[heap] Provide ObjectMarking with marking transitions

[heap] Provide ObjectMarking with marking transitions

BUG=chromium:651354
Review-Url: https://codereview.chromium.org/2644523002
Cr-Commit-Position: refs/heads/master@{#42531}
Committed: https://chromium.googlesource.com/v8/v8/+/cbb8929e97ee475dab4f704a71637e76342e903a

[Michael Lippautz, 2017-01-18 11:43:26]

Description was changed from

==========
[heap] Provide ObjectMaring with marking transitions

BUG=
==========

to

==========
[heap] Provide ObjectMarking with marking transitions

BUG=
==========

[Michael Lippautz, 2017-01-18 11:44:49]

mlippautz@chromium.org changed reviewers:
+ hpayer@chromium.org

[Michael Lippautz, 2017-01-18 11:46:08]

wdyt? We could also have IsBlack/Grey/White on ObjectMarking, avoiding exposed
MarkBits for most places at all.

Inlining should take care of reducing the retrieved MarkBits then.

[Michael Lippautz, 2017-01-18 12:33:42]

The CQ bit was checked by mlippautz@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-01-18 12:33:46]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-01-18 12:39:37]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-01-18 12:39:37]

Dry run: Try jobs failed on following builders:
  v8_linux64_gyp_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_gyp_rel_ng/build...)

[Hannes Payer (out of office), 2017-01-18 14:43:35]

I like it. It is a bit "slower" since you have to query in several cases the
mark bits again but this is probably not measurable. I left a couple of
comments, WDYT?

https://codereview.chromium.org/2644523002/diff/1/src/heap/incremental-markin...
File src/heap/incremental-marking.cc (right):

https://codereview.chromium.org/2644523002/diff/1/src/heap/incremental-markin...
src/heap/incremental-marking.cc:122: void
IncrementalMarking::WhiteToGreyAndPush(HeapObject* obj, MarkBit mark_bit) {
mark_bit is now not used anymore. That was an optimization to not read out the
mark_bit again.

https://codereview.chromium.org/2644523002/diff/1/src/heap/incremental-markin...
src/heap/incremental-marking.cc:162: Marking::WhiteToGrey(new_mark_bit);
Why not calling WhiteToGreyAndPush?

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact-inl.h
File src/heap/mark-compact-inl.h (right):

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact-inl.h...
src/heap/mark-compact-inl.h:16:
DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(obj)));
That would also short cut the double accessors: ObjectMarking::IsBlack(obj)

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact.cc
File src/heap/mark-compact.cc (right):

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact.cc#ne...
src/heap/mark-compact.cc:1508: if ((object->map() != filler_map) &&
Marking::IsGrey(markbit)) {
It is a bit weird now that we still use MarkBit for getters. In this case, why
not have ObjectMarking::IsGrey(object)?

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact.cc#ne...
src/heap/mark-compact.cc:1521: MarkBit markbit =
ObjectMarking::MarkBitFrom(object);
Same here.

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact.h
File src/heap/mark-compact.h (right):

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact.h#new...
src/heap/mark-compact.h:56: 
Should we add DCHECKs to the transitions where we expect a color? The lower
level has the DCHECKs but this may change for whatever reason.

https://codereview.chromium.org/2644523002/diff/1/src/heap/spaces.cc
File src/heap/spaces.cc (right):

https://codereview.chromium.org/2644523002/diff/1/src/heap/spaces.cc#newcode2993
src/heap/spaces.cc:2993: // We cannot use ObjectMarking here as the object still
lacks a size.
This one is really unfortunate. However, we do not need the live byte count for
large objects because we can always check the liveness of the LO and return its
size.

[Michael Lippautz, 2017-01-18 15:58:07]

Thanks! Addressed all your comments and (hopefully) fixed the tests. Basically,
I also added the proper getters for the colors now. I would expect the cpp
optimizer to eliminate all the extra markbits copies since all these functions
should be inlined.

https://codereview.chromium.org/2644523002/diff/1/src/heap/incremental-markin...
File src/heap/incremental-marking.cc (right):

https://codereview.chromium.org/2644523002/diff/1/src/heap/incremental-markin...
src/heap/incremental-marking.cc:122: void
IncrementalMarking::WhiteToGreyAndPush(HeapObject* obj, MarkBit mark_bit) {
On 2017/01/18 14:43:35, Hannes Payer wrote:
> mark_bit is now not used anymore. That was an optimization to not read out the
> mark_bit again.

