[heap] Use struct Entry to fill inlined promotion queue entries.

src/heap/heap.h

 // 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.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 338 matching lines @@
     // If the to space top pointer is smaller or equal than the promotion
     // queue head, then the to-space objects are below the promotion queue.
     return reinterpret_cast<intptr_t*>(to_space_top) <= rear_;
   }
 
   bool is_empty() {
     return (front_ == rear_) &&
            (emergency_stack_ == NULL || emergency_stack_->length() == 0);
   }
 
-  inline void insert(HeapObject* target, int size);
+  inline void insert(HeapObject* target, intptr_t size);
 
-  void remove(HeapObject** target, int* size) {
+  void remove(HeapObject** target, intptr_t* size) {
     DCHECK(!is_empty());
     if (front_ == rear_) {
       Entry e = emergency_stack_->RemoveLast();
       *target = e.obj_;
       *size = e.size_;
       return;
     }
 
-    *target = reinterpret_cast<HeapObject*>(*(--front_));
-    *size = static_cast<int>(*(--front_));
+    front_ -= kEntrySizeInWords;
+    struct Entry* entry = reinterpret_cast<struct Entry*>(front_);
+    *target = entry->obj_;
+    *size = entry->size_;
+
     // Assert no underflow.
     SemiSpace::AssertValidRange(reinterpret_cast<Address>(rear_),
                                 reinterpret_cast<Address>(front_));
   }
 
  private:
   // The front of the queue is higher in the memory page chain than the rear.
   intptr_t* front_;
   intptr_t* rear_;
   intptr_t* limit_;
 
   static const int kEntrySizeInWords = 2;
 
   struct Entry {
-    Entry(HeapObject* obj, int size) : obj_(obj), size_(size) {}
+    Entry(HeapObject* obj, intptr_t size) : obj_(obj), size_(size) {}
 
     HeapObject* obj_;
-    int size_;
+    intptr_t size_;
   };
   List<Entry>* emergency_stack_;
 
   Heap* heap_;
 
   void RelocateQueueHead();
 
+  STATIC_ASSERT(sizeof(struct Entry) == kEntrySizeInWords * kPointerSize);
+
   DISALLOW_COPY_AND_ASSIGN(PromotionQueue);
 };
 
 
 enum ArrayStorageAllocationMode {
   DONT_INITIALIZE_ARRAY_ELEMENTS,
   INITIALIZE_ARRAY_ELEMENTS_WITH_HOLE
 };
 
 enum class ClearRecordedSlots { kYes, kNo };
@@ skipping 2218 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_