From: Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>
To: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
Cc: alan@lxorguk.ukuu.org.uk, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] include/asm-ARCH/page.h:get_order() Reorganize and optimize
Date: 13 Nov 2002 12:45:33 +0100 [thread overview]
Message-ID: <87y97xhew2.fsf@student.uni-tuebingen.de> (raw)
In-Reply-To: <E18BmqO-0000Za-00@milikk>
Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com> writes:
> s = --s >> PAGE_SHIFT;
This code has undefined behaviour.
> if (likely (s) < s)
What is that supposed to do?
BTW, I just noticed
#define likely(x) __builtin_expect((x),1)
I think this should rather be
#define likely(x) __builtin_expect((x)!=0,1)
So people can write
if (likely(pointer))
and indeed some people seem to assume that already.
--- linux-2.5.47/include/linux/compiler.h~ 2002-11-11 04:28:25.000000000 +0100
+++ linux-2.5.47/include/linux/compiler.h 2002-11-13 12:44:05.000000000 +0100
@@ -10,7 +10,7 @@
#define __builtin_expect(x, expected_value) (x)
#endif
-#define likely(x) __builtin_expect((x),1)
+#define likely(x) __builtin_expect((x)!=0,1)
#define unlikely(x) __builtin_expect((x),0)
/* This macro obfuscates arithmetic on a variable address so that gcc
--
Falk
prev parent reply other threads:[~2002-11-13 11:39 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-11-13 2:01 [PATCH] include/asm-ARCH/page.h:get_order() Reorganize and optimize Inaky Perez-Gonzalez
2002-11-13 11:45 ` Falk Hueffner [this message]
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