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 
MemoryFence()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 
CompareAndSwap(volatile sys::cas_flag * ptr,sys::cas_flag new_value,sys::cas_flag old_value)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 }
60