lib/Support/Atomic.cpp

   1 //===-- Atomic.cpp - Atomic Operations --------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 //  This file implements atomic operations.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Support/Atomic.h"
  14 #include "llvm/Config/llvm-config.h"
  15
  16 using namespace llvm;
  17
  18 #if defined(_MSC_VER)
  19 #include <intrin.h>
  20
  21 // We must include windows.h after intrin.h.
  22 #include <windows.h>
  23 #undef MemoryFence
  24 #endif
  25
  26 #if defined(__GNUC__) || (defined(__IBMCPP__) && __IBMCPP__ >= 1210)
  27 #define GNU_ATOMICS
  28 #endif
  29
  30 void sys::MemoryFence() {
  31 #if LLVM_HAS_ATOMICS == 0
  32   return;
  33 #else
  34 #  if defined(GNU_ATOMICS)
  35   __sync_synchronize();
  36 #  elif defined(_MSC_VER)
  37   MemoryBarrier();
  38 #  else
  39 # error No memory fence implementation for your platform!
  40 #  endif
  41 #endif
  42 }
  43
  44 sys::cas_flag sys::CompareAndSwap(volatile sys::cas_flag* ptr,
  45                                   sys::cas_flag new_value,
  46                                   sys::cas_flag old_value) {
  47 #if LLVM_HAS_ATOMICS == 0
  48   sys::cas_flag result = *ptr;
  49   if (result == old_value)
  50     *ptr = new_value;
  51   return result;
  52 #elif defined(GNU_ATOMICS)
  53   return __sync_val_compare_and_swap(ptr, old_value, new_value);
  54 #elif defined(_MSC_VER)
  55   return InterlockedCompareExchange(ptr, new_value, old_value);
  56 #else
  57 #  error No compare-and-swap implementation for your platform!
  58 #endif
  59 }