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authorEric Dumazet <dada1@cosmosbay.com>2008-04-29 11:58:35 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-29 19:05:59 +0400
commitede9c697bc7513f210103fa77a9031e89726ae40 (patch)
treea48eaac7da2877aa5600e5b4e99dedabd4b4b6fb /include/linux/bitops.h
parentcdac75e6f2fec9abc21d0abb4e5d80720eeebb10 (diff)
downloadlinux-ede9c697bc7513f210103fa77a9031e89726ae40.tar.xz
Avoid divides in BITS_TO_LONGS
BITS_PER_LONG is a signed value (32 or 64) DIV_ROUND_UP(nr, BITS_PER_LONG) performs signed arithmetic if "nr" is signed too. Converting BITS_TO_LONGS(nr) to DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long)) makes sure compiler can perform a right shift, even if "nr" is a signed value, instead of an expensive integer divide. Applying this patch saves 141 bytes on x86 when CONFIG_CC_OPTIMIZE_FOR_SIZE=y and speedup bitmap operations. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/bitops.h')
-rw-r--r--include/linux/bitops.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 48bde600a2db..8340a3aba49a 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -6,8 +6,8 @@
#define BIT(nr) (1UL << (nr))
#define BIT_MASK(nr) (1UL << ((nr) % BITS_PER_LONG))
#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
-#define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, BITS_PER_LONG)
#define BITS_PER_BYTE 8
+#define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
#endif
/*