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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] Redundant repz prefixes in generated amd64 code
Date: Fri, 16 Mar 2007 18:14:57 +0000
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To: qemu-devel@nongnu.org

> > 0000000000008b50 <op_goto_tb1>:
> >     8b50:       8b 05 00 00 00 00       mov    0(%rip),%eax
> >                         8b52: R_X86_64_PC32     __op_param1+0x3c
> >     8b56:       ff e0                   jmpq   *%rax
> >     8b58:       f3 c3                   repz retq
> >
> > qemu only strips the final ret off.
> > The prefixed ret is to avoid prefetch stalls on amd cpus.
>
> So the implication of this is that the generated code just happens to
> work only because the dangling F3 never ends up in front of some other
> instruction which it would change the meaning of?

Correct.

Paul