned by trans_malloc_boxed()
            // since we have more information than that function does;
            // specifically, we know how many type descriptors the outgoing
            // function has, which type_of() doesn't, as only we know which
            // item the function refers to.
            auto llfnty = type_of_fn(bcx.fcx.lcx.ccx,
                ty.ty_fn_proto(bcx.fcx.lcx.ccx.tcx, outgoing_fty),
                ty.ty_fn_args(bcx.fcx.lcx.ccx.tcx, outgoing_fty),
                ty.ty_fn_ret(bcx.fcx.lcx.ccx.tcx, outgoing_fty),
                ty_param_count);
            auto llclosurety = T_ptr(T_fn_pair(bcx.fcx.lcx.ccx.tn, llfnty));

            // Store thunk-target.
            auto bound_target =
                bcx.build.GEP(closure,
                              vec(C_int(0),
                                  C_int(abi.closure_elt_target)));
            auto src = bcx.build.Load(f_res.res.val);
            bound_target = bcx.build.PointerCast(bound_target, llclosurety);
            bcx.build.Store(src, bound_target);

            // Copy expr values into boxed bindings.
            i = 0u;
            auto bindings =
                bcx.build.GEP(closure,
                              vec(C_int(0),
                                  C_int(abi.closure_elt_bindings)));
            for (ValueRef v in bound_vals) {
                auto bound = bcx.build.GEP(bindings,
                                           vec(C_int(0), C_int(i as int)));
                bcx = copy_ty(bcx, INIT, bound, v, bound_tys.(i)).bcx;
                i += 1u;
            }

            // If necessary, copy tydescs describing type parameters into the
            // appropriate slot in the closure.
            alt (f_res.generic) {
                case (none[generic_info]) { /* nothing to do */ }
                case (some[generic_info](?ginfo)) {
                    auto ty_params_slot =
                        bcx.build.GEP(closure,
                                      vec(C_int(0),
                                          C_int(abi.closure_elt_ty_params)));
                    auto i = 0;
                    for (ValueRef td in ginfo.tydescs) {
                        auto ty_param_slot = bcx.build.GEP(ty_params_slot,
                                                           vec(C_int(0),
                                                               C_int(i)));
                        bcx.build.Store(td, ty_param_slot);
                        i += 1;
                    }

                    outgoing_fty = ginfo.item_type;
                }
            }

            // Make thunk and store thunk-ptr in outer pair's code slot.
            auto pair_code = bcx.build.GEP(pair_v,
                                           vec(C_int(0),
                                               C_int(abi.fn_field_code)));

            let ty.t pair_ty = node_ann_type(cx.fcx.lcx.ccx, ann);

            let ValueRef llthunk =
                trans_bind_thunk(cx.fcx.lcx, pair_ty, outgoing_fty,
                                 args, closure_ty, bound_tys,
                                 ty_param_count);

            bcx.build.Store(llthunk, pair_code);

            // Store box ptr in outer pair's box slot.
            auto pair_box = bcx.build.GEP(pair_v,
                                          vec(C_int(0),
                                              C_int(abi.fn_field_box)));
            bcx.build.Store
                (bcx.build.PointerCast
                 (box,
                  T_opaque_closure_ptr(bcx.fcx.lcx.ccx.tn)),
                 pair_box);

            find_scope_cx(cx).cleanups +=
                vec(clean(bind drop_slot(_, pair_v, pair_ty)));

            ret res(bcx, pair_v);
        }
    }
}

fn trans_arg_expr(@block_ctxt cx,
                  ty.arg arg,
                  TypeRef lldestty0,
                  @ast.expr e) -> result {

    auto val;
    auto bcx = cx;
    auto e_ty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, e);

    if (ty.type_is_structural(cx.fcx.lcx.ccx.tcx, e_ty)) {
        auto re = trans_expr(bcx, e);
        val = re.val;
        bcx = re.bcx;
    } else if (arg.mode == ast.alias) {
        let lval_result lv;
        if (ty.is_lval(e)) {
            lv = trans_lval(bcx, e);
        } else {
            auto r = trans_expr(bcx, e);
            if (type_is_immediate(cx.fcx.lcx.ccx, e_ty)) {
                lv = lval_val(r.bcx, r.val);
            } else {
                lv = lval_mem(r.bcx, r.val);
            }
        }
        bcx = lv.res.bcx;

        if (lv.is_mem) {
            val = lv.res.val;
        } else {
            // Non-mem but we're trying to alias; synthesize an
            // alloca, spill to it and pass its address.
            val = do_spill(lv.res.bcx, lv.res.val);
        }
    } else {
        auto re = trans_expr(bcx, e);
        val = re.val;
        bcx = re.bcx;
    }

    if (arg.mode != ast.alias) {
        bcx = take_ty(bcx, val, e_ty).bcx;
    }

    if (ty.type_contains_params(cx.fcx.lcx.ccx.tcx, arg.ty)) {
        auto lldestty = lldestty0;
        if (arg.mode == ast.val) {
            // FIXME: we'd prefer to use &&, but rustboot doesn't like it
            if (ty.type_is_structural(cx.fcx.lcx.ccx.tcx, e_ty)) {
                lldestty = T_ptr(lldestty);
            }
        }
        val = bcx.build.PointerCast(val, lldestty);
    }

    if (arg.mode == ast.val) {
        // FIXME: we'd prefer to use &&, but rustboot doesn't like it
        if (ty.type_is_structural(cx.fcx.lcx.ccx.tcx, e_ty)) {
            // Until here we've been treating structures by pointer;
            // we are now passing it as an arg, so need to load it.
            val = bcx.build.Load(val);
        }
    }
    ret res(bcx, val);
}

// NB: must keep 4 fns in sync:
//
//  - type_of_fn_full
//  - create_llargs_for_fn_args.
//  - new_fn_ctxt
//  - trans_args

fn trans_args(@block_ctxt cx,
              ValueRef llenv,
              option.t[ValueRef] llobj,
              option.t[generic_info] gen,
              option.t[ValueRef] lliterbody,
              &vec[@ast.expr] es,
              ty.t fn_ty)
    -> tup(@block_ctxt, vec[ValueRef], ValueRef) {

    let vec[ty.arg] args = ty.ty_fn_args(cx.fcx.lcx.ccx.tcx, fn_ty);
    let vec[ValueRef] llargs = vec();
    let vec[ValueRef] lltydescs = vec();
    let @block_ctxt bcx = cx;


    // Arg 0: Output pointer.
    auto retty = ty.ty_fn_ret(cx.fcx.lcx.ccx.tcx, fn_ty);
    auto llretslot_res = alloc_ty(bcx, retty);
    bcx = llretslot_res.bcx;
    auto llretslot = llretslot_res.val;

    alt (gen) {
        case (some[generic_info](?g)) {
            lltydescs = g.tydescs;
            args = ty.ty_fn_args(cx.fcx.lcx.ccx.tcx, g.item_type);
            retty = ty.ty_fn_ret(cx.fcx.lcx.ccx.tcx, g.item_type);
        }
        case (_) {
        }
    }
    if (ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, retty)) {
        llargs += vec(bcx.build.PointerCast
                      (llretslot, T_typaram_ptr(cx.fcx.lcx.ccx.tn)));
    } else if (ty.type_contains_params(cx.fcx.lcx.ccx.tcx, retty)) {
        // It's possible that the callee has some generic-ness somewhere in
        // its return value -- say a method signature within an obj or a fn
        // type deep in a structure -- which the caller has a concrete view
        // of. If so, cast the caller's view of the restlot to the callee's
        // view, for the sake of making a type-compatible call.
        llargs +=
            vec(cx.build.PointerCast(llretslot,
                                     T_ptr(type_of(bcx.fcx.lcx.ccx, retty))));
    } else {
        llargs += vec(llretslot);
    }


    // Arg 1: Task pointer.
    llargs += vec(bcx.fcx.lltaskptr);

    // Arg 2: Env (closure-bindings / self-obj)
    alt (llobj) {
        case (some[ValueRef](?ob)) {
            // Every object is always found in memory,
            // and not-yet-loaded (as part of an lval x.y
            // doted method-call).
            llargs += vec(bcx.build.Load(ob));
        }
        case (_) {
            llargs += vec(llenv);
        }
    }

    // Args >3: ty_params ...
    llargs += lltydescs;

    // ... then possibly an lliterbody argument.
    alt (lliterbody) {
        case (none[ValueRef]) {}
        case (some[ValueRef](?lli)) {
            llargs += vec(lli);
        }
    }

    // ... then explicit args.

    // First we figure out the caller's view of the types of the arguments.
    // This will be needed if this is a generic call, because the callee has
    // to cast her view of the arguments to the caller's view.
    auto arg_tys = type_of_explicit_args(cx.fcx.lcx.ccx, args);

    auto i = 0u;
    for (@ast.expr e in es) {
        auto r = trans_arg_expr(bcx, args.(i), arg_tys.(i), e);
        bcx = r.bcx;
        llargs += vec(r.val);
        i += 1u;
    }

    ret tup(bcx, llargs, llretslot);
}

fn trans_call(@block_ctxt cx, @ast.expr f,
              option.t[ValueRef] lliterbody,
              vec[@ast.expr] args,
              &ast.ann ann) -> result {

    // NB: 'f' isn't necessarily a function; it might be an entire self-call
    // expression because of the hack that allows us to process self-calls
    // with trans_call.

    auto f_res = trans_lval(cx, f);
    auto faddr = f_res.res.val;
    auto llenv = C_null(T_opaque_closure_ptr(cx.fcx.lcx.ccx.tn));

    alt (f_res.llobj) {
        case (some[ValueRef](_)) {
            // It's a vtbl entry.
            faddr = f_res.res.bcx.build.Load(faddr);
        }
        case (none[ValueRef]) {
            // It's a closure.
            auto bcx = f_res.res.bcx;
            auto pair = faddr;
            faddr = bcx.build.GEP(pair, vec(C_int(0),
                                            C_int(abi.fn_field_code)));
            faddr = bcx.build.Load(faddr);

            auto llclosure = bcx.build.GEP(pair,
                                           vec(C_int(0),
                                               C_int(abi.fn_field_box)));
            llenv = bcx.build.Load(llclosure);
        }
    }

    let ty.t fn_ty;
    alt (f_res.method_ty) {
        case (some[ty.t](?meth)) {
            // self-call
            fn_ty = meth;
        }

        case (_) {
            fn_ty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, f);

        }

    }

    auto ret_ty = ty.ann_to_type(ann);
    auto args_res = trans_args(f_res.res.bcx,
                               llenv, f_res.llobj,
                               f_res.generic,
                               lliterbody,
                               args, fn_ty);

    auto bcx = args_res._0;
    auto llargs = args_res._1;
    auto llretslot = args_res._2;

    /*
    log "calling: " + val_str(cx.fcx.lcx.ccx.tn, faddr);

    for (ValueRef arg in llargs) {
        log "arg: " + val_str(cx.fcx.lcx.ccx.tn, arg);
    }
    */

    bcx.build.FastCall(faddr, llargs);
    auto retval = C_nil();

    alt (lliterbody) {
        case (none[ValueRef]) {
            if (!ty.type_is_nil(cx.fcx.lcx.ccx.tcx, ret_ty)) {
                retval = load_if_immediate(bcx, llretslot, ret_ty);
                // Retval doesn't correspond to anything really tangible in
                // the frame, but it's a ref all the same, so we put a note
                // here to drop it when we're done in this scope.
                find_scope_cx(cx).cleanups +=
                    vec(clean(bind drop_ty(_, retval, ret_ty)));
            }
        }
        case (some[ValueRef](_)) {
            // If there was an lliterbody, it means we were calling an
            // iter, and we are *not* the party using its 'output' value,
            // we should ignore llretslot.
        }
    }
    ret res(bcx, retval);
}

fn trans_tup(@block_ctxt cx, vec[ast.elt] elts,
             &ast.ann ann) -> result {
    auto bcx = cx;
    auto t = node_ann_type(bcx.fcx.lcx.ccx, ann);
    auto tup_res = alloc_ty(bcx, t);
    auto tup_val = tup_res.val;
    bcx = tup_res.bcx;

    find_scope_cx(cx).cleanups +=
        vec(clean(bind drop_ty(_, tup_val, t)));
    let int i = 0;

    for (ast.elt e in elts) {
        auto e_ty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, e.expr);
        auto src_res = trans_expr(bcx, e.expr);
        bcx = src_res.bcx;
        auto dst_res = GEP_tup_like(bcx, t, tup_val, vec(0, i));
        bcx = dst_res.bcx;
        bcx = copy_ty(src_res.bcx, INIT, dst_res.val, src_res.val, e_ty).bcx;
        i += 1;
    }
    ret res(bcx, tup_val);
}

fn trans_vec(@block_ctxt cx, vec[@ast.expr] args,
             &ast.ann ann) -> result {
    auto t = node_ann_type(cx.fcx.lcx.ccx, ann);
    auto unit_ty = t;
    alt (ty.struct(cx.fcx.lcx.ccx.tcx, t)) {
        case (ty.ty_vec(?mt)) {
            unit_ty = mt.ty;
        }
        case (_) {
            cx.fcx.lcx.ccx.sess.bug("non-vec type in trans_vec");
        }
    }

    auto bcx = cx;
    auto unit_sz = size_of(bcx, unit_ty);
    bcx = unit_sz.bcx;
    auto data_sz = bcx.build.Mul(C_int(_vec.len[@ast.expr](args) as int),
                                 unit_sz.val);

    // FIXME: pass tydesc properly.
    auto sub = trans_upcall(bcx, "upcall_new_vec", vec(data_sz, C_int(0)));
    bcx = sub.bcx;

    auto llty = type_of(bcx.fcx.lcx.ccx, t);
    auto vec_val = vi2p(bcx, sub.val, llty);
    find_scope_cx(bcx).cleanups +=
        vec(clean(bind drop_ty(_, vec_val, t)));

    auto body = bcx.build.GEP(vec_val, vec(C_int(0),
                                           C_int(abi.vec_elt_data)));

    auto pseudo_tup_ty =
        ty.mk_imm_tup(cx.fcx.lcx.ccx.tcx,
                      _vec.init_elt[ty.t](unit_ty,
                                           _vec.len[@ast.expr](args)));
    let int i = 0;

    for (@ast.expr e in args) {
        auto src_res = trans_expr(bcx, e);
        bcx = src_res.bcx;
        auto dst_res = GEP_tup_like(bcx, pseudo_tup_ty, body, vec(0, i));
        bcx = dst_res.bcx;

        // Cast the destination type to the source type. This is needed to
        // make tags work, for a subtle combination of reasons:
        //
        // (1) "dst_res" above is derived from "body", which is in turn
        //     derived from "vec_val".
        // (2) "vec_val" has the LLVM type "llty".
        // (3) "llty" is the result of calling type_of() on a vector type.
        // (4) For tags, type_of() returns a different type depending on
        //     on whether the tag is behind a box or not. Vector types are
        //     considered boxes.
        // (5) "src_res" is derived from "unit_ty", which is not behind a box.

