[C++11] Replace LLVM atomics with std::atomic.

With C++11 we finally have a standardized way to specify atomic operations. Use
them to replace the existing custom implemention. Sadly the translation is not
entirely trivial as std::atomic allows more fine-grained control over the
atomicity. I tried to preserve the old semantics as well as possible.

Differential Revision: http://llvm-reviews.chandlerc.com/D2915

llvm-svn: 202730

1 files changed, 3 insertions, 3 deletions

diff --git a/llvm/lib/Support/Threading.cpp b/llvm/lib/Support/Threading.cpp
index 9d7ac6c18de..15dd8a98052 100644
--- a/llvm/lib/Support/Threading.cpp
+++ b/llvm/lib/Support/Threading.cpp
@@ -13,8 +13,8 @@
 
 #include "llvm/Support/Threading.h"
 #include "llvm/Config/config.h"
-#include "llvm/Support/Atomic.h"
 #include "llvm/Support/Mutex.h"
+#include <atomic>
 #include <cassert>
 
 using namespace llvm;
@@ -31,7 +31,7 @@ bool llvm::llvm_start_multithreaded() {
 
   // We fence here to ensure that all initialization is complete BEFORE we
   // return from llvm_start_multithreaded().
-  sys::MemoryFence();
+  std::atomic_thread_fence(std::memory_order_seq_cst);
   return true;
 #else
   return false;
@@ -44,7 +44,7 @@ void llvm::llvm_stop_multithreaded() {
 
   // We fence here to insure that all threaded operations are complete BEFORE we
   // return from llvm_stop_multithreaded().
-  sys::MemoryFence();
+  std::atomic_thread_fence(std::memory_order_seq_cst);
 
   multithreaded_mode = false;
   delete global_lock;