folly/folly/synchronization/detail/Hardware.h

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <atomic>

#include <folly/Portability.h>

namespace folly {

// Valid status values returned from rtmBegin.
// kRtmDisabled is a new return value indicating that RTM support is unavailable
// on the platform or the compiler.
constexpr unsigned kRtmDisabled = …;
constexpr unsigned kRtmBeginStarted = …;

// Valid abort status bits (when the status value is not kRtmBeginStarted or
// kRtmDisabled), defined as per the Intel RTM specifications:
// https://en.wikipedia.org/wiki/Transactional_Synchronization_Extensions.
constexpr unsigned kRtmAbortExplicit = …;
constexpr unsigned kRtmAbortRetry = …;
constexpr unsigned kRtmAbortConflict = …;
constexpr unsigned kRtmAbortCapacity = …;
constexpr unsigned kRtmAbortDebug = …;
constexpr unsigned kRtmAbortNested = …;

// False if there is no need for a dynamic check to see if
// the current environment supports RTM
constexpr bool kRtmSupportEnabled = …;

// Check on cpu support for tsx-rtm
extern bool rtmEnabled();

namespace detail {

// Use func ptrs to access the txn functions to avoid txn aborts
// due to plt mapping.
extern std::atomic<unsigned (*)()> rtmBeginV;
extern std::atomic<void (*)()> rtmEndV;
extern std::atomic<bool (*)()> rtmTestV;
extern std::atomic<void (*)(uint8_t)> rtmAbortV;

} // namespace detail

inline unsigned rtmBegin() { … }
inline void rtmEnd() { … }
inline bool rtmTest() { … }
inline void rtmAbort(uint8_t status) { … }
inline uint8_t rtmStatusToAbortCode(unsigned status) { … }

} // namespace folly