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[heap] Adds UndoLastAllocationAt

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If the object to be trimmed creates a filler object that is located just
before the current LAB, then we can immediately give back the memory.

Bug: v8:11872, v8:11883
Change-Id: I9ec37443482334003b3752a3f25fc5dcb6a476fc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2996643
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75475}
This commit is contained in:
Victor Gomes 2021-06-30 15:07:14 +02:00 committed by V8 LUCI CQ
parent 0626318282
commit 444fdfdef6
3 changed files with 17 additions and 8 deletions
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10
src/heap/factory.cc
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@ -290,18 +290,12 @@ void Factory::CodeBuilder::FinalizeOnHeapCode(Handle<Code> code) {
code->CopyRelocInfoToByteArray(code->unchecked_relocation_info(), code_desc_); code->CopyRelocInfoToByteArray(code->unchecked_relocation_info(), code_desc_);
code->RelocateFromDesc(heap, code_desc_); code->RelocateFromDesc(heap, code_desc_);
int buffer_size = code_desc_.origin->buffer_size(); int old_object_size = Code::SizeFor(code_desc_.origin->buffer_size());
// TODO(v8:11883): add a hook to GC to check if the filler is just before
// the current LAB, and if it is, immediately give back the memory.
int old_object_size = Code::SizeFor(buffer_size);
int new_object_size = int new_object_size =
Code::SizeFor(code_desc_.instruction_size() + code_desc_.metadata_size()); Code::SizeFor(code_desc_.instruction_size() + code_desc_.metadata_size());
int size_to_trim = old_object_size - new_object_size; int size_to_trim = old_object_size - new_object_size;
DCHECK_GE(size_to_trim, 0); DCHECK_GE(size_to_trim, 0);
if (size_to_trim > 0) { heap->UndoLastAllocationAt(code->address() + new_object_size, size_to_trim);
heap->CreateFillerObjectAt(code->address() + new_object_size, size_to_trim,
ClearRecordedSlots::kNo);
}
} }
MaybeHandle<Code> Factory::NewEmptyCode(CodeKind kind, int buffer_size) { MaybeHandle<Code> Factory::NewEmptyCode(CodeKind kind, int buffer_size) {

13
src/heap/heap.cc
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@ -3414,6 +3414,19 @@ void Heap::RightTrimWeakFixedArray(WeakFixedArray object,
elements_to_trim * kTaggedSize); elements_to_trim * kTaggedSize);
} }
void Heap::UndoLastAllocationAt(Address addr, int size) {
DCHECK_LE(size, 0);
if (size == 0) return;
if (code_space_->Contains(addr)) {
Address* top = code_space_->allocation_top_address();
if (addr + size == *top && code_space_->original_top() <= addr) {
*top = addr;
return;
}
}
CreateFillerObjectAt(addr, size, ClearRecordedSlots::kNo);
}
template <typename T> template <typename T>
void Heap::CreateFillerForArray(T object, int elements_to_trim, void Heap::CreateFillerForArray(T object, int elements_to_trim,
int bytes_to_trim) { int bytes_to_trim) {

2
src/heap/heap.h
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@ -576,6 +576,8 @@ class Heap {
int elements_to_trim); int elements_to_trim);
void RightTrimWeakFixedArray(WeakFixedArray obj, int elements_to_trim); void RightTrimWeakFixedArray(WeakFixedArray obj, int elements_to_trim);
void UndoLastAllocationAt(Address addr, int size);
// Converts the given boolean condition to JavaScript boolean value. // Converts the given boolean condition to JavaScript boolean value.
inline Oddball ToBoolean(bool condition); inline Oddball ToBoolean(bool condition);