Messages in this thread | | | From | Rasmus Villemoes <> | Subject | [PATCH 0/7] lib: bitmap: Simplify bitmap_shift_{left,right} | Date | Fri, 28 Nov 2014 17:01:03 +0100 |
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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.
Rasmus Villemoes (7): lib: bitmap: Change bitmap_shift_right to take unsigned parameters lib: bitmap: Eliminate branch in __bitmap_shift_right lib: bitmap: Remove redundant code from __bitmap_shift_right lib: bitmap: Yet another simplification in __bitmap_shift_right lib: bitmap: Change bitmap_shift_left to take unsigned parameters lib: bitmap: Eliminate branch in __bitmap_shift_left lib: bitmap: Remove redundant code from __bitmap_shift_left
include/linux/bitmap.h | 24 ++++++++++++------------ lib/bitmap.c | 47 ++++++++++++++++++++--------------------------- 2 files changed, 32 insertions(+), 39 deletions(-)
-- 2.0.4
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