Fix missing write barrier in store field stub.

src/x64/lithium-codegen-x64.cc

 // Copyright 2012 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 3300 matching lines @@
   CallRuntime(instr->function(), instr->arity(), instr);
 }
 
 
 void LCodeGen::DoStoreNamedField(LStoreNamedField* instr) {
   Register object = ToRegister(instr->object());
   Register value = ToRegister(instr->value());
   int offset = instr->offset();
 
   if (!instr->transition().is_null()) {
-    __ Move(FieldOperand(object, HeapObject::kMapOffset), instr->transition());
+    if (!instr->hydrogen()->NeedsWriteBarrierForMap()) {
+      __ Move(FieldOperand(object, HeapObject::kMapOffset),
+              instr->transition());
+    } else {
+      Register temp = ToRegister(instr->TempAt(0));
+      __ Move(kScratchRegister, instr->transition());
+      __ movq(FieldOperand(object, HeapObject::kMapOffset), kScratchRegister);
+      // Update the write barrier for the map field.
+      __ RecordWriteField(object,
+                          HeapObject::kMapOffset,
+                          kScratchRegister,
+                          temp,
+                          kSaveFPRegs,
+                          OMIT_REMEMBERED_SET,
+                          OMIT_SMI_CHECK);
+    }
   }
 
   // Do the store.
   HType type = instr->hydrogen()->value()->type();
   SmiCheck check_needed =
       type.IsHeapObject() ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
   if (instr->is_in_object()) {
     __ movq(FieldOperand(object, offset), value);
     if (instr->hydrogen()->NeedsWriteBarrier()) {
       Register temp = ToRegister(instr->TempAt(0));
@@ skipping 1547 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64