Done.

https://codereview.chromium.org/2644523002/diff/1/src/heap/incremental-markin...
src/heap/incremental-marking.cc:162: Marking::WhiteToGrey(new_mark_bit);
On 2017/01/18 14:43:35, Hannes Payer wrote:
> Why not calling WhiteToGreyAndPush?

WhiteToGreyAndPush uses ObjectMarking which potentially requires a valid object
to read out the size. (Currently we still increase live bytes on black only, but
we could change this to be !white and then it would break.)

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact-inl.h
File src/heap/mark-compact-inl.h (right):

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact-inl.h...
src/heap/mark-compact-inl.h:16:
DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(obj)));
On 2017/01/18 14:43:35, Hannes Payer wrote:
> That would also short cut the double accessors: ObjectMarking::IsBlack(obj)

Done.

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact.cc
File src/heap/mark-compact.cc (right):

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact.cc#ne...
src/heap/mark-compact.cc:1508: if ((object->map() != filler_map) &&
Marking::IsGrey(markbit)) {
On 2017/01/18 14:43:35, Hannes Payer wrote:
> It is a bit weird now that we still use MarkBit for getters. In this case, why
> not have ObjectMarking::IsGrey(object)?

Done.

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact.cc#ne...
src/heap/mark-compact.cc:1521: MarkBit markbit =
ObjectMarking::MarkBitFrom(object);
On 2017/01/18 14:43:35, Hannes Payer wrote:
> Same here.

Done.

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact.h
File src/heap/mark-compact.h (right):

https://codereview.chromium.org/2644523002/diff/1/src/heap/mark-compact.h#new...
src/heap/mark-compact.h:56: 
On 2017/01/18 14:43:35, Hannes Payer wrote:
> Should we add DCHECKs to the transitions where we expect a color? The lower
> level has the DCHECKs but this may change for whatever reason.

Done.

https://codereview.chromium.org/2644523002/diff/1/src/heap/spaces.cc
File src/heap/spaces.cc (right):

https://codereview.chromium.org/2644523002/diff/1/src/heap/spaces.cc#newcode2993
src/heap/spaces.cc:2993: // We cannot use ObjectMarking here as the object still
lacks a size.
On 2017/01/18 14:43:35, Hannes Payer wrote:
> This one is really unfortunate. However, we do not need the live byte count
for
> large objects because we can always check the liveness of the LO and return
its
> size.

Acknowledged.

[Michael Lippautz, 2017-01-18 15:58:30]

The CQ bit was checked by mlippautz@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-01-18 15:58:35]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-01-18 16:20:59]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-01-18 16:21:01]

Dry run: Try jobs failed on following builders:
  v8_linux64_avx2_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_avx2_rel_ng/buil...)
  v8_linux64_avx2_rel_ng_triggered on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_avx2_rel_ng_trig...)

[Michael Lippautz, 2017-01-18 18:08:23]

The CQ bit was checked by mlippautz@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-01-18 18:08:27]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-01-18 18:38:04]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-01-18 18:38:05]

Dry run: This issue passed the CQ dry run.

[Hannes Payer (out of office), 2017-01-19 14:41:51]

lgtm

https://codereview.chromium.org/2644523002/diff/60001/src/heap/mark-compact.cc
File src/heap/mark-compact.cc (right):

https://codereview.chromium.org/2644523002/diff/60001/src/heap/mark-compact.c...
src/heap/mark-compact.cc:1988: SetMark(site);
We may want to unify the marking functions a bit. Why is this on not MarkBlack?
Can you have a look in a follow-up cl?

[Michael Lippautz, 2017-01-19 18:50:12]

https://codereview.chromium.org/2644523002/diff/60001/src/heap/mark-compact.cc
File src/heap/mark-compact.cc (right):

https://codereview.chromium.org/2644523002/diff/60001/src/heap/mark-compact.c...
src/heap/mark-compact.cc:1988: SetMark(site);
On 2017/01/19 14:41:51, Hannes Payer wrote:
> We may want to unify the marking functions a bit. Why is this on not
MarkBlack?
> Can you have a look in a follow-up cl?

Acknowledged.

