rewriter.cpp

/*
 * Copyright 1998-2005 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.
 *
 */

# include "incls/_precompiled.incl"
# include "incls/_rewriter.cpp.incl"


// Computes an index_map (new_index -> original_index) for contant pool entries
// that are referred to by the interpreter at runtime via the constant pool cache.
void Rewriter::compute_index_maps(constantPoolHandle pool, intArray*& index_map, intStack*& inverse_index_map) {
  const int length  = pool->length();
  index_map         = new intArray(length, -1);
  // Choose an initial value large enough that we don't get frequent
  // calls to grow().
  inverse_index_map = new intStack(length / 2);
  for (int i = 0; i < length; i++) {
    switch (pool->tag_at(i).value()) {
      case JVM_CONSTANT_Fieldref          : // fall through
      case JVM_CONSTANT_Methodref         : // fall through
      case JVM_CONSTANT_InterfaceMethodref: {
        index_map->at_put(i, inverse_index_map->length());
        inverse_index_map->append(i);
      }
    }
  }
}


// Creates a constant pool cache given an inverse_index_map
// This creates the constant pool cache initially in a state
// that is unsafe for concurrent GC processing but sets it to
// a safe mode before the constant pool cache is returned.
constantPoolCacheHandle Rewriter::new_constant_pool_cache(intArray& inverse_index_map, TRAPS) {
  const int length = inverse_index_map.length();
  constantPoolCacheOop cache = oopFactory::new_constantPoolCache(length,
                                             methodOopDesc::IsUnsafeConc,
                                             CHECK_(constantPoolCacheHandle()));
  cache->initialize(inverse_index_map);
  return constantPoolCacheHandle(THREAD, cache);
}



// The new finalization semantics says that registration of
// finalizable objects must be performed on successful return from the
// Object.<init> constructor.  We could implement this trivially if
// <init> were never rewritten but since JVMTI allows this to occur, a
// more complicated solution is required.  A special return bytecode
// is used only by Object.<init> to signal the finalization
// registration point.  Additionally local 0 must be preserved so it's
// available to pass to the registration function.  For simplicty we
// require that local 0 is never overwritten so it's available as an
// argument for registration.

void Rewriter::rewrite_Object_init(methodHandle method, TRAPS) {
  RawBytecodeStream bcs(method);
  while (!bcs.is_last_bytecode()) {
    Bytecodes::Code opcode = bcs.raw_next();
    switch (opcode) {
      case Bytecodes::_return: *bcs.bcp() = Bytecodes::_return_register_finalizer; break;

      case Bytecodes::_istore:
      case Bytecodes::_lstore:
      case Bytecodes::_fstore:
      case Bytecodes::_dstore:
      case Bytecodes::_astore:
        if (bcs.get_index() != 0) continue;

        // fall through
      case Bytecodes::_istore_0:
      case Bytecodes::_lstore_0:
      case Bytecodes::_fstore_0:
      case Bytecodes::_dstore_0:
      case Bytecodes::_astore_0:
        THROW_MSG(vmSymbols::java_lang_IncompatibleClassChangeError(),
                  "can't overwrite local 0 in Object.<init>");
        break;
    }
  }
}


// Rewrites a method given the index_map information
methodHandle Rewriter::rewrite_method(methodHandle method, intArray& index_map, TRAPS) {

  int nof_jsrs = 0;
  bool has_monitor_bytecodes = false;

  {
    // We cannot tolerate a GC in this block, because we've
    // cached the bytecodes in 'code_base'. If the methodOop
    // moves, the bytecodes will also move.
    No_Safepoint_Verifier nsv;
    Bytecodes::Code c;

    // Bytecodes and their length
    const address code_base = method->code_base();
    const int code_length = method->code_size();

    int bc_length;
    for (int bci = 0; bci < code_length; bci += bc_length) {
      address bcp = code_base + bci;
      c = (Bytecodes::Code)(*bcp);

      // Since we have the code, see if we can get the length
      // directly. Some more complicated bytecodes will report
      // a length of zero, meaning we need to make another method
      // call to calculate the length.
      bc_length = Bytecodes::length_for(c);
      if (bc_length == 0) {
        bc_length = Bytecodes::length_at(bcp);

