From b9b60b3199b70fe3ce74ff493b1870ccd7554134 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 9 Apr 2024 11:55:07 -0700 Subject: 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 --- arch/x86/include/asm/bitops.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'arch') 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 -- cgit v1.2.3