Microoptimizations to the way we get the current heap.

Review URL: http://codereview.chromium.org/6759030

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7455 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/objects-inl.h

@@ -1158,12 +1158,9 @@ void HeapObject::VerifySmiField(int offset) {
 
 
 Heap* HeapObject::GetHeap() {
-  // During GC, the map pointer in HeapObject is used in various ways that
-  // prevent us from retrieving Heap from the map.
-  // Assert that we are not in GC, implement GC code in a way that it doesn't
-  // pull heap from the map.
-  ASSERT(HEAP->is_safe_to_read_maps());
-  return map()->heap();
+  uintptr_t addr = reinterpret_cast<uintptr_t>(this);
+  addr >>= kHeapDescriptorGranularityBits;
+  return heap_descriptors[addr].heap;
 }
 
 
@@ -2862,6 +2859,34 @@ Heap* Map::heap() {
 }
 
 
+Heap* Code::heap() {
+  // NOTE: address() helper is not used to save one instruction.
+  Heap* heap = Page::FromAddress(reinterpret_cast<Address>(this))->heap_;
+  ASSERT(heap != NULL);
+  ASSERT(heap->isolate() == Isolate::Current());
+  return heap;
+}
+
+
+Isolate* Code::isolate() {
+  return heap()->isolate();
+}
+
+
+Heap* JSGlobalPropertyCell::heap() {
+  // NOTE: address() helper is not used to save one instruction.
+  Heap* heap = Page::FromAddress(reinterpret_cast<Address>(this))->heap_;
+  ASSERT(heap != NULL);
+  ASSERT(heap->isolate() == Isolate::Current());
+  return heap;
+}
+
+
+Isolate* JSGlobalPropertyCell::isolate() {
+  return heap()->isolate();
+}
+
+
 Object* Code::GetObjectFromEntryAddress(Address location_of_address) {
   return HeapObject::
       FromAddress(Memory::Address_at(location_of_address) - Code::kHeaderSize);

src/objects.h

@@ -3487,6 +3487,10 @@ class Code: public HeapObject {
   void CodeVerify();
 #endif
 
+  // Returns the isolate/heap this code object belongs to.
+  inline Isolate* isolate();
+  inline Heap* heap();
+
   // Max loop nesting marker used to postpose OSR. We don't take loop
   // nesting that is deeper than 5 levels into account.
   static const int kMaxLoopNestingMarker = 6;
@@ -6009,6 +6013,10 @@ class JSGlobalPropertyCell: public HeapObject {
                               kValueOffset + kPointerSize,
                               kSize> BodyDescriptor;
 
+  // Returns the isolate/heap this cell object belongs to.
+  inline Isolate* isolate();
+  inline Heap* heap();
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSGlobalPropertyCell);
 };