        // length_at will put us at the bytecode after the one modified
        // by 'wide'. We don't currently examine any of the bytecodes
        // modified by wide, but in case we do in the future...
        if (c == Bytecodes::_wide) {
          c = (Bytecodes::Code)bcp[1];
        }
      }

      assert(bc_length != 0, "impossible bytecode length");

      switch (c) {
        case Bytecodes::_lookupswitch   : {
#ifndef CC_INTERP
          Bytecode_lookupswitch* bc = Bytecode_lookupswitch_at(bcp);
          bc->set_code(
            bc->number_of_pairs() < BinarySwitchThreshold
            ? Bytecodes::_fast_linearswitch
            : Bytecodes::_fast_binaryswitch
          );
#endif
          break;
        }
        case Bytecodes::_getstatic      : // fall through
        case Bytecodes::_putstatic      : // fall through
        case Bytecodes::_getfield       : // fall through
        case Bytecodes::_putfield       : // fall through
        case Bytecodes::_invokevirtual  : // fall through
        case Bytecodes::_invokespecial  : // fall through
        case Bytecodes::_invokestatic   : // fall through
        case Bytecodes::_invokeinterface: {
          address p = bcp + 1;
          Bytes::put_native_u2(p, index_map[Bytes::get_Java_u2(p)]);
          break;
        }
        case Bytecodes::_jsr            : // fall through
        case Bytecodes::_jsr_w          : nof_jsrs++;                   break;
        case Bytecodes::_monitorenter   : // fall through
        case Bytecodes::_monitorexit    : has_monitor_bytecodes = true; break;
      }
    }
  }

  // Update access flags
  if (has_monitor_bytecodes) {
    method->set_has_monitor_bytecodes();
  }

  // The present of a jsr bytecode implies that the method might potentially
  // have to be rewritten, so we run the oopMapGenerator on the method
  if (nof_jsrs > 0) {
    method->set_has_jsrs();
    ResolveOopMapConflicts romc(method);
    methodHandle original_method = method;
    method = romc.do_potential_rewrite(CHECK_(methodHandle()));
    if (method() != original_method()) {
      // Insert invalid bytecode into original methodOop and set
      // interpreter entrypoint, so that a executing this method
      // will manifest itself in an easy recognizable form.
      address bcp = original_method->bcp_from(0);
      *bcp = (u1)Bytecodes::_shouldnotreachhere;
      int kind = Interpreter::method_kind(original_method);
      original_method->set_interpreter_kind(kind);
    }

    // Update monitor matching info.
    if (romc.monitor_safe()) {
      method->set_guaranteed_monitor_matching();
    }
  }

  // Setup method entrypoints for compiler and interpreter
  method->link_method(method, CHECK_(methodHandle()));

  return method;
}


void Rewriter::rewrite(instanceKlassHandle klass, TRAPS) {
  // gather starting points
  ResourceMark rm(THREAD);
  constantPoolHandle pool (THREAD, klass->constants());
  objArrayHandle methods  (THREAD, klass->methods());
  assert(pool->cache() == NULL, "constant pool cache must not be set yet");

  // determine index maps for methodOop rewriting
  intArray* index_map         = NULL;
  intStack* inverse_index_map = NULL;
  compute_index_maps(pool, index_map, inverse_index_map);

  // allocate constant pool cache
  constantPoolCacheHandle cache = new_constant_pool_cache(*inverse_index_map, CHECK);
  pool->set_cache(cache());
  cache->set_constant_pool(pool());

  if (RegisterFinalizersAtInit && klass->name() == vmSymbols::java_lang_Object()) {
    int i = methods->length();
    while (i-- > 0) {
      methodOop method = (methodOop)methods->obj_at(i);
      if (method->intrinsic_id() == vmIntrinsics::_Object_init) {
        // rewrite the return bytecodes of Object.<init> to register the
        // object for finalization if needed.
        methodHandle m(THREAD, method);
        rewrite_Object_init(m, CHECK);
        break;
      }
    }
  }

  // rewrite methods
  { int i = methods->length();
    while (i-- > 0) {
      methodHandle m(THREAD, (methodOop)methods->obj_at(i));
      m = rewrite_method(m, *index_map, CHECK);
      // Method might have gotten rewritten.
      methods->obj_at_put(i, m());
    }
  }
}