From: David Newall <davidn@davidnewall.com>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Screwy arch/x86/include/asm/string_32.h
Date: Sun, 15 Mar 2009 02:36:49 +1030 [thread overview]
Message-ID: <49BBD619.6050809@davidnewall.com> (raw)
There's a lot of weirdness in __constant_memcpy in
arch/x86/include/asm/string_32.h (2.6.29-rc7).
1. The first switch is missing a case for n equal 7.
2. When n < 20, the four tests (n > 16, n > 12, n > 8 & n > 4)
execute identical statements; always 'asm volatile("movsl" :
"=&D"(edi), "=&S"(esi) : "0"(edi), "1"(esi) : "memory")'.
I think it copies less than 4 bytes for values of n between 9 and 19.
next reply other threads:[~2009-03-14 16:07 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-14 16:06 David Newall [this message]
2009-03-14 22:53 ` Screwy arch/x86/include/asm/string_32.h Jeremy Fitzhardinge
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