lib/find_bit.c: micro-optimise find_next_*_bit
This saves 32 bytes on my x86-64 build, mostly due to alignment
considerations and sharing more code between find_next_bit and
find_next_zero_bit, but it does save a couple of instructions.
There's really two parts to this commit:
- First, the first half of the test: (!nbits || start >= nbits) is
trivially a subset of the second half, since nbits and start are both
unsigned
- Second, while looking at the disassembly, I noticed that GCC was
predicting the branch taken. Since this is a failure case, it's
clearly the less likely of the two branches, so add an unlikely() to
override GCC's heuristics.
[[email protected]: v2]
Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Matthew Wilcox <[email protected]>
Acked-by: Yury Norov <[email protected]>
Acked-by: Rasmus Villemoes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
2 files changed
