From 885b74476763355f037889adbd1005a6053d7e62 Mon Sep 17 00:00:00 2001 From: wm4 Date: Wed, 21 May 2014 01:27:54 +0200 Subject: atomics: more correct usage of gcc/clang __atomic builtins This should be more correct. The builtins were made to directly map to C11, and the way we use them is now relatively close to how gcc implements atomics in 4.9. In particular, we make use of the load and store builtins. I'm not entirely sure why gcc didn't support stdatomic.h in 4.8 already. Maybe support for the builtins was incomplete or broken - so there's a lot of room for doubt about the correctness of this. --- compat/atomics.h | 26 +++++++++++++++----------- 1 file changed, 15 insertions(+), 11 deletions(-) (limited to 'compat') diff --git a/compat/atomics.h b/compat/atomics.h index 56328ab354..01ecdc64d7 100644 --- a/compat/atomics.h +++ b/compat/atomics.h @@ -38,21 +38,25 @@ typedef struct { volatile unsigned long long v; } atomic_ullong; #define ATOMIC_VAR_INIT(x) \ {.v = (x)} + +#if HAVE_ATOMIC_BUILTINS + #define atomic_load(p) \ - (mp_memory_barrier(), (p)->v) + __atomic_load_n(&(p)->v, __ATOMIC_SEQ_CST) #define atomic_store(p, val) \ - ((p)->v = (val), mp_memory_barrier()) + __atomic_store_n(&(p)->v, val, __ATOMIC_SEQ_CST) +#define atomic_fetch_add(a, b) \ + __atomic_fetch_add(&(a)->v, b, __ATOMIC_SEQ_CST) -#if HAVE_ATOMIC_BUILTINS -# define mp_memory_barrier() \ - __atomic_thread_fence(__ATOMIC_SEQ_CST) -# define atomic_fetch_add(a, b) \ - __atomic_add_fetch(&(a)->v, b, __ATOMIC_SEQ_CST) #elif HAVE_SYNC_BUILTINS -# define mp_memory_barrier() \ - __sync_synchronize() -# define atomic_fetch_add(a, b) \ - (__sync_add_and_fetch(&(a)->v, b), mp_memory_barrier()) + +#define atomic_load(p) \ + (__sync_synchronize(), (p)->v) +#define atomic_store(p, val) \ + ((p)->v = (val), __sync_synchronize()) +#define atomic_fetch_add(a, b) \ + (__sync_add_and_fetch(&(a)->v, b), __sync_synchronize()) + #else # error "this should have been a configuration error, report a bug please" #endif -- cgit v1.2.3