[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 git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@241532 91177308-0d34-0410-b5e6-96231b3b80d8
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>); 