Clarify side effects of HTransitionElementsKind.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/22796011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16215 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-instructions.cc

@@ -3085,6 +3085,7 @@ void HTransitionElementsKind::PrintDataTo(StringStream* stream) {
               ElementsAccessor::ForKind(from_kind)->name(),
               *transitioned_map(),
               ElementsAccessor::ForKind(to_kind)->name());
+  if (IsSimpleMapChangeTransition(from_kind, to_kind)) stream->Add(" (simple)");
 }
 
 

src/hydrogen-instructions.h

@@ -6265,11 +6265,7 @@ class HTransitionElementsKind: public HTemplateInstruction<2> {
     SetOperandAt(1, context);
     SetFlag(kUseGVN);
     SetGVNFlag(kChangesElementsKind);
-    if (original_map->has_fast_double_elements()) {
-      SetGVNFlag(kChangesElementsPointer);
-      SetGVNFlag(kChangesNewSpacePromotion);
-    }
-    if (transitioned_map->has_fast_double_elements()) {
+    if (!IsSimpleMapChangeTransition(from_kind_, to_kind_)) {
       SetGVNFlag(kChangesElementsPointer);
       SetGVNFlag(kChangesNewSpacePromotion);
     }