LLVM  9.0.0svn
Atomic.cpp
Go to the documentation of this file.
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 
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 
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 }
This class represents lattice values for constants.
Definition: AllocatorList.h:23
cas_flag CompareAndSwap(volatile cas_flag *ptr, cas_flag new_value, cas_flag old_value)
Definition: Atomic.cpp:44
void MemoryFence()
Definition: Atomic.cpp:30