Revert "Refactor transitioning stores."

src/arm/lithium-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "v8.h"
 
 #include "lithium-allocator-inl.h"
 #include "arm/lithium-arm.h"
 #include "arm/lithium-codegen-arm.h"
 #include "hydrogen-osr.h"
@@ skipping 2261 matching lines @@
   LOperand* temp = TempRegister();
   LTrapAllocationMemento* result =
       new(zone()) LTrapAllocationMemento(object, temp);
   return AssignEnvironment(result);
 }
 
 
 LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
   bool is_in_object = instr->access().IsInobject();
   bool needs_write_barrier = instr->NeedsWriteBarrier();
+  bool needs_write_barrier_for_map = instr->has_transition() &&
+      instr->NeedsWriteBarrierForMap();
 
   LOperand* obj;
   if (needs_write_barrier) {
     obj = is_in_object
         ? UseRegister(instr->object())
         : UseTempRegister(instr->object());
   } else {
-    obj = UseRegisterAtStart(instr->object());
+    obj = needs_write_barrier_for_map
+        ? UseRegister(instr->object())
+        : UseRegisterAtStart(instr->object());
   }
 
   LOperand* val;
   if (needs_write_barrier || instr->field_representation().IsSmi()) {
     val = UseTempRegister(instr->value());
   } else if (instr->field_representation().IsDouble()) {
     val = UseRegisterAtStart(instr->value());
   } else {
     val = UseRegister(instr->value());
   }
 
-  LInstruction* result = new(zone()) LStoreNamedField(obj, val);
+  // We need a temporary register for write barrier of the map field.
+  LOperand* temp = needs_write_barrier_for_map ? TempRegister() : NULL;
+
+  LInstruction* result = new(zone()) LStoreNamedField(obj, val, temp);
   if (!instr->access().IsExternalMemory() &&
       instr->field_representation().IsHeapObject() &&
       !instr->value()->type().IsHeapObject()) {
     result = AssignEnvironment(result);
   }
   return result;
 }
 
 
 LInstruction* LChunkBuilder::DoStoreNamedGeneric(HStoreNamedGeneric* instr) {
@@ skipping 245 matching lines @@
 
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   LLoadFieldByIndex* load = new(zone()) LLoadFieldByIndex(object, index);
   LInstruction* result = DefineSameAsFirst(load);
   return AssignPointerMap(result);
 }
 
 } }  // namespace v8::internal