        auto dst_val;
        if (!ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, unit_ty)) {
            auto llunit_ty = type_of(cx.fcx.lcx.ccx, unit_ty);
            dst_val = bcx.build.PointerCast(dst_res.val, T_ptr(llunit_ty));
        } else {
            dst_val = dst_res.val;
        }

        bcx = copy_ty(bcx, INIT, dst_val, src_res.val, unit_ty).bcx;
        i += 1;
    }
    auto fill = bcx.build.GEP(vec_val,
                              vec(C_int(0), C_int(abi.vec_elt_fill)));
    bcx.build.Store(data_sz, fill);

    ret res(bcx, vec_val);
}

fn trans_rec(@block_ctxt cx, vec[ast.field] fields,
             option.t[@ast.expr] base, &ast.ann ann) -> result {

    auto bcx = cx;
    auto t = node_ann_type(bcx.fcx.lcx.ccx, ann);
    auto rec_res = alloc_ty(bcx, t);
    auto rec_val = rec_res.val;
    bcx = rec_res.bcx;

    find_scope_cx(cx).cleanups +=
        vec(clean(bind drop_ty(_, rec_val, t)));
    let int i = 0;

    auto base_val = C_nil();

    alt (base) {
        case (none[@ast.expr]) { }
        case (some[@ast.expr](?bexp)) {
            auto base_res = trans_expr(bcx, bexp);
            bcx = base_res.bcx;
            base_val = base_res.val;
        }
    }

    let vec[ty.field] ty_fields = vec();
    alt (ty.struct(cx.fcx.lcx.ccx.tcx, t)) {
        case (ty.ty_rec(?flds)) { ty_fields = flds; }
    }

    for (ty.field tf in ty_fields) {
        auto e_ty = tf.mt.ty;
        auto dst_res = GEP_tup_like(bcx, t, rec_val, vec(0, i));
        bcx = dst_res.bcx;

        auto expr_provided = false;
        auto src_res = res(bcx, C_nil());

        for (ast.field f in fields) {
            if (_str.eq(f.ident, tf.ident)) {
                expr_provided = true;
                src_res = trans_expr(bcx, f.expr);
            }
        }
        if (!expr_provided) {
            src_res = GEP_tup_like(bcx, t, base_val, vec(0, i));
            src_res = res(src_res.bcx,
                          load_if_immediate(bcx, src_res.val, e_ty));
        }

        bcx = src_res.bcx;
        bcx = copy_ty(bcx, INIT, dst_res.val, src_res.val, e_ty).bcx;
        i += 1;
    }
    ret res(bcx, rec_val);
}



fn trans_expr(@block_ctxt cx, @ast.expr e) -> result {
    alt (e.node) {
        case (ast.expr_lit(?lit, ?ann)) {
            ret res(cx, trans_lit(cx.fcx.lcx.ccx, *lit, ann));
        }

        case (ast.expr_unary(?op, ?x, ?ann)) {
            if (op != ast.deref) {
                ret trans_unary(cx, op, x, ann);
            }
        }

        case (ast.expr_binary(?op, ?x, ?y, _)) {
            ret trans_binary(cx, op, x, y);
        }

        case (ast.expr_if(?cond, ?thn, ?els, _)) {
            ret trans_if(cx, cond, thn, els);
        }

        case (ast.expr_for(?decl, ?seq, ?body, _)) {
            ret trans_for(cx, decl, seq, body);
        }

        case (ast.expr_for_each(?decl, ?seq, ?body, _)) {
            ret trans_for_each(cx, decl, seq, body);
        }

        case (ast.expr_while(?cond, ?body, _)) {
            ret trans_while(cx, cond, body);
        }

        case (ast.expr_do_while(?body, ?cond, _)) {
            ret trans_do_while(cx, body, cond);
        }

        case (ast.expr_alt(?expr, ?arms, ?ann)) {
            ret trans_alt(cx, expr, arms, ann);
        }

        case (ast.expr_block(?blk, _)) {
            auto sub_cx = new_scope_block_ctxt(cx, "block-expr body");
            auto next_cx = new_sub_block_ctxt(cx, "next");
            auto sub = trans_block(sub_cx, blk);

            cx.build.Br(sub_cx.llbb);
            sub.bcx.build.Br(next_cx.llbb);

            ret res(next_cx, sub.val);
        }

        case (ast.expr_assign(?dst, ?src, ?ann)) {
            auto lhs_res = trans_lval(cx, dst);
            check (lhs_res.is_mem);
            auto rhs_res = trans_expr(lhs_res.res.bcx, src);
            auto t = node_ann_type(cx.fcx.lcx.ccx, ann);
            // FIXME: calculate copy init-ness in typestate.
            ret copy_ty(rhs_res.bcx, DROP_EXISTING,
                        lhs_res.res.val, rhs_res.val, t);
        }

        case (ast.expr_assign_op(?op, ?dst, ?src, ?ann)) {
            auto t = node_ann_type(cx.fcx.lcx.ccx, ann);
            auto lhs_res = trans_lval(cx, dst);
            check (lhs_res.is_mem);
            auto rhs_res = trans_expr(lhs_res.res.bcx, src);
            if (ty.type_is_sequence(cx.fcx.lcx.ccx.tcx, t)) {
                alt (op) {
                    case (ast.add) {
                        ret trans_vec_append(rhs_res.bcx, t,
                                             lhs_res.res.val,
                                             rhs_res.val);
                    }
                    case (_) { }
                }
            }
            auto lhs_val = load_if_immediate(rhs_res.bcx,
                                             lhs_res.res.val, t);
            auto v = trans_eager_binop(rhs_res.bcx, op, t,
                                       lhs_val, rhs_res.val);
            // FIXME: calculate copy init-ness in typestate.
            ret copy_ty(v.bcx, DROP_EXISTING,
                        lhs_res.res.val, v.val, t);
        }

        case (ast.expr_bind(?f, ?args, ?ann)) {
            ret trans_bind(cx, f, args, ann);
        }

        case (ast.expr_call(?f, ?args, ?ann)) {
            ret trans_call(cx, f, none[ValueRef], args, ann);
        }

        case (ast.expr_cast(?e, _, ?ann)) {
            ret trans_cast(cx, e, ann);
        }

        case (ast.expr_vec(?args, _, ?ann)) {
            ret trans_vec(cx, args, ann);
        }

        case (ast.expr_tup(?args, ?ann)) {
            ret trans_tup(cx, args, ann);
        }

        case (ast.expr_rec(?args, ?base, ?ann)) {
            ret trans_rec(cx, args, base, ann);
        }

        case (ast.expr_ext(_, _, _, ?expanded, _)) {
            ret trans_expr(cx, expanded);
        }

        case (ast.expr_fail(_)) {
            ret trans_fail(cx, some[common.span](e.span), "explicit failure");
        }

        case (ast.expr_log(?lvl, ?a, _)) {
            ret trans_log(lvl, cx, a);
        }

        case (ast.expr_check_expr(?a, _)) {
            ret trans_check_expr(cx, a);
        }

        case (ast.expr_break(?a)) {
            ret trans_break(cx);
        }

        case (ast.expr_cont(?a)) {
            ret trans_cont(cx);
        }

        case (ast.expr_ret(?e, _)) {
            ret trans_ret(cx, e);
        }

        case (ast.expr_put(?e, _)) {
            ret trans_put(cx, e);
        }

        case (ast.expr_be(?e, _)) {
            ret trans_be(cx, e);
        }

        case (ast.expr_port(?ann)) {
            ret trans_port(cx, ann);
        }

        case (ast.expr_chan(?e, ?ann)) {
            ret trans_chan(cx, e, ann);
        }

        case (ast.expr_send(?lhs, ?rhs, ?ann)) {
            ret trans_send(cx, lhs, rhs, ann);
        }

        case (ast.expr_recv(?lhs, ?rhs, ?ann)) {
            ret trans_recv(cx, lhs, rhs, ann);
        }

        case (_) {
            // The expression is an lvalue. Fall through.
        }
    }

    // lval cases fall through to trans_lval and then
    // possibly load the result (if it's non-structural).

    auto t = ty.expr_ty(cx.fcx.lcx.ccx.tcx, e);
    auto sub = trans_lval(cx, e);
    ret res(sub.res.bcx, load_if_immediate(sub.res.bcx, sub.res.val, t));
}

// We pass structural values around the compiler "by pointer" and
// non-structural values (scalars, boxes, pointers) "by value". We call the
// latter group "immediates" and, in some circumstances when we know we have a
// pointer (or need one), perform load/store operations based on the
// immediate-ness of the type.

fn type_is_immediate(@crate_ctxt ccx, ty.t t) -> bool {
    ret ty.type_is_scalar(ccx.tcx, t) ||
        ty.type_is_boxed(ccx.tcx, t) ||
        ty.type_is_native(ccx.tcx, t);
}

fn do_spill(@block_ctxt cx, ValueRef v) -> ValueRef {
    // We have a value but we have to spill it to pass by alias.
    auto llptr = alloca(cx, val_ty(v));
    cx.build.Store(v, llptr);
    ret llptr;
}

fn spill_if_immediate(@block_ctxt cx, ValueRef v, ty.t t) -> ValueRef {
    if (type_is_immediate(cx.fcx.lcx.ccx, t)) {
        ret do_spill(cx, v);
    }
    ret v;
}

fn load_if_immediate(@block_ctxt cx, ValueRef v, ty.t t) -> ValueRef {
    if (type_is_immediate(cx.fcx.lcx.ccx, t)) {
        ret cx.build.Load(v);
    }
    ret v;
}

fn trans_log(int lvl, @block_ctxt cx, @ast.expr e) -> result {
    auto lcx = cx.fcx.lcx;
    auto modname = _str.connect(lcx.module_path, ".");
    auto global;
    if (lcx.ccx.module_data.contains_key(modname)) {
        global = lcx.ccx.module_data.get(modname);
    } else {
        global = llvm.LLVMAddGlobal(lcx.ccx.llmod, T_int(),
                                    _str.buf("_rust_mod_log_" + modname));
        llvm.LLVMSetGlobalConstant(global, False);
        llvm.LLVMSetInitializer(global, C_null(T_int()));
        llvm.LLVMSetLinkage(global, lib.llvm.LLVMInternalLinkage
                            as llvm.Linkage);
        lcx.ccx.module_data.insert(modname, global);
    }

    auto log_cx = new_scope_block_ctxt(cx, "log");
    auto after_cx = new_sub_block_ctxt(cx, "after");
    auto load = cx.build.Load(global);
    auto test = cx.build.ICmp(lib.llvm.LLVMIntSGE, load, C_int(lvl));
    cx.build.CondBr(test, log_cx.llbb, after_cx.llbb);

    auto sub = trans_expr(log_cx, e);
    auto e_ty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, e);

    if (ty.type_is_fp(cx.fcx.lcx.ccx.tcx, e_ty)) {
        let TypeRef tr;
        let bool is32bit = false;
        alt (ty.struct(cx.fcx.lcx.ccx.tcx, e_ty)) {
            case (ty.ty_machine(util.common.ty_f32)) {
                tr = T_f32();
                is32bit = true;
            }
            case (ty.ty_machine(util.common.ty_f64)) {
                tr = T_f64();
            }
            case (_) {
                tr = T_float();
            }
        }
        if (is32bit) {
            auto uval = trans_upcall(sub.bcx,
                                     "upcall_log_float",
                                     vec(C_int(lvl), sub.val));
            uval.bcx.build.Br(after_cx.llbb);
        } else {
            auto tmp = alloca(sub.bcx, tr);
            sub.bcx.build.Store(sub.val, tmp);
            auto uval = trans_upcall(sub.bcx,
                                     "upcall_log_double",
                                     vec(C_int(lvl), vp2i(sub.bcx, tmp)));
            uval.bcx.build.Br(after_cx.llbb);
        }
    } else {
        alt (ty.struct(cx.fcx.lcx.ccx.tcx, e_ty)) {
            case (ty.ty_str) {
                auto v = vp2i(sub.bcx, sub.val);
                trans_upcall(sub.bcx,
                             "upcall_log_str",
                             vec(C_int(lvl), v)).bcx.build.Br(after_cx.llbb);
            }
            case (_) {
                auto v = vec(C_int(lvl), sub.val);
                trans_upcall(sub.bcx,
                             "upcall_log_int",
                             v).bcx.build.Br(after_cx.llbb);
            }
        }
    }

    ret res(after_cx, C_nil());
}

fn trans_check_expr(@block_ctxt cx, @ast.expr e) -> result {
    auto cond_res = trans_expr(cx, e);

    auto expr_str = pretty.pprust.expr_to_str(e);
    auto fail_cx = new_sub_block_ctxt(cx, "fail");
    auto fail_res = trans_fail(fail_cx, some[common.span](e.span), expr_str);

    auto next_cx = new_sub_block_ctxt(cx, "next");
    cond_res.bcx.build.CondBr(cond_res.val,
                              next_cx.llbb,
                              fail_cx.llbb);
    ret res(next_cx, C_nil());
}

fn trans_fail(@block_ctxt cx, option.t[common.span] sp_opt, str fail_str)
        -> result {
    auto V_fail_str = p2i(C_cstr(cx.fcx.lcx.ccx, fail_str));

    auto V_filename; auto V_line;
    alt (sp_opt) {
        case (some[common.span](?sp)) {
            auto loc = cx.fcx.lcx.ccx.sess.lookup_pos(sp.lo);
            V_filename = p2i(C_cstr(cx.fcx.lcx.ccx, loc.filename));
            V_line = loc.line as int;
        }
        case (none[common.span]) {
            V_filename = p2i(C_str(cx.fcx.lcx.ccx, "<runtime>"));
            V_line = 0;
        }
    }

    auto args = vec(V_fail_str, V_filename, C_int(V_line));

    auto sub = trans_upcall(cx, "upcall_fail", args);
    sub.bcx.build.Unreachable();
    ret res(sub.bcx, C_nil());
}

fn trans_put(@block_ctxt cx, &option.t[@ast.expr] e) -> result {
    auto llcallee = C_nil();
    auto llenv = C_nil();

    alt (cx.fcx.lliterbody) {
        case (some[ValueRef](?lli)) {
            auto slot = alloca(cx, val_ty(lli));
            cx.build.Store(lli, slot);

            llcallee = cx.build.GEP(slot, vec(C_int(0),
                                              C_int(abi.fn_field_code)));
            llcallee = cx.build.Load(llcallee);

            llenv = cx.build.GEP(slot, vec(C_int(0),
                                           C_int(abi.fn_field_box)));
            llenv = cx.build.Load(llenv);
        }
    }
    auto bcx = cx;
    auto dummy_retslot = alloca(bcx, T_nil());
    let vec[ValueRef] llargs = vec(dummy_retslot, cx.fcx.lltaskptr, llenv);
    alt (e) {
        case (none[@ast.expr]) { }
        case (some[@ast.expr](?x)) {
            auto e_ty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, x);
            auto arg = rec(mode=ast.alias, ty=e_ty);
            auto arg_tys = type_of_explicit_args(cx.fcx.lcx.ccx, vec(arg));
            auto r = trans_arg_expr(bcx, arg, arg_tys.(0), x);
            bcx = r.bcx;
            llargs += vec(r.val);
        }
    }

    ret res(bcx, bcx.build.FastCall(llcallee, llargs));
}

fn trans_break_cont(@block_ctxt cx, bool to_end) -> result {
    auto bcx = cx;
    // Locate closest loop block, outputting cleanup as we go.
    auto cleanup_cx = cx;
    while (true) {
        bcx = trans_block_cleanups(bcx, cleanup_cx);
        alt (cleanup_cx.kind) {
            case (LOOP_SCOPE_BLOCK(?_cont, ?_break)) {
                if (to_end) {
                    bcx.build.Br(_break.llbb);
                } else {
                    alt (_cont) {
                        case (option.some[@block_ctxt](?_cont)) {
                            bcx.build.Br(_cont.llbb);
                        }
                        case (_) {
                            bcx.build.Br(cleanup_cx.llbb);
                        }
                    }
                }
                ret res(bcx, C_nil());
            }
            case (_) {
                alt (cleanup_cx.parent) {
                    case (parent_some(?cx)) { cleanup_cx = cx; }
                }
            }
        }
    }
    fail;
}

fn trans_break(@block_ctxt cx) -> result {
    ret trans_break_cont(cx, true);
}

fn trans_cont(@block_ctxt cx) -> result {
    ret trans_break_cont(cx, false);
}


fn trans_ret(@block_ctxt cx, &option.t[@ast.expr] e) -> result {
    auto bcx = cx;
    auto val = C_nil();

    alt (e) {
        case (some[@ast.expr](?x)) {
            auto t = ty.expr_ty(cx.fcx.lcx.ccx.tcx, x);
            auto r = trans_expr(cx, x);
            bcx = r.bcx;
            val = r.val;
            bcx = copy_ty(bcx, INIT, cx.fcx.llretptr, val, t).bcx;
        }
        case (_) {
            auto t = llvm.LLVMGetElementType(val_ty(cx.fcx.llretptr));
            auto null = lib.llvm.llvm.LLVMConstNull(t);
            bcx.build.Store(null, cx.fcx.llretptr);
        }
    }

