Split up HLoadNamedField and HStoreNamedField.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index e7ad219964b3946b35e81dbd76011d7e8ff2133f..c984f0fe625fa7a619c199bbacd3b8dc02e02c0b 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -1542,6 +1542,11 @@ void HCheckInstanceType::GetCheckMaskAndTag(uint8_t* mask, uint8_t* tag) {
 }
 
 
+static bool IsMapAccess(HObjectAccess access) {
+  return access.IsInobject() && access.offset() == JSObject::kMapOffset;
+}
+
+
 void HCheckMaps::HandleSideEffectDominator(GVNFlag side_effect,
                                            HValue* dominator) {
   ASSERT(side_effect == kChangesMaps);
@@ -1550,8 +1555,12 @@ void HCheckMaps::HandleSideEffectDominator(GVNFlag side_effect,
   // for which the map is known.
   if (HasNoUses() && dominator->IsStoreNamedField()) {
     HStoreNamedField* store = HStoreNamedField::cast(dominator);
-    if (!store->has_transition() || store->object() != value()) return;
-    HConstant* transition = HConstant::cast(store->transition());
+    if (!IsMapAccess(store->access()) ||
+        store->object() != value() ||
+        !store->value()->IsConstant()) {
+      return;
+    }
+    HConstant* transition = HConstant::cast(store->value());
     if (map_set_.Contains(transition->GetUnique())) {
       DeleteAndReplaceWith(NULL);
       return;
@@ -3258,9 +3267,6 @@ void HStoreNamedField::PrintDataTo(StringStream* stream) {
   if (NeedsWriteBarrier()) {
     stream->Add(" (write-barrier)");
   }
-  if (has_transition()) {
-    stream->Add(" (transition map %p)", *transition_map());
-  }
 }
 
 
@@ -4300,6 +4306,11 @@ HObjectAccess HObjectAccess::ForJSArrayOffset(int offset) {
 }
 
 
+HObjectAccess HObjectAccess::ForBackingStore() {
+  return HObjectAccess(kBackingStorePointer, JSObject::kPropertiesOffset);
+}
+
+
 HObjectAccess HObjectAccess::ForBackingStoreOffset(int offset,
     Representation representation) {
   ASSERT(offset >= 0);
@@ -4377,6 +4388,10 @@ void HObjectAccess::SetGVNFlags(HValue *instr, bool is_store) {
       instr->SetGVNFlag(is_store
           ? kChangesBackingStoreFields : kDependsOnBackingStoreFields);
       break;
+    case kBackingStorePointer:
+      instr->SetGVNFlag(is_store
+          ? kChangesBackingStore : kDependsOnBackingStore);
+      break;
     case kElementsPointer:
       instr->SetGVNFlag(is_store
           ? kChangesElementsPointer : kDependsOnElementsPointer);
@@ -4420,6 +4435,12 @@ void HObjectAccess::PrintTo(StringStream* stream) {
       }
       stream->Add("[backing-store]");
       break;
+    case kBackingStorePointer:
+      if (!name_.is_null()) {
+        stream->Add(String::cast(*name_)->ToCString().get());
+      }
+      stream->Add("[backing-store-pointer]");
+      break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;