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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