Q: gcc asm constraint for registers on ppc
Jay Kulpinski
jskulpin@eng01.gdds.com
Tue Dec 14 07:40:00 GMT 1999
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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