Re: Q: gcc asm constraint for registers on ppc

[Jay Kulpinski <jskulpin at eng01 dot gdds dot com>]

Ian Lance Taylor wrote:
> 
>    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.
> 


gcc info file
	Node: Machine Desc
		Node: Constraints
			Node: Machine Constraints

_IBM RS6000--`rs6000.h'_

    `b'
          Address base register



> Ian
> 
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