linux-kernel - [KERNEL]: Avoid divide in IS

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Message-ID: <20071120135607.GA18346@gondor.apana.org.au>
Date:	Tue, 20 Nov 2007 21:56:07 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [KERNEL]: Avoid divide in IS_ALIGN

Hi:

[KERNEL]: Avoid divide in IS_ALIGN

I was happy to discover the brand new IS_ALIGN macro and quickly
used it in my code.  To my dismay I found that the generated code
used division to perform the test.

This patch fixes it by changing the % test to an &.  This avoids
the division.

Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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--
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 94bc996..39b3fa6 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -35,7 +35,7 @@ extern const char linux_proc_banner[];
 #define ALIGN(x,a)		__ALIGN_MASK(x,(typeof(x))(a)-1)
 #define __ALIGN_MASK(x,mask)	(((x)+(mask))&~(mask))
 #define PTR_ALIGN(p, a)		((typeof(p))ALIGN((unsigned long)(p), (a)))
-#define IS_ALIGNED(x,a)		(((x) % ((typeof(x))(a))) == 0)
+#define IS_ALIGNED(x, a)		(((x) & ((typeof(x))(a) - 1)) == 0)
 
 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
 
-
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