From 89c1e79eb302349fcaf0697bc9116a4ff16bfeb0 Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Wed, 15 Apr 2015 16:17:42 -0700 Subject: linux/bitmap.h: improve BITMAP_{LAST,FIRST}_WORD_MASK The macro BITMAP_LAST_WORD_MASK can be implemented without a conditional, which will generally lead to slightly better generated code (221 bytes saved for allmodconfig-GCOV_KERNEL, ~2k with GCOV_KERNEL). As a small bonus, this also ensures that the nbits parameter is expanded exactly once. In BITMAP_FIRST_WORD_MASK, if start is signed gcc is technically allowed to assume it is positive (or divisible by BITS_PER_LONG), and hence just do the simple mask. It doesn't seem to use this, and even on an architecture like x86 where the shift only depends on the lower 5 or 6 bits, and these bits are not affected by the signedness of the expression, gcc still generates code to compute the C99 mandated value of start % BITS_PER_LONG. So just use a mask explicitly, also for consistency with BITMAP_LAST_WORD_MASK. Signed-off-by: Rasmus Villemoes Cc: Tejun Heo Reviewed-by: George Spelvin Cc: Yury Norov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/bitmap.h | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) (limited to 'include/linux/bitmap.h') diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index dbfbf4990005..be4fa5ddf36c 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -172,12 +172,8 @@ extern unsigned int bitmap_ord_to_pos(const unsigned long *bitmap, unsigned int extern int bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp, int nmaskbits); -#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG)) -#define BITMAP_LAST_WORD_MASK(nbits) \ -( \ - ((nbits) % BITS_PER_LONG) ? \ - (1UL<<((nbits) % BITS_PER_LONG))-1 : ~0UL \ -) +#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1))) +#define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1))) #define small_const_nbits(nbits) \ (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG) -- cgit v1.2.3 From 2afe27c718b669b551895595873611ac39cc31e3 Mon Sep 17 00:00:00 2001 From: Yury Norov Date: Thu, 16 Apr 2015 12:44:00 -0700 Subject: lib/bitmap.c: bitmap_[empty,full]: remove code duplication bitmap_empty() has its own implementation. But it's clearly as simple as: find_first_bit(src, nbits) == nbits The same is true for 'bitmap_full'. Signed-off-by: Yury Norov Cc: George Spelvin Cc: Alexey Klimov Cc: Rasmus Villemoes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/bitmap.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'include/linux/bitmap.h') diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index be4fa5ddf36c..ea17cca9e685 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -283,16 +283,16 @@ static inline int bitmap_empty(const unsigned long *src, unsigned nbits) { if (small_const_nbits(nbits)) return ! (*src & BITMAP_LAST_WORD_MASK(nbits)); - else - return __bitmap_empty(src, nbits); + + return find_first_bit(src, nbits) == nbits; } static inline int bitmap_full(const unsigned long *src, unsigned int nbits) { if (small_const_nbits(nbits)) return ! (~(*src) & BITMAP_LAST_WORD_MASK(nbits)); - else - return __bitmap_full(src, nbits); + + return find_first_zero_bit(src, nbits) == nbits; } static inline int bitmap_weight(const unsigned long *src, unsigned int nbits) -- cgit v1.2.3