lib/Support/Atomic.cpp

   1 //===-- Atomic.cpp - Atomic Operations --------------------------*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 //  This file implements atomic operations.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Support/Atomic.h"
  15 #include "llvm/Config/llvm-config.h"
  16
  17 using namespace llvm;
  18
  19 #if defined(_MSC_VER)
  20 #include <intrin.h>
  21
  22 // We must include windows.h after intrin.h.
  23 #include <windows.h>
  24 #undef MemoryFence
  25 #endif
  26
  27 #if defined(__GNUC__) || (defined(__IBMCPP__) && __IBMCPP__ >= 1210)
  28 #define GNU_ATOMICS
  29 #endif
  30
  31 void sys::MemoryFence() {
  32 #if LLVM_HAS_ATOMICS == 0
  33   return;
  34 #else
  35 #  if defined(GNU_ATOMICS)
  36   __sync_synchronize();
  37 #  elif defined(_MSC_VER)
  38   MemoryBarrier();
  39 #  else
  40 # error No memory fence implementation for your platform!
  41 #  endif
  42 #endif
  43 }
  44
  45 sys::cas_flag sys::CompareAndSwap(volatile sys::cas_flag* ptr,
  46                                   sys::cas_flag new_value,
  47                                   sys::cas_flag old_value) {
  48 #if LLVM_HAS_ATOMICS == 0
  49   sys::cas_flag result = *ptr;
  50   if (result == old_value)
  51     *ptr = new_value;
  52   return result;
  53 #elif defined(GNU_ATOMICS)
  54   return __sync_val_compare_and_swap(ptr, old_value, new_value);
  55 #elif defined(_MSC_VER)
  56   return InterlockedCompareExchange(ptr, new_value, old_value);
  57 #else
  58 #  error No compare-and-swap implementation for your platform!
  59 #endif
  60 }