[heap] Remove unecessary marking bit check in RecordWriteSlow.

src/heap/incremental-marking.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/heap/incremental-marking.h"
 
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
 #include "src/conversions.h"
 #include "src/heap/gc-idle-time-handler.h"
@@ skipping 61 matching lines @@
     }
   }
   if (!is_compacting_) return false;
   MarkBit obj_bit = Marking::MarkBitFrom(obj);
   return Marking::IsBlack(obj_bit);
 }
 
 
 void IncrementalMarking::RecordWriteSlow(HeapObject* obj, Object** slot,
                                          Object* value) {
   if (BaseRecordWrite(obj, slot, value) && slot != NULL) {

[Hannes Payer (out of office), 2015/11/03 22:51:14]

BaseRecordWrite already tells us if we have to record the slot, i.e. checks the
color of obj. No need to do it again.

[Michael Lippautz, 2015/11/03 22:54:25]

Acknowledged.

-    MarkBit obj_bit = Marking::MarkBitFrom(obj);
-    if (Marking::IsBlack(obj_bit)) {
-      // Object is not going to be rescanned we need to record the slot.
-      heap_->mark_compact_collector()->RecordSlot(obj, slot, value);
-    }
+    // Object is not going to be rescanned we need to record the slot.
+    heap_->mark_compact_collector()->RecordSlot(obj, slot, value);
   }
 }
 
 
 void IncrementalMarking::RecordWriteFromCode(HeapObject* obj, Object** slot,
                                              Isolate* isolate) {
   DCHECK(obj->IsHeapObject());
   IncrementalMarking* marking = isolate->heap()->incremental_marking();
 
   MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
@@ skipping 1056 matching lines @@
 void IncrementalMarking::IncrementIdleMarkingDelayCounter() {
   idle_marking_delay_counter_++;
 }
 
 
 void IncrementalMarking::ClearIdleMarkingDelayCounter() {
   idle_marking_delay_counter_ = 0;
 }
 }  // namespace internal
 }  // namespace v8