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

BUG=chromium:561449
LOG=n

Review URL: https://codereview.chromium.org/1783313003

Cr-Commit-Position: refs/heads/master@{#34722}

src/heap/heap-inl.h

@@ -25,20 +25,22 @@
 namespace v8 {
 namespace internal {
 
-void PromotionQueue::insert(HeapObject* target, int size) {
+void PromotionQueue::insert(HeapObject* target, intptr_t size) {
   if (emergency_stack_ != NULL) {
     emergency_stack_->Add(Entry(target, size));
     return;
   }
 
-  if ((rear_ - 2) < limit_) {
+  if ((rear_ - 1) < limit_) {
     RelocateQueueHead();
     emergency_stack_->Add(Entry(target, size));
     return;
   }
 
-  *(--rear_) = reinterpret_cast<intptr_t>(target);
-  *(--rear_) = size;
+  struct Entry* entry = reinterpret_cast<struct Entry*>(--rear_);
+  entry->obj_ = target;
+  entry->size_ = size;
+
 // Assert no overflow into live objects.
 #ifdef DEBUG
   SemiSpace::AssertValidRange(target->GetIsolate()->heap()->new_space()->top(),

src/heap/heap.cc

@@ -1561,8 +1561,8 @@ void PromotionQueue::Initialize() {
   DCHECK((Page::kPageSize - MemoryChunk::kBodyOffset) % (2 * kPointerSize) ==
          0);
   front_ = rear_ =
-      reinterpret_cast<intptr_t*>(heap_->new_space()->ToSpaceEnd());
-  limit_ = reinterpret_cast<intptr_t*>(
+      reinterpret_cast<struct Entry*>(heap_->new_space()->ToSpaceEnd());
+  limit_ = reinterpret_cast<struct Entry*>(
       Page::FromAllocationTop(reinterpret_cast<Address>(rear_))->area_start());
   emergency_stack_ = NULL;
 }
@@ -1572,8 +1572,9 @@ void PromotionQueue::RelocateQueueHead() {
   DCHECK(emergency_stack_ == NULL);
 
   Page* p = Page::FromAllocationTop(reinterpret_cast<Address>(rear_));
-  intptr_t* head_start = rear_;
-  intptr_t* head_end = Min(front_, reinterpret_cast<intptr_t*>(p->area_end()));
+  struct Entry* head_start = rear_;
+  struct Entry* head_end =
+      Min(front_, reinterpret_cast<struct Entry*>(p->area_end()));
 
   int entries_count =
       static_cast<int>(head_end - head_start) / kEntrySizeInWords;
@@ -1581,13 +1582,12 @@ void PromotionQueue::RelocateQueueHead() {
   emergency_stack_ = new List<Entry>(2 * entries_count);
 
   while (head_start != head_end) {
-    int size = static_cast<int>(*(head_start++));
-    HeapObject* obj = reinterpret_cast<HeapObject*>(*(head_start++));
+    struct Entry* entry = head_start++;
     // New space allocation in SemiSpaceCopyObject marked the region
     // overlapping with promotion queue as uninitialized.
-    MSAN_MEMORY_IS_INITIALIZED(&size, sizeof(size));
-    MSAN_MEMORY_IS_INITIALIZED(&obj, sizeof(obj));
-    emergency_stack_->Add(Entry(obj, size));
+    MSAN_MEMORY_IS_INITIALIZED(&entry->size_, sizeof(size));
+    MSAN_MEMORY_IS_INITIALIZED(&entry->obj_, sizeof(obj));
+    emergency_stack_->Add(*entry);
   }
   rear_ = head_end;
 }
@@ -1945,7 +1945,7 @@ Address Heap::DoScavenge(ObjectVisitor* scavenge_visitor,
     {
       while (!promotion_queue()->is_empty()) {
         HeapObject* target;
-        int size;
+        intptr_t size;
         promotion_queue()->remove(&target, &size);
 
         // Promoted object might be already partially visited
@@ -1954,7 +1954,8 @@ Address Heap::DoScavenge(ObjectVisitor* scavenge_visitor,
         // to new space.
         DCHECK(!target->IsMap());
 
-        IteratePointersToFromSpace(target, size, &Scavenger::ScavengeObject);
+        IteratePointersToFromSpace(target, static_cast<int>(size),
+                                   &Scavenger::ScavengeObject);
       }
     }
 

src/heap/heap.h

@@ -326,7 +326,7 @@ class PromotionQueue {
     // If the limit is not on the same page, we can ignore it.
     if (Page::FromAllocationTop(limit) != GetHeadPage()) return;
 
-    limit_ = reinterpret_cast<intptr_t*>(limit);
+    limit_ = reinterpret_cast<struct Entry*>(limit);
 
     if (limit_ <= rear_) {
       return;
@@ -348,7 +348,7 @@ class PromotionQueue {
     }
     // 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_;
+    return reinterpret_cast<struct Entry*>(to_space_top) <= rear_;
   }
 
   bool is_empty() {
@@ -356,9 +356,9 @@ class PromotionQueue {
            (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();
@@ -367,33 +367,38 @@ class PromotionQueue {
       return;
     }
 
-    *target = reinterpret_cast<HeapObject*>(*(--front_));
-    *size = static_cast<int>(*(--front_));
+    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_;
   };
+
+  // The front of the queue is higher in the memory page chain than the rear.
+  struct Entry* front_;
+  struct Entry* rear_;
+  struct Entry* limit_;
+
   List<Entry>* emergency_stack_;
 
   Heap* heap_;
 
   void RelocateQueueHead();
 
+  STATIC_ASSERT(sizeof(struct Entry) == kEntrySizeInWords * kPointerSize);
+
   DISALLOW_COPY_AND_ASSIGN(PromotionQueue);
 };