/* * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, * CA 95054 USA or visit www.sun.com if you need additional information or * have any questions. * */ // Portions of code courtesy of Clifford Click // Optimization - Graph Style #include "incls/_precompiled.incl" #include "incls/_memnode.cpp.incl" static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem, const TypePtr *tp, const TypePtr *adr_check, outputStream *st); //============================================================================= uint MemNode::size_of() const { return sizeof(*this); } const TypePtr *MemNode::adr_type() const { Node* adr = in(Address); const TypePtr* cross_check = NULL; DEBUG_ONLY(cross_check = _adr_type); return calculate_adr_type(adr->bottom_type(), cross_check); } #ifndef PRODUCT void MemNode::dump_spec(outputStream *st) const { if (in(Address) == NULL) return; // node is dead #ifndef ASSERT // fake the missing field const TypePtr* _adr_type = NULL; if (in(Address) != NULL) _adr_type = in(Address)->bottom_type()->isa_ptr(); #endif dump_adr_type(this, _adr_type, st); Compile* C = Compile::current(); if( C->alias_type(_adr_type)->is_volatile() ) st->print(" Volatile!"); } void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) { st->print(" @"); if (adr_type == NULL) { st->print("NULL"); } else { adr_type->dump_on(st); Compile* C = Compile::current(); Compile::AliasType* atp = NULL; if (C->have_alias_type(adr_type)) atp = C->alias_type(adr_type); if (atp == NULL) st->print(", idx=?\?;"); else if (atp->index() == Compile::AliasIdxBot) st->print(", idx=Bot;"); else if (atp->index() == Compile::AliasIdxTop) st->print(", idx=Top;"); else if (atp->index() == Compile::AliasIdxRaw) st->print(", idx=Raw;"); else { ciField* field = atp->field(); if (field) { st->print(", name="); field->print_name_on(st); } st->print(", idx=%d;", atp->index()); } } } extern void print_alias_types(); #endif Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypePtr *t_adr, PhaseGVN *phase) { const TypeOopPtr *tinst = t_adr->isa_oopptr(); if (tinst == NULL || !tinst->is_instance_field()) return mchain; // don't try to optimize non-instance types uint instance_id = tinst->instance_id(); Node *prev = NULL; Node *result = mchain; while (prev != result) { prev = result; // skip over a call which does not affect this memory slice if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) { Node *proj_in = result->in(0); if (proj_in->is_Call()) { CallNode *call = proj_in->as_Call(); if (!call->may_modify(t_adr, phase)) { result = call->in(TypeFunc::Memory); } } else if (proj_in->is_Initialize()) { AllocateNode* alloc = proj_in->as_Initialize()->allocation(); // Stop if this is the initialization for the object instance which // which contains this memory slice, otherwise skip over it. if (alloc != NULL && alloc->_idx != instance_id) { result = proj_in->in(TypeFunc::Memory); } } else if (proj_in->is_MemBar()) { result = proj_in->in(TypeFunc::Memory); } } else if (result->is_MergeMem()) { result = step_through_mergemem(phase, result->as_MergeMem(), t_adr, NULL, tty); } } return result; } Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, PhaseGVN *phase) { const TypeOopPtr *t_oop = t_adr->isa_oopptr(); bool is_instance = (t_oop != NULL) && t_oop->is_instance_field(); PhaseIterGVN *igvn = phase->is_IterGVN(); Node *result = mchain; result = optimize_simple_memory_chain(result, t_adr, phase); if (is_instance && igvn != NULL && result->is_Phi()) { PhiNode *mphi = result->as_Phi(); assert(mphi->bottom_type() == Type::MEMORY, "memory phi required"); const TypePtr *t = mphi->adr_type(); if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM) { // clone the Phi with our address type result = mphi->split_out_instance(t_adr, igvn); } else { assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain"); } } return result; } static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem, const TypePtr *tp, const TypePtr *adr_check, outputStream *st) { uint alias_idx = phase->C->get_alias_index(tp); Node *mem = mmem; #ifdef ASSERT { // Check that current type is consistent with the alias index used during graph construction assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx"); bool consistent = adr_check == NULL || adr_check->empty() || phase->C->must_alias(adr_check, alias_idx ); // Sometimes dead array references collapse to a[-1], a[-2], or a[-3] if( !consistent && adr_check != NULL && !adr_check->empty() && tp->isa_aryptr() && tp->offset() == Type::OffsetBot && adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot && ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() || adr_check->offset() == oopDesc::klass_offset_in_bytes() || adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) { // don't assert if it is dead code. consistent = true; } if( !consistent ) { st->print("alias_idx==%d, adr_check==", alias_idx); if( adr_check == NULL ) { st->print("NULL"); } else { adr_check->dump(); } st->cr(); print_alias_types(); assert(consistent, "adr_check must match alias idx"); } } #endif // TypeInstPtr::NOTNULL+any is an OOP with unknown offset - generally // means an array I have not precisely typed yet. Do not do any // alias stuff with it any time soon. const TypeOopPtr *tinst = tp->isa_oopptr(); if( tp->base() != Type::AnyPtr && !(tinst && tinst->klass()->is_java_lang_Object() && tinst->offset() == Type::OffsetBot) ) { // compress paths and change unreachable cycles to TOP // If not, we can update the input infinitely along a MergeMem cycle // Equivalent code in PhiNode::Ideal Node* m = phase->transform(mmem); // If tranformed to a MergeMem, get the desired slice // Otherwise the returned node represents memory for every slice mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m; // Update input if it is progress over what we have now } return mem; } //--------------------------Ideal_common--------------------------------------- // Look for degenerate control and memory inputs. Bypass MergeMem inputs. // Unhook non-raw memories from complete (macro-expanded) initializations. Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) { // If our control input is a dead region, kill all below the region Node *ctl = in(MemNode::Control); if (ctl && remove_dead_region(phase, can_reshape)) return this; // Ignore if memory is dead, or self-loop Node *mem = in(MemNode::Memory); if( phase->type( mem ) == Type::TOP ) return NodeSentinel; // caller will return NULL assert( mem != this, "dead loop in MemNode::Ideal" ); Node *address = in(MemNode::Address); const Type *t_adr = phase->type( address ); if( t_adr == Type::TOP ) return NodeSentinel; // caller will return NULL // Avoid independent memory operations Node* old_mem = mem; // The code which unhooks non-raw memories from complete (macro-expanded) // initializations was removed. After macro-expansion all stores catched // by Initialize node became raw stores and there is no information // which memory slices they modify. So it is unsafe to move any memory // operation above these stores. Also in most cases hooked non-raw memories // were already unhooked by using information from detect_ptr_independence() // and find_previous_store(). if (mem->is_MergeMem()) { MergeMemNode* mmem = mem->as_MergeMem(); const TypePtr *tp = t_adr->is_ptr(); mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty); } if (mem != old_mem) { set_req(MemNode::Memory, mem); return this; } // let the subclass continue analyzing... return NULL; } // Helper function for proving some simple control dominations. // Attempt to prove that all control inputs of 'dom' dominate 'sub'. // Already assumes that 'dom' is available at 'sub', and that 'sub' // is not a constant (dominated by the method's StartNode). // Used by MemNode::find_previous_store to prove that the // control input of a memory operation predates (dominates) // an allocation it wants to look past. bool MemNode::all_controls_dominate(Node* dom, Node* sub) { if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top()) return false; // Conservative answer for dead code // Check 'dom'. dom = dom->find_exact_control(dom); if (dom == NULL || dom->is_top()) return false; // Conservative answer for dead code if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub) return true; // 'dom' dominates 'sub' if its control edge and control edges // of all its inputs dominate or equal to sub's control edge. // Currently 'sub' is either Allocate, Initialize or Start nodes. assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start(), "expecting only these nodes"); // Get control edge of 'sub'. sub = sub->find_exact_control(sub->in(0)); if (sub == NULL || sub->is_top()) return false; // Conservative answer for dead code assert(sub->is_CFG(), "expecting control"); if (sub == dom) return true; if (sub->is_Start() || sub->is_Root()) return false; { // Check all control edges of 'dom'. ResourceMark rm; Arena* arena = Thread::current()->resource_area(); Node_List nlist(arena); Unique_Node_List dom_list(arena); dom_list.push(dom); bool only_dominating_controls = false; for (uint next = 0; next < dom_list.size(); next++) { Node* n = dom_list.at(next); if (!n->is_CFG() && n->pinned()) { // Check only own control edge for pinned non-control nodes. n = n->find_exact_control(n->in(0)); if (n == NULL || n->is_top()) return false; // Conservative answer for dead code assert(n->is_CFG(), "expecting control"); } if (n->is_Con() || n->is_Start() || n->is_Root()) { only_dominating_controls = true; } else if (n->is_CFG()) { if (n->dominates(sub, nlist)) only_dominating_controls = true; else return false; } else { // First, own control edge. Node* m = n->find_exact_control(n->in(0)); if (m != NULL) { if (m->is_top()) return false; // Conservative answer for dead code dom_list.push(m); } // Now, the rest of edges. uint cnt = n->req(); for (uint i = 1; i < cnt; i++) { m = n->find_exact_control(n->in(i)); if (m == NULL || m->is_top()) continue; dom_list.push(m); } } } return only_dominating_controls; } } //---------------------detect_ptr_independence--------------------------------- // Used by MemNode::find_previous_store to prove that two base // pointers are never equal. // The pointers are accompanied by their associated allocations, // if any, which have been previously discovered by the caller. bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1, Node* p2, AllocateNode* a2, PhaseTransform* phase) { // Attempt to prove that these two pointers cannot be aliased. // They may both manifestly be allocations, and they should differ. // Or, if they are not both allocations, they can be distinct constants. // Otherwise, one is an allocation and the other a pre-existing value. if (a1 == NULL && a2 == NULL) { // neither an allocation return (p1 != p2) && p1->is_Con() && p2->is_Con(); } else if (a1 != NULL && a2 != NULL) { // both allocations return (a1 != a2); } else if (a1 != NULL) { // one allocation a1 // (Note: p2->is_Con implies p2->in(0)->is_Root, which dominates.) return all_controls_dominate(p2, a1); } else { //(a2 != NULL) // one allocation a2 return all_controls_dominate(p1, a2); } return false; } // The logic for reordering loads and stores uses four steps: // (a) Walk carefully past stores and initializations which we // can prove are independent of this load. // (b) Observe that the next memory state makes an exact match // with self (load or store), and locate the relevant store. // (c) Ensure that, if we were to wire self directly to the store, // the optimizer would fold it up somehow. // (d) Do the rewiring, and return, depending on some other part of // the optimizer to fold up the load. // This routine handles steps (a) and (b). Steps (c) and (d) are // specific to loads and stores, so they are handled by the callers. // (Currently, only LoadNode::Ideal has steps (c), (d). More later.) // Node* MemNode::find_previous_store(PhaseTransform* phase) { Node* ctrl = in(MemNode::Control); Node* adr = in(MemNode::Address); intptr_t offset = 0; Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset); AllocateNode* alloc = AllocateNode::Ideal_allocation(base, phase); if (offset == Type::OffsetBot) return NULL; // cannot unalias unless there are precise offsets const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr(); intptr_t size_in_bytes = memory_size(); Node* mem = in(MemNode::Memory); // start searching here... int cnt = 50; // Cycle limiter for (;;) { // While we can dance past unrelated stores... if (--cnt < 0) break; // Caught in cycle or a complicated dance? if (mem->is_Store()) { Node* st_adr = mem->in(MemNode::Address); intptr_t st_offset = 0; Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset); if (st_base == NULL) break; // inscrutable pointer if (st_offset != offset && st_offset != Type::OffsetBot) { const int MAX_STORE = BytesPerLong; if (st_offset >= offset + size_in_bytes || st_offset <= offset - MAX_STORE || st_offset <= offset - mem->as_Store()->memory_size()) { // Success: The offsets are provably independent. // (You may ask, why not just test st_offset != offset and be done? // The answer is that stores of different sizes can co-exist // in the same sequence of RawMem effects. We sometimes initialize // a whole 'tile' of array elements with a single jint or jlong.) mem = mem->in(MemNode::Memory); continue; // (a) advance through independent store memory } } if (st_base != base && detect_ptr_independence(base, alloc, st_base, AllocateNode::Ideal_allocation(st_base, phase), phase)) { // Success: The bases are provably independent. mem = mem->in(MemNode::Memory); continue; // (a) advance through independent store memory } // (b) At this point, if the bases or offsets do not agree, we lose, // since we have not managed to prove 'this' and 'mem' independent. if (st_base == base && st_offset == offset) { return mem; // let caller handle steps (c), (d) } } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) { InitializeNode* st_init = mem->in(0)->as_Initialize(); AllocateNode* st_alloc = st_init->allocation(); if (st_alloc == NULL) break; // something degenerated bool known_identical = false; bool known_independent = false; if (alloc == st_alloc) known_identical = true; else if (alloc != NULL) known_independent = true; else if (all_controls_dominate(this, st_alloc)) known_independent = true; if (known_independent) { // The bases are provably independent: Either they are // manifestly distinct allocations, or else the control // of this load dominates the store's allocation. int alias_idx = phase->C->get_alias_index(adr_type()); if (alias_idx == Compile::AliasIdxRaw) { mem = st_alloc->in(TypeFunc::Memory); } else { mem = st_init->memory(alias_idx); } continue; // (a) advance through independent store memory } // (b) at this point, if we are not looking at a store initializing // the same allocation we are loading from, we lose. if (known_identical) { // From caller, can_see_stored_value will consult find_captured_store. return mem; // let caller handle steps (c), (d) } } else if (addr_t != NULL && addr_t->is_instance_field()) { // Can't use optimize_simple_memory_chain() since it needs PhaseGVN. if (mem->is_Proj() && mem->in(0)->is_Call()) { CallNode *call = mem->in(0)->as_Call(); if (!call->may_modify(addr_t, phase)) { mem = call->in(TypeFunc::Memory); continue; // (a) advance through independent call memory } } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) { mem = mem->in(0)->in(TypeFunc::Memory); continue; // (a) advance through independent MemBar memory } else if (mem->is_MergeMem()) { int alias_idx = phase->C->get_alias_index(adr_type()); mem = mem->as_MergeMem()->memory_at(alias_idx); continue; // (a) advance through independent MergeMem memory } } // Unless there is an explicit 'continue', we must bail out here, // because 'mem' is an inscrutable memory state (e.g., a call). break; } return NULL; // bail out } //----------------------calculate_adr_type------------------------------------- // Helper function. Notices when the given type of address hits top or bottom. // Also, asserts a cross-check of the type against the expected address type. const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) { if (t == Type::TOP) return NULL; // does not touch memory any more? #ifdef PRODUCT cross_check = NULL; #else if (!VerifyAliases || is_error_reported() || Node::in_dump()) cross_check = NULL; #endif const TypePtr* tp = t->isa_ptr(); if (tp == NULL) { assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide"); return TypePtr::BOTTOM; // touches lots of memory } else { #ifdef ASSERT // %%%% [phh] We don't check the alias index if cross_check is // TypeRawPtr::BOTTOM. Needs to be investigated. if (cross_check != NULL && cross_check != TypePtr::BOTTOM && cross_check != TypeRawPtr::BOTTOM) { // Recheck the alias index, to see if it has changed (due to a bug). Compile* C = Compile::current(); assert(C->get_alias_index(cross_check) == C->get_alias_index(tp), "must stay in the original alias category"); // The type of the address must be contained in the adr_type, // disregarding "null"-ness. // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.) const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr(); assert(cross_check->meet(tp_notnull) == cross_check, "real