From: Heiko Carstens Date: Mon, 4 Aug 2025 15:08:54 +0000 (+0200) Subject: s390/bitops: Slightly optimize ffs() and fls64() X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=de88e74889a30bd9ff4047726021cde857348b4b;p=thirdparty%2Fkernel%2Fstable.git s390/bitops: Slightly optimize ffs() and fls64() Use a simpler algorithm to calculate the result of ffs() and fls64(). This generates slightly better code and increases readability. Kernel image size is reduced by ~3kb (gcc 15.1.0 + defconfig). Suggested-by: Nina Schoetterl-Glausch Signed-off-by: Heiko Carstens Signed-off-by: Alexander Gordeev --- diff --git a/arch/s390/include/asm/bitops.h b/arch/s390/include/asm/bitops.h index a5ca0a9476916..10d7573d1582c 100644 --- a/arch/s390/include/asm/bitops.h +++ b/arch/s390/include/asm/bitops.h @@ -193,10 +193,9 @@ static inline unsigned long __ffs(unsigned long word) */ static inline int ffs(int word) { - unsigned long mask = 2 * BITS_PER_LONG - 1; unsigned int val = (unsigned int)word; - return (1 + (__flogr(-val & val) ^ (BITS_PER_LONG - 1))) & mask; + return BITS_PER_LONG - __flogr(-val & val); } /** @@ -223,9 +222,7 @@ static inline unsigned long __fls(unsigned long word) */ static inline int fls64(unsigned long word) { - unsigned long mask = 2 * BITS_PER_LONG - 1; - - return (1 + (__flogr(word) ^ (BITS_PER_LONG - 1))) & mask; + return BITS_PER_LONG - __flogr(word); } /**