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authorDavid S. Miller <davem@davemloft.net>2013-01-23 11:27:24 -0800
committerDavid S. Miller <davem@davemloft.net>2013-01-23 11:27:24 -0800
commitbae8e7f5ed0cdc8a81ae9b32efc77285d2f5bc7a (patch)
treeb2deb8c9c341212727f5c04750c5cc6401635698 /sysdeps/sparc/sparc64
parent67b3f58c83d4ffc29ab939e3d0bbeb9fb38103e7 (diff)
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Add a minor 'cas' atomic optimization on sparc.
	* sysdeps/sparc/sparc32/sparcv9/bits/atomic.h
	(__arch_compare_and_exchange_val_32_acq): Use %g0 as second
	argument of CAS if possible.
	* sysdeps/sparc/sparc64/bits/atomic.h
	(__arch_compare_and_exchange_val_32_acq): Likewise.
	(__arch_compare_and_exchange_val_64_acq): Likewise.
Diffstat (limited to 'sysdeps/sparc/sparc64')
-rw-r--r--sysdeps/sparc/sparc64/bits/atomic.h28
1 files changed, 20 insertions, 8 deletions
diff --git a/sysdeps/sparc/sparc64/bits/atomic.h b/sysdeps/sparc/sparc64/bits/atomic.h
index 0afbb4ba5e..96611de42f 100644
--- a/sysdeps/sparc/sparc64/bits/atomic.h
+++ b/sysdeps/sparc/sparc64/bits/atomic.h
@@ -55,20 +55,32 @@ typedef uintmax_t uatomic_max_t;
 ({									      \
   __typeof (*(mem)) __acev_tmp;						      \
   __typeof (mem) __acev_mem = (mem);					      \
-  __asm __volatile ("cas [%4], %2, %0"					      \
-		    : "=r" (__acev_tmp), "=m" (*__acev_mem)		      \
-		    : "r" (oldval), "m" (*__acev_mem), "r" (__acev_mem),      \
-		      "0" (newval) : "memory");				      \
+  if (__builtin_constant_p (oldval) && (oldval) == 0)			      \
+    __asm __volatile ("cas [%3], %%g0, %0"				      \
+		      : "=r" (__acev_tmp), "=m" (*__acev_mem)		      \
+		      : "m" (*__acev_mem), "r" (__acev_mem),		      \
+		        "0" (newval) : "memory");			      \
+  else									      \
+    __asm __volatile ("cas [%4], %2, %0"				      \
+		      : "=r" (__acev_tmp), "=m" (*__acev_mem)		      \
+		      : "r" (oldval), "m" (*__acev_mem), "r" (__acev_mem),    \
+		        "0" (newval) : "memory");			      \
   __acev_tmp; })
 
 #define __arch_compare_and_exchange_val_64_acq(mem, newval, oldval) \
 ({									      \
   __typeof (*(mem)) __acev_tmp;						      \
   __typeof (mem) __acev_mem = (mem);					      \
-  __asm __volatile ("casx [%4], %2, %0"					      \
-		    : "=r" (__acev_tmp), "=m" (*__acev_mem)		      \
-		    : "r" ((long) (oldval)), "m" (*__acev_mem),		      \
-		      "r" (__acev_mem), "0" ((long) (newval)) : "memory");    \
+  if (__builtin_constant_p (oldval) && (oldval) == 0)			      \
+    __asm __volatile ("casx [%3], %%g0, %0"				      \
+		      : "=r" (__acev_tmp), "=m" (*__acev_mem)		      \
+		      : "m" (*__acev_mem), "r" (__acev_mem),		      \
+		        "0" ((long) (newval)) : "memory");		      \
+  else									      \
+    __asm __volatile ("casx [%4], %2, %0"				      \
+		      : "=r" (__acev_tmp), "=m" (*__acev_mem)		      \
+		      : "r" ((long) (oldval)), "m" (*__acev_mem),	      \
+		        "r" (__acev_mem), "0" ((long) (newval)) : "memory");  \
   __acev_tmp; })
 
 #define atomic_exchange_acq(mem, newvalue) \