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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---
include/linux/bitmap.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index e9b0b9a..27bfc0b 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);
}
--
2.6.6
--
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