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| author |   Peter Zijlstra <peterz@infradead.org> | 2013-09-11 15:19:24 +0200 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2013-09-25 13:53:08 +0200 |
| commit | 0c44c2d0f459cd7e275242b72f500137c4fa834d (patch) | |
| tree | fdd16d5585a986cf8cbed140f533d08d152bbc4f /arch/x86/include/asm/local.h | |
| parent | sched: Micro-optimize by dropping unnecessary task_rq() calls (diff) | |
| download | linux-dev-0c44c2d0f459cd7e275242b72f500137c4fa834d.tar.xz linux-dev-0c44c2d0f459cd7e275242b72f500137c4fa834d.zip | |
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 <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-0mtn9siwbeo1d33bap1422se@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/local.h')
| -rw-r--r-- | arch/x86/include/asm/local.h | 28 |
1 files changed, 4 insertions, 24 deletions
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"); } /** |