    // Run all cleanups and back out.
    let bool more_cleanups = true;
    auto cleanup_cx = cx;
    while (more_cleanups) {
        bcx = trans_block_cleanups(bcx, cleanup_cx);
        alt (cleanup_cx.parent) {
            case (parent_some(?b)) {
                cleanup_cx = b;
            }
            case (parent_none) {
                more_cleanups = false;
            }
        }
    }

    bcx.build.RetVoid();
    ret res(bcx, C_nil());
}

fn trans_be(@block_ctxt cx, @ast.expr e) -> result {
    // FIXME: This should be a typestate precondition
    check (ast.is_call_expr(e));
    // FIXME: Turn this into a real tail call once
    // calling convention issues are settled
    ret trans_ret(cx, some(e));
}

fn trans_port(@block_ctxt cx, ast.ann ann) -> result {

    auto t = node_ann_type(cx.fcx.lcx.ccx, ann);
    auto unit_ty;
    alt (ty.struct(cx.fcx.lcx.ccx.tcx, t)) {
        case (ty.ty_port(?t)) {
            unit_ty = t;
        }
        case (_) {
            cx.fcx.lcx.ccx.sess.bug("non-port type in trans_port");
            fail;
        }
    }

    auto llunit_ty = type_of(cx.fcx.lcx.ccx, unit_ty);

    auto bcx = cx;
    auto unit_sz = size_of(bcx, unit_ty);
    bcx = unit_sz.bcx;
    auto sub = trans_upcall(bcx, "upcall_new_port", vec(unit_sz.val));
    bcx = sub.bcx;
    auto llty = type_of(cx.fcx.lcx.ccx, t);
    auto port_val = vi2p(bcx, sub.val, llty);
    auto dropref = clean(bind drop_ty(_, port_val, t));
    find_scope_cx(bcx).cleanups += vec(dropref);

    ret res(bcx, port_val);
}

fn trans_chan(@block_ctxt cx, @ast.expr e, ast.ann ann) -> result {

    auto bcx = cx;
    auto prt = trans_expr(bcx, e);
    bcx = prt.bcx;

    auto prt_val = vp2i(bcx, prt.val);
    auto sub = trans_upcall(bcx, "upcall_new_chan", vec(prt_val));
    bcx = sub.bcx;

    auto chan_ty = node_ann_type(bcx.fcx.lcx.ccx, ann);
    auto chan_llty = type_of(bcx.fcx.lcx.ccx, chan_ty);
    auto chan_val = vi2p(bcx, sub.val, chan_llty);
    auto dropref = clean(bind drop_ty(_, chan_val, chan_ty));
    find_scope_cx(bcx).cleanups += vec(dropref);

    ret res(bcx, chan_val);
}

fn trans_send(@block_ctxt cx, @ast.expr lhs, @ast.expr rhs,
              ast.ann ann) -> result {

    auto bcx = cx;
    auto chn = trans_expr(bcx, lhs);
    bcx = chn.bcx;
    auto data = trans_expr(bcx, rhs);
    bcx = data.bcx;

    auto chan_ty = node_ann_type(cx.fcx.lcx.ccx, ann);
    auto unit_ty;
    alt (ty.struct(cx.fcx.lcx.ccx.tcx, chan_ty)) {
        case (ty.ty_chan(?t)) {
            unit_ty = t;
        }
        case (_) {
            bcx.fcx.lcx.ccx.sess.bug("non-chan type in trans_send");
            fail;
        }
    }

    auto data_alloc = alloc_ty(bcx, unit_ty);
    bcx = data_alloc.bcx;
    auto data_tmp = copy_ty(bcx, INIT, data_alloc.val, data.val, unit_ty);
    bcx = data_tmp.bcx;

    find_scope_cx(bcx).cleanups +=
        vec(clean(bind drop_ty(_, data_alloc.val, unit_ty)));

    auto sub = trans_upcall(bcx, "upcall_send",
                            vec(vp2i(bcx, chn.val),
                                vp2i(bcx, data_alloc.val)));
    bcx = sub.bcx;

    ret res(bcx, chn.val);
}

fn trans_recv(@block_ctxt cx, @ast.expr lhs, @ast.expr rhs,
              ast.ann ann) -> result {

    auto bcx = cx;
    auto data = trans_lval(bcx, lhs);
    check (data.is_mem);
    bcx = data.res.bcx;
    auto unit_ty = node_ann_type(bcx.fcx.lcx.ccx, ann);

    // FIXME: calculate copy init-ness in typestate.
    ret recv_val(bcx, data.res.val, rhs, unit_ty, DROP_EXISTING);
 }

fn recv_val(@block_ctxt cx, ValueRef lhs, @ast.expr rhs,
            ty.t unit_ty, copy_action action) -> result {

    auto bcx = cx;
    auto prt = trans_expr(bcx, rhs);
    bcx = prt.bcx;

    auto sub = trans_upcall(bcx, "upcall_recv",
                            vec(vp2i(bcx, lhs),
                                vp2i(bcx, prt.val)));
    bcx = sub.bcx;

    auto data_load = load_if_immediate(bcx, lhs, unit_ty);
    auto cp = copy_ty(bcx, action, lhs, data_load, unit_ty);
    bcx = cp.bcx;

    // TODO: Any cleanup need to be done here?

    ret res(bcx, lhs);
}

fn init_local(@block_ctxt cx, @ast.local local) -> result {

    // Make a note to drop this slot on the way out.
    check (cx.fcx.lllocals.contains_key(local.id));
    auto llptr = cx.fcx.lllocals.get(local.id);
    auto ty = node_ann_type(cx.fcx.lcx.ccx, local.ann);
    auto bcx = cx;

    find_scope_cx(cx).cleanups +=
        vec(clean(bind drop_slot(_, llptr, ty)));

    alt (local.init) {
        case (some[ast.initializer](?init)) {
            alt (init.op) {
                case (ast.init_assign) {
                    auto sub = trans_expr(bcx, init.expr);
                    bcx = copy_ty(sub.bcx, INIT, llptr, sub.val, ty).bcx;
                }
                case (ast.init_recv) {
                    bcx = recv_val(bcx, llptr, init.expr, ty, INIT).bcx;
                }
            }
        }
        case (_) {
            bcx = zero_alloca(bcx, llptr, ty).bcx;
        }
    }
    ret res(bcx, llptr);
}

fn zero_alloca(@block_ctxt cx, ValueRef llptr, ty.t t) -> result {
    auto bcx = cx;
    if (ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, t)) {
        auto llsz = size_of(bcx, t);
        bcx = call_bzero(llsz.bcx, llptr, llsz.val).bcx;
    } else {
        auto llty = type_of(bcx.fcx.lcx.ccx, t);
        auto null = lib.llvm.llvm.LLVMConstNull(llty);
        bcx.build.Store(null, llptr);
    }
    ret res(bcx, llptr);
 }

fn trans_stmt(@block_ctxt cx, &ast.stmt s) -> result {
    auto bcx = cx;
    alt (s.node) {
        case (ast.stmt_expr(?e,_)) {
            bcx = trans_expr(cx, e).bcx;
        }

        case (ast.stmt_decl(?d,_)) {
            alt (d.node) {
                case (ast.decl_local(?local)) {
                    bcx = init_local(bcx, local).bcx;
                }
                case (ast.decl_item(?i)) {
                    trans_item(cx.fcx.lcx, *i);
                }
            }
        }
        case (_) {
            cx.fcx.lcx.ccx.sess.unimpl("stmt variant");
        }
    }
    ret res(bcx, C_nil());
}

fn new_builder(BasicBlockRef llbb) -> builder {
    let BuilderRef llbuild = llvm.LLVMCreateBuilder();
    llvm.LLVMPositionBuilderAtEnd(llbuild, llbb);
    ret builder(llbuild, @mutable false);
}

// You probably don't want to use this one. See the
// next three functions instead.
fn new_block_ctxt(@fn_ctxt cx, block_parent parent,
                  block_kind kind,
                  str name) -> @block_ctxt {
    let vec[cleanup] cleanups = vec();
    let BasicBlockRef llbb =
        llvm.LLVMAppendBasicBlock(cx.llfn,
                                  _str.buf(cx.lcx.ccx.names.next(name)));

    ret @rec(llbb=llbb,
             build=new_builder(llbb),
             parent=parent,
             kind=kind,
             mutable cleanups=cleanups,
             fcx=cx);
}

// Use this when you're at the top block of a function or the like.
fn new_top_block_ctxt(@fn_ctxt fcx) -> @block_ctxt {
    ret new_block_ctxt(fcx, parent_none, SCOPE_BLOCK,
                       "function top level");
}

// Use this when you're at a curly-brace or similar lexical scope.
fn new_scope_block_ctxt(@block_ctxt bcx, str n) -> @block_ctxt {
    ret new_block_ctxt(bcx.fcx, parent_some(bcx), SCOPE_BLOCK, n);
}

fn new_loop_scope_block_ctxt(@block_ctxt bcx, option.t[@block_ctxt] _cont,
                             @block_ctxt _break, str n) -> @block_ctxt {
    ret new_block_ctxt(bcx.fcx, parent_some(bcx),
                       LOOP_SCOPE_BLOCK(_cont, _break), n);
}

// Use this when you're making a general CFG BB within a scope.
fn new_sub_block_ctxt(@block_ctxt bcx, str n) -> @block_ctxt {
    ret new_block_ctxt(bcx.fcx, parent_some(bcx), NON_SCOPE_BLOCK, n);
}


fn trans_block_cleanups(@block_ctxt cx,
                        @block_ctxt cleanup_cx) -> @block_ctxt {
    auto bcx = cx;

    if (cleanup_cx.kind == NON_SCOPE_BLOCK) {
        check (_vec.len[cleanup](cleanup_cx.cleanups) == 0u);
    }

    auto i = _vec.len[cleanup](cleanup_cx.cleanups);
    while (i > 0u) {
        i -= 1u;
        auto c = cleanup_cx.cleanups.(i);
        alt (c) {
            case (clean(?cfn)) {
                bcx = cfn(bcx).bcx;
            }
        }
    }
    ret bcx;
}

iter block_locals(&ast.block b) -> @ast.local {
    // FIXME: putting from inside an iter block doesn't work, so we can't
    // use the index here.
    for (@ast.stmt s in b.node.stmts) {
        alt (s.node) {
            case (ast.stmt_decl(?d,_)) {
                alt (d.node) {
                    case (ast.decl_local(?local)) {
                        put local;
                    }
                    case (_) { /* fall through */ }
                }
            }
            case (_) { /* fall through */ }
        }
    }
}

fn llallocas_block_ctxt(@fn_ctxt fcx) -> @block_ctxt {
    let vec[cleanup] cleanups = vec();
    ret @rec(llbb=fcx.llallocas,
             build=new_builder(fcx.llallocas),
             parent=parent_none,
             kind=SCOPE_BLOCK,
             mutable cleanups=cleanups,
             fcx=fcx);
}

fn alloc_ty(@block_ctxt cx, ty.t t) -> result {
    auto val = C_int(0);
    if (ty.type_has_dynamic_size(cx.fcx.lcx.ccx.tcx, t)) {

        // NB: we have to run this particular 'size_of' in a
        // block_ctxt built on the llallocas block for the fn,
        // so that the size dominates the array_alloca that
        // comes next.

        auto n = size_of(llallocas_block_ctxt(cx.fcx), t);
        cx.fcx.llallocas = n.bcx.llbb;
        val = array_alloca(cx, T_i8(), n.val);
    } else {
        val = alloca(cx, type_of(cx.fcx.lcx.ccx, t));
    }
    // NB: since we've pushed all size calculations in this
    // function up to the alloca block, we actually return the
    // block passed into us unmodified; it doesn't really
    // have to be passed-and-returned here, but it fits
    // past caller conventions and may well make sense again,
    // so we leave it as-is.
    ret res(cx, val);
}

fn alloc_local(@block_ctxt cx, @ast.local local) -> result {
    auto t = node_ann_type(cx.fcx.lcx.ccx, local.ann);
    auto r = alloc_ty(cx, t);
    r.bcx.fcx.lllocals.insert(local.id, r.val);
    ret r;
}

fn trans_block(@block_ctxt cx, &ast.block b) -> result {
    auto bcx = cx;

    for each (@ast.local local in block_locals(b)) {
        bcx = alloc_local(bcx, local).bcx;
    }
    auto r = res(bcx, C_nil());

    for (@ast.stmt s in b.node.stmts) {
        r = trans_stmt(bcx, *s);
        bcx = r.bcx;
        // If we hit a terminator, control won't go any further so
        // we're in dead-code land. Stop here.
        if (is_terminated(bcx)) {
            ret r;
        }
    }

    alt (b.node.expr) {
        case (some[@ast.expr](?e)) {
            r = trans_expr(bcx, e);
            bcx = r.bcx;

            if (is_terminated(bcx)) {
                ret r;
            } else {
                auto r_ty = ty.expr_ty(cx.fcx.lcx.ccx.tcx, e);
                if (!ty.type_is_nil(cx.fcx.lcx.ccx.tcx, r_ty)) {
                    // The value resulting from the block gets copied into an
                    // alloca created in an outer scope and its refcount
                    // bumped so that it can escape this block. This means
                    // that it will definitely live until the end of the
                    // enclosing scope, even if nobody uses it, which may be
                    // something of a surprise.

                    // It's possible we never hit this block, so the alloca
                    // must be initialized to null, then when the potential
                    // value finally goes out of scope the drop glue will see
                    // that it was never used and ignore it.

