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Re: Q: gcc asm constraint for registers on ppc

To: tlr at netinsight dot se
Subject: Re: Q: gcc asm constraint for registers on ppc
From: Ian Lance Taylor <ian at zembu dot com>
Date: 14 Dec 1999 10:14:49 -0500
CC: crossgcc at sourceware dot cygnus dot com, johryd at netinsight dot net
References: <3856210A.D56F09CE@netinsight.se>

   Date: Tue, 14 Dec 1999 11:50:50 +0100
   From: Daniel Kahlin <tlr@netinsight.se>

   The problem here is that with the "r" constraint, gcc chooses "r0" sometimes
   which does not produce valid powerpc assembly code in this case.

   What asm constraint will make gcc use _any_ general purpose register except
   "r0" (on powerpc)?

Try "b".

I got this by inspecting gcc/config/rs6000/rs6000.h and looking at
REG_CLASS_CONTENTS and REG_CLASS_FROM_LETTER.  As far as I know
process-specific constraint are not documented anywhere.

Ian

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- Re: Q: gcc asm constraint for registers on ppc
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References:
- Q: gcc asm constraint for registers on ppc
  - From: Daniel Kahlin

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