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Re: ARM r12 usage
- To: gcc at gcc dot gnu dot org
- Subject: Re: ARM r12 usage
- From: "Andre" <armcc at lycos dot com>
- Date: Fri, 09 Mar 2001 17:48:45 -0800
- Cc: Richard dot Earnshaw at arm dot com
- Organization: Lycos Mail (http://mail.lycos.com:80)
- Reply-To: armcc at lycos dot com
On Fri, 09 Mar 2001 17:33:22, