From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Date: Fri, 13 Feb 2015 22:36:05 +0000 (-0800)
Subject: lib: bitmap: eliminate branch in __bitmap_shift_right
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=9d8a6b2a02c5fae53d47bfffaabd5f12bb6ec2c0;p=openwrt%2Fstaging%2Fblogic.git

lib: bitmap: eliminate branch in __bitmap_shift_right

We can shift the bits from lower and upper into place before assembling
dst[k]; moving the shift of upper 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>
---

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 45e7d14ebdfd..a7a8bc02892d 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -129,13 +129,13 @@ void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
 			upper = src[off + k + 1];
 			if (off + k + 1 == lim - 1 && left)
 				upper &= mask;
+			upper <<= (BITS_PER_LONG - rem);
 		}
 		lower = src[off + k];
 		if (left && off + k == lim - 1)
 			lower &= mask;
-		dst[k] = lower >> rem;
-		if (rem)
-			dst[k] |= upper << (BITS_PER_LONG - rem);
+		lower >>= rem;
+		dst[k] = lower | upper;
 		if (left && k == lim - 1)
 			dst[k] &= mask;
 	}