Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-12-02 17:11:33 +00:00
Code Issues Packages Projects Releases Wiki Activity

riscv: atomic: Optimize dec_if_positive functions

Browse Source 
Current implementation wastes another register to pass the
argument, but we only need addi to calculate the result. Optimize
the code with minimize the usage of registers.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/20220505035526.2974382-3-guoren@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Guo Ren 2022-05-05 11:55:23 +08:00 committed by Palmer Dabbelt
parent dd8437cd42
commit 1d7f6932c5
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
1 changed files with 10 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
arch/riscv/include/asm/atomic.h
View File

@ -310,47 +310,47 @@ 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.rl %[rc], %[rc], %[c]\n"
" bnez %[rc], 0b\n"
" fence rw, rw\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.rl %[rc], %[rc], %[c]\n"
" bnez %[rc], 0b\n"
" fence rw, rw\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 */