diff options
| author |   Rasmus Villemoes <linux@rasmusvillemoes.dk> | 2018-10-30 15:05:02 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2018-10-31 08:54:12 -0700 |
| commit | c8cebc553368209426f7279736db4f88f1853396 (patch) | |
| tree | 9e7a7962d243563191df1080d0221e9e5a4d746a /include/linux/bitmap.h | |
| parent | linux/bitmap.h: handle constant zero-size bitmaps correctly (diff) | |
| download | linux-dev-c8cebc553368209426f7279736db4f88f1853396.tar.xz linux-dev-c8cebc553368209426f7279736db4f88f1853396.zip | |
linux/bitmap.h: remove redundant uses of small_const_nbits()
In the _zero, _fill and _copy functions, the small_const_nbits branch is
redundant. If nbits is small and const, gcc knows full well that
BITS_TO_LONGS(nbits) is 1, so len is also a compile-time constant
(sizeof(long)), and calling memset or memcpy with a length argument of
sizeof(long) makes gcc generate the expected code anyway:
#include <string.h>
void a(unsigned long *x) { memset(x, 0, 8); }
void b(unsigned long *x) { memset(x, 0xff, 8); }
void c(unsigned long *x, const unsigned long *y) { memcpy(x, y, 8); }
turns into
0000000000000000 <a>:
0: 48 c7 07 00 00 00 00 movq $0x0,(%rdi)
7: c3 retq
8: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1)
f: 00
0000000000000010 <b>:
10: 48 c7 07 ff ff ff ff movq $0xffffffffffffffff,(%rdi)
17: c3 retq
18: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1)
1f: 00
0000000000000020 <c>:
20: 48 8b 06 mov (%rsi),%rax
23: 48 89 07 mov %rax,(%rdi)
26: c3 retq
Link: http://lkml.kernel.org/r/20180818131623.8755-4-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Yury Norov <ynorov@caviumnetworks.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/bitmap.h')
| -rw-r--r-- | include/linux/bitmap.h | 24 |
1 files changed, 6 insertions, 18 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index a9805bacbd7c..004cd42a3c4d 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -214,33 +214,21 @@ extern int bitmap_print_to_pagebuf(bool list, char *buf, static inline void bitmap_zero(unsigned long *dst, unsigned int nbits) { - if (small_const_nbits(nbits)) - *dst = 0UL; - else { - unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); - memset(dst, 0, len); - } + unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); + memset(dst, 0, len); } static inline void bitmap_fill(unsigned long *dst, unsigned int nbits) { - if (small_const_nbits(nbits)) - *dst = ~0UL; - else { - unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); - memset(dst, 0xff, len); - } + unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); + memset(dst, 0xff, len); } static inline void bitmap_copy(unsigned long *dst, const unsigned long *src, unsigned int nbits) { - if (small_const_nbits(nbits)) - *dst = *src; - else { - unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); - memcpy(dst, src, len); - } + unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); + memcpy(dst, src, len); } /* |