[PATCH] arm: Use builtins for ffs/fls

Tom Rini trini at konsulko.com
Mon Jul 31 23:36:40 CEST 2023

On Mon, Jul 31, 2023 at 05:27:33PM -0400, Sean Anderson wrote:

> Since ARMv5, the clz instruction allows for efficient implementation of
> ffs/fls with builtins. Until ARMv7 (with Thumb-2), this instruction is
> only available in ARM mode. LTO makes it difficult to force specific
> functions to be in ARM mode, as it is effectively a form of very
> aggressive inlining. To work around this, fls/ffs are implemented in
> assembly for ARMv5 and ARMv6 when compiling U-Boot in Thumb mode.
> Overall, this saves around 75 bytes per call.
> Signed-off-by: Sean Anderson <sean.anderson at seco.com>

This looks like it's synced from the kernel, what tag?

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