Use '+' modifier for a memory operand that is both an input and an output.

It was actually done in r86301 but reverted in r150182 because GCC 3.x was
not able to handle it for a memory operand.  Apparently, this problem was
fixed in GCC 4.1+ and several contrib sources already rely on this feature.

1 files changed, 16 insertions, 23 deletions

diff --git a/sys/amd64/include/atomic.h b/sys/amd64/include/atomic.h
index ef92c02..11e7b57 100644
--- a/sys/amd64/include/atomic.h
+++ b/sys/amd64/include/atomic.h
@@ -108,8 +108,8 @@ static __inline void					\
 atomic_##NAME##_##TYPE(volatile u_##TYPE *p, u_##TYPE v)\
 {							\
 	__asm __volatile(MPLOCKED OP			\
-	: "=m" (*p)					\
-	: CONS (V), "m" (*p)				\
+	: "+m" (*p)					\
+	: CONS (V)					\
 	: "cc");					\
 }							\
 							\
@@ -117,8 +117,8 @@ static __inline void					\
 atomic_##NAME##_barr_##TYPE(volatile u_##TYPE *p, u_##TYPE v)\
 {							\
 	__asm __volatile(MPLOCKED OP			\
-	: "=m" (*p)					\
-	: CONS (V), "m" (*p)				\
+	: "+m" (*p)					\
+	: CONS (V)					\
 	: "memory", "cc");				\
 }							\
 struct __hack
@@ -142,10 +142,9 @@ atomic_cmpset_int(volatile u_int *dst, u_int expect, u_int src)
 	"       sete	%0 ;		"
 	"# atomic_cmpset_int"
 	: "=a" (res),			/* 0 */
-	  "=m" (*dst)			/* 1 */
+	  "+m" (*dst)			/* 1 */
 	: "r" (src),			/* 2 */
-	  "a" (expect),			/* 3 */
-	  "m" (*dst)			/* 4 */
+	  "a" (expect)			/* 3 */
 	: "memory", "cc");
 
 	return (res);
@@ -162,10 +161,9 @@ atomic_cmpset_long(volatile u_long *dst, u_long expect, u_long src)
 	"       sete	%0 ;		"
 	"# atomic_cmpset_long"
 	: "=a" (res),			/* 0 */
-	  "=m" (*dst)			/* 1 */
+	  "+m" (*dst)			/* 1 */
 	: "r" (src),			/* 2 */
-	  "a" (expect),			/* 3 */
-	  "m" (*dst)			/* 4 */
+	  "a" (expect)			/* 3 */
 	: "memory", "cc");
 
 	return (res);
@@ -184,9 +182,8 @@ atomic_fetchadd_int(volatile u_int *p, u_int v)
 	"	xaddl	%0,%1 ;		"
 	"# atomic_fetchadd_int"
 	: "+r" (v),			/* 0 */
-	  "=m" (*p)			/* 1 */
-	: "m" (*p)			/* 2 */
-	: "cc");
+	  "+m" (*p)			/* 1 */
+	: : "cc");
 	return (v);
 }
 
@@ -203,9 +200,8 @@ atomic_fetchadd_long(volatile u_long *p, u_long v)
 	"	xaddq	%0,%1 ;		"
 	"# atomic_fetchadd_long"
 	: "+r" (v),			/* 0 */
-	  "=m" (*p)			/* 1 */
-	: "m" (*p)			/* 2 */
-	: "cc");
+	  "+m" (*p)			/* 1 */
+	: : "cc");
 	return (v);
 }
 
@@ -253,9 +249,8 @@ atomic_load_acq_##TYPE(volatile u_##TYPE *p)		\
 							\
 	__asm __volatile(MPLOCKED LOP			\
 	: "=a" (res),			/* 0 */		\
-	  "=m" (*p)			/* 1 */		\
-	: "m" (*p)			/* 2 */		\
-	: "memory", "cc");				\
+	  "+m" (*p)			/* 1 */		\
+	: : "memory", "cc");				\
 							\
 	return (res);					\
 }							\
@@ -314,8 +309,7 @@ atomic_readandclear_int(volatile u_int *p)
 	"	xchgl	%1,%0 ;		"
 	"# atomic_readandclear_int"
 	: "+r" (res),			/* 0 */
-	  "=m" (*p)			/* 1 */
-	: "m" (*p));
+	  "+m" (*p));			/* 1 */
 
 	return (res);
 }
@@ -330,8 +324,7 @@ atomic_readandclear_long(volatile u_long *p)
 	"	xchgq	%1,%0 ;		"
 	"# atomic_readandclear_long"
 	: "+r" (res),			/* 0 */
-	  "=m" (*p)			/* 1 */
-	: "m" (*p));
+	  "+m" (*p));			/* 1 */
 
 	return (res);
 }