From 7dd968163f7c12bcb2132792bf873133b397a2d2 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Wed, 25 May 2016 09:32:20 +0200 Subject: [PATCH] bitmap: bitmap_equal memcmp optimization The bitmap_equal function has optimized code for small bitmaps with less than BITS_PER_LONG bits. For larger bitmaps the out-of-line function __bitmap_equal is called. For a constant number of bits divisible by BITS_PER_LONG the memcmp function can be used. For s390 gcc knows how to optimize this function, memcmp calls with up to 256 bytes / 2048 bits are translated into a single instruction. Reviewed-by: David Hildenbrand Signed-off-by: Martin Schwidefsky --- include/linux/bitmap.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index e9b0b9ab07e5..27bfc0b631a9 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -267,6 +267,10 @@ static inline int bitmap_equal(const unsigned long *src1, { if (small_const_nbits(nbits)) return ! ((*src1 ^ *src2) & BITMAP_LAST_WORD_MASK(nbits)); +#ifdef CONFIG_S390 + else if (__builtin_constant_p(nbits) && (nbits % BITS_PER_LONG) == 0) + return !memcmp(src1, src2, nbits / 8); +#endif else return __bitmap_equal(src1, src2, nbits); } -- GitLab