                    // NB: Here we're building and initalizing the alloca in
                    // the alloca context, not this block's context.
                    auto res_alloca = alloc_ty(bcx, r_ty);
                    auto llbcx = llallocas_block_ctxt(bcx.fcx);
                    zero_alloca(llbcx, res_alloca.val, r_ty);

                    // Now we're working in our own block context again
                    auto res_copy = copy_ty(bcx, INIT,
                                            res_alloca.val, r.val, r_ty);
                    bcx = res_copy.bcx;

                    fn drop_hoisted_ty(@block_ctxt cx,
                                       ValueRef alloca_val,
                                       ty.t t) -> result {
                        auto reg_val = load_if_immediate(cx,
                                                            alloca_val, t);
                        ret drop_ty(cx, reg_val, t);
                    }

                    auto cleanup = bind drop_hoisted_ty(_, res_alloca.val,
                                                        r_ty);
                    find_outer_scope_cx(bcx).cleanups += vec(clean(cleanup));
                }
            }
        }
        case (none[@ast.expr]) {
            r = res(bcx, C_nil());
        }
    }

    bcx = trans_block_cleanups(bcx, find_scope_cx(bcx));
    ret res(bcx, r.val);
}

fn new_local_ctxt(@crate_ctxt ccx) -> @local_ctxt {
    let vec[str] pth = vec();
    let vec[ast.ty_param] obj_typarams = vec();
    let vec[ast.obj_field] obj_fields = vec();
    ret @rec(path=pth,
             module_path=vec(crate_name(ccx, "main")),
             obj_typarams = obj_typarams,
             obj_fields = obj_fields,
             ccx = ccx);
}

// NB: must keep 4 fns in sync:
//
//  - type_of_fn_full
//  - create_llargs_for_fn_args.
//  - new_fn_ctxt
//  - trans_args

fn new_fn_ctxt(@local_ctxt cx,
               ValueRef llfndecl) -> @fn_ctxt {

    let ValueRef llretptr = llvm.LLVMGetParam(llfndecl, 0u);
    let ValueRef lltaskptr = llvm.LLVMGetParam(llfndecl, 1u);
    let ValueRef llenv = llvm.LLVMGetParam(llfndecl, 2u);

    let hashmap[ast.def_id, ValueRef] llargs = new_def_hash[ValueRef]();
    let hashmap[ast.def_id, ValueRef] llobjfields = new_def_hash[ValueRef]();
    let hashmap[ast.def_id, ValueRef] lllocals = new_def_hash[ValueRef]();
    let hashmap[ast.def_id, ValueRef] llupvars = new_def_hash[ValueRef]();

    let BasicBlockRef llallocas =
        llvm.LLVMAppendBasicBlock(llfndecl, _str.buf("allocas"));

    ret @rec(llfn=llfndecl,
             lltaskptr=lltaskptr,
             llenv=llenv,
             llretptr=llretptr,
             mutable llallocas = llallocas,
             mutable llself=none[self_vt],
             mutable lliterbody=none[ValueRef],
             llargs=llargs,
             llobjfields=llobjfields,
             lllocals=lllocals,
             llupvars=llupvars,
             mutable lltydescs=_vec.empty[ValueRef](),
             lcx=cx);
}

// NB: must keep 4 fns in sync:
//
//  - type_of_fn_full
//  - create_llargs_for_fn_args.
//  - new_fn_ctxt
//  - trans_args

fn create_llargs_for_fn_args(&@fn_ctxt cx,
                             ast.proto proto,
                             option.t[tup(TypeRef, ty.t)] ty_self,
                             ty.t ret_ty,
                             &vec[ast.arg] args,
                             &vec[ast.ty_param] ty_params) {

    auto arg_n = 3u;

    alt (ty_self) {
        case (some[tup(TypeRef, ty.t)](?tt)) {
            cx.llself = some[self_vt](rec(v = cx.llenv, t = tt._1));
        }
        case (none[tup(TypeRef, ty.t)]) {
            auto i = 0u;
            for (ast.ty_param tp in ty_params) {
                auto llarg = llvm.LLVMGetParam(cx.llfn, arg_n);
                check (llarg as int != 0);
                cx.lltydescs += vec(llarg);
                arg_n += 1u;
                i += 1u;
            }
        }
    }

    if (proto == ast.proto_iter) {
        auto llarg = llvm.LLVMGetParam(cx.llfn, arg_n);
        check (llarg as int != 0);
        cx.lliterbody = some[ValueRef](llarg);
        arg_n += 1u;
    }

    for (ast.arg arg in args) {
        auto llarg = llvm.LLVMGetParam(cx.llfn, arg_n);
        check (llarg as int != 0);
        cx.llargs.insert(arg.id, llarg);
        arg_n += 1u;
    }
}

// Recommended LLVM style, strange though this is, is to copy from args to
// allocas immediately upon entry; this permits us to GEP into structures we
// were passed and whatnot. Apparently mem2reg will mop up.

fn copy_any_self_to_alloca(@fn_ctxt fcx,
                           option.t[tup(TypeRef, ty.t)] ty_self) {

    auto bcx = llallocas_block_ctxt(fcx);

    alt (fcx.llself) {
        case (some[self_vt](?s_vt)) {
            alt (ty_self) {
                case (some[tup(TypeRef, ty.t)](?tt)) {
                    auto a = alloca(bcx, tt._0);
                    bcx.build.Store(s_vt.v, a);
                    fcx.llself = some[self_vt](rec(v = a, t = s_vt.t));
                }
            }
        }
        case (_) {
        }
    }
}


fn copy_args_to_allocas(@fn_ctxt fcx,
                        vec[ast.arg] args,
                        vec[ty.arg] arg_tys) {

    auto bcx = llallocas_block_ctxt(fcx);

    let uint arg_n = 0u;

    for (ast.arg aarg in args) {
        if (aarg.mode != ast.alias) {
            auto arg_t = type_of_arg(fcx.lcx, arg_tys.(arg_n));
            auto a = alloca(bcx, arg_t);
            auto argval = fcx.llargs.get(aarg.id);
            bcx.build.Store(argval, a);
            // Overwrite the llargs entry for this arg with its alloca.
            fcx.llargs.insert(aarg.id, a);
        }

        arg_n += 1u;
    }

    fcx.llallocas = bcx.llbb;
}

fn add_cleanups_for_args(@block_ctxt bcx,
                         vec[ast.arg] args,
                         vec[ty.arg] arg_tys) {
    let uint arg_n = 0u;
    for (ast.arg aarg in args) {
        if (aarg.mode != ast.alias) {
            auto argval = bcx.fcx.llargs.get(aarg.id);
            find_scope_cx(bcx).cleanups +=
                vec(clean(bind drop_slot(_, argval, arg_tys.(arg_n).ty)));
        }
        arg_n += 1u;
    }
}


fn is_terminated(@block_ctxt cx) -> bool {
    auto inst = llvm.LLVMGetLastInstruction(cx.llbb);
    ret llvm.LLVMIsATerminatorInst(inst) as int != 0;
}

fn arg_tys_of_fn(@crate_ctxt ccx, ast.ann ann) -> vec[ty.arg] {
    alt (ty.struct(ccx.tcx, ty.ann_to_type(ann))) {
        case (ty.ty_fn(_, ?arg_tys, _)) {
            ret arg_tys;
        }
    }
    fail;
}

fn ret_ty_of_fn_ty(@crate_ctxt ccx, ty.t t) -> ty.t {
    alt (ty.struct(ccx.tcx, t)) {
        case (ty.ty_fn(_, _, ?ret_ty)) {
            ret ret_ty;
        }
    }
    fail;
}


fn ret_ty_of_fn(@crate_ctxt ccx, ast.ann ann) -> ty.t {
    ret ret_ty_of_fn_ty(ccx, ty.ann_to_type(ann));
}

fn populate_fn_ctxt_from_llself(@fn_ctxt fcx, self_vt llself) {
    auto bcx = llallocas_block_ctxt(fcx);

    let vec[ty.t] field_tys = vec();

    for (ast.obj_field f in bcx.fcx.lcx.obj_fields) {
        field_tys += vec(node_ann_type(bcx.fcx.lcx.ccx, f.ann));
    }

    // Synthesize a tuple type for the fields so that GEP_tup_like() can work
    // its magic.
    auto fields_tup_ty = ty.mk_imm_tup(fcx.lcx.ccx.tcx, field_tys);

    auto n_typarams = _vec.len[ast.ty_param](bcx.fcx.lcx.obj_typarams);
    let TypeRef llobj_box_ty = T_obj_ptr(bcx.fcx.lcx.ccx.tn, n_typarams);

    auto box_cell =
        bcx.build.GEP(llself.v,
                      vec(C_int(0),
                          C_int(abi.obj_field_box)));

    auto box_ptr = bcx.build.Load(box_cell);

    box_ptr = bcx.build.PointerCast(box_ptr, llobj_box_ty);

    auto obj_typarams = bcx.build.GEP(box_ptr,
                                     vec(C_int(0),
                                         C_int(abi.box_rc_field_body),
                                         C_int(abi.obj_body_elt_typarams)));

    // The object fields immediately follow the type parameters, so we skip
    // over them to get the pointer.
    auto obj_fields = bcx.build.Add(vp2i(bcx, obj_typarams),
        llsize_of(llvm.LLVMGetElementType(val_ty(obj_typarams))));

    // If we can (i.e. the type is statically sized), then cast the resulting
    // fields pointer to the appropriate LLVM type. If not, just leave it as
    // i8 *.
    if (!ty.type_has_dynamic_size(fcx.lcx.ccx.tcx, fields_tup_ty)) {
        auto llfields_ty = type_of(fcx.lcx.ccx, fields_tup_ty);
        obj_fields = vi2p(bcx, obj_fields, T_ptr(llfields_ty));
    } else {
        obj_fields = vi2p(bcx, obj_fields, T_ptr(T_i8()));
    }


    let int i = 0;

    for (ast.ty_param p in fcx.lcx.obj_typarams) {
        let ValueRef lltyparam = bcx.build.GEP(obj_typarams,
                                               vec(C_int(0),
                                                   C_int(i)));
        lltyparam = bcx.build.Load(lltyparam);
        fcx.lltydescs += vec(lltyparam);
        i += 1;
    }

    i = 0;
    for (ast.obj_field f in fcx.lcx.obj_fields) {
        auto rslt = GEP_tup_like(bcx, fields_tup_ty, obj_fields, vec(0, i));
        bcx = llallocas_block_ctxt(fcx);
        auto llfield = rslt.val;
        fcx.llobjfields.insert(f.id, llfield);
        i += 1;
    }

    fcx.llallocas = bcx.llbb;
}

fn trans_fn(@local_ctxt cx, &ast._fn f, ast.def_id fid,
            option.t[tup(TypeRef, ty.t)] ty_self,
            &vec[ast.ty_param] ty_params, &ast.ann ann) {

    auto llfndecl = cx.ccx.item_ids.get(fid);

    auto fcx = new_fn_ctxt(cx, llfndecl);
    create_llargs_for_fn_args(fcx, f.proto,
                              ty_self, ret_ty_of_fn(cx.ccx, ann),
                              f.decl.inputs, ty_params);

    copy_any_self_to_alloca(fcx, ty_self);

    alt (fcx.llself) {
        case (some[self_vt](?llself)) {
            populate_fn_ctxt_from_llself(fcx, llself);
        }
        case (_) {
        }
    }

    auto arg_tys = arg_tys_of_fn(fcx.lcx.ccx, ann);
    copy_args_to_allocas(fcx, f.decl.inputs, arg_tys);

    auto bcx = new_top_block_ctxt(fcx);

    add_cleanups_for_args(bcx, f.decl.inputs, arg_tys);

    auto lltop = bcx.llbb;

    auto res = trans_block(bcx, f.body);
    if (!is_terminated(res.bcx)) {
        // FIXME: until LLVM has a unit type, we are moving around
        // C_nil values rather than their void type.
        res.bcx.build.RetVoid();
    }

    // Tie up the llallocas -> lltop edge.
    new_builder(fcx.llallocas).Br(lltop);
}

fn trans_vtbl(@local_ctxt cx,
              TypeRef llself_ty,
              ty.t self_ty,
              &ast._obj ob,
              &vec[ast.ty_param] ty_params) -> ValueRef {
    let vec[ValueRef] methods = vec();

    fn meth_lteq(&@ast.method a, &@ast.method b) -> bool {
        ret _str.lteq(a.node.ident, b.node.ident);
    }

    auto meths = std.sort.merge_sort[@ast.method](bind meth_lteq(_,_),
                                                  ob.methods);

    for (@ast.method m in meths) {

        auto llfnty = T_nil();
        alt (ty.struct(cx.ccx.tcx, node_ann_type(cx.ccx, m.node.ann))) {
            case (ty.ty_fn(?proto, ?inputs, ?output)) {
                llfnty = type_of_fn_full(cx.ccx, proto,
                                         some[TypeRef](llself_ty),
                                         inputs, output,
                                         _vec.len[ast.ty_param](ty_params));
            }
        }

        let @local_ctxt mcx = extend_path(cx, m.node.ident);
        let str s = mangle_name_by_seq(mcx.ccx, mcx.path, "method");
        let ValueRef llfn = decl_internal_fastcall_fn(cx.ccx.llmod, s,
                                                      llfnty);
        cx.ccx.item_ids.insert(m.node.id, llfn);
        cx.ccx.item_symbols.insert(m.node.id, s);

        trans_fn(mcx, m.node.meth, m.node.id,
                 some[tup(TypeRef, ty.t)](tup(llself_ty, self_ty)),
                 ty_params, m.node.ann);
        methods += vec(llfn);
    }
    auto vtbl = C_struct(methods);
    auto vtbl_name = mangle_name_by_seq(cx.ccx, cx.path, "vtbl");
    auto gvar = llvm.LLVMAddGlobal(cx.ccx.llmod, val_ty(vtbl),
                                   _str.buf(vtbl_name));
    llvm.LLVMSetInitializer(gvar, vtbl);
    llvm.LLVMSetGlobalConstant(gvar, True);
    llvm.LLVMSetLinkage(gvar, lib.llvm.LLVMInternalLinkage
                        as llvm.Linkage);
    ret gvar;
}

fn trans_dtor(@local_ctxt cx,
              TypeRef llself_ty,
              ty.t self_ty,
              &vec[ast.ty_param] ty_params,
              &@ast.method dtor) -> ValueRef {

    auto llfnty = T_nil();
    alt (ty.struct(cx.ccx.tcx, node_ann_type(cx.ccx, dtor.node.ann))) {
        case (ty.ty_fn(?proto, ?inputs, ?output)) {
            llfnty = type_of_fn_full(cx.ccx, proto,
                                     some[TypeRef](llself_ty),
                                     inputs, output,
                                     _vec.len[ast.ty_param](ty_params));
        }
    }

    let @local_ctxt dcx = extend_path(cx, "drop");
    let str s = mangle_name_by_seq(dcx.ccx, dcx.path, "drop");
    let ValueRef llfn = decl_internal_fastcall_fn(cx.ccx.llmod, s, llfnty);
    cx.ccx.item_ids.insert(dtor.node.id, llfn);
    cx.ccx.item_symbols.insert(dtor.node.id, s);

    trans_fn(dcx, dtor.node.meth, dtor.node.id,
             some[tup(TypeRef, ty.t)](tup(llself_ty, self_ty)),
             ty_params, dtor.node.ann);

    ret llfn;
}

fn trans_obj(@local_ctxt cx, &ast._obj ob, ast.def_id oid,
             &vec[ast.ty_param] ty_params, &ast.ann ann) {
    auto ccx = cx.ccx;
    auto llctor_decl = ccx.item_ids.get(oid);

