[libcxx] Add atomic_support.h header to src that handles needed atomic operations.
Summary:
In some places in libc++ we need to use the `__atomic_*` builtins. This patch adds a header that provides access to those builtins in a uniform way from within the dylib source.
If the compiler building the dylib does not support these builtins then a warning is issued.
Only relaxed loads are needed within the headers. A singe function to do these relaxed loads has been added to `<memory>`.
This patch applies the new atomic builtins to `__shared_count` and `call_once`.
Reviewers: mclow.lists
Subscribers: majnemer, jroelofs, cfe-commits
Differential Revision: http://reviews.llvm.org/D10406
llvm-svn: 241532
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 1faf289e27bcb54e54b2e3e0f492d6f54d59cd9e
diff --git a/include/mutex b/include/mutex
index 0adf1e6..373d75b 100644
--- a/include/mutex
+++ b/include/mutex
@@ -175,6 +175,7 @@
#include <__config>
#include <__mutex_base>
#include <functional>
+#include <memory>
#ifndef _LIBCPP_HAS_NO_VARIADICS
#include <tuple>
#endif
@@ -539,7 +540,7 @@
void
call_once(once_flag& __flag, _Callable&& __func, _Args&&... __args)
{
- if (__flag.__state_ != ~0ul)
+ if (__libcpp_relaxed_load(&__flag.__state_) != ~0ul)
{
typedef tuple<_Callable&&, _Args&&...> _Gp;
_Gp __f(_VSTD::forward<_Callable>(__func), _VSTD::forward<_Args>(__args)...);
@@ -555,7 +556,7 @@
void
call_once(once_flag& __flag, _Callable& __func)
{
- if (__flag.__state_ != ~0ul)
+ if (__libcpp_relaxed_load(&__flag.__state_) != ~0ul)
{
__call_once_param<_Callable> __p(__func);
__call_once(__flag.__state_, &__p, &__call_once_proxy<_Callable>);