[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202730 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 5 deletions

diff --git a/include/llvm/Support/ManagedStatic.h b/include/llvm/Support/ManagedStatic.h
index 5587618d11..4a12a1ba8e 100644
--- a/include/llvm/Support/ManagedStatic.h
+++ b/include/llvm/Support/ManagedStatic.h
@@ -14,9 +14,9 @@
 #ifndef LLVM_SUPPORT_MANAGED_STATIC_H
 #define LLVM_SUPPORT_MANAGED_STATIC_H
 
-#include "llvm/Support/Atomic.h"
 #include "llvm/Support/Threading.h"
 #include "llvm/Support/Valgrind.h"
+#include <atomic>
 
 namespace llvm {
 
@@ -64,7 +64,8 @@ public:
   // Accessors.
   C &operator*() {
     void* tmp = Ptr;
-    if (llvm_is_multithreaded()) sys::MemoryFence();
+    if (llvm_is_multithreaded())
+      std::atomic_thread_fence(std::memory_order_seq_cst);
     if (!tmp) RegisterManagedStatic(object_creator<C>, object_deleter<C>::call);
     TsanHappensAfter(this);
 
@@ -72,7 +73,8 @@ public:
   }
   C *operator->() {
     void* tmp = Ptr;
-    if (llvm_is_multithreaded()) sys::MemoryFence();
+    if (llvm_is_multithreaded())
+      std::atomic_thread_fence(std::memory_order_seq_cst);
     if (!tmp) RegisterManagedStatic(object_creator<C>, object_deleter<C>::call);
     TsanHappensAfter(this);
 
@@ -80,7 +82,8 @@ public:
   }
   const C &operator*() const {
     void* tmp = Ptr;
-    if (llvm_is_multithreaded()) sys::MemoryFence();
+    if (llvm_is_multithreaded())
+      std::atomic_thread_fence(std::memory_order_seq_cst);
     if (!tmp) RegisterManagedStatic(object_creator<C>, object_deleter<C>::call);
     TsanHappensAfter(this);
 
@@ -88,7 +91,8 @@ public:
   }
   const C *operator->() const {
     void* tmp = Ptr;
-    if (llvm_is_multithreaded()) sys::MemoryFence();
+    if (llvm_is_multithreaded())
+      std::atomic_thread_fence(std::memory_order_seq_cst);
     if (!tmp) RegisterManagedStatic(object_creator<C>, object_deleter<C>::call);
     TsanHappensAfter(this);