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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2015-02-14 01:36:16 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-14 08:21:35 +0300
commit6d874eca6595629258a5d9af237c5ae53a9544e1 (patch)
tree444d682c304f39d2071ad1445ec0582abf5e46a6
parentdba94c2553da1928303c2a6c6410247c88cafc1d (diff)
downloadlinux-6d874eca6595629258a5d9af237c5ae53a9544e1.tar.xz
lib: bitmap: eliminate branch in __bitmap_shift_left
We can shift the bits from lower and upper into place before assembling dst[k + off]; moving the shift of lower into the branch where we already know that rem is non-zero allows us to remove a conditional. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--lib/bitmap.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 74bdf3601245..36e380da00c5 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -169,15 +169,14 @@ void __bitmap_shift_left(unsigned long *dst, const unsigned long *src,
* word below and make them the bottom rem bits of result.
*/
if (rem && k > 0)
- lower = src[k - 1];
+ lower = src[k - 1] >> (BITS_PER_LONG - rem);
else
lower = 0;
upper = src[k];
if (left && k == lim - 1)
upper &= (1UL << left) - 1;
- dst[k + off] = upper << rem;
- if (rem)
- dst[k + off] |= lower >> (BITS_PER_LONG - rem);
+ upper <<= rem;
+ dst[k + off] = lower | upper;
if (left && k + off == lim - 1)
dst[k + off] &= (1UL << left) - 1;
}