From: Ivan Maidanski <ivmai@mail.ru>
Date: Tue, 5 Apr 2016 21:10:56 +0000 (+0300)
Subject: Eliminate redundant lwsync 2nd call in CAS_full on fail (gcc/PowerPC)
X-Git-Tag: v7.6.0~225
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=157e8ad79a1bcc3d0ab331ab2217a9b81f35864c;p=libatomic_ops

Eliminate redundant lwsync 2nd call in CAS_full on fail (gcc/PowerPC)

* src/atomic_ops/sysdeps/gcc/powerpc.h (AO_compare_and_swap_full,
AO_fetch_compare_and_swap_full): Do not call AO_lwsync 2nd time if
CAS is not successful.
---

diff --git a/src/atomic_ops/sysdeps/gcc/powerpc.h b/src/atomic_ops/sysdeps/gcc/powerpc.h
index 94e83e7..5bee475 100644
--- a/src/atomic_ops/sysdeps/gcc/powerpc.h
+++ b/src/atomic_ops/sysdeps/gcc/powerpc.h
@@ -227,7 +227,8 @@ AO_test_and_set_full(volatile AO_TS_t *addr) {
     int result;
     AO_lwsync();
     result = AO_compare_and_swap(addr, old, new_val);
-    AO_lwsync();
+    if (result)
+      AO_lwsync();
     return result;
   }
 # define AO_HAVE_compare_and_swap_full
@@ -291,7 +292,8 @@ AO_fetch_compare_and_swap_full(volatile AO_t *addr, AO_t old_val,
   AO_t result;
   AO_lwsync();
   result = AO_fetch_compare_and_swap(addr, old_val, new_val);
-  AO_lwsync();
+  if (result == old_val)
+    AO_lwsync();
   return result;
 }
 #define AO_HAVE_fetch_compare_and_swap_full