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ARM: findbit: provide more efficient ARMv7 implementation

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Provide a more efficient ARMv7 implementation to determine the first
set bit in the supplied value.

Signed-off-by: Russell King (Oracle) <rmk@armlinux.org.uk>
This commit is contained in:
Russell King (Oracle)
2022-07-29 16:10:49 +01:00
parent 7e0093870e
commit bceab1431e
1 changed files with 5 additions and 1 deletions
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6
arch/arm/lib/findbit.S
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@@ -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