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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2024-04-09 20:55:07 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2024-05-22 23:12:11 +0200 |
| commit | b9b60b3199b70fe3ce74ff493b1870ccd7554134 (patch) | |
| tree | 232e0543c7015119bf752331a1642fa4b8f659de | |
| parent | x86: improve array_index_mask_nospec() code generation (diff) | |
| download | linux-b9b60b3199b70fe3ce74ff493b1870ccd7554134.tar.xz linux-b9b60b3199b70fe3ce74ff493b1870ccd7554134.zip | |
x86: improve bitop code generation with clang
This uses the new ASM_INPUT_RM macro to avoid the bad code generation
issue that clang has with more generic asm inputs.
This ends up avoiding generating code like this:
mov %r10,(%rsp)
tzcnt (%rsp),%rcx
which now becomes just
tzcnt %r10,%rcx
and in the process ends up also removing a few unnecessary stack frames
when the only use was that pointless "asm uses memory location off stack".
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | arch/x86/include/asm/bitops.h | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h index 990eb686ca67..b96d45944c59 100644 --- a/arch/x86/include/asm/bitops.h +++ b/arch/x86/include/asm/bitops.h @@ -250,7 +250,7 @@ static __always_inline unsigned long variable__ffs(unsigned long word) { asm("rep; bsf %1,%0" : "=r" (word) - : "rm" (word)); + : ASM_INPUT_RM (word)); return word; } @@ -297,7 +297,7 @@ static __always_inline unsigned long __fls(unsigned long word) asm("bsr %1,%0" : "=r" (word) - : "rm" (word)); + : ASM_INPUT_RM (word)); return word; } @@ -320,7 +320,7 @@ static __always_inline int variable_ffs(int x) */ asm("bsfl %1,%0" : "=r" (r) - : "rm" (x), "0" (-1)); + : ASM_INPUT_RM (x), "0" (-1)); #elif defined(CONFIG_X86_CMOV) asm("bsfl %1,%0\n\t" "cmovzl %2,%0" @@ -377,7 +377,7 @@ static __always_inline int fls(unsigned int x) */ asm("bsrl %1,%0" : "=r" (r) - : "rm" (x), "0" (-1)); + : ASM_INPUT_RM (x), "0" (-1)); #elif defined(CONFIG_X86_CMOV) asm("bsrl %1,%0\n\t" "cmovzl %2,%0" @@ -416,7 +416,7 @@ static __always_inline int fls64(__u64 x) */ asm("bsrq %1,%q0" : "+r" (bitpos) - : "rm" (x)); + : ASM_INPUT_RM (x)); return bitpos + 1; } #else |