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// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/351564777): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_ATOMIC_OPERATIONS_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_ATOMIC_OPERATIONS_H_
#include <atomic>
#include <cstddef>
#include <type_traits>
#include "base/check_op.h"
#include "base/compiler_specific.h"
#include "build/build_config.h"
#include "third_party/blink/renderer/platform/wtf/wtf_export.h"
namespace WTF {
// TOOD(omerkatz): Replace these casts with std::atomic_ref (C++20) once it
// becomes available.
template <typename T>
ALWAYS_INLINE std::atomic<T>* AsAtomicPtr(T* t) {
return reinterpret_cast<std::atomic<T>*>(t);
}
template <typename T>
ALWAYS_INLINE const std::atomic<T>* AsAtomicPtr(const T* t) {
return reinterpret_cast<const std::atomic<T>*>(t);
}
// Copies |bytes| bytes from |from| to |to| using atomic reads. Assumes |to|
// and |from| are size_t-aligned (or halfword-aligned for 64-bit platforms) and
// point to buffers of size |bytes|. Note that atomicity is guaranteed only per
// word/halfword, not for the entire |bytes| bytes as a whole. The function
// copies elements one by one, so overlapping regions are not supported.
WTF_EXPORT void AtomicReadMemcpy(void* to, const void* from, size_t bytes);
namespace internal {
template <size_t bytes, typename AlignmentType>
ALWAYS_INLINE void AtomicReadMemcpyAligned(void* to, const void* from) {
static constexpr size_t kAlignment = sizeof(AlignmentType);
DCHECK_EQ(0u, reinterpret_cast<uintptr_t>(to) & (kAlignment - 1));
DCHECK_EQ(0u, reinterpret_cast<uintptr_t>(from) & (kAlignment - 1));
#if defined(ARCH_CPU_64_BITS)
if constexpr (bytes == sizeof(uint32_t)) {
*reinterpret_cast<uint32_t*>(to) =
AsAtomicPtr(reinterpret_cast<const uint32_t*>(from))
->load(std::memory_order_relaxed);
return;
}
#endif // defined(ARCH_CPU_64_BITS)
if constexpr (bytes % kAlignment == 0 && bytes >= kAlignment &&
bytes <= 3 * kAlignment) {
*reinterpret_cast<AlignmentType*>(to) =
AsAtomicPtr(reinterpret_cast<const AlignmentType*>(from))
->load(std::memory_order_relaxed);
if constexpr (bytes >= 2 * kAlignment) {
*(reinterpret_cast<AlignmentType*>(to) + 1) =
AsAtomicPtr(reinterpret_cast<const AlignmentType*>(from) + 1)
->load(std::memory_order_relaxed);
}
if constexpr (bytes == 3 * kAlignment) {
*(reinterpret_cast<AlignmentType*>(to) + 2) =
AsAtomicPtr(reinterpret_cast<const AlignmentType*>(from) + 2)
->load(std::memory_order_relaxed);
}
} else {
AtomicReadMemcpy(to, from, bytes);
}
}
} // namespace internal
template <size_t bytes, size_t alignment>
ALWAYS_INLINE void AtomicReadMemcpy(void* to, const void* from) {
static_assert(bytes > 0, "Number of copied bytes should be greater than 0");
if constexpr (alignment == sizeof(size_t)) {
internal::AtomicReadMemcpyAligned<bytes, size_t>(to, from);
} else if constexpr (alignment == sizeof(uint32_t)) {
internal::AtomicReadMemcpyAligned<bytes, uint32_t>(to, from);
} else {
AtomicReadMemcpy(to, from, bytes);
}
}
// Copies |bytes| bytes from |from| to |to| using atomic writes. Assumes |to|
// and |from| are size_t-aligned (or halfword-aligned for 64-bit platforms) and
// point to buffers of size |bytes|. Note that atomicity is guaranteed only per
// word/halfword, not for the entire |bytes| bytes as a whole. The function
// copies elements one by one, so overlapping regions are not supported.
