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// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/heap/cppgc/visitor.h"
#include "src/base/sanitizer/msan.h"
#include "src/heap/cppgc/gc-info-table.h"
#include "src/heap/cppgc/heap-object-header.h"
#include "src/heap/cppgc/heap-page.h"
#include "src/heap/cppgc/object-view.h"
#include "src/heap/cppgc/page-memory.h"
namespace cppgc {
#ifdef V8_ENABLE_CHECKS
void Visitor::CheckObjectNotInConstruction(const void* address) {
// TODO(chromium:1056170): |address| is an inner pointer of an object. Check
// that the object is not in construction.
}
#endif // V8_ENABLE_CHECKS
namespace internal {
ConservativeTracingVisitor::ConservativeTracingVisitor(
HeapBase& heap, PageBackend& page_backend, cppgc::Visitor& visitor)
: heap_(heap), page_backend_(page_backend), visitor_(visitor) {}
namespace {
void TraceConservatively(ConservativeTracingVisitor* conservative_visitor,
const HeapObjectHeader& header) {
const auto object_view = ObjectView(header);
Address* object = reinterpret_cast<Address*>(object_view.Start());
for (size_t i = 0; i < (object_view.Size() / sizeof(Address)); ++i) {
Address maybe_ptr = object[i];
#if defined(MEMORY_SANITIZER)
// |object| may be uninitialized by design or just contain padding bytes.
// Copy into a local variable that is not poisoned for conservative marking.
// Copy into a temporary variable to maintain the original MSAN state.
MSAN_MEMORY_IS_INITIALIZED(&maybe_ptr, sizeof(maybe_ptr));
#endif
if (maybe_ptr) {
conservative_visitor->TraceConservativelyIfNeeded(maybe_ptr);
}
}
}
} // namespace
void ConservativeTracingVisitor::TraceConservativelyIfNeeded(
const void* address) {
const BasePage* page = reinterpret_cast<const BasePage*>(
page_backend_.Lookup(static_cast<ConstAddress>(address)));
if (!page) return;
DCHECK_EQ(&heap_, &page->heap());
auto* header = page->TryObjectHeaderFromInnerAddress(
const_cast<Address>(reinterpret_cast<ConstAddress>(address)));
if (!header) return;
TraceConservativelyIfNeeded(*header);
}
void ConservativeTracingVisitor::TraceConservativelyIfNeeded(
HeapObjectHeader& header) {
if (!header.IsInConstruction<AccessMode::kNonAtomic>()) {
VisitFullyConstructedConservatively(header);
} else {
VisitInConstructionConservatively(header, TraceConservatively);
}
}
void ConservativeTracingVisitor::VisitFullyConstructedConservatively(
HeapObjectHeader& header) {
visitor_.Visit(
header.ObjectStart(),
{header.ObjectStart(),
GlobalGCInfoTable::GCInfoFromIndex(header.GetGCInfoIndex()).trace});
}
} // namespace internal
} // namespace cppgc
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