From: Russell King (Oracle) Date: Fri, 29 Jul 2022 15:10:49 +0000 (+0100) Subject: ARM: findbit: provide more efficient ARMv7 implementation X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=bceab1431e0789794cbcc8bb71d500a74c8213f2;p=linux.git ARM: findbit: provide more efficient ARMv7 implementation Provide a more efficient ARMv7 implementation to determine the first set bit in the supplied value. Signed-off-by: Russell King (Oracle) --- diff --git a/arch/arm/lib/findbit.S b/arch/arm/lib/findbit.S index 4c584bc4704b8..256e095d490bb 100644 --- a/arch/arm/lib/findbit.S +++ b/arch/arm/lib/findbit.S @@ -170,7 +170,11 @@ ENDPROC(_find_next_bit_be) * One or more bits in the LSB of r3 are assumed to be set. */ .L_found: -#if __LINUX_ARM_ARCH__ >= 5 +#if __LINUX_ARM_ARCH__ >= 7 + rbit r3, r3 @ reverse bits + clz r3, r3 @ count high zero bits + add r0, r2, r3 @ add offset of first set bit +#elif __LINUX_ARM_ARCH__ >= 5 rsb r0, r3, #0 and r3, r3, r0 @ mask out lowest bit set clz r3, r3 @ count high zero bits