Unify the IsShortcutCandidate predicate.

R=yangguo@chromium.org
BUG=v8:2803
LOG=N

Review URL: https://codereview.chromium.org/390193007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22399 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.cc

@@ -2193,10 +2193,6 @@ class ScavengingVisitor : public StaticVisitorBase {
   }
 
 
-  static inline bool IsShortcutCandidate(int type) {
-    return ((type & kShortcutTypeMask) == kShortcutTypeTag);
-  }
-
   static inline void EvacuateShortcutCandidate(Map* map,
                                                HeapObject** slot,
                                                HeapObject* object) {

src/mark-compact.cc

@@ -1355,7 +1355,7 @@ static inline HeapObject* ShortCircuitConsString(Object** p) {
   if (!FLAG_clever_optimizations) return object;
   Map* map = object->map();
   InstanceType type = map->instance_type();
-  if ((type & kShortcutTypeMask) != kShortcutTypeTag) return object;
+  if (!IsShortcutCandidate(type)) return object;
 
   Object* second = reinterpret_cast<ConsString*>(object)->second();
   Heap* heap = map->GetHeap();

src/objects-visiting.cc

@@ -11,11 +11,6 @@ namespace v8 {
 namespace internal {
 
 
-static inline bool IsShortcutCandidate(int type) {
-  return ((type & kShortcutTypeMask) == kShortcutTypeTag);
-}
-
-
 StaticVisitorBase::VisitorId StaticVisitorBase::GetVisitorId(
     int instance_type,
     int instance_size) {

src/objects.h

@@ -619,16 +619,21 @@ const uint32_t kShortExternalStringTag = 0x10;
 
 
 // A ConsString with an empty string as the right side is a candidate
-// for being shortcut by the garbage collector unless it is internalized.
-// It's not common to have non-flat internalized strings, so we do not
-// shortcut them thereby avoiding turning internalized strings into strings.
-// See heap.cc and mark-compact.cc.
+// for being shortcut by the garbage collector. We don't allocate any
+// non-flat internalized strings, so we do not shortcut them thereby
+// avoiding turning internalized strings into strings. The bit-masks
+// below contain the internalized bit as additional safety.
+// See heap.cc, mark-compact.cc and objects-visiting.cc.
 const uint32_t kShortcutTypeMask =
     kIsNotStringMask |
     kIsNotInternalizedMask |
     kStringRepresentationMask;
 const uint32_t kShortcutTypeTag = kConsStringTag | kNotInternalizedTag;
 
+static inline bool IsShortcutCandidate(int type) {
+  return ((type & kShortcutTypeMask) == kShortcutTypeTag);
+}
+
 
 enum InstanceType {
   // String types.