Re: [PATCH] arm: Use builtins for ffs/fls

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@seco.com

I'll add some wording about when this was synced from the kernel when applying.

Reviewed-by: Tom Rini trini@konsulko.com