Commit 11ec50ca authored Dec 12, 2013 by Will Deacon Committed by Linus Torvalds Dec 12, 2013

word-at-a-time: provide generic big-endian zero_bytemask implementation



Whilst architectures may be able to do better than this (which they can,
by simply defining their own macro), this is a generic stab at a
zero_bytemask implementation for the asm-generic, big-endian
word-at-a-time implementation.

On arm64, a clz instruction is used to implement the fls efficiently.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a5c21dce

include/asm-generic/word-at-a-time.h

+8 −0

Original line number	Diff line number	Diff line
		@@ -49,4 +49,12 @@ static inline bool has_zero(unsigned long val, unsigned long *data, const struct
		return (val + c->high_bits) & ~rhs;
		}

		#ifndef zero_bytemask
		#ifdef CONFIG_64BIT
		#define zero_bytemask(mask) (~0ul << fls64(mask))
		#else
		#define zero_bytemask(mask) (~0ul << fls(mask))
		#endif /* CONFIG_64BIT */
		#endif /* zero_bytemask */

		#endif /* _ASM_WORD_AT_A_TIME_H */