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 <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
htbegin · Feb 14, 2015 · 6d874ec · 6d874ec
1 parent dba94c2
commit 6d874ec
Showing 1 changed file with 3 additions and 4 deletions.
diff --git 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;
 	}