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deps: cherry-pick b93c80a from v8 upstream#7689

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matthewloring wants to merge 2 commits into from
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deps: cherry-pick b93c80a from v8 upstream #7689

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271a498
deps: cherry-pick b93c80a from v8 upstream
Jul 12, 2016
965ff41
deps: cherry-pick a76d133 from v8 upstream
Jul 20, 2016
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27 changes: 20 additions & 7 deletions deps/v8/src/objects.cc
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Original file line numberDiff line numberDiff line change
Expand Up@@ -17389,7 +17389,7 @@ Handle<Derived> HashTable<Derived, Shape, Key>::EnsureCapacity(
int capacity = table->Capacity();
int nof = table->NumberOfElements() + n;

if (table->HasSufficientCapacity(n)) return table;
if (table->HasSufficientCapacityToAdd(n)) return table;

const int kMinCapacityForPretenure = 256;
bool should_pretenure = pretenure == TENURED ||
Expand All@@ -17405,16 +17405,16 @@ Handle<Derived> HashTable<Derived, Shape, Key>::EnsureCapacity(
return new_table;
}


template <typename Derived, typename Shape, typename Key>
bool HashTable<Derived, Shape, Key>::HasSufficientCapacity(int n) {
bool HashTable<Derived, Shape, Key>::HasSufficientCapacityToAdd(
int number_of_additional_elements) {
int capacity = Capacity();
int nof = NumberOfElements() + n;
int nof = NumberOfElements() + number_of_additional_elements;
int nod = NumberOfDeletedElements();
// Return true if:
// 50% is still free after adding n elements and
// 50% is still free after adding number_of_additional_elements elements and
// at most 50% of the free elements are deleted elements.
if (nod <= (capacity - nof) >> 1) {
if ((nof < capacity) && ((nod <= (capacity - nof) >> 1))) {
int needed_free = nof >> 1;
if (nof + needed_free <= capacity) return true;
}
Expand DownExpand Up@@ -18332,7 +18332,7 @@ void Dictionary<Derived, Shape, Key>::SetRequiresCopyOnCapacityChange() {
DCHECK_EQ(0, DerivedHashTable::NumberOfDeletedElements());
// Make sure that HashTable::EnsureCapacity will create a copy.
DerivedHashTable::SetNumberOfDeletedElements(DerivedHashTable::Capacity());
DCHECK(!DerivedHashTable::HasSufficientCapacity(1));
DCHECK(!DerivedHashTable::HasSufficientCapacityToAdd(1));
}


Expand DownExpand Up@@ -18740,6 +18740,19 @@ Handle<ObjectHashTable> ObjectHashTable::Put(Handle<ObjectHashTable> table,
if ((table->NumberOfDeletedElements() << 1) > table->NumberOfElements()) {
table->Rehash(isolate->factory()->undefined_value());
}
// If we're out of luck, we didn't get a GC recently, and so rehashing
// isn't enough to avoid a crash.
if (!table->HasSufficientCapacityToAdd(1)) {
int nof = table->NumberOfElements() + 1;
int capacity = ObjectHashTable::ComputeCapacity(nof * 2);
if (capacity > ObjectHashTable::kMaxCapacity) {
for (size_t i = 0; i < 2; ++i) {
isolate->heap()->CollectAllGarbage(
Heap::kFinalizeIncrementalMarkingMask, "full object hash table");

@bnoordhuisbnoordhuisJul 13, 2016

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I don't understand why the calls to CollectAllGarbage() are necessary. Rehash() doesn't do heap allocations, does it?

@jeisingerjeisingerJul 19, 2016

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Rehash can only free entries that are garbage, and we need at least two major GCs to guarantee that all garbage in weak sets/maps is found: the first GC might finish an already started GC round where a now garbage entry was still alive at the beginning of the GC round.

@bnoordhuisbnoordhuisJul 20, 2016

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Okay, it's a little implicit but your explanation makes sense.

}
table->Rehash(isolate->factory()->undefined_value());
}
}

// Check whether the hash table should be extended.
table = EnsureCapacity(table, 1, key);
Expand Down
2 changes: 1 addition & 1 deletion deps/v8/src/objects.h
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Original file line numberDiff line numberDiff line change
Expand Up@@ -3331,7 +3331,7 @@ class HashTable : public HashTableBase {
PretenureFlag pretenure = NOT_TENURED);

// Returns true if this table has sufficient capacity for adding n elements.
bool HasSufficientCapacity(int n);
bool HasSufficientCapacityToAdd(int number_of_additional_elements);

// Sets the capacity of the hash table.
void SetCapacity(int capacity) {
Expand Down