linux-kernel - Screwy arch/x86/include/asm/string

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Message-ID: <49BBD619.6050809@davidnewall.com>
Date:	Sun, 15 Mar 2009 02:36:49 +1030
From:	David Newall <davidn@...idnewall.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Screwy arch/x86/include/asm/string_32.h

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.
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