Reviewers: Hannes Payer,
Description:
Serializer: canonicalize cleared weak cells.
[email protected]
BUG=v8:4050
LOG=N
Please review this at https://codereview.chromium.org/1072923003/
Base URL: https://chromium.googlesource.com/v8/v8.git@master
Affected files (+25, -1 lines):
M src/heap/heap.h
M src/heap/heap.cc
M src/objects.h
M src/objects-inl.h
M src/snapshot/serialize.h
M src/snapshot/serialize.cc
Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index
2f3a1a8c1c7d300e892223b0a9d40a3aad530e49..cff796ab4a9730e8ad3869d764cdee2e4e08186e
100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -3108,6 +3108,9 @@ void Heap::CreateInitialObjects() {
*factory->NewFixedArray(kAllocationSiteScratchpadSize, TENURED));
InitializeAllocationSitesScratchpad();
+ set_cleared_weak_cell(*factory->NewWeakCell(factory->undefined_value()));
+ cleared_weak_cell()->unchecked_clear();
+
// Initialize keyed lookup cache.
isolate_->keyed_lookup_cache()->Clear();
Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index
9dd4b1466272b534b98c2f10d97a8855c749dd77..5ac70f872a3c9297bac5c50d539f1a9ed61353e2
100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -185,7 +185,8 @@ namespace internal {
V(FixedArray, keyed_load_dummy_vector,
KeyedLoadDummyVector) \
V(FixedArray, detached_contexts,
DetachedContexts) \
V(ArrayList, retained_maps,
RetainedMaps) \
- V(WeakHashTable, weak_object_to_code_table, WeakObjectToCodeTable)
+ V(WeakHashTable, weak_object_to_code_table,
WeakObjectToCodeTable) \
+ V(WeakCell, cleared_weak_cell, ClearedWeakCell)
// Entries in this list are limited to Smis and are not visited during GC.
#define SMI_ROOT_LIST(V)
\
Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index
5f3d0747e6a5b4c5aa337c01d89fc72ca86e21c2..d8e1f579a75ff9f2b033ba218fe28e69f8a64266
100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -1909,6 +1909,11 @@ void WeakCell::clear() {
}
+void WeakCell::unchecked_clear() {
+ WRITE_FIELD(this, kValueOffset, Smi::FromInt(0));
+}
+
+
void WeakCell::initialize(HeapObject* val) {
WRITE_FIELD(this, kValueOffset, val);
WRITE_BARRIER(GetHeap(), this, kValueOffset, val);
Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index
0b85008b032e78809e526aa1a007eb6c0b548ddb..8b9883a61750cb7beb1c3bea4e3a034b7b0be121
100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -9866,6 +9866,8 @@ class WeakCell : public HeapObject {
// This should not be called by anyone except GC.
inline void clear();
+ inline void unchecked_clear();
+
// This should not be called by anyone except allocator.
inline void initialize(HeapObject* value);
Index: src/snapshot/serialize.cc
diff --git a/src/snapshot/serialize.cc b/src/snapshot/serialize.cc
index
b7c7dc1dd1c012264705860fd832e087910fc67e..713f245f668fb507e8ae5788c5ecfabe31619084
100644
--- a/src/snapshot/serialize.cc
+++ b/src/snapshot/serialize.cc
@@ -1092,6 +1092,12 @@ void Deserializer::ReadData(Object** current,
Object** limit, int source_space,
break;
}
+ case kClearedWeakCell: {
+ Object* cleared_weak_cell = isolate_->heap()->cleared_weak_cell();
+ UnalignedCopy(current++, &cleared_weak_cell);
+ break;
+ }
+
case kSynchronize:
// If we get here then that indicates that you have a mismatch
between
// the number of GC roots when serializing and deserializing.
@@ -1462,6 +1468,11 @@ bool
Serializer::BackReferenceIsAlreadyAllocated(BackReference reference) {
bool Serializer::SerializeKnownObject(HeapObject* obj, HowToCode
how_to_code,
WhereToPoint where_to_point, int
skip) {
+ if (obj->IsWeakCell() && WeakCell::cast(obj)->cleared()) {
+ FlushSkip(skip);
+ sink_->Put(kClearedWeakCell, "ClearedWeakCell");
+ return true;
+ }
if (how_to_code == kPlain && where_to_point == kStartOfObject) {
// Encode a reference to a hot object by its index in the working set.
int index = hot_objects_.Find(obj);
Index: src/snapshot/serialize.h
diff --git a/src/snapshot/serialize.h b/src/snapshot/serialize.h
index
36514e13d391927aa247a4714ff519194effacad..f6a88f05436fb753435061d1a538754106eb5e48
100644
--- a/src/snapshot/serialize.h
+++ b/src/snapshot/serialize.h
@@ -373,6 +373,8 @@ class SerializerDeserializer: public ObjectVisitor {
static const int kNop = 0x3d;
// Move to next reserved chunk.
static const int kNextChunk = 0x3e;
+ // Canonical cleared weak cell.
+ static const int kClearedWeakCell = 0x3f;
// A tag emitted at strategic points in the snapshot to delineate
sections.
// If the deserializer does not find these at the expected moments then
it
// is an indication that the snapshot and the VM do not fit together.
--
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