address must not escape from expected memory type"); } #endif return tp; } } //------------------------adr_phi_is_loop_invariant---------------------------- // A helper function for Ideal_DU_postCCP to check if a Phi in a counted // loop is loop invariant. Make a quick traversal of Phi and associated // CastPP nodes, looking to see if they are a closed group within the loop. bool MemNode::adr_phi_is_loop_invariant(Node* adr_phi, Node* cast) { // The idea is that the phi-nest must boil down to only CastPP nodes // with the same data. This implies that any path into the loop already // includes such a CastPP, and so the original cast, whatever its input, // must be covered by an equivalent cast, with an earlier control input. ResourceMark rm; // The loop entry input of the phi should be the unique dominating // node for every Phi/CastPP in the loop. Unique_Node_List closure; closure.push(adr_phi->in(LoopNode::EntryControl)); // Add the phi node and the cast to the worklist. Unique_Node_List worklist; worklist.push(adr_phi); if( cast != NULL ){ if( !cast->is_ConstraintCast() ) return false; worklist.push(cast); } // Begin recursive walk of phi nodes. while( worklist.size() ){ // Take a node off the worklist Node *n = worklist.pop(); if( !closure.member(n) ){ // Add it to the closure. closure.push(n); // Make a sanity check to ensure we don't waste too much time here. if( closure.size() > 20) return false; // This node is OK if: // - it is a cast of an identical value // - or it is a phi node (then we add its inputs to the worklist) // Otherwise, the node is not OK, and we presume the cast is not invariant if( n->is_ConstraintCast() ){ worklist.push(n->in(1)); } else if( n->is_Phi() ) { for( uint i = 1; i < n->req(); i++ ) { worklist.push(n->in(i)); } } else { return false; } } } // Quit when the worklist is empty, and we've found no offending nodes. return true; } //------------------------------Ideal_DU_postCCP------------------------------- // Find any cast-away of null-ness and keep its control. Null cast-aways are // going away in this pass and we need to make this memory op depend on the // gating null check. // I tried to leave the CastPP's in. This makes the graph more accurate in // some sense; we get to keep around the knowledge that an oop is not-null // after some test. Alas, the CastPP's interfere with GVN (some values are // the regular oop, some are the CastPP of the oop, all merge at Phi's which // cannot collapse, etc). This cost us 10% on SpecJVM, even when I removed // some of the more trivial cases in the optimizer. Removing more useless // Phi's started allowing Loads to illegally float above null checks. I gave // up on this approach. CNC 10/20/2000 Node *MemNode::Ideal_DU_postCCP( PhaseCCP *ccp ) { Node *ctr = in(MemNode::Control); Node *mem = in(MemNode::Memory); Node *adr = in(MemNode::Address); Node *skipped_cast = NULL; // Need a null check? Regular static accesses do not because they are // from constant addresses. Array ops are gated by the range check (which // always includes a NULL check). Just check field ops. if( !ctr ) { // Scan upwards for the highest location we can place this memory op. while( true ) { switch( adr->Opcode() ) { case Op_AddP: // No change to NULL-ness, so peek thru AddP's adr = adr->in(AddPNode::Base); continue; case Op_DecodeN: // No change to NULL-ness, so peek thru adr = adr->in(1); continue; case Op_CastPP: // If the CastPP is useless, just peek on through it. if( ccp->type(adr) == ccp->type(adr->in(1)) ) { // Remember the cast that we've peeked though. If we peek // through more than one, then we end up remembering the highest // one, that is, if in a loop, the one closest to the top. skipped_cast = adr; adr = adr->in(1); continue; } // CastPP is going away in this pass! We need this memory op to be // control-dependent on the test that is guarding the CastPP. ccp->hash_delete(this); set_req(MemNode::Control, adr->in(0)); ccp->hash_insert(this); return this; case Op_Phi: // Attempt to float above a Phi to some dominating point. if (adr->in(0) != NULL && adr->in(0)->is_CountedLoop()) { // If we've already peeked through a Cast (which could have set the // control), we can't float above a Phi, because the skipped Cast // may not be loop invariant. if (adr_phi_is_loop_invariant(adr, skipped_cast)) { adr = adr->in(1); continue; } } // Intentional fallthrough! // No obvious dominating point. The mem op is pinned below the Phi // by the Phi itself. If the Phi goes away (no true value is merged) // then the mem op can float, but not indefinitely. It must be pinned // behind the controls leading to the Phi. case Op_CheckCastPP: // These usually stick around to change address type, however a // useless one can be elided and we still need to pick up a control edge if (adr->in(0) == NULL) { // This CheckCastPP node has NO control and is likely useless. But we // need check further up the ancestor chain for a control input to keep // the node in place. 4959717. skipped_cast = adr; adr = adr->in(1); continue; } ccp->hash_delete(this); set_req(MemNode::Control, adr->in(0)); ccp->hash_insert(this); return this; // List of "safe" opcodes; those that implicitly block the memory // op below any null check. case Op_CastX2P: // no null checks on native pointers case Op_Parm: // 'this' pointer is not null case Op_LoadP: // Loading from within a klass case Op_LoadN: // Loading from within a klass case Op_LoadKlass: // Loading from within a klass case Op_ConP: // Loading from a klass case Op_CreateEx: // Sucking up the guts of an exception oop case Op_Con: // Reading from TLS case Op_CMoveP: // CMoveP is pinned break; // No progress case Op_Proj: // Direct call to an allocation routine case Op_SCMemProj: // Memory state from store conditional ops #ifdef ASSERT { assert(adr->as_Proj()->_con == TypeFunc::Parms, "must be return value"); const Node* call = adr->in(0); if (call->is_CallStaticJava()) { const CallStaticJavaNode* call_java = call->as_CallStaticJava(); const TypeTuple *r = call_java->tf()->range(); assert(r->cnt() > TypeFunc::Parms, "must return value"); const Type* ret_type = r->field_at(TypeFunc::Parms); assert(ret_type && ret_type->isa_ptr(), "must return pointer"); // We further presume that this is one of // new_instance_Java, new_array_Java, or // the like, but do not assert for this. } else if (call->is_Allocate()) { // similar case to new_instance_Java, etc. } else if (!call->is_CallLeaf()) { // Projections from fetch_oop (OSR) are allowed as well. ShouldNotReachHere(); } } #endif break; default: ShouldNotReachHere(); } break; } } return NULL; // No progress } //============================================================================= uint LoadNode::size_of() const { return sizeof(*this); } uint LoadNode::cmp( const Node &n ) const { return !Type::cmp( _type, ((LoadNode&)n)._type ); } const Type *LoadNode::bottom_type() const { return _type; } uint LoadNode::ideal_reg() const { return Matcher::base2reg[_type->base()]; } #ifndef PRODUCT void LoadNode::dump_spec(outputStream *st) const { MemNode::dump_spec(st); if( !Verbose && !WizardMode ) { // standard dump does this in Verbose and WizardMode st->print(" #"); _type->dump_on(st); } } #endif //----------------------------LoadNode::make----------------------------------- // Polymorphic factory method: Node *LoadNode::make( PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt ) { Compile* C = gvn.C; // sanity check the alias category against the created node type assert(!(adr_type->isa_oopptr() && adr_type->offset() == oopDesc::klass_offset_in_bytes()), "use LoadKlassNode instead"); assert(!(adr_type->isa_aryptr() && adr_type->offset() == arrayOopDesc::length_offset_in_bytes()), "use LoadRangeNode instead"); switch (bt) { case T_BOOLEAN: case T_BYTE: return new (C, 3) LoadBNode(ctl, mem, adr, adr_type, rt->is_int() ); case T_INT: return new (C, 3) LoadINode(ctl, mem, adr, adr_type, rt->is_int() ); case T_CHAR: return new (C, 3) LoadCNode(ctl, mem, adr, adr_type, rt->is_int() ); case T_SHORT: return new (C, 3) LoadSNode(ctl, mem, adr, adr_type, rt->is_int() ); case T_LONG: return new (C, 3) LoadLNode(ctl, mem, adr, adr_type, rt->is_long() ); case T_FLOAT: return new (C, 3) LoadFNode(ctl, mem, adr, adr_type, rt ); case T_DOUBLE: return new (C, 3) LoadDNode(ctl, mem, adr, adr_type, rt ); case T_ADDRESS: return new (C, 3) LoadPNode(ctl, mem, adr, adr_type, rt->is_ptr() ); case T_OBJECT: #ifdef _LP64 if (adr->bottom_type()->is_narrow()) { const TypeNarrowOop* narrowtype; if (rt->isa_narrowoop()) { narrowtype = rt->is_narrowoop(); } else { narrowtype = rt->is_oopptr()->make_narrowoop(); } Node* load = gvn.transform(new (C, 3) LoadNNode(ctl, mem, adr, adr_type, narrowtype)); return DecodeNNode::decode(&gvn, load); } else #endif { assert(!adr->bottom_type()->is_narrow(), "should have got back a narrow oop"); return new (C, 3) LoadPNode(ctl, mem, adr, adr_type, rt->is_oopptr()); } } ShouldNotReachHere(); return (LoadNode*)NULL; } LoadLNode* LoadLNode::make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt) { bool require_atomic = true; return new (C, 3) LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), require_atomic); } //------------------------------hash------------------------------------------- uint LoadNode::hash() const { // unroll addition of interesting fields return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address); } //---------------------------can_see_stored_value------------------------------ // This routine exists to make sure this set of tests is done the same // everywhere. We need to make a coordinated change: first LoadNode::Ideal // will change the graph shape in a way which makes memory alive twice at the // same time (uses the Oracle model of aliasing), then some // LoadXNode::Identity will fold things back to the equivalence-class model // of aliasing. Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const { Node* ld_adr = in(MemNode::Address); const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr(); Compile::AliasType* atp = tp != NULL ? phase->C->alias_type(tp) : NULL; if (EliminateAutoBox && atp != NULL && atp->index() >= Compile::AliasIdxRaw && atp->field() != NULL && !atp->field()->is_volatile()) { uint alias_idx = atp->index(); bool final = atp->field()->is_final(); Node* result = NULL; Node* current = st; // Skip through chains of MemBarNodes checking the MergeMems for // new states for the slice of this load. Stop once any other // kind of node is encountered. Loads from final memory can skip // through any kind of MemBar but normal loads shouldn't skip // through MemBarAcquire since the could allow them to move out of // a synchronized region. while (current->is_Proj()) { int opc = current->in(0)->Opcode(); if ((final && opc == Op_MemBarAcquire) || opc == Op_MemBarRelease || opc == Op_MemBarCPUOrder) { Node* mem = current->in(0)->in(TypeFunc::Memory); if (mem->is_MergeMem()) { MergeMemNode* merge = mem->as_MergeMem(); Node* new_st = merge->memory_at(alias_idx); if (new_st == merge->base_memory()) { // Keep searching current = merge->base_memory(); continue; } // Save the new memory state for the slice and fall through // to exit. result = new_st; } } break; } if (result != NULL) { st = result; } } // Loop around twice in the case Load -> Initialize -> Store. // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.) for (int trip = 0; trip <= 1; trip++) { if (st->is_Store()) { Node* st_adr = st->in(MemNode::Address); if (!phase->eqv(st_adr, ld_adr)) { // Try harder before giving up... Match raw and non-raw pointers. intptr_t st_off = 0; AllocateNode* alloc = AllocateNode::Ideal_allocation(st_adr, phase, st_off); if (alloc == NULL) return NULL; intptr_t ld_off = 0; AllocateNode* allo2 = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off); if (alloc != allo2) return NULL; if (ld_off != st_off) return NULL; // At this point we have proven something like this setup: // A = Allocate(...) // L = LoadQ(, AddP(CastPP(, A.Parm),, #Off)) // S = StoreQ(, AddP(, A.Parm , #Off), V) // (Actually, we haven't yet proven the Q's are the same.) // In other words, we are loading from a casted version of // the same pointer-and-offset that we stored to. // Thus, we are able to replace L by V. } // Now prove that we have a LoadQ matched to a StoreQ, for some Q. if (store_Opcode() != st->Opcode()) return NULL; return st->in(MemNode::ValueIn); } intptr_t offset = 0; // scratch // A load from a freshly-created object always returns zero. // (This can happen after LoadNode::Ideal resets the load's memory input // to find_captured_store, which returned InitializeNode::zero_memory.) if (st->is_Proj() && st->in(0)->is_Allocate() && st->in(0) == AllocateNode::Ideal_allocation(ld_adr, phase, offset) && offset >= st->in(0)->as_Allocate()->minimum_header_size()) { // return a zero value for the load's basic type // (This is one of the few places where a generic PhaseTransform // can create new nodes. Think of it as lazily manifesting // virtually pre-existing constants.) return phase->zerocon(memory_type()); } // A load from an initialization barrier can match a captured store. if (st->is_Proj() && st->in(0)->is_Initialize()) { InitializeNode* init = st->in(0)->as_Initialize(); AllocateNode* alloc = init->allocation(); if (alloc != NULL && alloc == AllocateNode::Ideal_allocation(ld_adr, phase, offset)) { // examine a captured store value st = init->find_captured_store(offset, memory_size(), phase); if (st != NULL) continue; // take one more trip around } } break; } return NULL; } //----------------------is_instance_field_load_with_local_phi------------------ bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) { if( in(MemNode::Memory)->is_Phi() && in(MemNode::Memory)->in(0) == ctrl && in(MemNode::Address)->is_AddP() ) { const TypeOopPtr* t_oop = in(MemNode::Address)->bottom_type()->isa_oopptr(); // Only instances. if( t_oop != NULL && t_oop->is_instance_field() && t_oop->offset() != Type::OffsetBot && t_oop->offset() != Type::OffsetTop) { return true; } } return false; } //------------------------------Identity--------------------------------------- // Loads are identity if previous store is to same address Node *LoadNode::Identity( PhaseTransform *phase ) { // If the previous store-maker is the right kind of Store, and the store is // to the same address, then we are equal to the value stored. Node* mem = in(MemNode::Memory); Node* value = can_see_stored_value(mem, phase); if( value ) { // byte, short & char stores truncate naturally. // A load has to load the truncated value which requires // some sort of masking operation and that requires an // Ideal call instead of an Identity call. if (memory_size() < BytesPerInt) { // If the input to the store does not fit with the load's result type, // it must be truncated via an Ideal call. if (!phase->type(value)->higher_equal(phase->type(this))) return this; } // (This works even when value is a Con, but LoadNode::Value // usually runs first, producing the singleton type of the Con.) return value; } // Search for an existing data phi which was generated before for the same // instance's field to avoid infinite genertion of phis in a loop. Node *region = mem->in(0); if (is_instance_field_load_with_local_phi(region)) { const TypePtr *addr_t = in(MemNode::Address)->bottom_type()->isa_ptr(); int this_index = phase->C->get_alias_index(addr_t); int this_offset = addr_t->offset(); int this_id = addr_t->is_oopptr()->instance_id(); const Type* this_type = bottom_type(); for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) { Node* phi = region->fast_out(i); if (phi->is_Phi() && phi != mem && phi->as_Phi()->is_same_inst_field(this_type, this_id, this_index, this_offset)) { return phi; } } } return this; } // Returns true if the AliasType refers to the field that holds the // cached box array. Currently only handles the IntegerCache case. static bool is_autobox_cache(Compile::AliasType* atp) { if (atp != NULL && atp->field() != NULL) { ciField* field = atp->field(); ciSymbol* klass = field->holder()->name(); if (field->name() == ciSymbol::cache_field_name() && field->holder()->uses_default_loader() && klass == ciSymbol::java_lang_Integer_IntegerCache()) { return true; } } return false; } // Fetch the base value in the autobox array static bool fetch_autobox_base(Compile::AliasType* atp, int& cache_offset) { if (atp != NULL && atp->field() != NULL) { ciField* field = atp->field(); ciSymbol* klass = field->holder()->name(); if (field->name() == ciSymbol::cache_field_name() && field->holder()->uses_default_loader() && klass == ciSymbol::java_lang_Integer_IntegerCache()) { assert(field->is_constant(), "what?"); ciObjArray* array = field->constant_value().as_object()->as_obj_array(); // Fetch the box object at the base of the array and get its value ciInstance* box = array->obj_at(0)->as_instance(); ciInstanceKlass* ik = box->klass()->as_instance_klass(); if (ik->nof_nonstatic_fields() == 1) { // This should be true nonstatic_field_at requires calling // nof_nonstatic_fields so check it anyway ciConstant c = box->field_value(ik->nonstatic_field_at(0)); cache_offset = c.as_int(); } return