WTF_EXPORT void AtomicWriteMemcpy(void* to, const void* from, size_t bytes);
namespace internal {
template <size_t bytes, typename AlignmentType>
ALWAYS_INLINE void AtomicWriteMemcpyAligned(void* to, const void* from) {
static constexpr size_t kAlignment = sizeof(AlignmentType);
DCHECK_EQ(0u, reinterpret_cast<uintptr_t>(to) & (kAlignment - 1));
DCHECK_EQ(0u, reinterpret_cast<uintptr_t>(from) & (kAlignment - 1));
#if defined(ARCH_CPU_64_BITS)
if constexpr (bytes == sizeof(uint32_t)) {
AsAtomicPtr(reinterpret_cast<uint32_t*>(to))
->store(*reinterpret_cast<const uint32_t*>(from),
std::memory_order_relaxed);
return;
}
#endif // defined(ARCH_CPU_64_BITS)
if constexpr (bytes % kAlignment == 0 && bytes >= kAlignment &&
bytes <= 3 * kAlignment) {
AsAtomicPtr(reinterpret_cast<AlignmentType*>(to))
->store(*reinterpret_cast<const AlignmentType*>(from),
std::memory_order_relaxed);
if constexpr (bytes >= 2 * kAlignment) {
AsAtomicPtr(reinterpret_cast<AlignmentType*>(to) + 1)
->store(*(reinterpret_cast<const AlignmentType*>(from) + 1),
std::memory_order_relaxed);
}
if constexpr (bytes == 3 * kAlignment) {
AsAtomicPtr(reinterpret_cast<AlignmentType*>(to) + 2)
->store(*(reinterpret_cast<const AlignmentType*>(from) + 2),
std::memory_order_relaxed);
}
} else {
AtomicWriteMemcpy(to, from, bytes);
}
}
} // namespace internal
template <size_t bytes, size_t alignment>
ALWAYS_INLINE void AtomicWriteMemcpy(void* to, const void* from) {
static_assert(bytes > 0, "Number of copied bytes should be greater than 0");
if constexpr (alignment == sizeof(size_t)) {
internal::AtomicWriteMemcpyAligned<bytes, size_t>(to, from);
} else if constexpr (alignment == sizeof(uint32_t)) {
internal::AtomicWriteMemcpyAligned<bytes, uint32_t>(to, from);
} else {
AtomicWriteMemcpy(to, from, bytes);
}
}
// Set the first |bytes| bytes of |buf| to 0 using atomic writes. Assumes |buf|
// is size_t-aligned (or halfword-aligned for 64-bit platforms) and points to a
// buffer of size at least |bytes|. Note that atomicity is guaranteed only per
// word/halfword, not for the entire |bytes| bytes as a whole.
WTF_EXPORT void AtomicMemzero(void* buf, size_t bytes);
namespace internal {
template <size_t bytes, typename AlignmentType>
ALWAYS_INLINE void AtomicMemzeroAligned(void* buf) {
static constexpr size_t kAlignment = sizeof(AlignmentType);
DCHECK_EQ(0u, reinterpret_cast<size_t>(buf) & (kAlignment - 1));
#if defined(ARCH_CPU_64_BITS)
if constexpr (bytes == sizeof(uint32_t)) {
AsAtomicPtr(reinterpret_cast<uint32_t*>(buf))
->store(0, std::memory_order_relaxed);
return;
}
#endif // defined(ARCH_CPU_64_BITS)
if constexpr (bytes % kAlignment == 0 && bytes >= kAlignment &&
bytes <= 3 * kAlignment) {
AsAtomicPtr(reinterpret_cast<AlignmentType*>(buf))
->store(0, std::memory_order_relaxed);
if constexpr (bytes >= 2 * kAlignment) {
AsAtomicPtr(reinterpret_cast<AlignmentType*>(buf) + 1)
->store(0, std::memory_order_relaxed);
}
if constexpr (bytes == 3 * kAlignment) {
AsAtomicPtr(reinterpret_cast<AlignmentType*>(buf) + 2)
->store(0, std::memory_order_relaxed);
}
} else {
AtomicMemzero(buf, bytes);
}
}
} // namespace internal
template <size_t bytes, size_t alignment>
ALWAYS_INLINE void AtomicMemzero(void* buf) {
static_assert(bytes > 0, "Number of copied bytes should be greater than 0");
if constexpr (alignment == sizeof(size_t)) {
internal::AtomicMemzeroAligned<bytes, size_t>(buf);
} else if constexpr (alignment == sizeof(uint32_t)) {
internal::AtomicMemzeroAligned<bytes, uint32_t>(buf);
} else {
AtomicMemzero(buf, bytes);
}
}
// Swaps values using atomic writes.
template <typename T>
ALWAYS_INLINE void AtomicWriteSwap(T& lhs, T& rhs) {
T tmp_val = rhs;
AsAtomicPtr(&rhs)->store(lhs, std::memory_order_relaxed);
AsAtomicPtr(&lhs)->store(tmp_val, std::memory_order_relaxed);
}
} // namespace WTF
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_ATOMIC_OPERATIONS_H_
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