[Michael Lippautz, 2017-01-19 18:51:41]

Description was changed from

==========
[heap] Provide ObjectMarking with marking transitions

BUG=
==========

to

==========
[heap] Provide ObjectMarking with marking transitions

BUG=chromium:651354
==========

[Michael Lippautz, 2017-01-19 21:29:11]

The CQ bit was checked by mlippautz@chromium.org

[commit-bot: I haz the power, 2017-01-19 21:29:25]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-01-19 23:21:11]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-01-19 23:21:12]

Failed to apply patch for src/heap/mark-compact.cc:
While running git apply --index -p1;
  error: patch failed: src/heap/mark-compact.cc:1437
  error: src/heap/mark-compact.cc: patch does not apply

Patch:       src/heap/mark-compact.cc
Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index
c931f520b7aea13f03a45941eca58e76d05b65cb..c2682104ca680668a0722b5dcc5cbd1b9efaf297
100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -107,7 +107,7 @@ static void VerifyMarking(Heap* heap, Address bottom,
Address top) {
     // One word fillers at the end of a black area can be grey.
     if (MarkCompactCollector::IsMarked(object) &&
         object->map() != heap->one_pointer_filler_map()) {
-      CHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
+      CHECK(ObjectMarking::IsBlack(object));
       CHECK(current >= next_object_must_be_here_or_later);
       object->Iterate(&visitor);
       next_object_must_be_here_or_later = current + object->Size();
@@ -348,8 +348,7 @@ void MarkCompactCollector::VerifyMarkbitsAreClean() {
 
   LargeObjectIterator it(heap_->lo_space());
   for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
-    MarkBit mark_bit = ObjectMarking::MarkBitFrom(obj);
-    CHECK(Marking::IsWhite(mark_bit));
+    CHECK(ObjectMarking::IsWhite(obj));
     CHECK_EQ(0, Page::FromAddress(obj->address())->LiveBytes());
   }
 }
@@ -398,7 +397,7 @@ void MarkCompactCollector::ClearMarkbits() {
 
   LargeObjectIterator it(heap_->lo_space());
   for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
-    Marking::MarkWhite(ObjectMarking::MarkBitFrom(obj));
+    ObjectMarking::ClearMarkBit(obj);
     MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
     chunk->ResetProgressBar();
     chunk->ResetLiveBytes();
@@ -909,8 +908,7 @@ void CodeFlusher::ProcessJSFunctionCandidates() {
     SharedFunctionInfo* shared = candidate->shared();
 
     Code* code = shared->code();
-    MarkBit code_mark = ObjectMarking::MarkBitFrom(code);
-    if (Marking::IsWhite(code_mark)) {
+    if (ObjectMarking::IsWhite(code)) {
       if (FLAG_trace_code_flushing && shared->is_compiled()) {
         PrintF("[code-flushing clears: ");
         shared->ShortPrint();
@@ -928,7 +926,7 @@ void CodeFlusher::ProcessJSFunctionCandidates() {
         candidate->set_code(lazy_compile);
       }
     } else {
-      DCHECK(Marking::IsBlack(code_mark));
+      DCHECK(ObjectMarking::IsBlack(code));
       candidate->set_code(code);
     }
 
@@ -962,8 +960,7 @@ void CodeFlusher::ProcessSharedFunctionInfoCandidates() {
     ClearNextCandidate(candidate);
 
     Code* code = candidate->code();
-    MarkBit code_mark = ObjectMarking::MarkBitFrom(code);
-    if (Marking::IsWhite(code_mark)) {
+    if (ObjectMarking::IsWhite(code)) {
       if (FLAG_trace_code_flushing && candidate->is_compiled()) {
         PrintF("[code-flushing clears: ");
         candidate->ShortPrint();
@@ -1103,9 +1100,8 @@ class StaticYoungGenerationMarkingVisitor
     StackLimitCheck check(heap->isolate());
     if (check.HasOverflowed()) return false;
 