true; } } return false; } // Returns true if the AliasType refers to the value field of an // autobox object. Currently only handles Integer. static bool is_autobox_object(Compile::AliasType* atp) { if (atp != NULL && atp->field() != NULL) { ciField* field = atp->field(); ciSymbol* klass = field->holder()->name(); if (field->name() == ciSymbol::value_name() && field->holder()->uses_default_loader() && klass == ciSymbol::java_lang_Integer()) { return true; } } return false; } // We're loading from an object which has autobox behaviour. // If this object is result of a valueOf call we'll have a phi // merging a newly allocated object and a load from the cache. // We want to replace this load with the original incoming // argument to the valueOf call. Node* LoadNode::eliminate_autobox(PhaseGVN* phase) { Node* base = in(Address)->in(AddPNode::Base); if (base->is_Phi() && base->req() == 3) { AllocateNode* allocation = NULL; int allocation_index = -1; int load_index = -1; for (uint i = 1; i < base->req(); i++) { allocation = AllocateNode::Ideal_allocation(base->in(i), phase); if (allocation != NULL) { allocation_index = i; load_index = 3 - allocation_index; break; } } LoadNode* load = NULL; if (allocation != NULL && base->in(load_index)->is_Load()) { load = base->in(load_index)->as_Load(); } if (load != NULL && in(Memory)->is_Phi() && in(Memory)->in(0) == base->in(0)) { // Push the loads from the phi that comes from valueOf up // through it to allow elimination of the loads and the recovery // of the original value. Node* mem_phi = in(Memory); Node* offset = in(Address)->in(AddPNode::Offset); Node* in1 = clone(); Node* in1_addr = in1->in(Address)->clone(); in1_addr->set_req(AddPNode::Base, base->in(allocation_index)); in1_addr->set_req(AddPNode::Address, base->in(allocation_index)); in1_addr->set_req(AddPNode::Offset, offset); in1->set_req(0, base->in(allocation_index)); in1->set_req(Address, in1_addr); in1->set_req(Memory, mem_phi->in(allocation_index)); Node* in2 = clone(); Node* in2_addr = in2->in(Address)->clone(); in2_addr->set_req(AddPNode::Base, base->in(load_index)); in2_addr->set_req(AddPNode::Address, base->in(load_index)); in2_addr->set_req(AddPNode::Offset, offset); in2->set_req(0, base->in(load_index)); in2->set_req(Address, in2_addr); in2->set_req(Memory, mem_phi->in(load_index)); in1_addr = phase->transform(in1_addr); in1 = phase->transform(in1); in2_addr = phase->transform(in2_addr); in2 = phase->transform(in2); PhiNode* result = PhiNode::make_blank(base->in(0), this); result->set_req(allocation_index, in1); result->set_req(load_index, in2); return result; } } else if (base->is_Load()) { // Eliminate the load of Integer.value for integers from the cache // array by deriving the value from the index into the array. // Capture the offset of the load and then reverse the computation. Node* load_base = base->in(Address)->in(AddPNode::Base); if (load_base != NULL) { Compile::AliasType* atp = phase->C->alias_type(load_base->adr_type()); intptr_t cache_offset; int shift = -1; Node* cache = NULL; if (is_autobox_cache(atp)) { shift = exact_log2(type2aelembytes(T_OBJECT)); cache = AddPNode::Ideal_base_and_offset(load_base->in(Address), phase, cache_offset); } if (cache != NULL && base->in(Address)->is_AddP()) { Node* elements[4]; int count = base->in(Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements)); int cache_low; if (count > 0 && fetch_autobox_base(atp, cache_low)) { int offset = arrayOopDesc::base_offset_in_bytes(memory_type()) - (cache_low << shift); // Add up all the offsets making of the address of the load Node* result = elements[0]; for (int i = 1; i < count; i++) { result = phase->transform(new (phase->C, 3) AddXNode(result, elements[i])); } // Remove the constant offset from the address and then // remove the scaling of the offset to recover the original index. result = phase->transform(new (phase->C, 3) AddXNode(result, phase->MakeConX(-offset))); if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) { // Peel the shift off directly but wrap it in a dummy node // since Ideal can't return existing nodes result = new (phase->C, 3) RShiftXNode(result->in(1), phase->intcon(0)); } else { result = new (phase->C, 3) RShiftXNode(result, phase->intcon(shift)); } #ifdef _LP64 result = new (phase->C, 2) ConvL2INode(phase->transform(result)); #endif return result; } } } } return NULL; } //------------------------------Ideal------------------------------------------ // If the load is from Field memory and the pointer is non-null, we can // zero out the control input. // If the offset is constant and the base is an object allocation, // try to hook me up to the exact initializing store. Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) { Node* p = MemNode::Ideal_common(phase, can_reshape); if (p) return (p == NodeSentinel) ? NULL : p; Node* ctrl = in(MemNode::Control); Node* address = in(MemNode::Address); // Skip up past a SafePoint control. Cannot do this for Stores because // pointer stores & cardmarks must stay on the same side of a SafePoint. if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw ) { ctrl = ctrl->in(0); set_req(MemNode::Control,ctrl); } // Check for useless control edge in some common special cases if (in(MemNode::Control) != NULL) { intptr_t ignore = 0; Node* base = AddPNode::Ideal_base_and_offset(address, phase, ignore); if (base != NULL && phase->type(base)->higher_equal(TypePtr::NOTNULL) && all_controls_dominate(base, phase->C->start())) { // A method-invariant, non-null address (constant or 'this' argument). set_req(MemNode::Control, NULL); } } if (EliminateAutoBox && can_reshape && in(Address)->is_AddP()) { Node* base = in(Address)->in(AddPNode::Base); if (base != NULL) { Compile::AliasType* atp = phase->C->alias_type(adr_type()); if (is_autobox_object(atp)) { Node* result = eliminate_autobox(phase); if (result != NULL) return result; } } } Node* mem = in(MemNode::Memory); const TypePtr *addr_t = phase->type(address)->isa_ptr(); if (addr_t != NULL) { // try to optimize our memory input Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, phase); if (opt_mem != mem) { set_req(MemNode::Memory, opt_mem); return this; } const TypeOopPtr *t_oop = addr_t->isa_oopptr(); if (can_reshape && opt_mem->is_Phi() && (t_oop != NULL) && t_oop->is_instance_field()) { assert(t_oop->offset() != Type::OffsetBot && t_oop->offset() != Type::OffsetTop, ""); Node *region = opt_mem->in(0); uint cnt = opt_mem->req(); for( uint i = 1; i < cnt; i++ ) { Node *in = opt_mem->in(i); if( in == NULL ) { region = NULL; // Wait stable graph break; } } if (region != NULL) { // Check for loop invariant. if (cnt == 3) { for( uint i = 1; i < cnt; i++ ) { Node *in = opt_mem->in(i); Node* m = MemNode::optimize_memory_chain(in, addr_t, phase); if (m == opt_mem) { set_req(MemNode::Memory, opt_mem->in(cnt - i)); // Skip this phi. return this; } } } // Split through Phi (see original code in loopopts.cpp). assert(phase->C->have_alias_type(addr_t), "instance should have alias type"); // Do nothing here if Identity will find a value // (to avoid infinite chain of value phis generation). if ( !phase->eqv(this, this->Identity(phase)) ) return NULL; const Type* this_type = this->bottom_type(); int this_index = phase->C->get_alias_index(addr_t); int this_offset = addr_t->offset(); int this_iid = addr_t->is_oopptr()->instance_id(); int wins = 0; PhaseIterGVN *igvn = phase->is_IterGVN(); Node *phi = new (igvn->C, region->req()) PhiNode(region, this_type, NULL, this_iid, this_index, this_offset); for( uint i = 1; i < region->req(); i++ ) { Node *x; Node* the_clone = NULL; if( region->in(i) == phase->C->top() ) { x = phase->C->top(); // Dead path? Use a dead data op } else { x = this->clone(); // Else clone up the data op the_clone = x; // Remember for possible deletion. // Alter data node to use pre-phi inputs if( this->in(0) == region ) { x->set_req( 0, region->in(i) ); } else { x->set_req( 0, NULL ); } for( uint j = 1; j < this->req(); j++ ) { Node *in = this->in(j); if( in->is_Phi() && in->in(0) == region ) x->set_req( j, in->in(i) ); // Use pre-Phi input for the clone } } // Check for a 'win' on some paths const Type *t = x->Value(igvn); bool singleton = t->singleton(); // See comments in PhaseIdealLoop::split_thru_phi(). if( singleton && t == Type::TOP ) { singleton &= region->is_Loop() && (i != LoopNode::EntryControl); } if( singleton ) { wins++; x = igvn->makecon(t); } else { // We now call Identity to try to simplify the cloned node. // Note that some Identity methods call phase->type(this). // Make sure that the type array is big enough for // our new node, even though we may throw the node away. // (This tweaking with igvn only works because x is a new node.) igvn->set_type(x, t); Node *y = x->Identity(igvn); if( y != x ) { wins++; x = y; } else { y = igvn->hash_find(x); if( y ) { wins++; x = y; } else { // Else x is a new node we are keeping // We do not need register_new_node_with_optimizer // because set_type has already been called. igvn->_worklist.push(x); } } } if (x != the_clone && the_clone != NULL) igvn->remove_dead_node(the_clone); phi->set_req(i, x); } if( wins > 0 ) { // Record Phi igvn->register_new_node_with_optimizer(phi); return phi; } else { igvn->remove_dead_node(phi); } } } } // Check for prior store with a different base or offset; make Load // independent. Skip through any number of them. Bail out if the stores // are in an endless dead cycle and report no progress. This is a key // transform for Reflection. However, if after skipping through the Stores // we can't then fold up against a prior store do NOT do the transform as // this amounts to using the 'Oracle' model of aliasing. It leaves the same // array memory alive twice: once for the hoisted Load and again after the // bypassed Store. This situation only works if EVERYBODY who does // anti-dependence work knows how to bypass. I.e. we need all // anti-dependence checks to ask the same Oracle. Right now, that Oracle is // the alias index stuff. So instead, peek through Stores and IFF we can // fold up, do so. Node* prev_mem = find_previous_store(phase); // Steps (a), (b): Walk past independent stores to find an exact match. if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) { // (c) See if we can fold up on the spot, but don't fold up here. // Fold-up might require truncation (for LoadB/LoadS/LoadC) or // just return a prior value, which is done by Identity calls. if (can_see_stored_value(prev_mem, phase)) { // Make ready for step (d): set_req(MemNode::Memory, prev_mem); return this; } } return NULL; // No further progress } // Helper to recognize certain Klass fields which are invariant across // some group of array types (e.g., int[] or all T[] where T < Object). const Type* LoadNode::load_array_final_field(const TypeKlassPtr *tkls, ciKlass* klass) const { if (tkls->offset() == Klass::modifier_flags_offset_in_bytes() + (int)sizeof(oopDesc)) { // The field is Klass::_modifier_flags. Return its (constant) value. // (Folds up the 2nd indirection in aClassConstant.getModifiers().) assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags"); return TypeInt::make(klass->modifier_flags()); } if (tkls->offset() == Klass::access_flags_offset_in_bytes() + (int)sizeof(oopDesc)) { // The field is Klass::_access_flags. Return its (constant) value. // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).) assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags"); return TypeInt::make(klass->access_flags()); } if (tkls->offset() == Klass::layout_helper_offset_in_bytes() + (int)sizeof(oopDesc)) { // The field is Klass::_layout_helper. Return its constant value if known. assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper"); return TypeInt::make(klass->layout_helper()); } // No match. return NULL; } //------------------------------Value----------------------------------------- const Type *LoadNode::Value( PhaseTransform *phase ) const { // Either input is TOP ==> the result is TOP Node* mem = in(MemNode::Memory); const Type *t1 = phase->type(mem); if (t1 == Type::TOP) return Type::TOP; Node* adr = in(MemNode::Address); const TypePtr* tp = phase->type(adr)->isa_ptr(); if (tp == NULL || tp->empty()) return Type::TOP; int off = tp->offset(); assert(off != Type::OffsetTop, "case covered by TypePtr::empty"); // Try to guess loaded type from pointer type if (tp->base() == Type::AryPtr) { const Type *t = tp->is_aryptr()->elem(); // Don't do this for integer types. There is only potential profit if // the element type t is lower than _type; that is, for int types, if _type is // more restrictive than t. This only happens here if one is short and the other // char (both 16 bits), and in those cases we've made an intentional decision // to use one kind of load over the other. See AndINode::Ideal and 4965907. // Also, do not try to narrow the type for a LoadKlass, regardless of offset. // // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8)) // where the _gvn.type of the AddP is wider than 8. This occurs when an earlier // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been // subsumed by p1. If p1 is on the worklist but has not yet been re-transformed, // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any. // In fact, that could have been the original type of p1, and p1 could have // had an original form like p1:(AddP x x (LShiftL quux 3)), where the // expression (LShiftL quux 3) independently optimized to the constant 8. if ((t->isa_int() == NULL) && (t->isa_long() == NULL) && Opcode() != Op_LoadKlass) { // t might actually be lower than _type, if _type is a unique // concrete subclass of abstract class t. // Make sure the reference is not into the header, by comparing // the offset against the offset of the start of the array's data. // Different array types begin at slightly different offsets (12 vs. 16). // We choose T_BYTE as an example base type that is least restrictive // as to alignment, which will therefore produce the smallest // possible base offset. const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE); if ((uint)off >= (uint)min_base_off) { // is the offset beyond the header? const Type* jt = t->join(_type); // In any case, do not allow the join, per se, to empty out the type. if (jt->empty() && !t->empty()) { // This can happen if a interface-typed array narrows to a class type. jt = _type; } if (EliminateAutoBox) { // The pointers in the autobox arrays are always non-null Node* base = in(Address)->in(AddPNode::Base); if (base != NULL) { Compile::AliasType* atp = phase->C->alias_type(base->adr_type()); if (is_autobox_cache(atp)) { return jt->join(TypePtr::NOTNULL)->is_ptr(); } } } return jt; } } } else if (tp->base() == Type::InstPtr) { assert( off != Type::OffsetBot || // arrays can be cast to Objects tp->is_oopptr()->klass()->is_java_lang_Object() || // unsafe field access may not have a constant offset phase->C->has_unsafe_access(), "Field accesses must be precise" ); // For oop loads, we expect the _type to be precise } else if (tp->base() == Type::KlassPtr) { assert( off != Type::OffsetBot || // arrays can be cast to Objects tp->is_klassptr()->klass()->is_java_lang_Object() || // also allow array-loading from the primary supertype // array during subtype checks Opcode() == Op_LoadKlass, "Field accesses must be precise" ); // For klass/static loads, we expect the _type to be precise } const TypeKlassPtr *tkls = tp->isa_klassptr(); if (tkls != NULL && !StressReflectiveCode) { ciKlass* klass = tkls->klass(); if (klass->is_loaded() && tkls->klass_is_exact()) { // We are loading a field from a Klass metaobject whose identity // is known at compile time (the type is "exact" or "precise"). // Check for fields we know are maintained as constants by the VM. if (tkls->offset() == Klass::super_check_offset_offset_in_bytes() + (int)sizeof(oopDesc)) { // The field is Klass::_super_check_offset. Return its (constant) value. // (Folds up type checking code.) assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset"); return TypeInt::make(klass->super_check_offset()); } // Compute index into primary_supers array juint depth = (tkls->offset() - (Klass::primary_supers_offset_in_bytes() + (int)sizeof(oopDesc))) / sizeof(klassOop); // Check for overflowing; use unsigned compare to handle the negative case. if( depth < ciKlass::primary_super_limit() ) { // The field is an element of Klass::_primary_supers. Return its (constant) value. // (Folds up type checking code.) assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers"); ciKlass *ss = klass->super_of_depth(depth); return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR; } const Type* aift = load_array_final_field(tkls, klass); if (aift != NULL) return aift; if (tkls->offset() == in_bytes(arrayKlass::component_mirror_offset()) + (int)sizeof(oopDesc) && klass->is_array_klass()) { // The field is arrayKlass::_component_mirror. Return its (constant) value. // (Folds up aClassConstant.getComponentType, common in Arrays.copyOf.) assert(Opcode() == Op_LoadP, "must load an oop from _component_mirror"); return TypeInstPtr::make(klass->as_array_klass()->component_mirror()); } if (tkls->offset() == Klass::java_mirror_offset_in_bytes() + (int)sizeof(oopDesc)) { // The