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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>
hifive-unleashed-5.1
Rasmus Villemoes 2015-02-13 14:36:16 -08:00 committed by Linus Torvalds
parent dba94c2553
commit 6d874eca65
1 changed files with 3 additions and 4 deletions
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7
lib/bitmap.c
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@ -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;
}