Remember to update the write barrier when storing into...

src/ia32/macro-assembler-ia32.cc

 // Copyright 2006-2009 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 197 matching lines @@
     // record write code isn't going to save us any memory.
     if (generating_stub()) {
       RecordWriteHelper(this, object, dst, value);
     } else {
       RecordWriteStub stub(object, dst, value);
       CallStub(&stub);
     }
   }
 
   bind(&done);
+
+  // Clobber all input registers when running with the debug-code flag
+  // turned on to provoke errors.
+  if (FLAG_debug_code) {
+    mov(object, Immediate(bit_cast<int32_t>(kZapValue)));
+    mov(value, Immediate(bit_cast<int32_t>(kZapValue)));
+    mov(scratch, Immediate(bit_cast<int32_t>(kZapValue)));
+  }
 }
 
 
 void MacroAssembler::StackLimitCheck(Label* on_stack_overflow) {
   cmp(esp,
       Operand::StaticVariable(ExternalReference::address_of_stack_limit()));
   j(below, on_stack_overflow);
 }
 
 
@@ skipping 1355 matching lines @@
   // Indicate that code has changed.
   CPU::FlushICache(address_, size_);
 
   // Check that the code was patched as expected.
   ASSERT(masm_.pc_ == address_ + size_);
   ASSERT(masm_.reloc_info_writer.pos() == address_ + size_ + Assembler::kGap);
 }
 
 
 } }  // namespace v8::internal