Messages in this thread Patch in this message | | | From | guoren@kernel ... | Subject | [PATCH V3 4/5] riscv: atomic: Optimize dec_if_positive functions | Date | Wed, 20 Apr 2022 22:44:16 +0800 |
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From: Guo Ren <guoren@linux.alibaba.com>
The arch_atomic_sub_if_positive is unnecessary for current Linux, and it causes another register allocation. Implementing the dec_if_positive function directly is more efficient.
Signed-off-by: Guo Ren <guoren@linux.alibaba.com> Signed-off-by: Guo Ren <guoren@kernel.org> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Dan Lustig <dlustig@nvidia.com> Cc: Andrea Parri <parri.andrea@gmail.com> --- arch/riscv/include/asm/atomic.h | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/arch/riscv/include/asm/atomic.h b/arch/riscv/include/asm/atomic.h index 4aaf5b01e7c6..5589e1de2c80 100644 --- a/arch/riscv/include/asm/atomic.h +++ b/arch/riscv/include/asm/atomic.h @@ -374,45 +374,45 @@ ATOMIC_OPS() #undef ATOMIC_OPS #undef ATOMIC_OP -static __always_inline int arch_atomic_sub_if_positive(atomic_t *v, int offset) +static __always_inline int arch_atomic_dec_if_positive(atomic_t *v) { int prev, rc; __asm__ __volatile__ ( "0: lr.w %[p], %[c]\n" - " sub %[rc], %[p], %[o]\n" + " addi %[rc], %[p], -1\n" " bltz %[rc], 1f\n" " sc.w.aqrl %[rc], %[rc], %[c]\n" " bnez %[rc], 0b\n" "1:\n" : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter) - : [o]"r" (offset) + : : "memory"); - return prev - offset; + return prev - 1; } -#define arch_atomic_dec_if_positive(v) arch_atomic_sub_if_positive(v, 1) +#define arch_atomic_dec_if_positive arch_atomic_dec_if_positive #ifndef CONFIG_GENERIC_ATOMIC64 -static __always_inline s64 arch_atomic64_sub_if_positive(atomic64_t *v, s64 offset) +static __always_inline s64 arch_atomic64_dec_if_positive(atomic64_t *v) { s64 prev; long rc; __asm__ __volatile__ ( "0: lr.d %[p], %[c]\n" - " sub %[rc], %[p], %[o]\n" + " addi %[rc], %[p], -1\n" " bltz %[rc], 1f\n" " sc.d.aqrl %[rc], %[rc], %[c]\n" " bnez %[rc], 0b\n" "1:\n" : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter) - : [o]"r" (offset) + : : "memory"); - return prev - offset; + return prev - 1; } -#define arch_atomic64_dec_if_positive(v) arch_atomic64_sub_if_positive(v, 1) +#define arch_atomic64_dec_if_positive arch_atomic64_dec_if_positive #endif #endif /* _ASM_RISCV_ATOMIC_H */ -- 2.25.1
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