field is Klass::_java_mirror. Return its (constant) value. // (Folds up the 2nd indirection in anObjConstant.getClass().) assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror"); return TypeInstPtr::make(klass->java_mirror()); } } // We can still check if we are loading from the primary_supers array at a // shallow enough depth. Even though the klass is not exact, entries less // than or equal to its super depth are correct. if (klass->is_loaded() ) { ciType *inner = klass->klass(); while( inner->is_obj_array_klass() ) inner = inner->as_obj_array_klass()->base_element_type(); if( inner->is_instance_klass() && !inner->as_instance_klass()->flags().is_interface() ) { // Compute index into primary_supers array juint depth = (tkls->offset() - (Klass::primary_supers_offset_in_bytes() + (int)sizeof(oopDesc))) / sizeof(klassOop); // Check for overflowing; use unsigned compare to handle the negative case. if( depth < ciKlass::primary_super_limit() && depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case // The field is an element of Klass::_primary_supers. Return its (constant) value. // (Folds up type checking code.) assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers"); ciKlass *ss = klass->super_of_depth(depth); return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR; } } } // If the type is enough to determine that the thing is not an array, // we can give the layout_helper a positive interval type. // This will help short-circuit some reflective code. if (tkls->offset() == Klass::layout_helper_offset_in_bytes() + (int)sizeof(oopDesc) && !klass->is_array_klass() // not directly typed as an array && !klass->is_interface() // specifically not Serializable & Cloneable && !klass->is_java_lang_Object() // not the supertype of all T[] ) { // Note: When interfaces are reliable, we can narrow the interface // test to (klass != Serializable && klass != Cloneable). assert(Opcode() == Op_LoadI, "must load an int from _layout_helper"); jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false); // The key property of this type is that it folds up tests // for array-ness, since it proves that the layout_helper is positive. // Thus, a generic value like the basic object layout helper works fine. return TypeInt::make(min_size, max_jint, Type::WidenMin); } } // If we are loading from a freshly-allocated object, produce a zero, // if the load is provably beyond the header of the object. // (Also allow a variable load from a fresh array to produce zero.) if (ReduceFieldZeroing) { Node* value = can_see_stored_value(mem,phase); if (value != NULL && value->is_Con()) return value->bottom_type(); } const TypeOopPtr *tinst = tp->isa_oopptr(); if (tinst != NULL && tinst->is_instance_field()) { // If we have an instance type and our memory input is the // programs's initial memory state, there is no matching store, // so just return a zero of the appropriate type Node *mem = in(MemNode::Memory); if (mem->is_Parm() && mem->in(0)->is_Start()) { assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm"); return Type::get_zero_type(_type->basic_type()); } } return _type; } //------------------------------match_edge------------------------------------- // Do we Match on this edge index or not? Match only the address. uint LoadNode::match_edge(uint idx) const { return idx == MemNode::Address; } //--------------------------LoadBNode::Ideal-------------------------------------- // // If the previous store is to the same address as this load, // and the value stored was larger than a byte, replace this load // with the value stored truncated to a byte. If no truncation is // needed, the replacement is done in LoadNode::Identity(). // Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) { Node* mem = in(MemNode::Memory); Node* value = can_see_stored_value(mem,phase); if( value && !phase->type(value)->higher_equal( _type ) ) { Node *result = phase->transform( new (phase->C, 3) LShiftINode(value, phase->intcon(24)) ); return new (phase->C, 3) RShiftINode(result, phase->intcon(24)); } // Identity call will handle the case where truncation is not needed. return LoadNode::Ideal(phase, can_reshape); } //--------------------------LoadCNode::Ideal-------------------------------------- // // If the previous store is to the same address as this load, // and the value stored was larger than a char, replace this load // with the value stored truncated to a char. If no truncation is // needed, the replacement is done in LoadNode::Identity(). // Node *LoadCNode::Ideal(PhaseGVN *phase, bool can_reshape) { Node* mem = in(MemNode::Memory); Node* value = can_see_stored_value(mem,phase); if( value && !phase->type(value)->higher_equal( _type ) ) return new (phase->C, 3) AndINode(value,phase->intcon(0xFFFF)); // Identity call will handle the case where truncation is not needed. return LoadNode::Ideal(phase, can_reshape); } //--------------------------LoadSNode::Ideal-------------------------------------- // // If the previous store is to the same address as this load, // and the value stored was larger than a short, replace this load // with the value stored truncated to a short. If no truncation is // needed, the replacement is done in LoadNode::Identity(). // Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) { Node* mem = in(MemNode::Memory); Node* value = can_see_stored_value(mem,phase); if( value && !phase->type(value)->higher_equal( _type ) ) { Node *result = phase->transform( new (phase->C, 3) LShiftINode(value, phase->intcon(16)) ); return new (phase->C, 3) RShiftINode(result, phase->intcon(16)); } // Identity call will handle the case where truncation is not needed. return LoadNode::Ideal(phase, can_reshape); } //============================================================================= //------------------------------Value------------------------------------------ const Type *LoadKlassNode::Value( PhaseTransform *phase ) const { // Either input is TOP ==> the result is TOP const Type *t1 = phase->type( in(MemNode::Memory) ); if (t1 == Type::TOP) return Type::TOP; Node *adr = in(MemNode::Address); const Type *t2 = phase->type( adr ); if (t2 == Type::TOP) return Type::TOP; const TypePtr *tp = t2->is_ptr(); if (TypePtr::above_centerline(tp->ptr()) || tp->ptr() == TypePtr::Null) return Type::TOP; // Return a more precise klass, if possible const TypeInstPtr *tinst = tp->isa_instptr(); if (tinst != NULL) { ciInstanceKlass* ik = tinst->klass()->as_instance_klass(); int offset = tinst->offset(); if (ik == phase->C->env()->Class_klass() && (offset == java_lang_Class::klass_offset_in_bytes() || offset == java_lang_Class::array_klass_offset_in_bytes())) { // We are loading a special hidden field from a Class mirror object, // the field which points to the VM's Klass metaobject. ciType* t = tinst->java_mirror_type(); // java_mirror_type returns non-null for compile-time Class constants. if (t != NULL) { // constant oop => constant klass if (offset == java_lang_Class::array_klass_offset_in_bytes()) { return TypeKlassPtr::make(ciArrayKlass::make(t)); } if (!t->is_klass()) { // a primitive Class (e.g., int.class) has NULL for a klass field return TypePtr::NULL_PTR; } // (Folds up the 1st indirection in aClassConstant.getModifiers().) return TypeKlassPtr::make(t->as_klass()); } // non-constant mirror, so we can't tell what's going on } if( !ik->is_loaded() ) return _type; // Bail out if not loaded if (offset == oopDesc::klass_offset_in_bytes()) { if (tinst->klass_is_exact()) { return TypeKlassPtr::make(ik); } // See if we can become precise: no subklasses and no interface // (Note: We need to support verified interfaces.) if (!ik->is_interface() && !ik->has_subklass()) { //assert(!UseExactTypes, "this code should be useless with exact types"); // Add a dependence; if any subclass added we need to recompile if (!ik->is_final()) { // %%% should use stronger assert_unique_concrete_subtype instead phase->C->dependencies()->assert_leaf_type(ik); } // Return precise klass return TypeKlassPtr::make(ik); } // Return root of possible klass return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/); } } // Check for loading klass from an array const TypeAryPtr *tary = tp->isa_aryptr(); if( tary != NULL ) { ciKlass *tary_klass = tary->klass(); if (tary_klass != NULL // can be NULL when at BOTTOM or TOP && tary->offset() == oopDesc::klass_offset_in_bytes()) { if (tary->klass_is_exact()) { return TypeKlassPtr::make(tary_klass); } ciArrayKlass *ak = tary->klass()->as_array_klass(); // If the klass is an object array, we defer the question to the // array component klass. if( ak->is_obj_array_klass() ) { assert( ak->is_loaded(), "" ); ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass(); if( base_k->is_loaded() && base_k->is_instance_klass() ) { ciInstanceKlass* ik = base_k->as_instance_klass(); // See if we can become precise: no subklasses and no interface if (!ik->is_interface() && !ik->has_subklass()) { //assert(!UseExactTypes, "this code should be useless with exact types"); // Add a dependence; if any subclass added we need to recompile if (!ik->is_final()) { phase->C->dependencies()->assert_leaf_type(ik); } // Return precise array klass return TypeKlassPtr::make(ak); } } return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/); } else { // Found a type-array? //assert(!UseExactTypes, "this code should be useless with exact types"); assert( ak->is_type_array_klass(), "" ); return TypeKlassPtr::make(ak); // These are always precise } } } // Check for loading klass from an array klass const TypeKlassPtr *tkls = tp->isa_klassptr(); if (tkls != NULL && !StressReflectiveCode) { ciKlass* klass = tkls->klass(); if( !klass->is_loaded() ) return _type; // Bail out if not loaded if( klass->is_obj_array_klass() && (uint)tkls->offset() == objArrayKlass::element_klass_offset_in_bytes() + sizeof(oopDesc)) { ciKlass* elem = klass->as_obj_array_klass()->element_klass(); // // Always returning precise element type is incorrect, // // e.g., element type could be object and array may contain strings // return TypeKlassPtr::make(TypePtr::Constant, elem, 0); // The array's TypeKlassPtr was declared 'precise' or 'not precise' // according to the element type's subclassing. return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/); } if( klass->is_instance_klass() && tkls->klass_is_exact() && (uint)tkls->offset() == Klass::super_offset_in_bytes() + sizeof(oopDesc)) { ciKlass* sup = klass->as_instance_klass()->super(); // The field is Klass::_super. Return its (constant) value. // (Folds up the 2nd indirection in aClassConstant.getSuperClass().) return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR; } } // Bailout case return LoadNode::Value(phase); } //------------------------------Identity--------------------------------------- // To clean up reflective code, simplify k.java_mirror.as_klass to plain k. // Also feed through the klass in Allocate(...klass...)._klass. Node* LoadKlassNode::Identity( PhaseTransform *phase ) { Node* x = LoadNode::Identity(phase); if (x != this) return x; // Take apart the address into an oop and and offset. // Return 'this' if we cannot. Node* adr = in(MemNode::Address); intptr_t offset = 0; Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset); if (base == NULL) return this; const TypeOopPtr* toop = phase->type(adr)->isa_oopptr(); if (toop == NULL) return this; // We can fetch the klass directly through an AllocateNode. // This works even if the klass is not constant (clone or newArray). if (offset == oopDesc::klass_offset_in_bytes()) { Node* allocated_klass = AllocateNode::Ideal_klass(base, phase); if (allocated_klass != NULL) { return allocated_klass; } } // Simplify k.java_mirror.as_klass to plain k, where k is a klassOop. // Simplify ak.component_mirror.array_klass to plain ak, ak an arrayKlass. // See inline_native_Class_query for occurrences of these patterns. // Java Example: x.getClass().isAssignableFrom(y) // Java Example: Array.newInstance(x.getClass().getComponentType(), n) // // This improves reflective code, often making the Class // mirror go completely dead. (Current exception: Class // mirrors may appear in debug info, but we could clean them out by // introducing a new debug info operator for klassOop.java_mirror). if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass() && (offset == java_lang_Class::klass_offset_in_bytes() || offset == java_lang_Class::array_klass_offset_in_bytes())) { // We are loading a special hidden field from a Class mirror, // the field which points to its Klass or arrayKlass metaobject. if (base->is_Load()) { Node* adr2 = base->in(MemNode::Address); const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr(); if (tkls != NULL && !tkls->empty() && (tkls->klass()->is_instance_klass() || tkls->klass()->is_array_klass()) && adr2->is_AddP() ) { int mirror_field = Klass::java_mirror_offset_in_bytes(); if (offset == java_lang_Class::array_klass_offset_in_bytes()) { mirror_field = in_bytes(arrayKlass::component_mirror_offset()); } if (tkls->offset() == mirror_field + (int)sizeof(oopDesc)) { return adr2->in(AddPNode::Base); } } } } return this; } //------------------------------Value----------------------------------------- const Type *LoadRangeNode::Value( PhaseTransform *phase ) const { // Either input is TOP ==> the result is TOP const Type *t1 = phase->type( in(MemNode::Memory) ); if( t1 == Type::TOP ) return Type::TOP; Node *adr = in(MemNode::Address); const Type *t2 = phase->type( adr ); if( t2 == Type::TOP ) return Type::TOP; const TypePtr *tp = t2->is_ptr(); if (TypePtr::above_centerline(tp->ptr())) return Type::TOP; const TypeAryPtr *tap = tp->isa_aryptr(); if( !tap ) return _type; return tap->size(); } //------------------------------Identity--------------------------------------- // Feed through the length in AllocateArray(...length...)._length. Node* LoadRangeNode::Identity( PhaseTransform *phase ) { Node* x = LoadINode::Identity(phase); if (x != this) return x; // Take apart the address into an oop and and offset. // Return 'this' if we cannot. Node* adr = in(MemNode::Address); intptr_t offset = 0; Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset); if (base == NULL) return this; const TypeAryPtr* tary = phase->type(adr)->isa_aryptr(); if (tary == NULL) return this; // We can fetch the length directly through an AllocateArrayNode. // This works even if the length is not constant (clone or newArray). if (offset == arrayOopDesc::length_offset_in_bytes()) { Node* allocated_length = AllocateArrayNode::Ideal_length(base, phase); if (allocated_length != NULL) { return allocated_length; } } return this; } //============================================================================= //---------------------------StoreNode::make----------------------------------- // Polymorphic factory method: StoreNode* StoreNode::make( PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt ) { Compile* C = gvn.C; switch (bt) { case T_BOOLEAN: case T_BYTE: return new (C, 4) StoreBNode(ctl, mem, adr, adr_type, val); case T_INT: return new (C, 4) StoreINode(ctl, mem, adr, adr_type, val); case T_CHAR: case T_SHORT: return new (C, 4) StoreCNode(ctl, mem, adr, adr_type, val); case T_LONG: return new (C, 4) StoreLNode(ctl, mem, adr, adr_type, val); case T_FLOAT: return new (C, 4) StoreFNode(ctl, mem, adr, adr_type, val); case T_DOUBLE: return new (C, 4) StoreDNode(ctl, mem, adr, adr_type, val); case T_ADDRESS: case T_OBJECT: #ifdef _LP64 if (adr->bottom_type()->is_narrow() || (UseCompressedOops && val->bottom_type()->isa_klassptr() && adr->bottom_type()->isa_rawptr())) { const TypePtr* type = val->bottom_type()->is_ptr(); Node* cp = EncodePNode::encode(&gvn, val); return new (C, 4) StoreNNode(ctl, mem, adr, adr_type, cp); } else #endif { return new (C, 4) StorePNode(ctl, mem, adr, adr_type, val); } } ShouldNotReachHere(); return (StoreNode*)NULL; } StoreLNode* StoreLNode::make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val) { bool require_atomic = true; return new (C, 4) StoreLNode(ctl, mem, adr, adr_type, val, require_atomic); } //--------------------------bottom_type---------------------------------------- const Type *StoreNode::bottom_type() const { return Type::MEMORY; } //------------------------------hash------------------------------------------- uint StoreNode::hash() const { // unroll addition of interesting fields //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn); // Since they are not commoned, do not hash them: return NO_HASH; } //------------------------------Ideal------------------------------------------ // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x). // When a store immediately follows a relevant allocation/initialization, // try to capture it into the initialization, or hoist it above. Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) { Node* p = MemNode::Ideal_common(phase, can_reshape); if (p) return (p == NodeSentinel) ? NULL : p; Node* mem = in(MemNode::Memory); Node* address = in(MemNode::Address); // Back-to-back stores to same address? Fold em up. // Generally unsafe if I have intervening uses... if (mem->is_Store() && phase->eqv_uncast(mem->in(MemNode::Address), address)) { // Looking at a dead closed cycle of memory? assert(mem != mem->in(MemNode::Memory), "dead loop in StoreNode::Ideal"); assert(Opcode() == mem->Opcode() || phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw, "no mismatched stores, except on raw memory"); if (mem->outcnt() == 1 && // check for intervening uses mem->as_Store()->memory_size() <= this->memory_size()) { // If anybody other than 'this' uses 'mem', we cannot fold 'mem' away. // For example, 'mem' might be the final state at a conditional return. // Or, 'mem' might be used by some node which is live at the same time // 'this' is live, which might be unschedulable. So, require exactly // ONE user, the 'this' store, until such time as we clone 'mem' for // each of 'mem's uses (thus making the exactly-1-user-rule hold true). if (can_reshape) { // (%%% is this an anachronism?) set_req_X(MemNode::Memory, mem->in(MemNode::Memory), phase->is_IterGVN()); } else { // It's OK to do this in the parser, since DU info is always accurate, // and the parser always refers to nodes via SafePointNode maps. set_req(MemNode::Memory, mem->in(MemNode::Memory)); } return this; } } // Capture an unaliased, unconditional, simple store into an initializer. // Or, if it is independent of the allocation, hoist it above the allocation. if (ReduceFieldZeroing && /*can_reshape &&*/ mem->is_Proj() && mem->in(0)->is_Initialize()) { InitializeNode* init = mem->in(0)->as_Initialize(); intptr_t offset = init->can_capture_store(this, phase); if (offset > 0) { Node* moved = init->capture_store(this, offset, phase); // If the InitializeNode captured me, it made a raw copy of me, // and I need to disappear. if (moved != NULL) { // %%% hack to ensure that Ideal returns a new node: mem = MergeMemNode::make(phase->C, mem); return mem; // fold me away } } } return NULL; // No further progress } //------------------------------Value----------------------------------------- const Type *StoreNode::Value( PhaseTransform *phase ) const { // Either input is TOP ==> the result is TOP const Type *t1 = phase->type( in(MemNode::Memory) ); if( t1 == Type::TOP ) return Type::TOP; const Type *t2 = phase->type( in(MemNode::Address) ); if( t2 == Type::TOP ) return Type::TOP; const Type *t3 = phase->type( in(MemNode::ValueIn) ); if( t3 == Type::TOP ) return Type::TOP; return Type::MEMORY; } //------------------------------Identity--------------------------------------- // Remove redundant stores: // Store(m, p, Load(m, p)) changes to m. // Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x). Node *StoreNode::Identity( PhaseTransform *phase ) { Node* mem = in(MemNode::Memory); Node* adr = in(MemNode::Address); Node* val = in(MemNode::ValueIn); // Load then Store? Then the Store is useless if (val->is_Load() && phase->eqv_uncast( val->in(MemNode::Address), adr ) && phase->eqv_uncast( val->in(MemNode::Memory ), mem ) && val->as_Load()->store_Opcode() == Opcode()) { return mem; } // Two stores in a row of the same value? if (mem->is_Store() && phase->eqv_uncast( mem->in(MemNode::Address), adr ) && phase->eqv_uncast( mem->in(MemNode::ValueIn), val ) && mem->Opcode() == Opcode()) { return mem; } // Store of zero anywhere into a freshly-allocated object? // Then the store is useless. // (It must already have been captured by the InitializeNode.) if (ReduceFieldZeroing && phase->type(val)->is_zero_type()) { // a newly allocated object is already all-zeroes everywhere if (mem->is_Proj() && mem->in(0)->is_Allocate()) { return mem; } // the store may also apply to zero-bits in an earlier object Node* prev_mem = find_previous_store(phase); // Steps (a), (b): Walk past independent stores to find an exact match. if (prev_mem != NULL) { Node* prev_val = can_see_stored_value(prev_mem, phase); if (prev_val != NULL && phase->eqv(prev_val, val)) { // prev_val and val might differ by a cast; it would be good // to keep the more informative of the two. return mem; } } } return this; } //------------------------------match_edge------------------------------------- // Do we Match on this edge index or not? Match only memory & value uint StoreNode::match_edge(uint idx) const { return idx == MemNode::Address || idx == MemNode::ValueIn; } //------------------------------cmp-------------------------------------------- // Do not common stores up together. They generally have to be split // back up anyways, so do not bother. uint StoreNode::cmp( const Node &n ) const { return (&n == this); // Always fail except on self } //------------------------------Ideal_masked_input----------------------------- // Check for a useless mask before a partial-word store // (StoreB ... (AndI valIn conIa) ) // If (conIa & mask == mask) this simplifies to // (StoreB ... (valIn) ) Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) { Node *val = in(MemNode::ValueIn); if( val->Opcode() == Op_AndI ) { const TypeInt *t = phase->type( val->in(2) )->isa_int(); if( t && t->is_con() && (t->get_con() & mask) == mask ) { set_req(MemNode::ValueIn, val->in(1)); return this; } } return NULL; } //------------------------------Ideal_sign_extended_input---------------------- // Check for useless sign-extension before a partial-word store // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) ) // If (conIL == conIR && conIR <= num_bits) this simplifies to // (StoreB ... (valIn) ) Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) { Node *val = in(MemNode::ValueIn); if( val->Opcode() == Op_RShiftI ) { const TypeInt *t = phase->type( val->in(2) )->isa_int(); if( t && t->is_con() && (t->get_con() <= num_bits) ) { Node *shl = val->in(1); if( shl->Opcode() == Op_LShiftI ) { const TypeInt *t2 = phase->type( shl->in(2) )->isa_int(); if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) { set_req(MemNode::ValueIn, shl->in(1)); return this; } } } } return NULL; } //------------------------------value_never_loaded----------------------------------- // Determine whether there are any possible loads of the value stored. // For simplicity, we actually check if there are any loads from the // address stored to, not just for loads of the value stored by this node. // bool StoreNode::value_never_loaded( PhaseTransform *phase) const { Node *adr = in(Address); const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr(); if (adr_oop == NULL) return false; if (!adr_oop->is_instance_field()) return false; // if not a distinct instance, there may be aliases of the address for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) { Node *use = adr->fast_out(i); int opc = use->Opcode(); if (use->is_Load() || use->is_LoadStore()) { return false; } } return true; } //============================================================================= //------------------------------Ideal------------------------------------------ // If the store is from an AND mask that leaves the low bits untouched, then // we can skip the AND operation. If the store is from a sign-extension // (a left shift, then right shift) we can skip both. Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){ Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF); if( progress != NULL ) return progress; progress = StoreNode::Ideal_sign_extended_input(phase, 24); if( progress != NULL ) return progress; // Finally check the default case return StoreNode::Ideal(phase, can_reshape); } //============================================================================= //------------------------------Ideal------------------------------------------ // If the store is from an AND mask that leaves the low bits untouched, then // we can skip the AND operation Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){ Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF); if( progress != NULL ) return progress; progress = StoreNode::Ideal_sign_extended_input(phase, 16); if( progress != NULL ) return progress; // Finally check the default case return StoreNode::Ideal(phase, can_reshape); } //============================================================================= //------------------------------Identity--------------------------------------- Node *StoreCMNode::Identity( PhaseTransform *phase ) { // No need to card mark when storing a null ptr Node* my_store = in(MemNode::OopStore); if (my_store->is_Store()) { const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) ); if( t1 == TypePtr::NULL_PTR ) { return in(MemNode::Memory); } } return this; } //------------------------------Value----------------------------------------- const Type *StoreCMNode::Value( PhaseTransform *phase ) const { // Either input is TOP ==> the result is TOP const Type *t = phase->type( in(MemNode::Memory) ); if( t == Type::TOP ) return Type::TOP; t = phase->type( in(MemNode::Address) ); if( t == Type::TOP ) return Type::TOP; t = phase->type( in(MemNode::ValueIn) ); if( t == Type::TOP ) return Type::TOP; // If extra input is TOP ==> the result is TOP t = phase->type( in(MemNode::OopStore) ); if( t == Type::TOP ) return Type::TOP; return StoreNode::Value( phase ); } //============================================================================= //----------------------------------SCMemProjNode------------------------------ const Type * SCMemProjNode::Value( PhaseTransform *phase ) const { return bottom_type(); } //============================================================================= LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : Node(5) { init_req(MemNode::Control, c ); init_req(MemNode::Memory , mem); init_req(MemNode::Address, adr); init_req(MemNode::ValueIn, val); init_req( ExpectedIn, ex ); init_class_id(Class_LoadStore); } //============================================================================= //-------------------------------adr_type-------------------------------------- // Do we Match on this edge index or not? Do not match memory const TypePtr* ClearArrayNode::adr_type() const { Node *adr = in(3); return MemNode::calculate_adr_type(adr->bottom_type()); } //------------------------------match_edge------------------------------------- // Do we Match on this edge index or not? Do not match memory uint ClearArrayNode::match_edge(uint idx) const { return idx > 1; } //------------------------------Identity--------------------------------------- // Clearing a zero length array does nothing Node *ClearArrayNode::Identity( PhaseTransform *phase ) { return phase->type(in(2))->higher_equal(TypeX::ZERO) ? in(1) : this; } //------------------------------Idealize--------------------------------------- // Clearing a short array is faster with stores Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape){ const int unit = BytesPerLong; const TypeX* t = phase->type(in(2))->isa_intptr_t(); if (!t) return NULL; if (!t->is_con()) return NULL; intptr_t raw_count = t->get_con(); intptr_t size = raw_count; if (!Matcher::init_array_count_is_in_bytes) size *= unit; // Clearing nothing uses the Identity call. // Negative clears are possible on dead ClearArrays // (see jck test stmt114.stmt11402.val). if (size <= 0 || size % unit != 0) return NULL; intptr_t count = size / unit; // Length too long; use fast hardware clear if (size > Matcher::init_array_short_size) return NULL; Node *mem = in(1); if( phase->type(mem)==Type::TOP ) return NULL; Node *adr = in(3); const Type* at = phase->type(adr); if( at==Type::TOP ) return NULL; const TypePtr* atp = at->isa_ptr(); // adjust atp to be the correct array element address type if (atp == NULL) atp = TypePtr::BOTTOM; else atp = atp->add_offset(Type::OffsetBot); // Get base for derived pointer purposes if( adr->Opcode() != Op_AddP ) Unimplemented(); Node *base = adr->in(1); Node *zero = phase->makecon(TypeLong::ZERO); Node *off = phase->MakeConX(BytesPerLong); mem = new (phase->C, 4) StoreLNode(in(0),mem,adr,atp,zero); count--; while( count-- ) { mem = phase->transform(mem); adr = phase->transform(new (phase->C, 4) AddPNode(base,adr,off)); mem = new (phase->C, 4) StoreLNode(in(0),mem,adr,atp,zero); } return mem; } //----------------------------clear_memory------------------------------------- // Generate code to initialize object storage to zero. Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest, intptr_t start_offset, Node* end_offset, PhaseGVN* phase) { Compile* C = phase->C; intptr_t offset = start_offset; int unit = BytesPerLong; if ((offset % unit) != 0) { Node* adr = new (C, 4) AddPNode(dest, dest, phase->MakeConX(offset)); adr = phase->transform(adr); const TypePtr* atp = TypeRawPtr::BOTTOM; mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT); mem = phase->transform(mem); offset += BytesPerInt; } assert((offset % unit) == 0, ""); // Initialize the remaining stuff, if any, with a ClearArray. return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase); } Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest, Node* start_offset, Node* end_offset, PhaseGVN* phase) { if (start_offset == end_offset) { // nothing to do return mem; } Compile* C = phase->C; int unit = BytesPerLong; Node* zbase = start_offset; Node* zend = end_offset; // Scale to the unit required by the CPU: if (!Matcher::init_array_count_is_in_bytes) { Node* shift = phase->intcon(exact_log2(unit)); zbase = phase->transform( new(C,3) URShiftXNode(zbase, shift) ); zend = phase->transform( new(C,3) URShiftXNode(zend, shift) ); } Node* zsize = phase->transform( new(C,3) SubXNode(zend, zbase) ); Node* zinit = phase->zerocon((unit == BytesPerLong) ? T_LONG : T_INT); // Bulk clear double-words Node* adr = phase->transform( new(C,4) AddPNode(dest, dest, start_offset) ); mem = new (C, 4) ClearArrayNode(ctl, mem, zsize, adr); return phase->transform(mem); } Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest, intptr_t start_offset, intptr_t end_offset, PhaseGVN* phase) { if (start_offset == end_offset) { // nothing to do return mem; } Compile* C = phase->C; assert((end_offset % BytesPerInt) == 0, "odd end offset"); intptr_t done_offset = end_offset; if ((done_offset % BytesPerLong) != 0) { done_offset -= BytesPerInt; } if (done_offset > start_offset) { mem = clear_memory(ctl, mem, dest, start_offset, phase->MakeConX(done_offset), phase); } if (done_offset < end_offset) { // emit the final 32-bit store Node* adr = new (C, 4) AddPNode(dest, dest, phase->MakeConX(done_offset)); adr = phase->transform(adr); const TypePtr* atp = TypeRawPtr::BOTTOM; mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT); mem = phase->transform(mem); done_offset += BytesPerInt; } assert(done_offset == end_offset, ""); return mem; } //============================================================================= // Do we match on this edge? No memory edges uint StrCompNode::match_edge(uint idx) const { return idx == 5 || idx == 6; } //------------------------------Ideal------------------------------------------ // Return a node which is more "ideal" than the current node. Strip out // control copies Node *StrCompNode::Ideal(PhaseGVN *phase, bool can_reshape){ return remove_dead_region(phase, can_reshape) ? this : NULL; } //============================================================================= MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent) : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)), _adr_type(C->get_adr_type(alias_idx)) { init_class_id(Class_MemBar); Node* top = C->top(); init_req(TypeFunc::I_O,top); init_req(TypeFunc::FramePtr,top); init_req(TypeFunc::ReturnAdr,top); if (precedent != NULL) init_req(TypeFunc::Parms, precedent); } //------------------------------cmp-------------------------------------------- uint MemBarNode::hash() const { return NO_HASH; } uint MemBarNode::cmp( const Node &n ) const { return (&n == this); // Always fail except on self } //------------------------------make------------------------------------------- MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) { int len = Precedent + (pn == NULL? 0: 1); switch (opcode) { case Op_MemBarAcquire: return new(C, len) MemBarAcquireNode(C, atp, pn); case Op_MemBarRelease: return new(C, len) MemBarReleaseNode(C, atp, pn); case Op_MemBarVolatile: return new(C, len) MemBarVolatileNode(C, atp, pn); case Op_MemBarCPUOrder: return new(C, len) MemBarCPUOrderNode(C, atp, pn); case Op_Initialize: return new(C, len) InitializeNode(C, atp, pn); default: ShouldNotReachHere(); return NULL; } } //------------------------------Ideal------------------------------------------ // Return a node which is more "ideal" than the current node. Strip out // control copies Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) { if (remove_dead_region(phase, can_reshape)) return this; return NULL; } //------------------------------Value------------------------------------------ const Type *MemBarNode::Value( PhaseTransform *phase ) const { if( !in(0) ) return Type::TOP; if( phase->type(in(0)) == Type::TOP ) return Type::TOP; return TypeTuple::MEMBAR; } //------------------------------match------------------------------------------ // Construct projections for memory. Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) { switch (proj->_con) { case TypeFunc::Control: case TypeFunc::Memory: return new (m->C, 1) MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj); } ShouldNotReachHere(); return NULL; } //===========================InitializeNode==================================== // SUMMARY: // This node acts as a memory barrier on raw memory, after some raw stores. // The 'cooked' oop value feeds from the Initialize, not the Allocation. // The Initialize can 'capture' suitably constrained stores as raw inits. // It can coalesce related raw stores into larger units (called 'tiles'). // It can avoid zeroing new storage for memory units which have raw inits. // At macro-expansion, it is marked 'complete', and does not optimize further. // // EXAMPLE: // The object 'new short[2]' occupies 16 bytes in a 32-bit machine. // ctl = incoming control; mem* = incoming memory // (Note: A star * on a memory edge denotes I/O and other standard edges.) // First allocate uninitialized memory and fill in the header: // alloc = (Allocate ctl mem* 16 #short[].klass ...) // ctl := alloc.Control; mem* := alloc.Memory* // rawmem = alloc.Memory; rawoop = alloc.RawAddress // Then initialize to zero the non-header parts of the raw memory block: // init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress) // ctl := init.Control; mem.SLICE(#short[*]) := init.Memory // After the initialize node executes, the object is ready for service: // oop := (CheckCastPP init.Control alloc.RawAddress #short[]) // Suppose its body is immediately initialized as {1,2}: // store1 = (StoreC init.Control init.Memory (+ oop 12) 1) // store2 = (StoreC init.Control store1 (+ oop 14) 2) // mem.SLICE(#short[*]) := store2 // // DETAILS: // An InitializeNode collects and isolates object initialization after // an AllocateNode and before the next possible safepoint. As a // memory barrier (MemBarNode), it keeps critical stores from drifting // down past any safepoint or any publication of the allocation. // Before this barrier, a newly-allocated object may have uninitialized bits. // After this barrier, it may be treated as a real oop, and GC is allowed. // // The semantics of the InitializeNode include an implicit zeroing of // the new object from object header to the end of the object. // (The object header and end are determined by the AllocateNode.) // // Certain stores may be added as direct inputs to the InitializeNode. // These stores must update raw memory, and they must be to addresses // derived from the raw address produced by AllocateNode, and with // a constant offset. They must be ordered by increasing offset. // The first one is at in(RawStores), the last at in(req()-1). // Unlike most memory operations, they are not linked in a chain, // but are displayed in parallel as users of the rawmem output of // the allocation. // // (See comments in InitializeNode::capture_store, which continue // the example given above.) // // When the associated Allocate is macro-expanded, the InitializeNode // may be rewritten to optimize collected stores. A ClearArrayNode // may also be created at that point to represent any required zeroing. // The InitializeNode is then marked 'complete', prohibiting further // capturing of nearby memory operations. // // During macro-expansion, all captured initializations which store // constant values of 32 bits or smaller are coalesced (if advantagous) // into larger 'tiles' 32 or 64 bits. This allows an object to be // initialized in fewer memory operations. Memory words which are // covered by neither tiles nor non-constant stores are pre-zeroed // by explicit stores of zero. (The code shape happens to do all // zeroing first, then all other stores, with both sequences occurring // in order of ascending offsets.) // // Alternatively, code may be inserted between an AllocateNode and its // InitializeNode, to perform arbitrary initialization of the new object. // E.g., the object copying intrinsics insert complex data transfers here. // The initialization must then be marked as 'complete' disable the // built-in zeroing semantics and the collection of initializing stores. // // While an InitializeNode is incomplete, reads from the memory state // produced by it are optimizable if they match the control edge and // new oop address associated with the allocation/initialization. // They return a stored value (if the offset matches) or else zero. // A write to the memory state, if it matches control and address, // and if it is to a constant offset, may be 'captured' by the // InitializeNode. It is cloned as a raw memory operation and rewired // inside the initialization, to the raw oop produced by the allocation. // Operations on addresses which are provably distinct (e.g., to // other AllocateNodes) are allowed to bypass the initialization. // // The effect of all this is to consolidate object initialization // (both arrays and non-arrays, both piecewise and bulk) into a // single location, where it can be optimized as a unit. // // Only stores with an offset less than TrackedInitializationLimit words // will be considered for capture by an InitializeNode. This puts a // reasonable limit on the complexity of optimized initializations. //---------------------------InitializeNode------------------------------------ InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop) : _is_complete(false), MemBarNode(C, adr_type, rawoop) { init_class_id(Class_Initialize); assert(adr_type == Compile::AliasIdxRaw, "only valid atp"); assert(in(RawAddress) == rawoop, "proper init"); // Note: allocation() can be NULL, for secondary initialization barriers } // Since this node is not matched, it will be processed by the // register allocator. Declare that there are no constraints // on the allocation of the RawAddress edge. const RegMask &InitializeNode::in_RegMask(uint idx) const { // This edge should be set to top, by the set_complete. But be conservative. if (idx == InitializeNode::RawAddress) return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]); return RegMask::Empty; } Node* InitializeNode::memory(uint alias_idx) { Node* mem = in(Memory); if (mem->is_MergeMem()) { return mem->as_MergeMem()->memory_at(alias_idx); } else { // incoming raw memory is not split return mem; } } bool InitializeNode::is_non_zero() { if (is_complete()) return false; remove_extra_zeroes(); return (req() > RawStores); } void InitializeNode::set_complete(PhaseGVN* phase) { assert(!is_complete(), "caller responsibility"); _is_complete = true; // After this node is complete, it contains a bunch of // raw-memory initializations. There is no need for // it to have anything to do with non-raw memory effects. // Therefore, tell all non-raw users to re-optimize themselves, // after skipping the memory effects of this initialization. PhaseIterGVN* igvn = phase->is_IterGVN(); if (igvn) igvn->add_users_to_worklist(this); } // convenience function // return false if the init contains any stores already bool AllocateNode::maybe_set_complete(PhaseGVN* phase) { InitializeNode* init = initialization(); if (init == NULL || init->is_complete()) return false; init->remove_extra_zeroes(); // for now, if this allocation has already collected any inits, bail: if (init->is_non_zero()) return false; init->set_complete(phase); return true; } void InitializeNode::remove_extra_zeroes() { if (req() == RawStores) return; Node* zmem = zero_memory(); uint fill = RawStores; for (uint i = fill; i < req(); i++) { Node* n = in(i); if (n->is_top() || n == zmem) continue; // skip if (fill < i) set_req(fill, n); // compact ++fill; } // delete any empty spaces created: while (fill < req()) { del_req(fill); } } // Helper for remembering which stores go with which offsets. intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) { if (!st->is_Store()) return -1; // can happen to dead code via subsume_node intptr_t offset = -1; Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address), phase, offset); if (base == NULL) return -1; // something is dead, if (offset < 0) return -1; // dead, dead return offset; } // Helper for proving that an initialization expression is // "simple enough" to be folded into an object initialization. // Attempts to prove that a store's initial value 'n' can be captured // within the initialization without creating a vicious cycle, such as: // { Foo p = new Foo(); p.next = p; } // True for constants and parameters and small combinations thereof. bool InitializeNode::detect_init_independence(Node* n, bool st_is_pinned, int& count) { if (n == NULL) return true; // (can this really happen?) if (n->is_Proj()) n = n->in(0); if (n == this) return false; // found a cycle if (n->is_Con()) return true; if (n->is_Start()) return true; // params, etc., are OK if (n->is_Root()) return true; // even better Node* ctl = n->in(0); if (ctl != NULL && !ctl->is_top()) { if (ctl->is_Proj()) ctl = ctl->in(0); if (ctl == this) return false; // If we already know that the enclosing memory op is pinned right after // the init, then any control flow that the store has picked up // must have preceded the init, or else be equal to the init. // Even after loop optimizations (which might change control edges) // a store is never pinned *before* the availability of its inputs. if (!MemNode::all_controls_dominate(n, this)) return false; // failed to prove a good control } // Check data edges for possible dependencies on 'this'. if ((count += 1) > 20) return false; // complexity limit for (uint i = 1; i < n->req(); i++) { Node* m = n->in(i); if (m == NULL || m == n || m->is_top()) continue; uint first_i = n->find_edge(m); if (i != first_i) continue; // process duplicate edge just once if (!detect_init_independence(m, st_is_pinned, count)) { return false; } } return true; } // Here are all the checks a Store must pass before it can be moved into // an initialization. Returns zero if a check fails. // On success, returns the (constant) offset to which the store applies, // within the initialized memory. intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase) { const int FAIL = 0; if (st->req() != MemNode::ValueIn + 1) return FAIL; // an inscrutable StoreNode (card mark?) Node* ctl = st->in(MemNode::Control); if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this)) return FAIL; // must be unconditional after the initialization Node* mem = st->in(MemNode::Memory); if (!(mem->is_Proj() && mem->in(0) == this)) return FAIL; // must not be preceded by other stores Node* adr = st->in(MemNode::Address); intptr_t offset; AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset); if (alloc == NULL) return FAIL; // inscrutable address if (alloc != allocation()) return FAIL; // wrong allocation! (store needs to float up) Node* val = st->in(MemNode::ValueIn); int complexity_count = 0; if (!detect_init_independence(val, true, complexity_count)) return FAIL; // stored value must be 'simple enough' return offset; // success } // Find the captured store in(i) which corresponds to the range // [start..start+size) in the initialized object. // If there is one, return its index i. If there isn't, return the // negative of the index where it should be inserted. // Return 0 if the queried range overlaps an initialization boundary // or if dead code is encountered. // If size_in_bytes is zero, do not bother with overlap checks. int InitializeNode::captured_store_insertion_point(intptr_t start, int size_in_bytes, PhaseTransform* phase) { const int FAIL = 0, MAX_STORE = BytesPerLong; if (is_complete()) return FAIL; // arraycopy got here first; punt assert(allocation() != NULL, "must be present"); // no negatives, no header fields: if (start < (intptr_t) allocation()->minimum_header_size()) return FAIL; // after a certain size, we bail out on tracking all the stores: intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize); if (start >= ti_limit) return FAIL; for (uint i = InitializeNode::RawStores, limit = req(); ; ) { if (i >= limit) return -(int)i; // not found; here is where to put it Node* st = in(i); intptr_t st_off = get_store_offset(st, phase); if (st_off < 0) { if (st != zero_memory()) { return FAIL; // bail out if there is dead garbage } } else if (st_off > start) { // ...we are done, since stores are ordered if (st_off < start + size_in_bytes) { return FAIL; // the next store overlaps } return -(int)i; // not found; here is where to put it } else if (st_off < start) { if (size_in_bytes != 0 && start < st_off + MAX_STORE && start < st_off + st->as_Store()->memory_size()) { return FAIL; // the previous store overlaps } } else { if (size_in_bytes != 0 && st->as_Store()->memory_size() != size_in_bytes) { return FAIL; // mismatched store size } return i; } ++i; } } // Look for a captured store which initializes at the offset 'start' // with the given size. If there is no such store, and no other // initialization interferes, then return zero_memory (the memory // projection of the AllocateNode). Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes, PhaseTransform* phase) { assert(stores_are_sane(phase), ""); int i = captured_store_insertion_point(start, size_in_bytes, phase); if (i == 0) { return NULL; // something is dead } else if (i < 0) { return zero_memory(); // just primordial zero bits here } else { Node* st = in(i); // here is the store at this position assert(get_store_offset(st->as_Store(), phase) == start, "sanity"); return st; } } // Create, as a raw pointer, an address within my new object at 'offset'. Node* InitializeNode::make_raw_address(intptr_t offset, PhaseTransform* phase) { Node* addr = in(RawAddress); if (offset != 0) { Compile* C = phase->C; addr = phase->transform( new (C, 4) AddPNode(C->top(), addr, phase->MakeConX(offset)) ); } return addr; } // Clone the given store, converting it into a raw store // initializing a field or element of my new object. // Caller is responsible for retiring the original store, // with subsume_node or the like. // // From the example above InitializeNode::InitializeNode, // here are the old stores to be captured: // store1 = (StoreC init.Control init.Memory (+ oop 12) 1) // store2 = (StoreC init.Control store1 (+ oop 14) 2) // // Here is the changed code; note the extra edges on init: // alloc = (Allocate ...) // rawoop = alloc.RawAddress // rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1) // rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2) // init = (Initialize alloc.Control alloc.Memory rawoop // rawstore1 rawstore2) // Node* InitializeNode::capture_store(StoreNode* st, intptr_t start, PhaseTransform* phase) { assert(stores_are_sane(phase), ""); if (start < 0) return NULL; assert(can_capture_store(st, phase) == start, "sanity"); Compile* C = phase->C; int size_in_bytes = st->memory_size(); int i = captured_store_insertion_point(start, size_in_bytes, phase); if (i == 0) return NULL; // bail out Node* prev_mem = NULL; // raw memory for the captured store if (i > 0) { prev_mem = in(i); // there is a pre-existing store under this one set_req(i, C->top()); // temporarily disconnect it // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect. } else { i = -i; // no pre-existing store prev_mem = zero_memory(); // a slice of the newly allocated object if (i > InitializeNode::RawStores && in(i-1) == prev_mem) set_req(--i, C->top()); // reuse this edge; it has been folded away else ins_req(i, C->top()); // build a new edge } Node* new_st = st->clone(); new_st->set_req(MemNode::Control, in(Control)); new_st->set_req(MemNode::Memory, prev_mem); new_st->set_req(MemNode::Address, make_raw_address(start, phase)); new_st = phase->transform(new_st); // At this point, new_st might have swallowed a pre-existing store // at the same offset, or perhaps new_st might have disappeared, // if it redundantly stored the same value (or zero to fresh memory). // In any case, wire it in: set_req(i, new_st); // The caller may now kill the old guy. DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase)); assert(check_st == new_st || check_st == NULL, "must be findable"); assert(!is_complete(), ""); return new_st; } static bool store_constant(jlong* tiles, int num_tiles, intptr_t st_off, int st_size, jlong con) { if ((st_off & (st_size-1)) != 0) return false; // strange store offset (assume size==2**N) address addr = (address)tiles + st_off; assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob"); switch (st_size) { case sizeof(jbyte): *(jbyte*) addr = (jbyte) con; break; case sizeof(jchar): *(jchar*) addr = (jchar) con; break; case sizeof(jint): *(jint*) addr = (jint) con; break; case sizeof(jlong): *(jlong*) addr = (jlong) con; break; default: return false; // strange store size (detect size!