[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, 1 insertions, 2 deletions

diff --git a/llvm/lib/Support/ManagedStatic.cpp b/llvm/lib/Support/ManagedStatic.cpp
index 098cccb68df..c19f8cb4859 100644
--- a/llvm/lib/Support/ManagedStatic.cpp
+++ b/llvm/lib/Support/ManagedStatic.cpp
@@ -13,7 +13,6 @@
 
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Config/config.h"
-#include "llvm/Support/Atomic.h"
 #include <cassert>
 using namespace llvm;
 
@@ -28,7 +27,7 @@ void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
       void* tmp = Creator ? Creator() : 0;
 
       TsanHappensBefore(this);
-      sys::MemoryFence();
+      std::atomic_thread_fence(std::memory_order_seq_cst);
 
       // This write is racy against the first read in the ManagedStatic
       // accessors. The race is benign because it does a second read after a