From: Hans Boehm <boehm@acm.org>
Date: Thu, 26 Jan 2017 07:16:54 +0000 (+0300)
Subject: Implement compiler_barrier using C11 __atomic_signal_fence (GCC)
X-Git-Tag: v7.6.0~121
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=01b8da7d71c5030bb35dd67d88c0b0f4b6131a88;p=libatomic_ops

Implement compiler_barrier using C11 __atomic_signal_fence (GCC)

Use __atomic_signal_fence(__ATOMIC_SEQ_CST) as AO_compiler_barrier.
That was the intended use of __atomic_signal_fence.  The only
standards-relevant context in which you can tell apart a compiler and
real fence is in the case if signal handlers.

* src/atomic_ops/sysdeps/gcc/generic.h (AO_compiler_barrier): Redefine
using GCC atomic intrinsic (__atomic_signal_fence).
---

diff --git a/src/atomic_ops/sysdeps/gcc/generic.h b/src/atomic_ops/sysdeps/gcc/generic.h
index ba82e0d..3f736ef 100644
--- a/src/atomic_ops/sysdeps/gcc/generic.h
+++ b/src/atomic_ops/sysdeps/gcc/generic.h
@@ -45,6 +45,9 @@
 # define AO_GCC_HAVE_SYNC_CAS
 #endif
 
+#undef AO_compiler_barrier
+#define AO_compiler_barrier() __atomic_signal_fence(__ATOMIC_SEQ_CST)
+
 #ifdef AO_UNIPROCESSOR
   /* If only a single processor (core) is used, AO_UNIPROCESSOR could   */
   /* be defined by the client to avoid unnecessary memory barrier.      */