Bitmap operations are much simpler and faster in case of small bitmaps which fit into a single word. In linux/bitmap.c we have a machinery that allows compiler to replace actual function call with a few instructions if bitmaps passed into the function are small and their size is known at compile time.
find_*_bit() API lacks this functionality; but users will benefit from it a lot. One important example is cpumask subsystem when NR_CPUS <= BITS_PER_LONG. v1: https://www.spinics.net/lists/kernel/msg3804727.html v2: https://www.spinics.net/lists/linux-m68k/msg16945.html v3: https://www.spinics.net/lists/kernel/msg3837020.html v4: https://patchwork.kernel.org/project/linux-sh/cover/20210316015424.1999082-1-yury.no...@gmail.com/ v5: - drop BITS_{FIRST,LAST} patch; - minor changes. Yury Norov (12): tools: disable -Wno-type-limits tools: bitmap: sync function declarations with the kernel tools: sync BITMAP_LAST_WORD_MASK() macro with the kernel arch: rearrange headers inclusion order in asm/bitops for m68k and sh lib: extend the scope of small_const_nbits() macro tools: sync small_const_nbits() macro with the kernel lib: inline _find_next_bit() wrappers tools: sync find_next_bit implementation lib: add fast path for find_next_*_bit() lib: add fast path for find_first_*_bit() and find_last_bit() tools: sync lib/find_bit implementation MAINTAINERS: Add entry for the bitmap API MAINTAINERS | 16 ++++ arch/m68k/include/asm/bitops.h | 6 +- arch/sh/include/asm/bitops.h | 5 +- include/asm-generic/bitops/find.h | 108 +++++++++++++++++++++--- include/asm-generic/bitops/le.h | 38 ++++++++- include/asm-generic/bitsperlong.h | 12 +++ include/linux/bitmap.h | 8 -- include/linux/bitops.h | 12 --- lib/find_bit.c | 68 ++------------- tools/include/asm-generic/bitops/find.h | 85 +++++++++++++++++-- tools/include/asm-generic/bitsperlong.h | 3 + tools/include/linux/bitmap.h | 18 ++-- tools/lib/bitmap.c | 4 +- tools/lib/find_bit.c | 56 +++++------- tools/scripts/Makefile.include | 1 + 15 files changed, 284 insertions(+), 156 deletions(-) -- 2.25.1
