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| author | Rasmus Villemoes <linux@rasmusvillemoes.dk> | 2015-02-13 14:36:16 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-02-13 21:21:35 -0800 |
| commit | 6d874eca6595629258a5d9af237c5ae53a9544e1 (patch) | |
| tree | 444d682c304f39d2071ad1445ec0582abf5e46a6 /lib | |
| parent | dba94c2553da1928303c2a6c6410247c88cafc1d (diff) | |
| download | lwn-6d874eca6595629258a5d9af237c5ae53a9544e1.tar.gz lwn-6d874eca6595629258a5d9af237c5ae53a9544e1.zip | |
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>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/bitmap.c | 7 |
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; } |