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[vm, gc] Don't enqueue pre-marked Instructions.

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Change-Id: Ic9a3b5f83fc45e363162c0531d474a663d243c6c
Reviewed-on: https://dart-review.googlesource.com/c/92666
Reviewed-by: Régis Crelier <regis@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>
This commit is contained in:
Ryan Macnak 2019-02-12 00:53:44 +00:00 committed by commit-bot@chromium.org
parent 553e20863c
commit ecd7a88606
1 changed files with 14 additions and 9 deletions
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23
runtime/vm/heap/marker.cc
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@ -368,12 +368,6 @@ class MarkingVisitorBase : public ObjectPointerVisitor {
}
static bool TryAcquireMarkBit(RawObject* raw_obj) {
// While it might seem this is redundant with TryAcquireMarkBit, we must
// do this check first to avoid attempting an atomic::fetch_and on the
// read-only vm-isolate or image pages, which can fault even if there is no
// change in the value.
if (raw_obj->IsMarked()) return false;
if (!sync) {
raw_obj->SetMarkBitUnsynchronized();
return true;
@ -383,17 +377,28 @@ class MarkingVisitorBase : public ObjectPointerVisitor {
}
void MarkObject(RawObject* raw_obj) {
// Fast exit if the raw object is a Smi.
// Fast exit if the raw object is immediate or in new space. No memory
// access.
if (raw_obj->IsSmiOrNewObject()) {
return;
}
// While it might seem this is redundant with TryAcquireMarkBit, we must
// do this check first to avoid attempting an atomic::fetch_and on the
// read-only vm-isolate or image pages, which can fault even if there is no
// change in the value.
// Doing this before checking for an Instructions object avoids
// unnecessary queueing of pre-marked objects.
if (raw_obj->IsMarked()) {
return;
}
intptr_t class_id = raw_obj->GetClassId();
ASSERT(class_id != kFreeListElement);
if (sync && UNLIKELY(class_id == kInstructionsCid)) {
// If this is the concurrent marker, instruction pages may be
// non-writable.
// If this is the concurrent marker, this object may be non-writable due
// to W^X (--write-protect-code).
deferred_work_list_.Push(raw_obj);
return;
}