tree 7d2df62ee83092d7b8b6032f48a980b2a212df8c
parent 14ba0a8bbc342a677982acc787ae542b84ed7993
author Sean Anderson <sean.anderson@seco.com> 1690838853 -0400
committer Tom Rini <trini@konsulko.com> 1692304760 -0400

arm: Use builtins for ffs/fls

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.

This code is synced with v5.15 of the Linux kernel.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Reviewed-by: Tom Rini <trini@konsulko.com>