Retire ShortCircuitConsString.

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 1183 matching lines @@
 
 
 MarkCompactCollector::~MarkCompactCollector() {
   if (code_flusher_ != NULL) {
     delete code_flusher_;
     code_flusher_ = NULL;
   }
 }
 
 
-static inline HeapObject* ShortCircuitConsString(Object** p) {
-  // Optimization: If the heap object pointed to by p is a non-internalized
-  // cons string whose right substring is HEAP->empty_string, update
-  // it in place to its left substring.  Return the updated value.
-  //
-  // Here we assume that if we change *p, we replace it with a heap object
-  // (i.e., the left substring of a cons string is always a heap object).
-  //
-  // The check performed is:
-  //   object->IsConsString() && !object->IsInternalizedString() &&
-  //   (ConsString::cast(object)->second() == HEAP->empty_string())
-  // except the maps for the object and its possible substrings might be
-  // marked.
-  HeapObject* object = HeapObject::cast(*p);
-  Map* map = object->map();
-  InstanceType type = map->instance_type();
-  if (!IsShortcutCandidate(type)) return object;
-
-  Object* second = reinterpret_cast<ConsString*>(object)->second();
-  Heap* heap = map->GetHeap();
-  if (second != heap->empty_string()) {
-    return object;
-  }
-
-  // Since we don't have the object's start, it is impossible to update the
-  // page dirty marks. Therefore, we only replace the string with its left
-  // substring when page dirty marks do not change.
-  Object* first = reinterpret_cast<ConsString*>(object)->first();
-  if (!heap->InNewSpace(object) && heap->InNewSpace(first)) return object;
-
-  *p = first;
-  return HeapObject::cast(first);
-}
-
-
 class MarkCompactMarkingVisitor
     : public StaticMarkingVisitor<MarkCompactMarkingVisitor> {
  public:
   static void ObjectStatsVisitBase(StaticVisitorBase::VisitorId id, Map* map,
                                    HeapObject* obj);
 
   static void ObjectStatsCountFixedArray(
       FixedArrayBase* fixed_array, FixedArraySubInstanceType fast_type,
       FixedArraySubInstanceType dictionary_type);
 
@@ skipping 37 matching lines @@
       heap->mark_compact_collector()->SetMark(object, mark_bit);
       return true;
     }
     return false;
   }
 
   // Mark object pointed to by p.
   INLINE(static void MarkObjectByPointer(MarkCompactCollector* collector,
                                          HeapObject* object, Object** p)) {
     if (!(*p)->IsHeapObject()) return;
-    HeapObject* target_object = ShortCircuitConsString(p);
+    HeapObject* target_object = HeapObject::cast(*p);
     collector->RecordSlot(object, p, target_object);
     MarkBit mark = Marking::MarkBitFrom(target_object);
     collector->MarkObject(target_object, mark);
   }
 
 
   // Visit an unmarked object.
   INLINE(static void VisitUnmarkedObject(MarkCompactCollector* collector,
                                          HeapObject* obj)) {
 #ifdef DEBUG
@@ skipping 357 matching lines @@
 
   // Skip the weak next code link in a code object, which is visited in
   // ProcessTopOptimizedFrame.
   void VisitNextCodeLink(Object** p) {}
 
  private:
   void MarkObjectByPointer(Object** p) {
     if (!(*p)->IsHeapObject()) return;
 
     // Replace flat cons strings in place.
-    HeapObject* object = ShortCircuitConsString(p);
+    HeapObject* object = HeapObject::cast(*p);
     MarkBit mark_bit = Marking::MarkBitFrom(object);
     if (Marking::IsBlackOrGrey(mark_bit)) return;
 
     Map* map = object->map();
     // Mark the object.
     collector_->SetMark(object, mark_bit);
 
     // Mark the map pointer and body, and push them on the marking stack.
     MarkBit map_mark = Marking::MarkBitFrom(map);
     collector_->MarkObject(map, map_mark);
@@ skipping 3116 matching lines @@
   SlotsBuffer* buffer = *buffer_address;
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 }  // namespace internal
 }  // namespace v8