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lib: bitmap: yet another simplification in __bitmap_shift_right

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If left is 0, we can just let mask be ~0UL, so that anding with it is a
no-op.  Conveniently, BITMAP_LAST_WORD_MASK provides precisely what we
need, and we can eliminate left.

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>
This commit is contained in:
Rasmus Villemoes 2015-02-13 14:36:10 -08:00 • committed by Linus Torvalds
parent 97fb8e940b
commit cfac1d080a
1 changed files with 4 additions and 4 deletions
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8
lib/bitmap.c
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@ -113,9 +113,9 @@ EXPORT_SYMBOL(__bitmap_complement);
void __bitmap_shift_right(unsigned long *dst, const unsigned long *src, void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
unsigned shift, unsigned nbits) unsigned shift, unsigned nbits)
{ {
unsigned k, lim = BITS_TO_LONGS(nbits), left = nbits % BITS_PER_LONG; unsigned k, lim = BITS_TO_LONGS(nbits);
unsigned off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG; unsigned off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
unsigned long mask = (1UL << left) - 1; unsigned long mask = BITMAP_LAST_WORD_MASK(nbits);
for (k = 0; off + k < lim; ++k) { for (k = 0; off + k < lim; ++k) {
unsigned long upper, lower; unsigned long upper, lower;
@ -127,12 +127,12 @@ void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
upper = 0; upper = 0;
else { else {
upper = src[off + k + 1]; upper = src[off + k + 1];
if (off + k + 1 == lim - 1 && left) if (off + k + 1 == lim - 1)
upper &= mask; upper &= mask;
upper <<= (BITS_PER_LONG - rem); upper <<= (BITS_PER_LONG - rem);
} }
lower = src[off + k]; lower = src[off + k];
if (left && off + k == lim - 1) if (off + k == lim - 1)
lower &= mask; lower &= mask;
lower >>= rem; lower >>= rem;
dst[k] = lower | upper; dst[k] = lower | upper;