Version 4.9.385.29 (cherry-pick)

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 829 matching lines @@
 void IncrementalMarking::MarkObject(Heap* heap, HeapObject* obj) {
   MarkBit mark_bit = Marking::MarkBitFrom(obj);
   if (Marking::IsWhite(mark_bit)) {
     heap->incremental_marking()->WhiteToGreyAndPush(obj, mark_bit);
   }
 }
 
 
 intptr_t IncrementalMarking::ProcessMarkingDeque(intptr_t bytes_to_process) {
   intptr_t bytes_processed = 0;
-  Map* filler_map = heap_->one_pointer_filler_map();
+  Map* one_pointer_filler_map = heap_->one_pointer_filler_map();
+  Map* two_pointer_filler_map = heap_->two_pointer_filler_map();
   MarkingDeque* marking_deque =
       heap_->mark_compact_collector()->marking_deque();
   while (!marking_deque->IsEmpty() && bytes_processed < bytes_to_process) {
     HeapObject* obj = marking_deque->Pop();
 
-    // Explicitly skip one word fillers. Incremental markbit patterns are
-    // correct only for objects that occupy at least two words.
+    // Explicitly skip one and two word fillers. Incremental markbit patterns
+    // are correct only for objects that occupy at least two words.
+    // Moreover, slots filtering for left-trimmed arrays works only when
+    // the distance between the old array start and the new array start
+    // is greater than two if both starts are marked.
     Map* map = obj->map();
-    if (map == filler_map) continue;
+    if (map == one_pointer_filler_map || map == two_pointer_filler_map)
+      continue;
 
     int size = obj->SizeFromMap(map);
     unscanned_bytes_of_large_object_ = 0;
     VisitObject(map, obj, size);
     bytes_processed += size - unscanned_bytes_of_large_object_;
   }
   return bytes_processed;
 }
 
 
@@ skipping 376 matching lines @@
 void IncrementalMarking::IncrementIdleMarkingDelayCounter() {
   idle_marking_delay_counter_++;
 }
 
 
 void IncrementalMarking::ClearIdleMarkingDelayCounter() {
   idle_marking_delay_counter_ = 0;
 }
 }  // namespace internal
 }  // namespace v8