diff options
| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-05-25 09:32:20 +0200 |
|---|---|---|
| committer | Mister Oyster <oysterized@gmail.com> | 2017-04-11 10:59:39 +0200 |
| commit | 4e8f65e1f5d2f24701c4bcfb2ebc77b838c254a0 (patch) | |
| tree | b362a61bcb4533b5ed150eba6a480d8fb5c3590f | |
| parent | 5d28a28602751c31e941844782c0f317a55a4448 (diff) | |
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>
| -rw-r--r-- | include/linux/bitmap.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index bb1550047..a2f036c8a 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -249,6 +249,10 @@ 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); } |