-    MarkBit mark = ObjectMarking::MarkBitFrom(object);
-    if (Marking::IsBlackOrGrey(mark)) return true;
-    heap->mark_compact_collector()->SetMark(object, mark);
+    if (ObjectMarking::IsBlackOrGrey(object)) return true;
+    heap->mark_compact_collector()->SetMark(object);
     IterateBody(object->map(), object);
     return true;
   }
@@ -1143,9 +1139,8 @@ class MarkCompactMarkingVisitor
   // Marks the object black without pushing it on the marking stack.
   // Returns true if object needed marking and false otherwise.
   INLINE(static bool MarkObjectWithoutPush(Heap* heap, HeapObject* object)) {
-    MarkBit mark_bit = ObjectMarking::MarkBitFrom(object);
-    if (Marking::IsWhite(mark_bit)) {
-      heap->mark_compact_collector()->SetMark(object, mark_bit);
+    if (ObjectMarking::IsWhite(object)) {
+      heap->mark_compact_collector()->SetMark(object);
       return true;
     }
     return false;
@@ -1171,8 +1166,7 @@ class MarkCompactMarkingVisitor
 #endif
     Map* map = obj->map();
     Heap* heap = obj->GetHeap();
-    MarkBit mark = ObjectMarking::MarkBitFrom(obj);
-    heap->mark_compact_collector()->SetMark(obj, mark);
+    heap->mark_compact_collector()->SetMark(obj);
     // Mark the map pointer and the body.
     MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
     heap->mark_compact_collector()->MarkObject(map, map_mark);
@@ -1194,8 +1188,7 @@ class MarkCompactMarkingVisitor
       if (!o->IsHeapObject()) continue;
       collector->RecordSlot(object, p, o);
       HeapObject* obj = HeapObject::cast(o);
-      MarkBit mark = ObjectMarking::MarkBitFrom(obj);
-      if (Marking::IsBlackOrGrey(mark)) continue;
+      if (ObjectMarking::IsBlackOrGrey(obj)) continue;
       VisitUnmarkedObject(collector, obj);
     }
     return true;
@@ -1228,7 +1221,7 @@ class MarkCompactMarkingVisitor
       // was marked through the compilation cache before marker reached
JSRegExp
       // object.
       FixedArray* data = FixedArray::cast(re->data());
-      if (Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(data))) {
+      if (ObjectMarking::IsBlackOrGrey(data)) {
         Object** slot =
             data->data_start() + JSRegExp::saved_code_index(is_one_byte);
         heap->mark_compact_collector()->RecordSlot(data, slot, code);
@@ -1394,12 +1387,11 @@ class RootMarkingVisitor : public ObjectVisitor {
         !collector_->heap()->InNewSpace(object))
       return;
 
-    MarkBit mark_bit = ObjectMarking::MarkBitFrom(object);
-    if (Marking::IsBlackOrGrey(mark_bit)) return;
+    if (ObjectMarking::IsBlackOrGrey(object)) return;
 
     Map* map = object->map();
     // Mark the object.
-    collector_->SetMark(object, mark_bit);
+    collector_->SetMark(object);
 
     switch (mode) {
       case MarkCompactMode::FULL: {
@@ -1437,7 +1429,7 @@ class StringTableCleaner : public ObjectVisitor {
     for (Object** p = start; p < end; p++) {
       Object* o = *p;
       if (o->IsHeapObject()) {
-        if (Marking::IsWhite(ObjectMarking::MarkBitFrom(HeapObject::cast(o))))
{
+        if (ObjectMarking::IsWhite(HeapObject::cast(o))) {
           if (finalize_external_strings) {
             DCHECK(o->IsExternalString());
             heap_->FinalizeExternalString(String::cast(*p));
@@ -1474,9 +1466,8 @@ typedef StringTableCleaner<true, false>
ExternalStringTableCleaner;
 class MarkCompactWeakObjectRetainer : public WeakObjectRetainer {
  public:
   virtual Object* RetainAs(Object* object) {
-    MarkBit mark_bit = ObjectMarking::MarkBitFrom(HeapObject::cast(object));
-    DCHECK(!Marking::IsGrey(mark_bit));
-    if (Marking::IsBlack(mark_bit)) {
+    DCHECK(!ObjectMarking::IsGrey(HeapObject::cast(object)));
+    if (ObjectMarking::IsBlack(HeapObject::cast(object))) {
       return object;
     } else if (object->IsAllocationSite() &&
                !(AllocationSite::cast(object)->IsZombie())) {
@@ -1504,9 +1495,8 @@ void
MarkCompactCollector::DiscoverGreyObjectsWithIterator(T* it) {
 
