Don't emit a write barrier when storing a known old space value.

src/ia32/lithium-ia32.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1921 matching lines @@
 
   ASSERT(instr->object()->representation().IsTagged());
   ASSERT(instr->key()->representation().IsTagged());
   ASSERT(instr->value()->representation().IsTagged());
 
   return MarkAsCall(new LStoreKeyedGeneric(obj, key, val), instr);
 }
 
 
 LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
-  bool needs_write_barrier = !instr->value()->type().IsSmi();
+  bool needs_write_barrier = instr->NeedsWriteBarrier();
 
   LOperand* obj = needs_write_barrier
       ? UseTempRegister(instr->object())
       : UseRegisterAtStart(instr->object());
 
   LOperand* val = needs_write_barrier
       ? UseTempRegister(instr->value())
       : UseRegister(instr->value());
 
   // We only need a scratch register if we have a write barrier or we
@@ skipping 174 matching lines @@
 void LPointerMap::PrintTo(StringStream* stream) const {
   stream->Add("{");
   for (int i = 0; i < pointer_operands_.length(); ++i) {
     if (i != 0) stream->Add(";");
     pointer_operands_[i]->PrintTo(stream);
   }
   stream->Add("} @%d", position());
 }
 
 } }  // namespace v8::internal