    // Translate obj ctor args to function arguments.
    let vec[ast.arg] fn_args = vec();
    for (ast.obj_field f in ob.fields) {
        fn_args += vec(rec(mode=ast.alias,
                           ty=f.ty,
                           ident=f.ident,
                           id=f.id));
    }

    auto fcx = new_fn_ctxt(cx, llctor_decl);
    create_llargs_for_fn_args(fcx, ast.proto_fn,
                              none[tup(TypeRef, ty.t)],
                              ret_ty_of_fn(cx.ccx, ann),
                              fn_args, ty_params);

    let vec[ty.arg] arg_tys = arg_tys_of_fn(cx.ccx, ann);
    copy_args_to_allocas(fcx, fn_args, arg_tys);

    auto bcx = new_top_block_ctxt(fcx);
    auto lltop = bcx.llbb;

    auto self_ty = ret_ty_of_fn(cx.ccx, ann);
    auto llself_ty = type_of(ccx, self_ty);
    auto pair = bcx.fcx.llretptr;
    auto vtbl = trans_vtbl(cx, llself_ty, self_ty, ob, ty_params);
    auto pair_vtbl = bcx.build.GEP(pair,
                                   vec(C_int(0),
                                       C_int(abi.obj_field_vtbl)));
    auto pair_box = bcx.build.GEP(pair,
                                  vec(C_int(0),
                                      C_int(abi.obj_field_box)));
    bcx.build.Store(vtbl, pair_vtbl);

    let TypeRef llbox_ty = T_opaque_obj_ptr(ccx.tn);

    if (_vec.len[ast.ty_param](ty_params) == 0u &&
        _vec.len[ty.arg](arg_tys) == 0u) {
        // Store null into pair, if no args or typarams.
        bcx.build.Store(C_null(llbox_ty), pair_box);
    } else {
        // Malloc a box for the body and copy args in.
        let vec[ty.t] obj_fields = vec();
        for (ty.arg a in arg_tys) {
            _vec.push[ty.t](obj_fields, a.ty);
        }

        // Synthesize an obj body type.
        auto tydesc_ty = ty.mk_type(cx.ccx.tcx);
        let vec[ty.t] tps = vec();
        for (ast.ty_param tp in ty_params) {
            _vec.push[ty.t](tps, tydesc_ty);
        }

        let ty.t typarams_ty = ty.mk_imm_tup(cx.ccx.tcx, tps);
        let ty.t fields_ty = ty.mk_imm_tup(cx.ccx.tcx, obj_fields);
        let ty.t body_ty = ty.mk_imm_tup(cx.ccx.tcx,
                                          vec(tydesc_ty,
                                              typarams_ty,
                                              fields_ty));
        let ty.t boxed_body_ty = ty.mk_imm_box(cx.ccx.tcx, body_ty);

        // Malloc a box for the body.
        auto box = trans_malloc_boxed(bcx, body_ty);
        bcx = box.bcx;
        auto rc = GEP_tup_like(bcx, boxed_body_ty, box.val,
                               vec(0, abi.box_rc_field_refcnt));
        bcx = rc.bcx;
        auto body = GEP_tup_like(bcx, boxed_body_ty, box.val,
                                 vec(0, abi.box_rc_field_body));
        bcx = body.bcx;
        bcx.build.Store(C_int(1), rc.val);

        // Store body tydesc.
        auto body_tydesc =
            GEP_tup_like(bcx, body_ty, body.val,
                         vec(0, abi.obj_body_elt_tydesc));
        bcx = body_tydesc.bcx;

        auto dtor = C_null(T_ptr(T_glue_fn(ccx.tn)));
        alt (ob.dtor) {
            case (some[@ast.method](?d)) {
                dtor = trans_dtor(cx, llself_ty, self_ty, ty_params, d);
            }
            case (none[@ast.method]) {}
        }

        auto body_td = get_tydesc(bcx, body_ty);
        bcx = body_td.bcx;
        bcx.build.Store(body_td.val, body_tydesc.val);

        // Copy typarams into captured typarams.
        auto body_typarams =
            GEP_tup_like(bcx, body_ty, body.val,
                         vec(0, abi.obj_body_elt_typarams));
        bcx = body_typarams.bcx;
        let int i = 0;
        for (ast.ty_param tp in ty_params) {
            auto typaram = bcx.fcx.lltydescs.(i);
            auto capture = GEP_tup_like(bcx, typarams_ty, body_typarams.val,
                                        vec(0, i));
            bcx = capture.bcx;
            bcx = copy_ty(bcx, INIT, capture.val, typaram, tydesc_ty).bcx;
            i += 1;
        }

        // Copy args into body fields.
        auto body_fields =
            GEP_tup_like(bcx, body_ty, body.val,
                         vec(0, abi.obj_body_elt_fields));
        bcx = body_fields.bcx;

        i = 0;
        for (ast.obj_field f in ob.fields) {
            auto arg = bcx.fcx.llargs.get(f.id);
            arg = load_if_immediate(bcx, arg, arg_tys.(i).ty);
            auto field = GEP_tup_like(bcx, fields_ty, body_fields.val,
                                      vec(0, i));
            bcx = field.bcx;
            bcx = copy_ty(bcx, INIT, field.val, arg, arg_tys.(i).ty).bcx;
            i += 1;
        }
        // Store box ptr in outer pair.
        auto p = bcx.build.PointerCast(box.val, llbox_ty);
        bcx.build.Store(p, pair_box);
    }
    bcx.build.RetVoid();

    // Tie up the llallocas -> lltop edge.
    new_builder(fcx.llallocas).Br(lltop);
}

fn trans_tag_variant(@local_ctxt cx, ast.def_id tag_id,
                     &ast.variant variant, int index,
                     &vec[ast.ty_param] ty_params) {
    if (_vec.len[ast.variant_arg](variant.node.args) == 0u) {
        ret;    // nullary constructors are just constants
    }

    // Translate variant arguments to function arguments.
    let vec[ast.arg] fn_args = vec();
    auto i = 0u;
    for (ast.variant_arg varg in variant.node.args) {
        fn_args += vec(rec(mode=ast.alias,
                           ty=varg.ty,
                           ident="arg" + _uint.to_str(i, 10u),
                           id=varg.id));
    }

    check (cx.ccx.item_ids.contains_key(variant.node.id));
    let ValueRef llfndecl = cx.ccx.item_ids.get(variant.node.id);

    auto fcx = new_fn_ctxt(cx, llfndecl);

    create_llargs_for_fn_args(fcx, ast.proto_fn,
                              none[tup(TypeRef, ty.t)],
                              ret_ty_of_fn(cx.ccx, variant.node.ann),
                              fn_args, ty_params);

    let vec[ty.t] ty_param_substs = vec();
    i = 0u;
    for (ast.ty_param tp in ty_params) {
        ty_param_substs += vec(ty.mk_param(cx.ccx.tcx, i));
        i += 1u;
    }

    auto arg_tys = arg_tys_of_fn(cx.ccx, variant.node.ann);
    copy_args_to_allocas(fcx, fn_args, arg_tys);

    auto bcx = new_top_block_ctxt(fcx);
    auto lltop = bcx.llbb;

    // Cast the tag to a type we can GEP into.
    auto lltagptr = bcx.build.PointerCast(fcx.llretptr,
                                          T_opaque_tag_ptr(fcx.lcx.ccx.tn));

    auto lldiscrimptr = bcx.build.GEP(lltagptr,
                                      vec(C_int(0), C_int(0)));
    bcx.build.Store(C_int(index), lldiscrimptr);

    auto llblobptr = bcx.build.GEP(lltagptr,
                                   vec(C_int(0), C_int(1)));

    i = 0u;
    for (ast.variant_arg va in variant.node.args) {
        auto rslt = GEP_tag(bcx, llblobptr, tag_id, variant.node.id,
                            ty_param_substs, i as int);
        bcx = rslt.bcx;
        auto lldestptr = rslt.val;

        // If this argument to this function is a tag, it'll have come in to
        // this function as an opaque blob due to the way that type_of()
        // works. So we have to cast to the destination's view of the type.
        auto llargptr = bcx.build.PointerCast(fcx.llargs.get(va.id),
            val_ty(lldestptr));

        auto arg_ty = arg_tys.(i).ty;
        auto llargval;
        if (ty.type_is_structural(cx.ccx.tcx, arg_ty) ||
                ty.type_has_dynamic_size(cx.ccx.tcx, arg_ty)) {
            llargval = llargptr;
        } else {
            llargval = bcx.build.Load(llargptr);
        }

        rslt = copy_ty(bcx, INIT, lldestptr, llargval, arg_ty);
        bcx = rslt.bcx;

        i += 1u;
    }

    bcx = trans_block_cleanups(bcx, find_scope_cx(bcx));
    bcx.build.RetVoid();

    // Tie up the llallocas -> lltop edge.
    new_builder(fcx.llallocas).Br(lltop);
}

// FIXME: this should do some structural hash-consing to avoid
// duplicate constants. I think. Maybe LLVM has a magical mode
// that does so later on?

fn trans_const_expr(@crate_ctxt cx, @ast.expr e) -> ValueRef {
    alt (e.node) {
        case (ast.expr_lit(?lit, ?ann)) {
            ret trans_lit(cx, *lit, ann);
        }
    }
}

fn trans_const(@crate_ctxt cx, @ast.expr e,
               &ast.def_id cid, &ast.ann ann) {
    auto t = node_ann_type(cx, ann);
    auto v = trans_const_expr(cx, e);

    // The scalars come back as 1st class LLVM vals
    // which we have to stick into global constants.
    auto g = cx.consts.get(cid);
    llvm.LLVMSetInitializer(g, v);
    llvm.LLVMSetGlobalConstant(g, True);
}

fn trans_item(@local_ctxt cx, &ast.item item) {
    alt (item.node) {
        case (ast.item_fn(?name, ?f, ?tps, ?fid, ?ann)) {
            auto sub_cx = extend_path(cx, name);
            trans_fn(sub_cx, f, fid, none[tup(TypeRef, ty.t)], tps, ann);
        }
        case (ast.item_obj(?name, ?ob, ?tps, ?oid, ?ann)) {
            auto sub_cx = @rec(obj_typarams=tps,
                               obj_fields=ob.fields with
                               *extend_path(cx, name));
            trans_obj(sub_cx, ob, oid.ctor, tps, ann);
        }
        case (ast.item_mod(?name, ?m, _)) {
            auto sub_cx = @rec(path = cx.path + vec(name),
                               module_path = cx.module_path + vec(name)
                               with *cx);
            trans_mod(sub_cx, m);
        }
        case (ast.item_tag(?name, ?variants, ?tps, ?tag_id, _)) {
            auto sub_cx = extend_path(cx, name);
            auto i = 0;
            for (ast.variant variant in variants) {
                trans_tag_variant(sub_cx, tag_id, variant, i, tps);
                i += 1;
            }
        }
        case (ast.item_const(?name, _, ?expr, ?cid, ?ann)) {
            trans_const(cx.ccx, expr, cid, ann);
        }
        case (_) { /* fall through */ }
    }
}

fn trans_mod(@local_ctxt cx, &ast._mod m) {
    for (@ast.item item in m.items) {
        trans_item(cx, *item);
    }
}

fn get_pair_fn_ty(TypeRef llpairty) -> TypeRef {
    // Bit of a kludge: pick the fn typeref out of the pair.
    let vec[TypeRef] pair_tys = vec(T_nil(), T_nil());
    llvm.LLVMGetStructElementTypes(llpairty,
                                   _vec.buf[TypeRef](pair_tys));
    ret llvm.LLVMGetElementType(pair_tys.(0));
}

fn decl_fn_and_pair(@crate_ctxt ccx,
                    vec[str] path,
                    str flav,
                    vec[ast.ty_param] ty_params,
                    &ast.ann ann,
                    ast.def_id id) {

    auto llfty;
    auto llpairty;
    alt (ty.struct(ccx.tcx, node_ann_type(ccx, ann))) {
        case (ty.ty_fn(?proto, ?inputs, ?output)) {
            llfty = type_of_fn(ccx, proto, inputs, output,
                               _vec.len[ast.ty_param](ty_params));
            llpairty = T_fn_pair(ccx.tn, llfty);
        }
        case (_) {
            ccx.sess.bug("decl_fn_and_pair(): fn item doesn't have fn type!");
            fail;
        }
    }

    // Declare the function itself.
    let str s = mangle_name_by_seq(ccx, path, flav);
    let ValueRef llfn = decl_internal_fastcall_fn(ccx.llmod, s, llfty);

    // Declare the global constant pair that points to it.
    let str ps = mangle_name_by_type(ccx, path, node_ann_type(ccx, ann));

    register_fn_pair(ccx, ps, llpairty, llfn, id);
}

fn register_fn_pair(@crate_ctxt cx, str ps, TypeRef llpairty, ValueRef llfn,
                    ast.def_id id) {
    let ValueRef gvar = llvm.LLVMAddGlobal(cx.llmod, llpairty,
                                           _str.buf(ps));
    auto pair = C_struct(vec(llfn,
                             C_null(T_opaque_closure_ptr(cx.tn))));

    llvm.LLVMSetInitializer(gvar, pair);
    llvm.LLVMSetGlobalConstant(gvar, True);
    llvm.LLVMSetVisibility(gvar,
                           lib.llvm.LLVMProtectedVisibility
                           as llvm.Visibility);

    cx.item_ids.insert(id, llfn);
    cx.item_symbols.insert(id, ps);
    cx.fn_pairs.insert(id, gvar);
}

// Returns the number of type parameters that the given native function has.
fn native_fn_ty_param_count(@crate_ctxt cx, &ast.def_id id) -> uint {
    auto count;
    auto native_item = cx.native_items.get(id);
    alt (native_item.node) {
        case (ast.native_item_ty(_,_)) {
            cx.sess.bug("decl_native_fn_and_pair(): native fn isn't " +
                        "actually a fn?!");
            fail;
        }
        case (ast.native_item_fn(_, _, _, ?tps, _, _)) {
            count = _vec.len[ast.ty_param](tps);
        }
    }
    ret count;
}

fn native_fn_wrapper_type(@crate_ctxt cx, uint ty_param_count, ty.t x)
        -> TypeRef {
    alt (ty.struct(cx.tcx, x)) {
        case (ty.ty_native_fn(?abi, ?args, ?out)) {
            ret type_of_fn(cx, ast.proto_fn, args, out, ty_param_count);
        }
    }
    fail;
}

fn decl_native_fn_and_pair(@crate_ctxt ccx,
                           vec[str] path,
                           str name,
                           &ast.ann ann,
                           ast.def_id id) {
    auto num_ty_param = native_fn_ty_param_count(ccx, id);

    // Declare the wrapper.
    auto t = node_ann_type(ccx, ann);
    auto wrapper_type = native_fn_wrapper_type(ccx, num_ty_param, t);
    let str s = mangle_name_by_seq(ccx, path, "wrapper");
    let ValueRef wrapper_fn = decl_internal_fastcall_fn(ccx.llmod, s,
                                                        wrapper_type);

    // Declare the global constant pair that points to it.
    auto wrapper_pair_type = T_fn_pair(ccx.tn, wrapper_type);
    let str ps = mangle_name_by_type(ccx, path, node_ann_type(ccx, ann));

    register_fn_pair(ccx, ps, wrapper_pair_type, wrapper_fn, id);

    // Build the wrapper.
    auto fcx = new_fn_ctxt(new_local_ctxt(ccx), wrapper_fn);
    auto bcx = new_top_block_ctxt(fcx);
    auto lltop = bcx.llbb;

