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Re: Why does arm-*-as issue a warning for "strb r3, [r3], #1"?

From: Daniel Jacobowitz <drow at false dot org>
To: binutils at sources dot redhat dot com, kazu at codesourcery dot com
Date: Fri, 24 Jun 2005 10:14:41 -0400
Subject: Re: Why does arm-*-as issue a warning for "strb r3, [r3], #1"?
References: <200506240502.j5O529P4023042@sethra.codesourcery.com> <m364w42cn2.fsf@gossamer.airs.com>

On Fri, Jun 24, 2005 at 07:54:41AM -0400, Ian Lance Taylor wrote:
> According to my copy of the ARM ARM: "If <addressing mode> specifies
> base register writeback, and the same register is specified for <Rd>
> and <Rn>, the results are UNPREDICTABLE."
> 
> So I think the assembler is correct to warn about this construct, and
> the compiler should not generate it.

Yes, that's correct.  Kazu, unfortunately you weren't here for it, but
Richard Earnshaw and a group of us discussed this problem at length
yesterday.  It's a thorny reload issue.

-- 
Daniel Jacobowitz
CodeSourcery, LLC

References:
- Why does arm-*-as issue a warning for "strb r3, [r3], #1"?
  - From: Kazu Hirata
- Re: Why does arm-*-as issue a warning for "strb r3, [r3], #1"?
  - From: Ian Lance Taylor

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