Make the marking stack into a deque

src/incremental-marking.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 194 matching lines @@
           CodeStub::RecordWrite) {
         Object* e = stubs->ValueAt(i);
         if (e->IsCode()) {
           RecordWriteStub::Patch(Code::cast(e), enable);
         }
       }
     }
   }
 }
 
-static VirtualMemory* marking_stack_memory = NULL;
+static VirtualMemory* marking_deque_memory = NULL;
 
-static void EnsureMarkingStackIsCommitted() {
-  if (marking_stack_memory == NULL) {
-    marking_stack_memory = new VirtualMemory(4*MB);
-    marking_stack_memory->Commit(
-        reinterpret_cast<Address>(marking_stack_memory->address()),
-        marking_stack_memory->size(),
+static void EnsureMarkingDequeIsCommitted() {
+  if (marking_deque_memory == NULL) {
+    marking_deque_memory = new VirtualMemory(4*MB);
+    marking_deque_memory->Commit(
+        reinterpret_cast<Address>(marking_deque_memory->address()),
+        marking_deque_memory->size(),
         false);  // Not executable.
   }
 }
 
 
 void IncrementalMarking::Start() {
   if (FLAG_trace_incremental_marking) {
     PrintF("[IncrementalMarking] Start\n");
   }
   ASSERT(FLAG_incremental_marking);
   ASSERT(state_ == STOPPED);
   state_ = MARKING;
 
   ResetStepCounters();
 
   PatchIncrementalMarkingRecordWriteStubs(true);
 
-  EnsureMarkingStackIsCommitted();
+  EnsureMarkingDequeIsCommitted();
 
   // Initialize marking stack.
-  Address addr = static_cast<Address>(marking_stack_memory->address());
-  marking_stack_.Initialize(addr,
-                            addr + marking_stack_memory->size());
+  Address addr = static_cast<Address>(marking_deque_memory->address());
+  marking_deque_.Initialize(addr,
+                            addr + marking_deque_memory->size());
 
   // Clear markbits.
   Address new_space_low = heap_->new_space()->ToSpaceLow();
   Address new_space_high = heap_->new_space()->ToSpaceHigh();
   heap_->marking()->ClearRange(
       new_space_low, static_cast<int>(new_space_high - new_space_low));
 
   ClearMarkbits();
 
 #ifdef DEBUG
@@ skipping 16 matching lines @@
 void IncrementalMarking::PrepareForScavenge() {
   if (IsStopped()) return;
 
   Address new_space_low = heap_->new_space()->FromSpaceLow();
   Address new_space_high = heap_->new_space()->FromSpaceHigh();
   heap_->marking()->ClearRange(
       new_space_low, static_cast<int>(new_space_high - new_space_low));
 }
 
 
-void IncrementalMarking::UpdateMarkingStackAfterScavenge() {
+void IncrementalMarking::UpdateMarkingDequeAfterScavenge() {
   if (IsStopped()) return;
 
-  HeapObject** current = marking_stack_.low();
-  HeapObject** top = marking_stack_.top();
-  HeapObject** new_top = current;
+  intptr_t current = marking_deque_.bottom();
+  intptr_t mask = marking_deque_.mask();
+  intptr_t limit = marking_deque_.top();
+  HeapObject** array = marking_deque_.array();
+  intptr_t new_top = current;
 
-  while (current < top) {
-    HeapObject* obj = *current++;
+  while (current != limit) {
+    HeapObject* obj = array[current];
+    current = ((current + 1) & mask);
     if (heap_->InNewSpace(obj)) {
       MapWord map_word = obj->map_word();
       if (map_word.IsForwardingAddress()) {
         HeapObject* dest = map_word.ToForwardingAddress();
         WhiteToGrey(dest, heap_->marking()->MarkBitFrom(dest));
-        *new_top++ = dest;
+        array[new_top] = dest;
+        new_top = ((new_top + 1) & mask);
         ASSERT(Color(obj) == Color(dest));
       }
     } else {
-      *new_top++ = obj;
+      array[new_top] = obj;
+      new_top = ((new_top + 1) & mask);
     }
   }
 