    // Declare the function itself.
    auto item = ccx.native_items.get(id);
    auto fn_type = node_ann_type(ccx, ann);  // NB: has no type params

    auto abi = ty.ty_fn_abi(ccx.tcx, fn_type);
    auto llfnty = type_of_native_fn(ccx, abi,
        ty.ty_fn_args(ccx.tcx, fn_type),
        ty.ty_fn_ret(ccx.tcx, fn_type), num_ty_param);

    // FIXME: If the returned type is not nil, then we assume it's 32 bits
    // wide. This is obviously wildly unsafe. We should have a better FFI
    // that allows types of different sizes to be returned.
    auto rty_is_nil = ty.type_is_nil(ccx.tcx, ty.ty_fn_ret(ccx.tcx, fn_type));

    let vec[ValueRef] call_args = vec();
    auto arg_n = 3u;
    auto pass_task;

    auto lltaskptr = vp2i(bcx, fcx.lltaskptr);
    alt (abi) {
        case (ast.native_abi_rust) {
            pass_task = true;
            call_args += vec(lltaskptr);
            for each (uint i in _uint.range(0u, num_ty_param)) {
                auto llarg = llvm.LLVMGetParam(fcx.llfn, arg_n);
                fcx.lltydescs += vec(llarg);
                check (llarg as int != 0);
                call_args += vec(vp2i(bcx, llarg));
                arg_n += 1u;
            }
        }
        case (ast.native_abi_cdecl) {
            pass_task = false;
        }
        case (ast.native_abi_llvm) {
            pass_task = false;
            // We handle this case below.
        }
    }

    fn push_arg(@block_ctxt cx,
                &mutable vec[ValueRef] args,
                ValueRef v,
                ty.t t,
                ast.mode mode) {
        if (mode == ast.val) {
            if (ty.type_is_integral(cx.fcx.lcx.ccx.tcx, t)) {
                auto lldsttype = T_int();
                auto llsrctype = type_of(cx.fcx.lcx.ccx, t);
                if (llvm.LLVMGetIntTypeWidth(lldsttype) >
                    llvm.LLVMGetIntTypeWidth(llsrctype)) {
                    args += vec(cx.build.ZExtOrBitCast(v, T_int()));
                } else {
                    args += vec(cx.build.TruncOrBitCast(v, T_int()));
                }
                ret;
            }
            if (ty.type_is_fp(cx.fcx.lcx.ccx.tcx, t)) {
                args += vec(cx.build.FPToSI(v, T_int()));
                ret;
            }
        }

        args += vec(vp2i(cx, v));
    }

    auto r;
    auto rptr;
    auto args = ty.ty_fn_args(ccx.tcx, fn_type);
    if (abi == ast.native_abi_llvm) {
        let vec[ValueRef] call_args = vec();
        let vec[TypeRef] call_arg_tys = vec();
        auto i = 0u;
        while (i < _vec.len[ty.arg](args)) {
            auto call_arg = llvm.LLVMGetParam(fcx.llfn, i + 3u);
            call_args += vec(call_arg);
            call_arg_tys += vec(val_ty(call_arg));
            i += 1u;
        }
        auto llnativefnty = T_fn(call_arg_tys,
                                 type_of(ccx,
                                         ty.ty_fn_ret(ccx.tcx, fn_type)));
        auto llnativefn = get_extern_fn(ccx.externs, ccx.llmod, name,
                                        lib.llvm.LLVMCCallConv, llnativefnty);
        r = bcx.build.Call(llnativefn, call_args);
        rptr = fcx.llretptr;
    } else {

        let vec[tup(ValueRef, ty.t)] drop_args = vec();

        for (ty.arg arg in args) {
            auto llarg = llvm.LLVMGetParam(fcx.llfn, arg_n);
            check (llarg as int != 0);
            push_arg(bcx, call_args, llarg, arg.ty, arg.mode);
            if (arg.mode == ast.val) {
                drop_args += vec(tup(llarg, arg.ty));
            }
            arg_n += 1u;
        }

        r = trans_native_call(bcx.build, ccx.glues, lltaskptr, ccx.externs,
                              ccx.tn, ccx.llmod, name, pass_task, call_args);
        rptr = bcx.build.BitCast(fcx.llretptr, T_ptr(T_i32()));

        for (tup(ValueRef, ty.t) d in drop_args) {
            bcx = drop_ty(bcx, d._0, d._1).bcx;
        }
    }

    // We don't store the return value if it's nil, to avoid stomping on a nil
    // pointer. This is the only concession made to non-i32 return values. See
    // the FIXME above.
    if (!rty_is_nil) { bcx.build.Store(r, rptr); }

    bcx.build.RetVoid();

    // Tie up the llallocas -> lltop edge.
    new_builder(fcx.llallocas).Br(lltop);
}

type walk_ctxt = rec(mutable vec[str] path);
fn new_walk_ctxt() -> @walk_ctxt {
    let vec[str] path = vec();
    ret @rec(mutable path=path);
}

fn enter_item(@walk_ctxt cx, @ast.item item) {
    alt (item.node) {
        case (ast.item_fn(?name, _, _, _, _)) {
            _vec.push[str](cx.path, name);
        }
        case (ast.item_obj(?name, _, _, _, _)) {
            _vec.push[str](cx.path, name);
        }
        case (ast.item_mod(?name, _, _)) {
            _vec.push[str](cx.path, name);
        }
        case (_) { }
    }
}

fn leave_item(@walk_ctxt cx, @ast.item item) {
    alt (item.node) {
        case (ast.item_fn(_, _, _, _, _)) {
            _vec.pop[str](cx.path);
        }
        case (ast.item_obj(_, _, _, _, _)) {
            _vec.pop[str](cx.path);
        }
        case (ast.item_mod(_, _, _)) {
            _vec.pop[str](cx.path);
        }
        case (_) { }
    }
}

fn collect_native_item(@crate_ctxt ccx, @walk_ctxt wcx, @ast.native_item i) {
    alt (i.node) {
        case (ast.native_item_fn(?name, _, _, _, ?fid, ?ann)) {
            ccx.native_items.insert(fid, i);
            if (!ccx.obj_methods.contains_key(fid)) {
                decl_native_fn_and_pair(ccx, wcx.path, name, ann, fid);
            }
        }
        case (ast.native_item_ty(_, ?tid)) {
            ccx.native_items.insert(tid, i);
        }
    }
}

fn collect_item_1(@crate_ctxt ccx, @walk_ctxt wcx, @ast.item i) {
    enter_item(wcx, i);

    alt (i.node) {
        case (ast.item_const(?name, _, _, ?cid, ?ann)) {
            auto typ = node_ann_type(ccx, ann);
            auto g = llvm.LLVMAddGlobal(ccx.llmod, type_of(ccx, typ),
                                        _str.buf(ccx.names.next(name)));
            llvm.LLVMSetLinkage(g, lib.llvm.LLVMInternalLinkage
                                as llvm.Linkage);
            ccx.items.insert(cid, i);
            ccx.consts.insert(cid, g);
        }
        case (ast.item_mod(?name, ?m, ?mid)) {
            ccx.items.insert(mid, i);
        }
        case (ast.item_ty(_, _, _, ?did, _)) {
            ccx.items.insert(did, i);
        }
        case (ast.item_tag(?name, ?variants, ?tps, ?tag_id, _)) {
            ccx.items.insert(tag_id, i);
        }
        case (_) {}
    }
}

fn collect_item_2(@crate_ctxt ccx, @walk_ctxt wcx, @ast.item i) {
    enter_item(wcx, i);

    alt (i.node) {
        case (ast.item_fn(?name, ?f, ?tps, ?fid, ?ann)) {
            ccx.items.insert(fid, i);
            if (!ccx.obj_methods.contains_key(fid)) {
                decl_fn_and_pair(ccx, wcx.path, "fn", tps, ann, fid);
            }
        }
        case (ast.item_obj(?name, ?ob, ?tps, ?oid, ?ann)) {
            ccx.items.insert(oid.ctor, i);
            decl_fn_and_pair(ccx, wcx.path, "obj_ctor", tps, ann, oid.ctor);
            for (@ast.method m in ob.methods) {
                ccx.obj_methods.insert(m.node.id, ());
            }
        }
        case (_) {}
    }
}

fn collect_items(@crate_ctxt ccx, @ast.crate crate) {
    auto wcx = new_walk_ctxt();
    auto visitor0 = walk.default_visitor();
    auto visitor1 = rec(visit_native_item_pre =
                          bind collect_native_item(ccx, wcx, _),
                        visit_item_pre = bind collect_item_1(ccx, wcx, _),
                        visit_item_post = bind leave_item(wcx, _)
                        with visitor0);
    auto visitor2 = rec(visit_item_pre = bind collect_item_2(ccx, wcx, _),
                        visit_item_post = bind leave_item(wcx, _)
                        with visitor0);
    walk.walk_crate(visitor1, *crate);
    walk.walk_crate(visitor2, *crate);
}

fn collect_tag_ctor(@crate_ctxt ccx, @walk_ctxt wcx, @ast.item i) {
    enter_item(wcx, i);

    alt (i.node) {
        case (ast.item_tag(_, ?variants, ?tps, _, _)) {
            for (ast.variant variant in variants) {
                if (_vec.len[ast.variant_arg](variant.node.args) != 0u) {
                    decl_fn_and_pair(ccx, wcx.path + vec(variant.node.name),
                                     "tag", tps, variant.node.ann,
                                     variant.node.id);
                }
            }
        }

        case (_) { /* fall through */ }
    }
}

fn collect_tag_ctors(@crate_ctxt ccx, @ast.crate crate) {
    auto wcx = new_walk_ctxt();
    auto visitor = rec(visit_item_pre = bind collect_tag_ctor(ccx, wcx, _),
                       visit_item_post = bind leave_item(wcx, _)
                       with walk.default_visitor());
    walk.walk_crate(visitor, *crate);
}

// The constant translation pass.

fn trans_constant(@crate_ctxt ccx, @walk_ctxt wcx, @ast.item it) {
    enter_item(wcx, it);

    alt (it.node) {
        case (ast.item_tag(?ident, ?variants, _, ?tag_id, _)) {
            auto i = 0u;
            auto n_variants = _vec.len[ast.variant](variants);
            while (i < n_variants) {
                auto variant = variants.(i);

                auto discrim_val = C_int(i as int);

                auto s = mangle_name_by_seq(ccx, wcx.path,
                                            #fmt("_rust_tag_discrim_%s_%u",
                                                 ident, i));
                auto discrim_gvar = llvm.LLVMAddGlobal(ccx.llmod, T_int(),
                                                       _str.buf(s));

                llvm.LLVMSetInitializer(discrim_gvar, discrim_val);
                llvm.LLVMSetGlobalConstant(discrim_gvar, True);

                ccx.discrims.insert(variant.node.id, discrim_gvar);
                ccx.discrim_symbols.insert(variant.node.id, s);

                i += 1u;
            }
        }

        case (ast.item_const(?name, _, ?expr, ?cid, ?ann)) {
            // FIXME: The whole expr-translation system needs cloning to deal
            // with consts.
            auto v = C_int(1);
            ccx.item_ids.insert(cid, v);
            auto s = mangle_name_by_type(ccx, wcx.path + vec(name),
                                         node_ann_type(ccx, ann));
            ccx.item_symbols.insert(cid, s);
        }

        case (_) {}
    }
}

fn trans_constants(@crate_ctxt ccx, @ast.crate crate) {
    auto wcx = new_walk_ctxt();
    auto visitor = rec(visit_item_pre = bind trans_constant(ccx, wcx, _),
                       visit_item_post = bind leave_item(wcx, _)
                       with walk.default_visitor());
    walk.walk_crate(visitor, *crate);
}


fn vp2i(@block_ctxt cx, ValueRef v) -> ValueRef {
    ret cx.build.PtrToInt(v, T_int());
}


fn vi2p(@block_ctxt cx, ValueRef v, TypeRef t) -> ValueRef {
    ret cx.build.IntToPtr(v, t);
}

fn p2i(ValueRef v) -> ValueRef {
    ret llvm.LLVMConstPtrToInt(v, T_int());
}

fn i2p(ValueRef v, TypeRef t) -> ValueRef {
    ret llvm.LLVMConstIntToPtr(v, t);
}

fn trans_exit_task_glue(@glue_fns glues,
                        &hashmap[str, ValueRef] externs,
                        type_names tn, ModuleRef llmod) {
    let vec[TypeRef] T_args = vec();
    let vec[ValueRef] V_args = vec();

    auto llfn = glues.exit_task_glue;
    let ValueRef lltaskptr = llvm.LLVMGetParam(llfn, 4u);

    auto entrybb = llvm.LLVMAppendBasicBlock(llfn, _str.buf("entry"));
    auto build = new_builder(entrybb);
    auto tptr = build.PtrToInt(lltaskptr, T_int());
    auto V_args2 = vec(tptr) + V_args;
    trans_native_call(build, glues, lltaskptr,
                      externs, tn, llmod, "upcall_exit", true, V_args2);
    build.RetVoid();
}

fn create_typedefs(@crate_ctxt cx) {
    llvm.LLVMAddTypeName(cx.llmod, _str.buf("crate"), T_crate(cx.tn));
    llvm.LLVMAddTypeName(cx.llmod, _str.buf("task"), T_task(cx.tn));
    llvm.LLVMAddTypeName(cx.llmod, _str.buf("tydesc"), T_tydesc(cx.tn));
}

fn create_crate_constant(ValueRef crate_ptr, @glue_fns glues) {

    let ValueRef crate_addr = p2i(crate_ptr);

    let ValueRef activate_glue_off =
        llvm.LLVMConstSub(p2i(glues.activate_glue), crate_addr);

    let ValueRef yield_glue_off =
        llvm.LLVMConstSub(p2i(glues.yield_glue), crate_addr);

    let ValueRef exit_task_glue_off =
        llvm.LLVMConstSub(p2i(glues.exit_task_glue), crate_addr);

    let ValueRef crate_val =
        C_struct(vec(C_null(T_int()),     // ptrdiff_t image_base_off
                     p2i(crate_ptr),      // uintptr_t self_addr
                     C_null(T_int()),     // ptrdiff_t debug_abbrev_off
                     C_null(T_int()),     // size_t debug_abbrev_sz
                     C_null(T_int()),     // ptrdiff_t debug_info_off
                     C_null(T_int()),     // size_t debug_info_sz
                     activate_glue_off,   // size_t activate_glue_off
                     yield_glue_off,      // size_t yield_glue_off
                     C_null(T_int()),     // size_t unwind_glue_off
                     C_null(T_int()),     // size_t gc_glue_off
                     exit_task_glue_off,  // size_t main_exit_task_glue_off
                     C_null(T_int()),     // int n_rust_syms
                     C_null(T_int()),     // int n_c_syms
                     C_null(T_int()),     // int n_libs
                     C_int(abi.abi_x86_rustc_fastcall) // uintptr_t abi_tag
                     ));

    llvm.LLVMSetInitializer(crate_ptr, crate_val);
}

fn find_main_fn(@crate_ctxt cx) -> ValueRef {
    auto e = sep() + "main";
    let ValueRef v = C_nil();
    let uint n = 0u;
    for each (@tup(ast.def_id, str) i in cx.item_symbols.items()) {
        if (_str.ends_with(i._1, e)) {
            n += 1u;
            v = cx.item_ids.get(i._0);
        }
    }
    alt (n) {
        case (0u) {
            cx.sess.err("main fn not found");
        }
        case (1u) {
            ret v;
        }
        case (_) {
            cx.sess.err("multiple main fns found");
        }
    }
    fail;
}

fn trans_main_fn(@local_ctxt cx, ValueRef llcrate, ValueRef crate_map) {
    auto T_main_args = vec(T_int(), T_int());
    auto T_rust_start_args = vec(T_int(), T_int(), T_int(), T_int(), T_int());

    auto main_name;
    if (_str.eq(std.os.target_os(), "win32")) {
        main_name = "WinMain@16";
    } else {
        main_name = "main";
    }

    auto llmain =
        decl_cdecl_fn(cx.ccx.llmod, main_name, T_fn(T_main_args, T_int()));

    auto llrust_start = decl_cdecl_fn(cx.ccx.llmod, "rust_start",
                                      T_fn(T_rust_start_args, T_int()));

    auto llargc = llvm.LLVMGetParam(llmain, 0u);
    auto llargv = llvm.LLVMGetParam(llmain, 1u);
    auto llrust_main = find_main_fn(cx.ccx);

