From ede9c697bc7513f210103fa77a9031e89726ae40 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 29 Apr 2008 00:58:35 -0700 Subject: 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/bitops.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/bitops.h') diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 48bde600a2d..8340a3aba49 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 /* -- cgit v1.2.3