=2**N here) } return true; // return success to caller } // Coalesce subword constants into int constants and possibly // into long constants. The goal, if the CPU permits, // is to initialize the object with a small number of 64-bit tiles. // Also, convert floating-point constants to bit patterns. // Non-constants are not relevant to this pass. // // In terms of the running example on InitializeNode::InitializeNode // and InitializeNode::capture_store, here is the transformation // of rawstore1 and rawstore2 into rawstore12: // alloc = (Allocate ...) // rawoop = alloc.RawAddress // tile12 = 0x00010002 // rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12) // init = (Initialize alloc.Control alloc.Memory rawoop rawstore12) // void InitializeNode::coalesce_subword_stores(intptr_t header_size, Node* size_in_bytes, PhaseGVN* phase) { Compile* C = phase->C; assert(stores_are_sane(phase), ""); // Note: After this pass, they are not completely sane, // since there may be some overlaps. int old_subword = 0, old_long = 0, new_int = 0, new_long = 0; intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize); intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit); size_limit = MIN2(size_limit, ti_limit); size_limit = align_size_up(size_limit, BytesPerLong); int num_tiles = size_limit / BytesPerLong; // allocate space for the tile map: const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small jlong tiles_buf[small_len]; Node* nodes_buf[small_len]; jlong inits_buf[small_len]; jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0] : NEW_RESOURCE_ARRAY(jlong, num_tiles)); Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0] : NEW_RESOURCE_ARRAY(Node*, num_tiles)); jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0] : NEW_RESOURCE_ARRAY(jlong, num_tiles)); // tiles: exact bitwise model of all primitive constants // nodes: last constant-storing node subsumed into the tiles model // inits: which bytes (in each tile) are touched by any initializations //// Pass A: Fill in the tile model with any relevant stores. Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles); Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles); Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles); Node* zmem = zero_memory(); // initially zero memory state for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) { Node* st = in(i); intptr_t st_off = get_store_offset(st, phase); // Figure out the store's offset and constant value: if (st_off < header_size) continue; //skip (ignore header) if (st->in(MemNode::Memory) != zmem) continue; //skip (odd store chain) int st_size = st->as_Store()->memory_size(); if (st_off + st_size > size_limit) break; // Record which bytes are touched, whether by constant or not. if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1)) continue; // skip (strange store size) const Type* val = phase->type(st->in(MemNode::ValueIn)); if (!val->singleton()) continue; //skip (non-con store) BasicType type = val->basic_type(); jlong con = 0; switch (type) { case T_INT: con = val->is_int()->get_con(); break; case T_LONG: con = val->is_long()->get_con(); break; case T_FLOAT: con = jint_cast(val->getf()); break; case T_DOUBLE: con = jlong_cast(val->getd()); break; default: continue; //skip (odd store type) } if (type == T_LONG && Matcher::isSimpleConstant64(con) && st->Opcode() == Op_StoreL) { continue; // This StoreL is already optimal. } // Store down the constant. store_constant(tiles, num_tiles, st_off, st_size, con); intptr_t j = st_off >> LogBytesPerLong; if (type == T_INT && st_size == BytesPerInt && (st_off & BytesPerInt) == BytesPerInt) { jlong lcon = tiles[j]; if (!Matcher::isSimpleConstant64(lcon) && st->Opcode() == Op_StoreI) { // This StoreI is already optimal by itself. jint* intcon = (jint*) &tiles[j]; intcon[1] = 0; // undo the store_constant() // If the previous store is also optimal by itself, back up and // undo the action of the previous loop iteration... if we can. // But if we can't, just let the previous half take care of itself. st = nodes[j]; st_off -= BytesPerInt; con = intcon[0]; if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) { assert(st_off >= header_size, "still ignoring header"); assert(get_store_offset(st, phase) == st_off, "must be"); assert(in(i-1) == zmem, "must be"); DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn))); assert(con == tcon->is_int()->get_con(), "must be"); // Undo the effects of the previous loop trip, which swallowed st: intcon[0] = 0; // undo store_constant() set_req(i-1, st); // undo set_req(i, zmem) nodes[j] = NULL; // undo nodes[j] = st --old_subword; // undo ++old_subword } continue; // This StoreI is already optimal. } } // This store is not needed. set_req(i, zmem); nodes[j] = st; // record for the moment if (st_size < BytesPerLong) // something has changed ++old_subword; // includes int/float, but who's counting... else ++old_long; } if ((old_subword + old_long) == 0) return; // nothing more to do //// Pass B: Convert any non-zero tiles into optimal constant stores. // Be sure to insert them before overlapping non-constant stores. // (E.g., byte[] x = { 1,2,y,4 } => x[int 0] = 0x01020004, x[2]=y.) for (int j = 0; j < num_tiles; j++) { jlong con = tiles[j]; jlong init = inits[j]; if (con == 0) continue; jint con0, con1; // split the constant, address-wise jint init0, init1; // split the init map, address-wise { union { jlong con; jint intcon[2]; } u; u.con = con; con0 = u.intcon[0]; con1 = u.intcon[1]; u.con = init; init0 = u.intcon[0]; init1 = u.intcon[1]; } Node* old = nodes[j]; assert(old != NULL, "need the prior store"); intptr_t offset = (j * BytesPerLong); bool split = !Matcher::isSimpleConstant64(con); if (offset < header_size) { assert(offset + BytesPerInt >= header_size, "second int counts"); assert(*(jint*)&tiles[j] == 0, "junk in header"); split = true; // only the second word counts // Example: int a[] = { 42 ... } } else if (con0 == 0 && init0 == -1) { split = true; // first word is covered by full inits // Example: int a[] = { ... foo(), 42 ... } } else if (con1 == 0 && init1 == -1) { split = true; // second word is covered by full inits // Example: int a[] = { ... 42, foo() ... } } // Here's a case where init0 is neither 0 nor -1: // byte a[] = { ... 0,0,foo(),0, 0,0,0,42 ... } // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF. // In this case the tile is not split; it is (jlong)42. // The big tile is stored down, and then the foo() value is inserted. // (If there were foo(),foo() instead of foo(),0, init0 would be -1.) Node* ctl = old->in(MemNode::Control); Node* adr = make_raw_address(offset, phase); const TypePtr* atp = TypeRawPtr::BOTTOM; // One or two coalesced stores to plop down. Node* st[2]; intptr_t off[2]; int nst = 0; if (!split) { ++new_long; off[nst] = offset; st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp, phase->longcon(con), T_LONG); } else { // Omit either if it is a zero. if (con0 != 0) { ++new_int; off[nst] = offset; st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp, phase->intcon(con0), T_INT); } if (con1 != 0) { ++new_int; offset += BytesPerInt; adr = make_raw_address(offset, phase); off[nst] = offset; st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp, phase->intcon(con1), T_INT); } } // Insert second store first, then the first before the second. // Insert each one just before any overlapping non-constant stores. while (nst > 0) { Node* st1 = st[--nst]; C->copy_node_notes_to(st1, old); st1 = phase->transform(st1); offset = off[nst]; assert(offset >= header_size, "do not smash header"); int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase); guarantee(ins_idx != 0, "must re-insert constant store"); if (ins_idx < 0) ins_idx = -ins_idx; // never overlap if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem) set_req(--ins_idx, st1); else ins_req(ins_idx, st1); } } if (PrintCompilation && WizardMode) tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long", old_subword, old_long, new_int, new_long); if (C->log() != NULL) C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'", old_subword, old_long, new_int, new_long); // Clean up any remaining occurrences of zmem: remove_extra_zeroes(); } // Explore forward from in(start) to find the first fully initialized // word, and return its offset. Skip groups of subword stores which // together initialize full words. If in(start) is itself part of a // fully initialized word, return the offset of in(start). If there // are no following full-word stores, or if something is fishy, return // a negative value. intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) { int int_map = 0; intptr_t int_map_off = 0; const int FULL_MAP = right_n_bits(BytesPerInt); // the int_map we hope for for (uint i = start, limit = req(); i < limit; i++) { Node* st = in(i); intptr_t st_off = get_store_offset(st, phase); if (st_off < 0) break; // return conservative answer int st_size = st->as_Store()->memory_size(); if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) { return st_off; // we found a complete word init } // update the map: intptr_t this_int_off = align_size_down(st_off, BytesPerInt); if (this_int_off != int_map_off) { // reset the map: int_map = 0; int_map_off = this_int_off; } int subword_off = st_off - this_int_off; int_map |= right_n_bits(st_size) << subword_off; if ((int_map & FULL_MAP) == FULL_MAP) { return this_int_off; // we found a complete word init } // Did this store hit or cross the word boundary? intptr_t next_int_off = align_size_down(st_off + st_size, BytesPerInt); if (next_int_off == this_int_off + BytesPerInt) { // We passed the current int, without fully initializing it. int_map_off = next_int_off; int_map >>= BytesPerInt; } else if (next_int_off > this_int_off + BytesPerInt) { // We passed the current and next int. return this_int_off + BytesPerInt; } } return -1; } // Called when the associated AllocateNode is expanded into CFG. // At this point, we may perform additional optimizations. // Linearize the stores by ascending offset, to make memory // activity as coherent as possible. Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr, intptr_t header_size, Node* size_in_bytes, PhaseGVN* phase) { assert(!is_complete(), "not already complete"); assert(stores_are_sane(phase), ""); assert(allocation() != NULL, "must be present"); remove_extra_zeroes(); if (ReduceFieldZeroing || ReduceBulkZeroing) // reduce instruction count for common initialization patterns coalesce_subword_stores(header_size, size_in_bytes, phase); Node* zmem = zero_memory(); // initially zero memory state Node* inits = zmem; // accumulating a linearized chain of inits #ifdef ASSERT intptr_t first_offset = allocation()->minimum_header_size(); intptr_t last_init_off = first_offset; // previous init offset intptr_t last_init_end = first_offset; // previous init offset+size intptr_t last_tile_end = first_offset; // previous tile offset+size #endif intptr_t zeroes_done = header_size; bool do_zeroing = true; // we might give up if inits are very sparse int big_init_gaps = 0; // how many large gaps have we seen? if (ZeroTLAB) do_zeroing = false; if (!ReduceFieldZeroing && !ReduceBulkZeroing) do_zeroing = false; for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) { Node* st = in(i); intptr_t st_off = get_store_offset(st, phase); if (st_off < 0) break; // unknown junk in the inits if (st->in(MemNode::Memory) != zmem) break; // complicated store chains somehow in list int st_size = st->as_Store()->memory_size(); intptr_t next_init_off = st_off + st_size; if (do_zeroing && zeroes_done < next_init_off) { // See if this store needs a zero before it or under it. intptr_t zeroes_needed = st_off; if (st_size < BytesPerInt) { // Look for subword stores which only partially initialize words. // If we find some, we must lay down some word-level zeroes first, // underneath the subword stores. // // Examples: // byte[] a = { p,q,r,s } => a[0]=p,a[1]=q,a[2]=r,a[3]=s // byte[] a = { x,y,0,0 } => a[0..3] = 0, a[0]=x,a[1]=y // byte[] a = { 0,0,z,0 } => a[0..3] = 0, a[2]=z // // Note: coalesce_subword_stores may have already done this, // if it was prompted by constant non-zero subword initializers. // But this case can still arise with non-constant stores. intptr_t next_full_store = find_next_fullword_store(i, phase); // In the examples above: // in(i) p q r s x y z // st_off 12 13 14 15 12 13 14 // st_size 1 1 1 1 1 1 1 // next_full_s. 12 16 16 16 16 16 16 // z's_done 12 16 16 16 12 16 12 // z's_needed 12 16 16 16 16 16 16 // zsize 0 0 0 0 4 0 4 if (next_full_store < 0) { // Conservative tack: Zero to end of current word. zeroes_needed = align_size_up(zeroes_needed, BytesPerInt); } else { // Zero to beginning of next fully initialized word. // Or, don't zero at all, if we are already in that word. assert(next_full_store >= zeroes_needed, "must go forward"); assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary"); zeroes_needed = next_full_store; } } if (zeroes_needed > zeroes_done) { intptr_t zsize = zeroes_needed - zeroes_done; // Do some incremental zeroing on rawmem, in parallel with inits. zeroes_done = align_size_down(zeroes_done, BytesPerInt); rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr, zeroes_done, zeroes_needed, phase); zeroes_done = zeroes_needed; if (zsize > Matcher::init_array_short_size && ++big_init_gaps > 2) do_zeroing = false; // leave the hole, next time } } // Collect the store and move on: st->set_req(MemNode::Memory, inits); inits = st; // put it on the linearized chain set_req(i, zmem); // unhook from previous position if (zeroes_done == st_off) zeroes_done = next_init_off; assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any"); #ifdef ASSERT // Various order invariants. Weaker than stores_are_sane because // a large constant tile can be filled in by smaller non-constant stores. assert(st_off >= last_init_off, "inits do not reverse"); last_init_off = st_off; const Type* val = NULL; if (st_size >= BytesPerInt && (val = phase->type(st->in(MemNode::ValueIn)))->singleton() && (int)val->basic_type() < (int)T_OBJECT) { assert(st_off >= last_tile_end, "tiles do not overlap"); assert(st_off >= last_init_end, "tiles do not overwrite inits"); last_tile_end = MAX2(last_tile_end, next_init_off); } else { intptr_t st_tile_end = align_size_up(next_init_off, BytesPerLong); assert(st_tile_end >= last_tile_end, "inits stay with tiles"); assert(st_off >= last_init_end, "inits do not overlap"); last_init_end = next_init_off; // it's a non-tile } #endif //ASSERT } remove_extra_zeroes(); // clear out all the zmems left over add_req(inits); if (!ZeroTLAB) { // If anything remains to be zeroed, zero it all now. zeroes_done = align_size_down(zeroes_done, BytesPerInt); // if it is the last unused 4 bytes of an instance, forget about it intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint); if (zeroes_done + BytesPerLong >= size_limit) { assert(allocation() != NULL, ""); Node* klass_node = allocation()->in(AllocateNode::KlassNode); ciKlass* k = phase->type(klass_node)->is_klassptr()->klass(); if (zeroes_done == k->layout_helper()) zeroes_done = size_limit; } if (zeroes_done < size_limit) { rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr, zeroes_done, size_in_bytes, phase); } } set_complete(phase); return rawmem; } #ifdef ASSERT bool InitializeNode::stores_are_sane(PhaseTransform* phase) { if (is_complete()) return true; // stores could be anything at this point assert(allocation() != NULL, "must be present"); intptr_t last_off = allocation()->minimum_header_size(); for (uint i = InitializeNode::RawStores; i < req(); i++) { Node* st = in(i); intptr_t st_off = get_store_offset(st, phase); if (st_off < 0) continue; // ignore dead garbage if (last_off > st_off) { tty->print_cr("*** bad store offset at %d: %d > %d", i, last_off, st_off); this->dump(2); assert(false, "ascending store offsets"); return false; } last_off = st_off + st->as_Store()->memory_size(); } return true; } #endif //ASSERT //============================MergeMemNode===================================== // // SEMANTICS OF MEMORY MERGES: A MergeMem is a memory state assembled from several // contributing store or call operations. Each contributor provides the memory // state for a particular "alias type" (see Compile::alias_type). For example, // if a MergeMem has an input X for alias category #6, then any memory reference // to alias category #6 may use X as its memory state input, as an exact equivalent // to using the MergeMem as a whole. // Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p) // // (Here, the notation gives the index of the relevant adr_type.) // // In one special case (and more cases in the future), alias categories overlap. // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory // states. Therefore, if a MergeMem has only one contributing input W for Bot, // it is exactly equivalent to that state W: // MergeMem(: W) <==> W // // Usually, the merge has more than one input. In that case, where inputs // overlap (i.e., one is Bot), the narrower alias type determines the memory // state for that type, and the wider alias type (Bot) fills in everywhere else: // Load<5>( MergeMem(: W, <6>: X), p ) <==> Load<5>(W,p) // Load<6>( MergeMem(: W, <6>: X), p ) <==> Load<6>(X,p) // // A merge can take a "wide" memory state as one of its narrow inputs. // This simply means that the merge observes out only the relevant parts of // the wide input. That is, wide memory states arriving at narrow merge inputs // are implicitly "filtered" or "sliced" as necessary. (This is rare.) // // These rules imply that MergeMem nodes may cascade (via their links), // and that memory slices "leak through": // MergeMem(: MergeMem(: W, <7>: Y)) <==> MergeMem(: W, <7>: Y) // // But, in such a cascade, repeated memory slices can "block the leak": // MergeMem(: MergeMem(: W, <7>: Y), <7>: Y') <==> MergeMem(: W, <7>: Y') // // In the last example, Y is not part of the combined memory state of