    //
    // Emit the moral equivalent of:
    //
    // main(int argc, char **argv) {
    //     rust_start(&_rust.main, &crate, argc, argv);
    // }
    //

    let BasicBlockRef llbb =
        llvm.LLVMAppendBasicBlock(llmain, _str.buf(""));
    auto b = new_builder(llbb);

    auto start_args = vec(p2i(llrust_main), p2i(llcrate), llargc, llargv,
                          p2i(crate_map));

    b.Ret(b.Call(llrust_start, start_args));
}

fn declare_intrinsics(ModuleRef llmod) -> hashmap[str,ValueRef] {

    let vec[TypeRef] T_trap_args = vec();
    auto trap = decl_cdecl_fn(llmod, "llvm.trap",
                              T_fn(T_trap_args, T_void()));

    auto intrinsics = new_str_hash[ValueRef]();
    intrinsics.insert("llvm.trap", trap);
    ret intrinsics;
}


fn trace_str(@block_ctxt cx, str s) {
    trans_upcall(cx, "upcall_trace_str", vec(p2i(C_cstr(cx.fcx.lcx.ccx, s))));
}

fn trace_word(@block_ctxt cx, ValueRef v) {
    trans_upcall(cx, "upcall_trace_word", vec(v));
}

fn trace_ptr(@block_ctxt cx, ValueRef v) {
    trace_word(cx, cx.build.PtrToInt(v, T_int()));
}

fn trap(@block_ctxt bcx) {
    let vec[ValueRef] v = vec();
    bcx.build.Call(bcx.fcx.lcx.ccx.intrinsics.get("llvm.trap"), v);
}
tag output_type {
    output_type_none;
    output_type_bitcode;
    output_type_assembly;
    output_type_object;
}

// Decides what to call an intermediate file, given the name of the output and
// the extension to use.
fn mk_intermediate_name(str output_path, str extension) -> str {
    auto dot_pos = _str.index(output_path, '.' as u8);
    auto stem;
    if (dot_pos < 0) {
        stem = output_path;
    } else {
        stem = _str.substr(output_path, 0u, dot_pos as uint);
    }
    ret stem + "." + extension;
}

fn is_object_or_assembly(output_type ot) -> bool {
    if (ot == output_type_assembly) {
        ret true;
    }
    if (ot == output_type_object) {
        ret true;
    }
    ret false;
}

fn run_passes(ModuleRef llmod, bool opt, bool verify, bool save_temps,
              str output, output_type ot) {
    auto pm = mk_pass_manager();

    // TODO: run the linter here also, once there are llvm-c bindings for it.

    // Generate a pre-optimization intermediate file if -save-temps was
    // specified.
    if (save_temps) {
        alt (ot) {
            case (output_type_bitcode) {
                if (opt) {
                    auto filename = mk_intermediate_name(output, "no-opt.bc");
                    llvm.LLVMWriteBitcodeToFile(llmod, _str.buf(filename));
                }
            }
            case (_) {
                auto filename = mk_intermediate_name(output, "bc");
                llvm.LLVMWriteBitcodeToFile(llmod, _str.buf(filename));
            }
        }
    }

    // FIXME: This is mostly a copy of the bits of opt's -O2 that are
    // available in the C api.
    // FIXME2: We might want to add optmization levels like -O1, -O2, -Os, etc
    // FIXME3: Should we expose and use the pass lists used by the opt tool?
    if (opt) {
        auto fpm = mk_pass_manager();

        // createStandardFunctionPasses
        llvm.LLVMAddTypeBasedAliasAnalysisPass(fpm.llpm);
        llvm.LLVMAddBasicAliasAnalysisPass(fpm.llpm);
        llvm.LLVMAddCFGSimplificationPass(fpm.llpm);
        llvm.LLVMAddScalarReplAggregatesPass(fpm.llpm);
        llvm.LLVMAddEarlyCSEPass(fpm.llpm);

        llvm.LLVMRunPassManager(fpm.llpm, llmod);

        // createStandardModulePasses
        llvm.LLVMAddTypeBasedAliasAnalysisPass(pm.llpm);
        llvm.LLVMAddBasicAliasAnalysisPass(pm.llpm);
        llvm.LLVMAddGlobalOptimizerPass(pm.llpm);
        llvm.LLVMAddIPSCCPPass(pm.llpm);
        llvm.LLVMAddDeadArgEliminationPass(pm.llpm);
        llvm.LLVMAddInstructionCombiningPass(pm.llpm);
        llvm.LLVMAddCFGSimplificationPass(pm.llpm);
        llvm.LLVMAddPruneEHPass(pm.llpm);
        llvm.LLVMAddFunctionInliningPass(pm.llpm);
        llvm.LLVMAddFunctionAttrsPass(pm.llpm);
        llvm.LLVMAddScalarReplAggregatesPassSSA(pm.llpm);
        llvm.LLVMAddEarlyCSEPass(pm.llpm);
        llvm.LLVMAddSimplifyLibCallsPass(pm.llpm);
        llvm.LLVMAddJumpThreadingPass(pm.llpm);
        llvm.LLVMAddCorrelatedValuePropagationPass(pm.llpm);
        llvm.LLVMAddCFGSimplificationPass(pm.llpm);
        llvm.LLVMAddInstructionCombiningPass(pm.llpm);
        llvm.LLVMAddTailCallEliminationPass(pm.llpm);
        llvm.LLVMAddCFGSimplificationPass(pm.llpm);
        llvm.LLVMAddReassociatePass(pm.llpm);
        llvm.LLVMAddLoopRotatePass(pm.llpm);
        llvm.LLVMAddLICMPass(pm.llpm);
        llvm.LLVMAddLoopUnswitchPass(pm.llpm);
        llvm.LLVMAddInstructionCombiningPass(pm.llpm);
        llvm.LLVMAddIndVarSimplifyPass(pm.llpm);
        llvm.LLVMAddLoopIdiomPass(pm.llpm);
        llvm.LLVMAddLoopDeletionPass(pm.llpm);
        llvm.LLVMAddLoopUnrollPass(pm.llpm);
        llvm.LLVMAddInstructionCombiningPass(pm.llpm);
        llvm.LLVMAddGVNPass(pm.llpm);
        llvm.LLVMAddMemCpyOptPass(pm.llpm);
        llvm.LLVMAddSCCPPass(pm.llpm);
        llvm.LLVMAddInstructionCombiningPass(pm.llpm);
        llvm.LLVMAddJumpThreadingPass(pm.llpm);
        llvm.LLVMAddCorrelatedValuePropagationPass(pm.llpm);
        llvm.LLVMAddDeadStoreEliminationPass(pm.llpm);
        llvm.LLVMAddAggressiveDCEPass(pm.llpm);
        llvm.LLVMAddCFGSimplificationPass(pm.llpm);
        llvm.LLVMAddStripDeadPrototypesPass(pm.llpm);
        llvm.LLVMAddDeadTypeEliminationPass(pm.llpm);
        llvm.LLVMAddConstantMergePass(pm.llpm);
    }

    if (verify) {
        llvm.LLVMAddVerifierPass(pm.llpm);
    }

    // TODO: Write .s if -c was specified and -save-temps was on.
    if (is_object_or_assembly(ot)) {
        let int LLVMAssemblyFile = 0;
        let int LLVMObjectFile = 1;
        let int LLVMNullFile = 2;
        auto FileType;
        if (ot == output_type_object) {
            FileType = LLVMObjectFile;
        } else {
            FileType = LLVMAssemblyFile;
        }

        // Write optimized bitcode if --save-temps was on.
        if (save_temps) {
            alt (ot) {
                case (output_type_bitcode) { /* nothing to do */ }
                case (_) {
                    auto filename = mk_intermediate_name(output, "opt.bc");
                    llvm.LLVMRunPassManager(pm.llpm, llmod);
                    llvm.LLVMWriteBitcodeToFile(llmod, _str.buf(filename));
                    pm = mk_pass_manager();
                }
            }
        }

        llvm.LLVMRustWriteOutputFile(pm.llpm, llmod,
                                     _str.buf(x86.get_target_triple()),
                                     _str.buf(output),
                                     FileType);
        llvm.LLVMDisposeModule(llmod);
        ret;
    }

    llvm.LLVMRunPassManager(pm.llpm, llmod);

    llvm.LLVMWriteBitcodeToFile(llmod, _str.buf(output));
    llvm.LLVMDisposeModule(llmod);
}

fn decl_no_op_type_glue(ModuleRef llmod, type_names tn) -> ValueRef {
    auto ty = T_fn(vec(T_taskptr(tn), T_ptr(T_i8())), T_void());
    ret decl_fastcall_fn(llmod, abi.no_op_type_glue_name(), ty);
}

fn make_no_op_type_glue(ValueRef fun) {
    auto bb_name = _str.buf("_rust_no_op_type_glue_bb");
    auto llbb = llvm.LLVMAppendBasicBlock(fun, bb_name);
    new_builder(llbb).RetVoid();
}

fn decl_memcpy_glue(ModuleRef llmod) -> ValueRef {
    auto p8 = T_ptr(T_i8());

    auto ty = T_fn(vec(p8, p8, T_int()), T_void());
    ret decl_fastcall_fn(llmod, abi.memcpy_glue_name(), ty);
}

fn make_memcpy_glue(ValueRef fun) {
    // We're not using the LLVM memcpy intrinsic. It appears to call through
    // to the platform memcpy in some cases, which is not terribly safe to run
    // on a rust stack.
    auto initbb = llvm.LLVMAppendBasicBlock(fun, _str.buf("init"));
    auto hdrbb = llvm.LLVMAppendBasicBlock(fun, _str.buf("hdr"));
    auto loopbb = llvm.LLVMAppendBasicBlock(fun, _str.buf("loop"));
    auto endbb = llvm.LLVMAppendBasicBlock(fun, _str.buf("end"));

    auto dst = llvm.LLVMGetParam(fun, 0u);
    auto src = llvm.LLVMGetParam(fun, 1u);
    auto count = llvm.LLVMGetParam(fun, 2u);

    // Init block.
    auto ib = new_builder(initbb);
    auto ip = ib.Alloca(T_int());
    ib.Store(C_int(0), ip);
    ib.Br(hdrbb);

    // Loop-header block
    auto hb = new_builder(hdrbb);
    auto i = hb.Load(ip);
    hb.CondBr(hb.ICmp(lib.llvm.LLVMIntEQ, count, i), endbb, loopbb);

    // Loop-body block
    auto lb = new_builder(loopbb);
    i = lb.Load(ip);
    lb.Store(lb.Load(lb.GEP(src, vec(i))),
             lb.GEP(dst, vec(i)));
    lb.Store(lb.Add(i, C_int(1)), ip);
    lb.Br(hdrbb);

    // End block
    auto eb = new_builder(endbb);
    eb.RetVoid();
}

fn decl_bzero_glue(ModuleRef llmod) -> ValueRef {
    auto p8 = T_ptr(T_i8());

    auto ty = T_fn(vec(p8, T_int()), T_void());
    ret decl_fastcall_fn(llmod, abi.bzero_glue_name(), ty);
}

fn make_bzero_glue(ValueRef fun) -> ValueRef {
    // We're not using the LLVM memset intrinsic. Same as with memcpy.
    auto initbb = llvm.LLVMAppendBasicBlock(fun, _str.buf("init"));
    auto hdrbb = llvm.LLVMAppendBasicBlock(fun, _str.buf("hdr"));
    auto loopbb = llvm.LLVMAppendBasicBlock(fun, _str.buf("loop"));
    auto endbb = llvm.LLVMAppendBasicBlock(fun, _str.buf("end"));

    auto dst = llvm.LLVMGetParam(fun, 0u);
    auto count = llvm.LLVMGetParam(fun, 1u);

    // Init block.
    auto ib = new_builder(initbb);
    auto ip = ib.Alloca(T_int());
    ib.Store(C_int(0), ip);
    ib.Br(hdrbb);

    // Loop-header block
    auto hb = new_builder(hdrbb);
    auto i = hb.Load(ip);
    hb.CondBr(hb.ICmp(lib.llvm.LLVMIntEQ, count, i), endbb, loopbb);

    // Loop-body block
    auto lb = new_builder(loopbb);
    i = lb.Load(ip);
    lb.Store(C_integral(0, T_i8()), lb.GEP(dst, vec(i)));
    lb.Store(lb.Add(i, C_int(1)), ip);
    lb.Br(hdrbb);

