373803c959
The TraceTrait<T> checks whether T is a mixin to decide whether we can use the fast (arithmetic) or slow (bitmap) method to look up the HoH. Before this CL, the mixin application would also be considered as a mixin because the marker is present, resulting in all cases going through the object start bitmap. The initial intention was to use the arithmetic for the mixin applications as those inherit from GCed. Bug: chromium:1056170 Change-Id: Ib0ba82a8f98e0481d2879ebacc1ca9bd9e675858 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2643395 Commit-Queue: Michael Lippautz <mlippautz@chromium.org> Reviewed-by: Omer Katz <omerkatz@chromium.org> Cr-Commit-Position: refs/heads/master@{#72262}
117 lines
3.1 KiB
C++
117 lines
3.1 KiB
C++
// Copyright 2020 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef INCLUDE_CPPGC_TRACE_TRAIT_H_
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#define INCLUDE_CPPGC_TRACE_TRAIT_H_
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#include <type_traits>
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#include "cppgc/type-traits.h"
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#include "v8config.h" // NOLINT(build/include_directory)
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namespace cppgc {
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class Visitor;
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namespace internal {
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// Implementation of the default TraceTrait handling GarbageCollected and
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// GarbageCollectedMixin.
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template <typename T,
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bool =
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IsGarbageCollectedMixinTypeV<typename std::remove_const<T>::type>>
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struct TraceTraitImpl;
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} // namespace internal
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/**
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* Callback for invoking tracing on a given object.
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*
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* \param visitor The visitor to dispatch to.
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* \param object The object to invoke tracing on.
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*/
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using TraceCallback = void (*)(Visitor* visitor, const void* object);
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/**
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* Describes how to trace an object, i.e., how to visit all Oilpan-relevant
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* fields of an object.
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*/
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struct TraceDescriptor {
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/**
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* Adjusted base pointer, i.e., the pointer to the class inheriting directly
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* from GarbageCollected, of the object that is being traced.
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*/
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const void* base_object_payload;
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/**
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* Callback for tracing the object.
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*/
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TraceCallback callback;
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};
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namespace internal {
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struct V8_EXPORT TraceTraitFromInnerAddressImpl {
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static TraceDescriptor GetTraceDescriptor(const void* address);
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};
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/**
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* Trait specifying how the garbage collector processes an object of type T.
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*
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* Advanced users may override handling by creating a specialization for their
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* type.
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*/
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template <typename T>
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struct TraceTraitBase {
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static_assert(internal::IsTraceableV<T>, "T must have a Trace() method");
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/**
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* Accessor for retrieving a TraceDescriptor to process an object of type T.
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*
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* \param self The object to be processed.
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* \returns a TraceDescriptor to process the object.
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*/
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static TraceDescriptor GetTraceDescriptor(const void* self) {
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return internal::TraceTraitImpl<T>::GetTraceDescriptor(
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static_cast<const T*>(self));
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}
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/**
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* Function invoking the tracing for an object of type T.
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*
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* \param visitor The visitor to dispatch to.
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* \param self The object to invoke tracing on.
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*/
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static void Trace(Visitor* visitor, const void* self) {
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static_cast<const T*>(self)->Trace(visitor);
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}
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};
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} // namespace internal
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template <typename T>
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struct TraceTrait : public internal::TraceTraitBase<T> {};
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namespace internal {
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template <typename T>
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struct TraceTraitImpl<T, false> {
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static_assert(IsGarbageCollectedTypeV<T>,
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"T must be of type GarbageCollected or GarbageCollectedMixin");
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static TraceDescriptor GetTraceDescriptor(const void* self) {
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return {self, TraceTrait<T>::Trace};
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}
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};
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template <typename T>
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struct TraceTraitImpl<T, true> {
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static TraceDescriptor GetTraceDescriptor(const void* self) {
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return internal::TraceTraitFromInnerAddressImpl::GetTraceDescriptor(self);
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}
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};
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} // namespace internal
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} // namespace cppgc
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#endif // INCLUDE_CPPGC_TRACE_TRAIT_H_
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