u-boot/include/asm-generic/bitops/builtin-ffs.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_GENERIC_BITOPS_BUILTIN_FFS_H_
#define _ASM_GENERIC_BITOPS_BUILTIN_FFS_H_

/**
 * ffs - find first bit set
 * @x: the word to search
 *
 * This is defined the same way as
 * the libc and compiler builtin ffs routines, therefore
 * differs in spirit from ffz (man ffs).
 */
#define ffs(x) __builtin_ffs(x)

#endif
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> 2023-07-31 21:27:33 +00:00			`/* SPDX-License-Identifier: GPL-2.0 */`
			`#ifndef _ASM_GENERIC_BITOPS_BUILTIN_FFS_H_`
			`#define _ASM_GENERIC_BITOPS_BUILTIN_FFS_H_`

			`/**`
			`* ffs - find first bit set`
			`* @x: the word to search`
			`*`
			`* This is defined the same way as`
			`* the libc and compiler builtin ffs routines, therefore`
			`* differs in spirit from ffz (man ffs).`
			`*/`
			`#define ffs(x) __builtin_ffs(x)`

			`#endif`