    // End block
    auto eb = new_builder(endbb);
    eb.RetVoid();
    ret fun;
}

fn make_vec_append_glue(ModuleRef llmod, type_names tn) -> ValueRef {
    /*
     * Args to vec_append_glue:
     *
     *   0. (Implicit) task ptr
     *
     *   1. Pointer to the tydesc of the vec, so that we can tell if it's gc
     *      mem, and have a tydesc to pass to malloc if we're allocating anew.
     *
     *   2. Pointer to the tydesc of the vec's stored element type, so that
     *      elements can be copied to a newly alloc'ed vec if one must be
     *      created.
     *
     *   3. Dst vec ptr (i.e. ptr to ptr to rust_vec).
     *
     *   4. Src vec (i.e. ptr to rust_vec).
     *
     *   5. Flag indicating whether to skip trailing null on dst.
     *
     */

    auto ty = T_fn(vec(T_taskptr(tn),
                       T_ptr(T_tydesc(tn)),
                       T_ptr(T_tydesc(tn)),
                       T_ptr(T_opaque_vec_ptr()),
                       T_opaque_vec_ptr(), T_bool()),
                   T_void());

    auto llfn = decl_fastcall_fn(llmod, abi.vec_append_glue_name(), ty);
    ret llfn;
}


fn vec_fill(@block_ctxt bcx, ValueRef v) -> ValueRef {
    ret bcx.build.Load(bcx.build.GEP(v, vec(C_int(0),
                                            C_int(abi.vec_elt_fill))));
}

fn put_vec_fill(@block_ctxt bcx, ValueRef v, ValueRef fill) -> ValueRef {
    ret bcx.build.Store(fill,
                        bcx.build.GEP(v,
                                      vec(C_int(0),
                                          C_int(abi.vec_elt_fill))));
}

fn vec_fill_adjusted(@block_ctxt bcx, ValueRef v,
                     ValueRef skipnull) -> ValueRef {
    auto f = bcx.build.Load(bcx.build.GEP(v,
                                          vec(C_int(0),
                                              C_int(abi.vec_elt_fill))));
    ret bcx.build.Select(skipnull, bcx.build.Sub(f, C_int(1)), f);
}

fn vec_p0(@block_ctxt bcx, ValueRef v) -> ValueRef {
    auto p = bcx.build.GEP(v, vec(C_int(0),
                                  C_int(abi.vec_elt_data)));
    ret bcx.build.PointerCast(p, T_ptr(T_i8()));
}


fn vec_p1(@block_ctxt bcx, ValueRef v) -> ValueRef {
    auto len = vec_fill(bcx, v);
    ret bcx.build.GEP(vec_p0(bcx, v), vec(len));
}

fn vec_p1_adjusted(@block_ctxt bcx, ValueRef v,
                   ValueRef skipnull) -> ValueRef {
    auto len = vec_fill_adjusted(bcx, v, skipnull);
    ret bcx.build.GEP(vec_p0(bcx, v), vec(len));
}

fn trans_vec_append_glue(@local_ctxt cx) {

    auto llfn = cx.ccx.glues.vec_append_glue;

    let ValueRef lltaskptr = llvm.LLVMGetParam(llfn, 0u);
    let ValueRef llvec_tydesc = llvm.LLVMGetParam(llfn, 1u);
    let ValueRef llelt_tydesc = llvm.LLVMGetParam(llfn, 2u);
    let ValueRef lldst_vec_ptr = llvm.LLVMGetParam(llfn, 3u);
    let ValueRef llsrc_vec = llvm.LLVMGetParam(llfn, 4u);
    let ValueRef llskipnull = llvm.LLVMGetParam(llfn, 5u);

    let BasicBlockRef llallocas =
        llvm.LLVMAppendBasicBlock(llfn, _str.buf("allocas"));

    auto fcx = @rec(llfn=llfn,
                    lltaskptr=lltaskptr,
                    llenv=C_null(T_ptr(T_nil())),
                    llretptr=C_null(T_ptr(T_nil())),
                    mutable llallocas = llallocas,
                    mutable llself=none[self_vt],
                    mutable lliterbody=none[ValueRef],
                    llargs=new_def_hash[ValueRef](),
                    llobjfields=new_def_hash[ValueRef](),
                    lllocals=new_def_hash[ValueRef](),
                    llupvars=new_def_hash[ValueRef](),
                    mutable lltydescs=_vec.empty[ValueRef](),
                    lcx=cx);

    auto bcx = new_top_block_ctxt(fcx);
    auto lltop = bcx.llbb;

    auto lldst_vec = bcx.build.Load(lldst_vec_ptr);

    // First the dst vec needs to grow to accommodate the src vec.
    // To do this we have to figure out how many bytes to add.

    auto llcopy_dst_ptr = alloca(bcx, T_int());
    auto llnew_vec_res =
        trans_upcall(bcx, "upcall_vec_grow",
                     vec(vp2i(bcx, lldst_vec),
                         vec_fill_adjusted(bcx, llsrc_vec, llskipnull),
                         vp2i(bcx, llcopy_dst_ptr),
                         vp2i(bcx, llvec_tydesc)));

    bcx = llnew_vec_res.bcx;
    auto llnew_vec = vi2p(bcx, llnew_vec_res.val,
                          T_opaque_vec_ptr());
    llvm.LLVMSetValueName(llnew_vec, _str.buf("llnew_vec"));

    auto copy_dst_cx = new_sub_block_ctxt(bcx, "copy new <- dst");
    auto copy_src_cx = new_sub_block_ctxt(bcx, "copy new <- src");

    auto pp0 = alloca(bcx, T_ptr(T_i8()));
    bcx.build.Store(vec_p1_adjusted(bcx, llnew_vec, llskipnull), pp0);
    llvm.LLVMSetValueName(pp0, _str.buf("pp0"));

    bcx.build.CondBr(bcx.build.TruncOrBitCast
                     (bcx.build.Load(llcopy_dst_ptr),
                      T_i1()),
                     copy_dst_cx.llbb,
                     copy_src_cx.llbb);


    fn copy_elts(@block_ctxt cx,
                 ValueRef elt_tydesc,
                 ValueRef dst,
                 ValueRef src,
                 ValueRef n_bytes) -> result {

        auto src_lim = cx.build.GEP(src, vec(n_bytes));
        llvm.LLVMSetValueName(src_lim, _str.buf("src_lim"));

        auto elt_llsz =
            cx.build.Load(cx.build.GEP(elt_tydesc,
                                       vec(C_int(0),
                                           C_int(abi.tydesc_field_size))));
        llvm.LLVMSetValueName(elt_llsz, _str.buf("elt_llsz"));

        fn take_one(ValueRef elt_tydesc,
                    @block_ctxt cx,
                    ValueRef dst, ValueRef src) -> result {
            call_tydesc_glue_full(cx, src,
                                  elt_tydesc,
                                  abi.tydesc_field_take_glue);
            ret res(cx, src);
        }

        auto bcx = iter_sequence_raw(cx, dst, src, src_lim,
                                     elt_llsz, bind take_one(elt_tydesc,
                                                             _, _, _)).bcx;

        ret call_memcpy(bcx, dst, src, n_bytes);
    }

    // Copy any dst elements in, omitting null if doing str.

    auto n_bytes = vec_fill_adjusted(copy_dst_cx, lldst_vec, llskipnull);
    llvm.LLVMSetValueName(n_bytes, _str.buf("n_bytes"));

    copy_dst_cx = copy_elts(copy_dst_cx,
                            llelt_tydesc,
                            vec_p0(copy_dst_cx, llnew_vec),
                            vec_p0(copy_dst_cx, lldst_vec),
                            n_bytes).bcx;

    put_vec_fill(copy_dst_cx, llnew_vec, vec_fill(copy_dst_cx, lldst_vec));

    copy_dst_cx.build.Store(vec_p1_adjusted(copy_dst_cx, llnew_vec,
                                            llskipnull), pp0);
    copy_dst_cx.build.Br(copy_src_cx.llbb);


    // Copy any src elements in, carrying along null if doing str.
    n_bytes = vec_fill(copy_src_cx, llsrc_vec);
    copy_src_cx = copy_elts(copy_src_cx,
                            llelt_tydesc,
                            copy_src_cx.build.Load(pp0),
                            vec_p0(copy_src_cx, llsrc_vec),
                            n_bytes).bcx;

    put_vec_fill(copy_src_cx, llnew_vec,
                 copy_src_cx.build.Add(vec_fill_adjusted(copy_src_cx,
                                                         llnew_vec,
                                                         llskipnull),
                                        n_bytes));

    // Write new_vec back through the alias we were given.
    copy_src_cx.build.Store(llnew_vec, lldst_vec_ptr);
    copy_src_cx.build.RetVoid();

    // Tie up the llallocas -> lltop edge.
    new_builder(fcx.llallocas).Br(lltop);
}


fn make_glues(ModuleRef llmod, type_names tn) -> @glue_fns {
    ret @rec(activate_glue = decl_glue(llmod, tn, abi.activate_glue_name()),
             yield_glue = decl_glue(llmod, tn, abi.yield_glue_name()),
             /*
              * Note: the signature passed to decl_cdecl_fn here looks unusual
              * because it is. It corresponds neither to a native signature
              * nor a normal rust-ABI signature. In fact it is a fake
              * signature, that exists solely to acquire the task pointer as
              * an argument to the upcall. It so happens that the runtime sets
              * up the task pointer as the sole incoming argument to the frame
              * that we return into when returning to the exit task glue. So
              * this is the signature required to retrieve it.
              */
             exit_task_glue = decl_cdecl_fn(llmod, abi.exit_task_glue_name(),
                                            T_fn(vec(T_int(),
                                                     T_int(),
                                                     T_int(),
                                                     T_int(),
                                                     T_taskptr(tn)),
                                                 T_void())),

             native_glues_rust =
             _vec.init_fn[ValueRef](bind decl_native_glue(llmod, tn, true,
                                                          _),
                                    abi.n_native_glues + 1 as uint),
             native_glues_cdecl =
             _vec.init_fn[ValueRef](bind decl_native_glue(llmod, tn, false,
                                                          _),
                                    abi.n_native_glues + 1 as uint),
             no_op_type_glue = decl_no_op_type_glue(llmod, tn),
             memcpy_glue = decl_memcpy_glue(llmod),
             bzero_glue = decl_bzero_glue(llmod),
             vec_append_glue = make_vec_append_glue(llmod, tn));
}

fn make_common_glue(str output, bool optimize, bool verify, bool save_temps,
                    output_type ot) {
    // FIXME: part of this is repetitive and is probably a good idea
    // to autogen it, but things like the memcpy implementation are not
    // and it might be better to just check in a .ll file.
    auto llmod =
        llvm.LLVMModuleCreateWithNameInContext(_str.buf("rust_out"),
                                               llvm.LLVMGetGlobalContext());

    llvm.LLVMSetDataLayout(llmod, _str.buf(x86.get_data_layout()));
    llvm.LLVMSetTarget(llmod, _str.buf(x86.get_target_triple()));
    auto td = mk_target_data(x86.get_data_layout());
    auto tn = mk_type_names();
    let ValueRef crate_ptr =
        llvm.LLVMAddGlobal(llmod, T_crate(tn), _str.buf("rust_crate"));

    auto intrinsics = declare_intrinsics(llmod);

    llvm.LLVMSetModuleInlineAsm(llmod, _str.buf(x86.get_module_asm()));

    auto glues = make_glues(llmod, tn);
    create_crate_constant(crate_ptr, glues);
    make_memcpy_glue(glues.memcpy_glue);
    make_bzero_glue(glues.bzero_glue);

    trans_exit_task_glue(glues, new_str_hash[ValueRef](), tn, llmod);

    run_passes(llmod, optimize, verify, save_temps, output, ot);
}

fn create_module_map(@crate_ctxt ccx) -> ValueRef {
    auto elttype = T_struct(vec(T_int(), T_int()));
    auto maptype = T_array(elttype, ccx.module_data.size() + 1u);
    auto map = llvm.LLVMAddGlobal(ccx.llmod, maptype,
                                  _str.buf("_rust_mod_map"));
    llvm.LLVMSetLinkage(map, lib.llvm.LLVMInternalLinkage as llvm.Linkage);
    let vec[ValueRef] elts = vec();
    for each (@tup(str, ValueRef) item in ccx.module_data.items()) {
        auto elt = C_struct(vec(p2i(C_cstr(ccx, item._0)), p2i(item._1)));
        _vec.push[ValueRef](elts, elt);
    }
    auto term = C_struct(vec(C_int(0), C_int(0)));
    _vec.push[ValueRef](elts, term);
    llvm.LLVMSetInitializer(map, C_array(elttype, elts));
    ret map;
}

fn crate_name(@crate_ctxt ccx, str deflt) -> str {
    for (@ast.meta_item item in ccx.sess.get_metadata()) {
        if (_str.eq(item.node.name, "name")) {
            ret item.node.value;
        }
    }
    ret deflt;
}

// FIXME use hashed metadata instead of crate names once we have that
fn create_crate_map(@crate_ctxt ccx) -> ValueRef {
    let vec[ValueRef] subcrates = vec();
    auto i = 1;
    while (ccx.sess.has_external_crate(i)) {
        auto name = ccx.sess.get_external_crate(i).name;
        auto cr = llvm.LLVMAddGlobal(ccx.llmod, T_int(),
                                     _str.buf("_rust_crate_map_" + name));
        _vec.push[ValueRef](subcrates, p2i(cr));
        i += 1;
    }
    _vec.push[ValueRef](subcrates, C_int(0));
    auto sym_name = "_rust_crate_map_" + crate_name(ccx, "__none__");
    auto arrtype = T_array(T_int(), _vec.len[ValueRef](subcrates));
    auto maptype = T_struct(vec(T_int(), arrtype));
    auto map = llvm.LLVMAddGlobal(ccx.llmod, maptype, _str.buf(sym_name));
    llvm.LLVMSetLinkage(map, lib.llvm.LLVMExternalLinkage as llvm.Linkage);
    llvm.LLVMSetInitializer(map, C_struct(vec(p2i(create_module_map(ccx)),
                                              C_array(T_int(), subcrates))));
    ret map;
}

fn trans_crate(session.session sess, @ast.crate crate, ty.ctxt tcx,
               &ty.type_cache type_cache, str output, bool shared,
               bool optimize, bool verify, bool save_temps, output_type ot) {
    auto llmod =
        llvm.LLVMModuleCreateWithNameInContext(_str.buf("rust_out"),
                                               llvm.LLVMGetGlobalContext());

    llvm.LLVMSetDataLayout(llmod, _str.buf(x86.get_data_layout()));
    llvm.LLVMSetTarget(llmod, _str.buf(x86.get_target_triple()));
    auto td = mk_target_data(x86.get_data_layout());
    auto tn = mk_type_names();
    let ValueRef crate_ptr =
        llvm.LLVMAddGlobal(llmod, T_crate(tn), _str.buf("rust_crate"));

    auto intrinsics = declare_intrinsics(llmod);

    auto glues = make_glues(llmod, tn);
    auto hasher = ty.hash_ty;
    auto eqer = ty.eq_ty;
    auto tag_sizes = map.mk_hashmap[ty.t,uint](hasher, eqer);
    auto tydescs = map.mk_hashmap[ty.t,@tydesc_info](hasher, eqer);
    auto lltypes = map.mk_hashmap[ty.t,TypeRef](hasher, eqer);
    auto sha1s = map.mk_hashmap[ty.t,str](hasher, eqer);
    auto abbrevs = map.mk_hashmap[ty.t,metadata.ty_abbrev](hasher, eqer);

    auto ccx = @rec(sess = sess,
                    llmod = llmod,
                    td = td,
                    tn = tn,
                    crate_ptr = crate_ptr,
                    externs = new_str_hash[ValueRef](),
                    intrinsics = intrinsics,
                    item_ids = new_def_hash[ValueRef](),
                    items = new_def_hash[@ast.item](),
                    native_items = new_def_hash[@ast.native_item](),
                    type_cache = type_cache,
                    item_symbols = new_def_hash[str](),
                    tag_sizes = tag_sizes,
                    discrims = new_def_hash[ValueRef](),
                    discrim_symbols = new_def_hash[str](),
                    fn_pairs = new_def_hash[ValueRef](),
                    consts = new_def_hash[ValueRef](),
                    obj_methods = new_def_hash[()](),
                    tydescs = tydescs,
                    module_data = new_str_hash[ValueRef](),
                    lltypes = lltypes,
                    glues = glues,
                    names = namegen(0),
                    sha = std.sha1.mk_sha1(),
                    type_sha1s = sha1s,
                    type_abbrevs = abbrevs,
                    tcx = tcx);
    auto cx = new_local_ctxt(ccx);

    create_typedefs(ccx);

    collect_items(ccx, crate);
    collect_tag_ctors(ccx, crate);
    trans_constants(ccx, crate);
    trans_mod(cx, crate.node.module);
    trans_vec_append_glue(cx);
    auto crate_map = create_crate_map(ccx);
    if (!shared) {
        trans_main_fn(cx, crate_ptr, crate_map);
    }

    // Translate the metadata.
    middle.metadata.write_metadata(cx.ccx, crate);

    run_passes(llmod, optimize, verify, save_temps, output, ot);
}

//
// Local Variables:
// mode: rust
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
// End:
//