From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.cz>
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH 4/7] lib: bitmap: Yet another simplification in __bitmap_shift_right
Date: Fri, 28 Nov 2014 17:01:07 +0100 [thread overview]
Message-ID: <1417190476-18066-5-git-send-email-linux@rasmusvillemoes.dk> (raw)
In-Reply-To: <1417190476-18066-1-git-send-email-linux@rasmusvillemoes.dk>
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>
---
lib/bitmap.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 20bb314..0d78c96 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -111,9 +111,9 @@ EXPORT_SYMBOL(__bitmap_complement);
void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
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 long mask = (1UL << left) - 1;
+ unsigned long mask = BITMAP_LAST_WORD_MASK(nbits);
for (k = 0; off + k < lim; ++k) {
unsigned long upper, lower;
@@ -125,12 +125,12 @@ void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
upper = 0;
else {
upper = src[off + k + 1];
- if (off + k + 1 == lim - 1 && left)
+ if (off + k + 1 == lim - 1)
upper &= mask;
upper <<= (BITS_PER_LONG - rem);
}
lower = src[off + k];
- if (left && off + k == lim - 1)
+ if (off + k == lim - 1)
lower &= mask;
lower >>= rem;
dst[k] = lower | upper;
--
2.0.4
next prev parent reply other threads:[~2014-11-28 16:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-28 16:01 [PATCH 0/7] lib: bitmap: Simplify bitmap_shift_{left,right} Rasmus Villemoes
2014-11-28 16:01 ` [PATCH 1/7] lib: bitmap: Change bitmap_shift_right to take unsigned parameters Rasmus Villemoes
2014-11-28 16:01 ` [PATCH 2/7] lib: bitmap: Eliminate branch in __bitmap_shift_right Rasmus Villemoes
2014-11-28 16:01 ` [PATCH 3/7] lib: bitmap: Remove redundant code from __bitmap_shift_right Rasmus Villemoes
2014-11-28 16:01 ` Rasmus Villemoes [this message]
2014-11-28 16:01 ` [PATCH 5/7] lib: bitmap: Change bitmap_shift_left to take unsigned parameters Rasmus Villemoes
2014-11-28 16:01 ` [PATCH 6/7] lib: bitmap: Eliminate branch in __bitmap_shift_left Rasmus Villemoes
2014-11-28 16:01 ` [PATCH 7/7] lib: bitmap: Remove redundant code from __bitmap_shift_left Rasmus Villemoes
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