   Map* filler_map = heap()->one_pointer_filler_map();
   for (HeapObject* object = it->Next(); object != NULL; object = it->Next()) {
-    MarkBit markbit = ObjectMarking::MarkBitFrom(object);
-    if ((object->map() != filler_map) && Marking::IsGrey(markbit)) {
-      Marking::GreyToBlack(markbit);
+    if ((object->map() != filler_map) && ObjectMarking::IsGrey(object)) {
+      ObjectMarking::GreyToBlack(object);
       PushBlack(object);
       if (marking_deque()->IsFull()) return;
     }
@@ -1518,9 +1508,8 @@ void
MarkCompactCollector::DiscoverGreyObjectsOnPage(MemoryChunk* p) {
   LiveObjectIterator<kGreyObjects> it(p);
   HeapObject* object = NULL;
   while ((object = it.Next()) != NULL) {
-    MarkBit markbit = ObjectMarking::MarkBitFrom(object);
-    DCHECK(Marking::IsGrey(markbit));
-    Marking::GreyToBlack(markbit);
+    DCHECK(ObjectMarking::IsGrey(object));
+    ObjectMarking::GreyToBlack(object);
     PushBlack(object);
     if (marking_deque()->IsFull()) return;
   }
@@ -1970,9 +1959,7 @@ void MarkCompactCollector::DiscoverGreyObjectsInNewSpace()
{
 bool MarkCompactCollector::IsUnmarkedHeapObject(Object** p) {
   Object* o = *p;
   if (!o->IsHeapObject()) return false;
-  HeapObject* heap_object = HeapObject::cast(o);
-  MarkBit mark = ObjectMarking::MarkBitFrom(heap_object);
-  return Marking::IsWhite(mark);
+  return ObjectMarking::IsWhite(HeapObject::cast(o));
 }
 
 
@@ -1980,19 +1967,16 @@ bool
MarkCompactCollector::IsUnmarkedHeapObjectWithHeap(Heap* heap,
                                                         Object** p) {
   Object* o = *p;
   DCHECK(o->IsHeapObject());
-  HeapObject* heap_object = HeapObject::cast(o);
-  MarkBit mark = ObjectMarking::MarkBitFrom(heap_object);
-  return Marking::IsWhite(mark);
+  return ObjectMarking::IsWhite(HeapObject::cast(o));
 }
 
 void MarkCompactCollector::MarkStringTable(
     RootMarkingVisitor<MarkCompactMode::FULL>* visitor) {
   StringTable* string_table = heap()->string_table();
   // Mark the string table itself.
-  MarkBit string_table_mark = ObjectMarking::MarkBitFrom(string_table);
-  if (Marking::IsWhite(string_table_mark)) {
+  if (ObjectMarking::IsWhite(string_table)) {
     // String table could have already been marked by visiting the handles
list.
-    SetMark(string_table, string_table_mark);
+    SetMark(string_table);
   }
   // Explicitly mark the prefix.
   string_table->IteratePrefix(visitor);
@@ -2001,8 +1985,7 @@ void MarkCompactCollector::MarkStringTable(
 
 
 void MarkCompactCollector::MarkAllocationSite(AllocationSite* site) {
-  MarkBit mark_bit = ObjectMarking::MarkBitFrom(site);
-  SetMark(site, mark_bit);
+  SetMark(site);
 }
 
 void MarkCompactCollector::MarkRoots(
@@ -2065,7 +2048,7 @@ void MarkCompactCollector::EmptyMarkingDeque() {
     DCHECK(!object->IsFiller());
     DCHECK(object->IsHeapObject());
 …
(message too large)

[Michael Lippautz, 2017-01-20 07:21:05]

The CQ bit was checked by mlippautz@chromium.org

[Michael Lippautz, 2017-01-20 07:21:05]

The patchset sent to the CQ was uploaded after l-g-t-m from hpayer@chromium.org
Link to the patchset: https://codereview.chromium.org/2644523002/#ps80001
(title: "Rebase")

[commit-bot: I haz the power, 2017-01-20 07:21:09]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-01-20 07:55:44]

CQ is committing da patch.

Bot data: {"patchset_id": 80001, "attempt_start_ts": 1484896865261130,
"parent_rev": "3e4070930dddff8e53067141d60add6f5a15b44a", "commit_rev":
"cbb8929e97ee475dab4f704a71637e76342e903a"}

[commit-bot: I haz the power, 2017-01-20 07:55:48]

Description was changed from

==========
[heap] Provide ObjectMarking with marking transitions

BUG=chromium:651354
==========

to

==========
[heap] Provide ObjectMarking with marking transitions

BUG=chromium:651354

Review-Url: https://codereview.chromium.org/2644523002
Cr-Commit-Position: refs/heads/master@{#42531}
Committed:
https://chromium.googlesource.com/v8/v8/+/cbb8929e97ee475dab4f704a71637e76342...
==========

[commit-bot: I haz the power, 2017-01-20 07:55:49]

Committed patchset #5 (id:80001) as
https://chromium.googlesource.com/v8/v8/+/cbb8929e97ee475dab4f704a71637e76342...

[Benedikt Meurer, 2017-01-20 08:29:58]

A revert of this CL (patchset #5 id:80001) has been created in
https://codereview.chromium.org/2647873002/ by bmeurer@chromium.org.

The reason for reverting is: Breaks the tree:
https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20gc%20stress/....