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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2016-05-25 09:32:20 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2016-06-13 15:58:21 +0200
commit7dd968163f7c12bcb2132792bf873133b397a2d2 (patch)
treeda3208182cf31c4dbee7863c908bc6e5a7e78251 /include/linux/bitmap.h
parenta9809407f6b6b4b55df7b6cf5522e39476b7e5e6 (diff)
downloadlinux-next-7dd968163f7c12bcb2132792bf873133b397a2d2.tar.gz
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 <dahi@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'include/linux/bitmap.h')
-rw-r--r--include/linux/bitmap.h4
1 files changed, 4 insertions, 0 deletions
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);
}