Fix missing write barrier in store field stub.

src/arm/lithium-arm.cc

Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index c97831aa13fb757b2e9d981df584150aa174c6bb..7618e3dd4478454fa895a8b1a0dd71b87bbcfcda 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -2105,16 +2105,28 @@ LInstruction* LChunkBuilder::DoTransitionElementsKind(
 
 LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
   bool needs_write_barrier = instr->NeedsWriteBarrier();
-
-  LOperand* obj = needs_write_barrier
-      ? UseTempRegister(instr->object())
-      : UseRegisterAtStart(instr->object());
+  bool needs_write_barrier_for_map = !instr->transition().is_null() &&
+      instr->NeedsWriteBarrierForMap();
+
+  LOperand* obj;
+  if (needs_write_barrier) {
+    obj = instr->is_in_object()
+        ? UseRegister(instr->object())
+        : UseTempRegister(instr->object());

[Vyacheslav Egorov (Google), 2012/05/29 15:09:26]

I don't think it has to be TempRegister. WriteBarrier does not destroy object
register anymore.

[Michael Starzinger, 2012/05/29 16:35:49]

Yes it does, the third of the three write-barriers uses "object" as a scratch
register after it set the value in the properties backing store.

+  } else {
+    obj = needs_write_barrier_for_map
+        ? UseRegister(instr->object())
+        : UseRegisterAtStart(instr->object());
+  }
 
   LOperand* val = needs_write_barrier
       ? UseTempRegister(instr->value())
       : UseRegister(instr->value());
 
-  return 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;
+
+  return new(zone()) LStoreNamedField(obj, val, temp);
 }