u-boot.git/include/asm-generic/bitops/builtin-__fls.h, branch master Unnamed repository; edit this file 'description' to name the repository. arm: Use builtins for ffs/fls 2023-08-17T20:39:20+00:00 Sean Anderson sean.anderson@seco.com 2023-07-31T21:27:33+00:00 726a802fdaf1ffb4ca95ebf6910a738781137ef5 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> 
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>