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 
MemoryFence()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 
CompareAndSwap(volatile sys::cas_flag * ptr,sys::cas_flag new_value,sys::cas_flag old_value)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 }
61