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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2015-02-13 14:36:02 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-13 21:21:35 -0800
commit2fbad29917c9852fa018d572cd3d43a13465d0f8 (patch)
treebb618a08b15ede2718fcaa1940683e5434e2e27e
parente8f24278329dc31b3b8223c83a5465c9df153d9d (diff)
lib: bitmap: change bitmap_shift_right to take unsigned parameters
I've previously changed the nbits parameter of most bitmap_* functions to unsigned; now it is bitmap_shift_{left,right}'s turn. This alone saves some .text, but while at it I found that there were a few other things one could do. The end result of these seven patches is $ scripts/bloat-o-meter /tmp/bitmap.o.{old,new} add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-328 (-328) function old new delta __bitmap_shift_right 384 226 -158 __bitmap_shift_left 306 136 -170 and less importantly also a smaller stack footprint $ stack-o-meter.pl master bitmap file function old new delta lib/bitmap.o __bitmap_shift_right 24 8 -16 lib/bitmap.o __bitmap_shift_left 24 0 -24 For each pair of 0 <= shift <= nbits <= 256 I've tested the end result with a few randomly filled src buffers (including garbage beyond nbits), in each case verifying that the shift {left,right}-most bits of dst are zero and the remaining nbits-shift bits correspond to src, so I'm fairly confident I didn't screw up. That hasn't stopped me from being wrong before, though. This patch (of 7): gcc can generate slightly better code for stuff like "nbits % BITS_PER_LONG" when it knows nbits is not negative. Since negative size bitmaps or shift amounts don't make sense, change these parameters of bitmap_shift_right to unsigned. The expressions involving "lim - 1" are still ok, since if lim is 0 the loop is never executed. Also use "shift" and "nbits" consistently for the parameter names. 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>
-rw-r--r--include/linux/bitmap.h12
-rw-r--r--lib/bitmap.c10
2 files changed, 11 insertions, 11 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index cffc89c23c02..c168a807ab9a 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -96,8 +96,8 @@ extern int __bitmap_equal(const unsigned long *bitmap1,
const unsigned long *bitmap2, unsigned int nbits);
extern void __bitmap_complement(unsigned long *dst, const unsigned long *src,
unsigned int nbits);
-extern void __bitmap_shift_right(unsigned long *dst,
- const unsigned long *src, int shift, int bits);
+extern void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
+ unsigned int shift, unsigned int nbits);
extern void __bitmap_shift_left(unsigned long *dst,
const unsigned long *src, int shift, int bits);
extern int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
@@ -313,13 +313,13 @@ static inline int bitmap_weight(const unsigned long *src, unsigned int nbits)
return __bitmap_weight(src, nbits);
}
-static inline void bitmap_shift_right(unsigned long *dst,
- const unsigned long *src, int n, int nbits)
+static inline void bitmap_shift_right(unsigned long *dst, const unsigned long *src,
+ unsigned int shift, int nbits)
{
if (small_const_nbits(nbits))
- *dst = (*src & BITMAP_LAST_WORD_MASK(nbits)) >> n;
+ *dst = (*src & BITMAP_LAST_WORD_MASK(nbits)) >> shift;
else
- __bitmap_shift_right(dst, src, n, nbits);
+ __bitmap_shift_right(dst, src, shift, nbits);
}
static inline void bitmap_shift_left(unsigned long *dst,
diff --git a/lib/bitmap.c b/lib/bitmap.c
index d2cd50cd4f5d..45e7d14ebdfd 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -104,17 +104,17 @@ EXPORT_SYMBOL(__bitmap_complement);
* @dst : destination bitmap
* @src : source bitmap
* @shift : shift by this many bits
- * @bits : bitmap size, in bits
+ * @nbits : bitmap size, in bits
*
* Shifting right (dividing) means moving bits in the MS -> LS bit
* direction. Zeros are fed into the vacated MS positions and the
* LS bits shifted off the bottom are lost.
*/
-void __bitmap_shift_right(unsigned long *dst,
- const unsigned long *src, int shift, int bits)
+void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
+ unsigned shift, unsigned nbits)
{
- int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
- int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
+ unsigned k, lim = BITS_TO_LONGS(nbits), left = nbits % BITS_PER_LONG;
+ unsigned off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
unsigned long mask = (1UL << left) - 1;
for (k = 0; off + k < lim; ++k) {
unsigned long upper, lower;