-  marking_stack_.set_top(new_top);
+  marking_deque_.set_top(new_top);
 }
 
 
 void IncrementalMarking::Hurry() {
   if (state() == MARKING) {
     double start = 0.0;
     if (FLAG_trace_incremental_marking) {
       PrintF("[IncrementalMarking] Hurry\n");
       start = OS::TimeCurrentMillis();
     }
     // TODO(gc) hurry can mark objects it encounters black as mutator
     // was stopped.
     Map* filler_map = heap_->one_pointer_filler_map();
     IncrementalMarkingMarkingVisitor marking_visitor(heap_, this);
-    while (!marking_stack_.is_empty()) {
-      HeapObject* obj = marking_stack_.Pop();
+    while (!marking_deque_.IsEmpty()) {
+      HeapObject* obj = marking_deque_.Pop();
 
       // Explicitly skip one word fillers. Incremental markbit patterns are
       // correct only for objects that occupy at least two words.
       if (obj->map() != filler_map) {
         obj->Iterate(&marking_visitor);
         MarkBit mark_bit = heap_->marking()->MarkBitFrom(obj);
         MarkBlack(mark_bit);
       }
     }
     state_ = COMPLETE;
     if (FLAG_trace_incremental_marking) {
       double end = OS::TimeCurrentMillis();
       PrintF("[IncrementalMarking] Complete (hurry), spent %d ms.\n",
              static_cast<int>(end - start));
     }
   }
 }
 
 
 void IncrementalMarking::Finalize() {
   Hurry();
   state_ = STOPPED;
   heap_->new_space()->LowerInlineAllocationLimit(0);
   IncrementalMarking::set_should_hurry(false);
   ResetStepCounters();
   PatchIncrementalMarkingRecordWriteStubs(false);
-  ASSERT(marking_stack_.is_empty());
+  ASSERT(marking_deque_.IsEmpty());
   ISOLATE->stack_guard()->Continue(GC_REQUEST);
 }
 
 
 void IncrementalMarking::MarkingComplete() {
   state_ = COMPLETE;
   // We will set the stack guard to request a GC now.  This will mean the rest
   // of the GC gets performed as soon as possible (we can't do a GC here in a
   // record-write context).  If a few things get allocated between now and then
   // that shouldn't make us do a scavenge and keep being incremental, so we set
@@ skipping 19 matching lines @@
       if (FLAG_trace_incremental_marking || FLAG_trace_gc) {
         start = OS::TimeCurrentMillis();
       }
 
       intptr_t bytes_to_process = allocated_ * allocation_marking_factor_;
       int count = 0;
 
       Map* filler_map = heap_->one_pointer_filler_map();
       IncrementalMarkingMarkingVisitor marking_visitor(heap_, this);
       Marking* marking = heap_->marking();
-      while (!marking_stack_.is_empty() && bytes_to_process > 0) {
-        HeapObject* obj = marking_stack_.Pop();
+      while (!marking_deque_.IsEmpty() && bytes_to_process > 0) {
+        HeapObject* obj = marking_deque_.Pop();
 
         // Explicitly skip one word fillers. Incremental markbit patterns are
         // correct only for objects that occupy at least two words.
         Map* map = obj->map();
         if (map != filler_map) {
           ASSERT(IsGrey(marking->MarkBitFrom(obj)));
           int size = obj->SizeFromMap(map);
           bytes_to_process -= size;
           MarkBit map_mark_bit = marking->MarkBitFromOldSpace(map);
           if (IsWhite(map_mark_bit)) WhiteToGreyAndPush(map, map_mark_bit);
           // TODO(gc) switch to static visitor instead of normal visitor.
           obj->IterateBody(map->instance_type(), size, &marking_visitor);
           MarkBit obj_mark_bit = marking->MarkBitFrom(obj);
           MarkBlack(obj_mark_bit);
         }
         count++;
       }
       allocated_ = 0;
-      if (marking_stack_.is_empty()) MarkingComplete();
+      if (marking_deque_.IsEmpty()) MarkingComplete();
       if (FLAG_trace_incremental_marking || FLAG_trace_gc) {
         double end = OS::TimeCurrentMillis();
         steps_took_ += (end - start);
       }
 
       steps_count_++;
 
       if ((steps_count_ % kAllocationMarkingFactorSpeedupInterval) == 0) {
         allocation_marking_factor_ += kAllocationMarkingFactorSpeedup;
         allocation_marking_factor_ *= 1.3;
         if (FLAG_trace_gc) {
           PrintF("Marking speed increased to %d\n", allocation_marking_factor_);
         }
       }
     }
   }
 }
 
 
 } }  // namespace v8::internal