the // outermost MergeMem. The system must, of course, prevent unschedulable // memory states from arising, so you can be sure that the state Y is somehow // a precursor to state Y'. // // // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array // of each MergeMemNode array are exactly the numerical alias indexes, including // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw. The functions // Compile::alias_type (and kin) produce and manage these indexes. // // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node. // (Note that this provides quick access to the top node inside MergeMem methods, // without the need to reach out via TLS to Compile::current.) // // As a consequence of what was just described, a MergeMem that represents a full // memory state has an edge in(AliasIdxBot) which is a "wide" memory state, // containing all alias categories. // // MergeMem nodes never (?) have control inputs, so in(0) is NULL. // // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either // a memory state for the alias type , or else the top node, meaning that // there is no particular input for that alias type. Note that the length of // a MergeMem is variable, and may be extended at any time to accommodate new // memory states at larger alias indexes. When merges grow, they are of course // filled with "top" in the unused in() positions. // // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable. // (Top was chosen because it works smoothly with passes like GCM.) // // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM. (It is // the type of random VM bits like TLS references.) Since it is always the // first non-Bot memory slice, some low-level loops use it to initialize an // index variable: for (i = AliasIdxRaw; i < req(); i++). // // // ACCESSORS: There is a special accessor MergeMemNode::base_memory which returns // the distinguished "wide" state. The accessor MergeMemNode::memory_at(N) returns // the memory state for alias type , or (if there is no particular slice at , // it returns the base memory. To prevent bugs, memory_at does not accept // or indexes. The iterator MergeMemStream provides robust iteration over // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited. // // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't // really that different from the other memory inputs. An abbreviation called // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy. // // // PARTIAL MEMORY STATES: During optimization, MergeMem nodes may arise that represent // partial memory states. When a Phi splits through a MergeMem, the copy of the Phi // that "emerges though" the base memory will be marked as excluding the alias types // of the other (narrow-memory) copies which "emerged through" the narrow edges: // // Phi(U, MergeMem(: W, <8>: Y)) // ==Ideal=> MergeMem(: Phi(U, W), Phi<8>(U, Y)) // // This strange "subtraction" effect is necessary to ensure IGVN convergence. // (It is currently unimplemented.) As you can see, the resulting merge is // actually a disjoint union of memory states, rather than an overlay. // //------------------------------MergeMemNode----------------------------------- Node* MergeMemNode::make_empty_memory() { Node* empty_memory = (Node*) Compile::current()->top(); assert(empty_memory->is_top(), "correct sentinel identity"); return empty_memory; } MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) { init_class_id(Class_MergeMem); // all inputs are nullified in Node::Node(int) // set_input(0, NULL); // no control input // Initialize the edges uniformly to top, for starters. Node* empty_mem = make_empty_memory(); for (uint i = Compile::AliasIdxTop; i < req(); i++) { init_req(i,empty_mem); } assert(empty_memory() == empty_mem, ""); if( new_base != NULL && new_base->is_MergeMem() ) { MergeMemNode* mdef = new_base->as_MergeMem(); assert(mdef->empty_memory() == empty_mem, "consistent sentinels"); for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) { mms.set_memory(mms.memory2()); } assert(base_memory() == mdef->base_memory(), ""); } else { set_base_memory(new_base); } } // Make a new, untransformed MergeMem with the same base as 'mem'. // If mem is itself a MergeMem, populate the result with the same edges. MergeMemNode* MergeMemNode::make(Compile* C, Node* mem) { return new(C, 1+Compile::AliasIdxRaw) MergeMemNode(mem); } //------------------------------cmp-------------------------------------------- uint MergeMemNode::hash() const { return NO_HASH; } uint MergeMemNode::cmp( const Node &n ) const { return (&n == this); // Always fail except on self } //------------------------------Identity--------------------------------------- Node* MergeMemNode::Identity(PhaseTransform *phase) { // Identity if this merge point does not record any interesting memory // disambiguations. Node* base_mem = base_memory(); Node* empty_mem = empty_memory(); if (base_mem != empty_mem) { // Memory path is not dead? for (uint i = Compile::AliasIdxRaw; i < req(); i++) { Node* mem = in(i); if (mem != empty_mem && mem != base_mem) { return this; // Many memory splits; no change } } } return base_mem; // No memory splits; ID on the one true input } //------------------------------Ideal------------------------------------------ // This method is invoked recursively on chains of MergeMem nodes Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) { // Remove chain'd MergeMems // // This is delicate, because the each "in(i)" (i >= Raw) is interpreted // relative to the "in(Bot)". Since we are patching both at the same time, // we have to be careful to read each "in(i)" relative to the old "in(Bot)", // but rewrite each "in(i)" relative to the new "in(Bot)". Node *progress = NULL; Node* old_base = base_memory(); Node* empty_mem = empty_memory(); if (old_base == empty_mem) return NULL; // Dead memory path. MergeMemNode* old_mbase; if (old_base != NULL && old_base->is_MergeMem()) old_mbase = old_base->as_MergeMem(); else old_mbase = NULL; Node* new_base = old_base; // simplify stacked MergeMems in base memory if (old_mbase) new_base = old_mbase->base_memory(); // the base memory might contribute new slices beyond my req() if (old_mbase) grow_to_match(old_mbase); // Look carefully at the base node if it is a phi. PhiNode* phi_base; if (new_base != NULL && new_base->is_Phi()) phi_base = new_base->as_Phi(); else phi_base = NULL; Node* phi_reg = NULL; uint phi_len = (uint)-1; if (phi_base != NULL && !phi_base->is_copy()) { // do not examine phi if degraded to a copy phi_reg = phi_base->region(); phi_len = phi_base->req(); // see if the phi is unfinished for (uint i = 1; i < phi_len; i++) { if (phi_base->in(i) == NULL) { // incomplete phi; do not look at it yet! phi_reg = NULL; phi_len = (uint)-1; break; } } } // Note: We do not call verify_sparse on entry, because inputs // can normalize to the base_memory via subsume_node or similar // mechanisms. This method repairs that damage. assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels"); // Look at each slice. for (uint i = Compile::AliasIdxRaw; i < req(); i++) { Node* old_in = in(i); // calculate the old memory value Node* old_mem = old_in; if (old_mem == empty_mem) old_mem = old_base; assert(old_mem == memory_at(i), ""); // maybe update (reslice) the old memory value // simplify stacked MergeMems Node* new_mem = old_mem; MergeMemNode* old_mmem; if (old_mem != NULL && old_mem->is_MergeMem()) old_mmem = old_mem->as_MergeMem(); else old_mmem = NULL; if (old_mmem == this) { // This can happen if loops break up and safepoints disappear. // A merge of BotPtr (default) with a RawPtr memory derived from a // safepoint can be rewritten to a merge of the same BotPtr with // the BotPtr phi coming into the loop. If that phi disappears // also, we can end up with a self-loop of the mergemem. // In general, if loops degenerate and memory effects disappear, // a mergemem can be left looking at itself. This simply means // that the mergemem's default should be used, since there is // no longer any apparent effect on this slice. // Note: If a memory slice is a MergeMem cycle, it is unreachable // from start. Update the input to TOP. new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base; } else if (old_mmem != NULL) { new_mem = old_mmem->memory_at(i); } // else preceeding memory was not a MergeMem // replace equivalent phis (unfortunately, they do not GVN together) if (new_mem != NULL && new_mem != new_base && new_mem->req() == phi_len && new_mem->in(0) == phi_reg) { if (new_mem->is_Phi()) { PhiNode* phi_mem = new_mem->as_Phi(); for (uint i = 1; i < phi_len; i++) { if (phi_base->in(i) != phi_mem->in(i)) { phi_mem = NULL; break; } } if (phi_mem != NULL) { // equivalent phi nodes; revert to the def new_mem = new_base; } } } // maybe store down a new value Node* new_in = new_mem; if (new_in == new_base) new_in = empty_mem; if (new_in != old_in) { // Warning: Do not combine this "if" with the previous "if" // A memory slice might have be be rewritten even if it is semantically // unchanged, if the base_memory value has changed. set_req(i, new_in); progress = this; // Report progress } } if (new_base != old_base) { set_req(Compile::AliasIdxBot, new_base); // Don't use set_base_memory(new_base), because we need to update du. assert(base_memory() == new_base, ""); progress = this; } if( base_memory() == this ) { // a self cycle indicates this memory path is dead set_req(Compile::AliasIdxBot, empty_mem); } // Resolve external cycles by calling Ideal on a MergeMem base_memory // Recursion must occur after the self cycle check above if( base_memory()->is_MergeMem() ) { MergeMemNode *new_mbase = base_memory()->as_MergeMem(); Node *m = phase->transform(new_mbase); // Rollup any cycles if( m != NULL && (m->is_top() || m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem) ) { // propagate rollup of dead cycle to self set_req(Compile::AliasIdxBot, empty_mem); } } if( base_memory() == empty_mem ) { progress = this; // Cut inputs during Parse phase only. // During Optimize phase a dead MergeMem node will be subsumed by Top. if( !can_reshape ) { for (uint i = Compile::AliasIdxRaw; i < req(); i++) { if( in(i) != empty_mem ) { set_req(i, empty_mem); } } } } if( !progress && base_memory()->is_Phi() && can_reshape ) { // Check if PhiNode::Ideal's "Split phis through memory merges" // transform should be attempted. Look for this->phi->this cycle. uint merge_width = req(); if (merge_width > Compile::AliasIdxRaw) { PhiNode* phi = base_memory()->as_Phi(); for( uint i = 1; i < phi->req(); ++i ) {// For all paths in if (phi->in(i) == this) { phase->is_IterGVN()->_worklist.push(phi); break; } } } } assert(progress || verify_sparse(), "please, no dups of base"); return progress; } //-------------------------set_base_memory------------------------------------- void MergeMemNode::set_base_memory(Node *new_base) { Node* empty_mem = empty_memory(); set_req(Compile::AliasIdxBot, new_base); assert(memory_at(req()) == new_base, "must set default memory"); // Clear out other occurrences of new_base: if (new_base != empty_mem) { for (uint i = Compile::AliasIdxRaw; i < req(); i++) { if (in(i) == new_base) set_req(i, empty_mem); } } } //------------------------------out_RegMask------------------------------------ const RegMask &MergeMemNode::out_RegMask() const { return RegMask::Empty; } //------------------------------dump_spec-------------------------------------- #ifndef PRODUCT void MergeMemNode::dump_spec(outputStream *st) const { st->print(" {"); Node* base_mem = base_memory(); for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) { Node* mem = memory_at(i); if (mem == base_mem) { st->print(" -"); continue; } st->print( " N%d:", mem->_idx ); Compile::current()->get_adr_type(i)->dump_on(st); } st->print(" }"); } #endif // !PRODUCT #ifdef ASSERT static bool might_be_same(Node* a, Node* b) { if (a == b) return true; if (!(a->is_Phi() || b->is_Phi())) return false; // phis shift around during optimization return true; // pretty stupid... } // verify a narrow slice (either incoming or outgoing) static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) { if (!VerifyAliases) return; // don't bother to verify unless requested if (is_error_reported()) return; // muzzle asserts when debugging an error if (Node::in_dump()) return; // muzzle asserts when printing assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel"); assert(n != NULL, ""); // Elide intervening MergeMem's while (n->is_MergeMem()) { n = n->as_MergeMem()->memory_at(alias_idx); } Compile* C = Compile::current(); const TypePtr* n_adr_type = n->adr_type(); if (n == m->empty_memory()) { // Implicit copy of base_memory() } else if (n_adr_type != TypePtr::BOTTOM) { assert(n_adr_type != NULL, "new memory must have a well-defined adr_type"); assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice"); } else { // A few places like make_runtime_call "know" that VM calls are narrow, // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM. bool expected_wide_mem = false; if (n == m->base_memory()) { expected_wide_mem = true; } else if (alias_idx == Compile::AliasIdxRaw || n == m->memory_at(Compile::AliasIdxRaw)) { expected_wide_mem = true; } else if (!C->alias_type(alias_idx)->is_rewritable()) { // memory can "leak through" calls on channels that // are write-once. Allow this also. expected_wide_mem = true; } assert(expected_wide_mem, "expected narrow slice replacement"); } } #else // !ASSERT #define verify_memory_slice(m,i,n) (0) // PRODUCT version is no-op #endif //-----------------------------memory_at--------------------------------------- Node* MergeMemNode::memory_at(uint alias_idx) const { assert(alias_idx >= Compile::AliasIdxRaw || alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0, "must avoid base_memory and AliasIdxTop"); // Otherwise, it is a narrow slice. Node* n = alias_idx < req() ? in(alias_idx) : empty_memory(); Compile *C = Compile::current(); if (is_empty_memory(n)) { // the array is sparse; empty slots are the "top" node n = base_memory(); assert(Node::in_dump() || n == NULL || n->bottom_type() == Type::TOP || n->adr_type() == TypePtr::BOTTOM || n->adr_type() == TypeRawPtr::BOTTOM || Compile::current()->AliasLevel() == 0, "must be a wide memory"); // AliasLevel == 0 if we are organizing the memory states manually. // See verify_memory_slice for comments on TypeRawPtr::BOTTOM. } else { // make sure the stored slice is sane #ifdef ASSERT if (is_error_reported() || Node::in_dump()) { } else if (might_be_same(n, base_memory())) { // Give it a pass: It is a mostly harmless repetition of the base. // This can arise normally from node subsumption during optimization. } else { verify_memory_slice(this, alias_idx, n); } #endif } return n; } //---------------------------set_memory_at------------------------------------- void MergeMemNode::set_memory_at(uint alias_idx, Node *n) { verify_memory_slice(this, alias_idx, n); Node* empty_mem = empty_memory(); if (n == base_memory()) n = empty_mem; // collapse default uint need_req = alias_idx+1; if (req() < need_req) { if (n == empty_mem) return; // already the default, so do not grow me // grow the sparse array do { add_req(empty_mem); } while (req() < need_req); } set_req( alias_idx, n ); } //--------------------------iteration_setup------------------------------------ void MergeMemNode::iteration_setup(const MergeMemNode* other) { if (other != NULL) { grow_to_match(other); // invariant: the finite support of mm2 is within mm->req() #ifdef ASSERT for (uint i = req(); i < other->req(); i++) { assert(other->is_empty_memory(other->in(i)), "slice left uncovered"); } #endif } // Replace spurious copies of base_memory by top. Node* base_mem = base_memory(); if (base_mem != NULL && !base_mem->is_top()) { for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) { if (in(i) == base_mem) set_req(i, empty_memory()); } } } //---------------------------grow_to_match------------------------------------- void MergeMemNode::grow_to_match(const MergeMemNode* other) { Node* empty_mem = empty_memory(); assert(other->is_empty_memory(empty_mem), "consistent sentinels"); // look for the finite support of the other memory for (uint i = other->req(); --i >= req(); ) { if (other->in(i) != empty_mem) { uint new_len = i+1; while (req() < new_len) add_req(empty_mem); break; } } } //---------------------------verify_sparse------------------------------------- #ifndef PRODUCT bool MergeMemNode::verify_sparse() const { assert(is_empty_memory(make_empty_memory()), "sane sentinel"); Node* base_mem = base_memory(); // The following can happen in degenerate cases, since empty==top. if (is_empty_memory(base_mem)) return true; for (uint i = Compile::AliasIdxRaw; i < req(); i++) { assert(in(i) != NULL, "sane slice"); if (in(i) == base_mem) return false; // should have been the sentinel value! } return true; } bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) { Node* n; n = mm->in(idx); if (mem == n) return true; // might be empty_memory() n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx); if (mem == n) return true; while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) { if (mem == n) return true; if (n == NULL) break; } return false; } #endif // !PRODUCT