[PATCH 05/12] lib: extend the scope of small_const_nbits() macro
From: Yury Norov <yury.norov@gmail.com>
Date: 2021-03-21 21:56:13
Also in:
linux-m68k, linux-sh, lkml
Subsystem:
bitmap api, generic include/asm header files, the rest · Maintainers:
Yury Norov, Arnd Bergmann, Linus Torvalds
find_bit would also benefit from small_const_nbits() optimizations. The detailed comment is provided by Rasmus Villemoes. Signed-off-by: Yury Norov <yury.norov@gmail.com> Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> --- include/asm-generic/bitsperlong.h | 12 ++++++++++++ include/linux/bitmap.h | 8 -------- 2 files changed, 12 insertions(+), 8 deletions(-)
diff --git a/include/asm-generic/bitsperlong.h b/include/asm-generic/bitsperlong.h
index 3905c1c93dc2..1023e2a4bd37 100644
--- a/include/asm-generic/bitsperlong.h
+++ b/include/asm-generic/bitsperlong.h@@ -23,4 +23,16 @@ #define BITS_PER_LONG_LONG 64 #endif +/* + * small_const_nbits(n) is true precisely when it is known at compile-time + * that BITMAP_SIZE(n) is 1, i.e. 1 <= n <= BITS_PER_LONG. This allows + * various bit/bitmap APIs to provide a fast inline implementation. Bitmaps + * of size 0 are very rare, and a compile-time-known-size 0 is most likely + * a sign of error. They will be handled correctly by the bit/bitmap APIs, + * but using the out-of-line functions, so that the inline implementations + * can unconditionally dereference the pointer(s). + */ +#define small_const_nbits(nbits) \ + (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0) + #endif /* __ASM_GENERIC_BITS_PER_LONG */
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 70a932470b2d..8c4adfa5cceb 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h@@ -222,14 +222,6 @@ extern int bitmap_print_to_pagebuf(bool list, char *buf, #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1))) #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1))) -/* - * The static inlines below do not handle constant nbits==0 correctly, - * so make such users (should any ever turn up) call the out-of-line - * versions. - */ -#define small_const_nbits(nbits) \ - (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0) - static inline void bitmap_zero(unsigned long *dst, unsigned int nbits) { unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
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2.25.1