From 0c44c2d0f459cd7e275242b72f500137c4fa834d Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 11 Sep 2013 15:19:24 +0200 Subject: x86: Use asm goto to implement better modify_and_test() functions Linus suggested using asm goto to get rid of the typical SETcc + TEST instruction pair -- which also clobbers an extra register -- for our typical modify_and_test() functions. Because asm goto doesn't allow output fields it has to include an unconditinal memory clobber when it changes a memory variable to force a reload. Luckily all atomic ops already imply a compiler barrier to go along with their memory barrier semantics. Suggested-by: Linus Torvalds Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-0mtn9siwbeo1d33bap1422se@git.kernel.org Signed-off-by: Ingo Molnar --- arch/x86/include/asm/local.h | 28 ++++------------------------ 1 file changed, 4 insertions(+), 24 deletions(-) (limited to 'arch/x86/include/asm/local.h') diff --git a/arch/x86/include/asm/local.h b/arch/x86/include/asm/local.h index 2d89e3980cbd..5b23e605e707 100644 --- a/arch/x86/include/asm/local.h +++ b/arch/x86/include/asm/local.h @@ -52,12 +52,7 @@ static inline void local_sub(long i, local_t *l) */ static inline int local_sub_and_test(long i, local_t *l) { - unsigned char c; - - asm volatile(_ASM_SUB "%2,%0; sete %1" - : "+m" (l->a.counter), "=qm" (c) - : "ir" (i) : "memory"); - return c; + GEN_BINARY_RMWcc(_ASM_SUB, l->a.counter, i, "%0", "e"); } /** @@ -70,12 +65,7 @@ static inline int local_sub_and_test(long i, local_t *l) */ static inline int local_dec_and_test(local_t *l) { - unsigned char c; - - asm volatile(_ASM_DEC "%0; sete %1" - : "+m" (l->a.counter), "=qm" (c) - : : "memory"); - return c != 0; + GEN_UNARY_RMWcc(_ASM_DEC, l->a.counter, "%0", "e"); } /** @@ -88,12 +78,7 @@ static inline int local_dec_and_test(local_t *l) */ static inline int local_inc_and_test(local_t *l) { - unsigned char c; - - asm volatile(_ASM_INC "%0; sete %1" - : "+m" (l->a.counter), "=qm" (c) - : : "memory"); - return c != 0; + GEN_UNARY_RMWcc(_ASM_INC, l->a.counter, "%0", "e"); } /** @@ -107,12 +92,7 @@ static inline int local_inc_and_test(local_t *l) */ static inline int local_add_negative(long i, local_t *l) { - unsigned char c; - - asm volatile(_ASM_ADD "%2,%0; sets %1" - : "+m" (l->a.counter), "=qm" (c) - : "ir" (i) : "memory"); - return c; + GEN_BINARY_RMWcc(_ASM_ADD, l->a.counter, i, "%0", "s"); } /** -- cgit v1.2.3