Reland r20974: Unify and simplify the FastCloneShallowArrayStub

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 1cdca4c46efa14ac1cfb764d52fff9c641790749..8f9dd3f7db7c7d4343a93a697bc5ff1bed159166 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -618,6 +618,8 @@ class HValue : public ZoneObject {
     // flag.
     kUint32,
     kHasNoObservableSideEffects,
+    // Indicates an instruction shouldn't be replaced by optimization.

[mvstanton, 2014/05/09 13:16:49]

Or alternatively, instead of commenting the usage of kCantBeReplaced in
hydrogen.cc, expand on this comment a bit to indicate why you might want to use
this (reload is cheaper than spilling, say).

[danno, 2014/05/09 15:51:25]

Done.

+    kCantBeReplaced,
     // Indicates the instruction is live during dead code elimination.
     kIsLive,
 
@@ -6245,6 +6247,7 @@ class HLoadNamedField V8_FINAL : public HTemplateInstruction<2> {
   virtual void PrintDataTo(StringStream* stream) V8_OVERRIDE;
 
   bool CanBeReplacedWith(HValue* other) const {
+    if (!CheckFlag(HValue::kCantBeReplaced)) return false;
     if (!type().Equals(other->type())) return false;
     if (!representation().Equals(other->representation())) return false;
     if (!other->IsLoadNamedField()) return true;
@@ -6308,7 +6311,9 @@ class HLoadNamedField V8_FINAL : public HTemplateInstruction<2> {
                   HObjectAccess access,
                   const UniqueSet<Map>* maps,
                   HType type)
-      : HTemplateInstruction<2>(type), access_(access), maps_(maps) {
+        : HTemplateInstruction<2>(type),
+          access_(access),
+          maps_(maps) {
     ASSERT_NOT_NULL(maps);
     ASSERT_NE(0, maps->size());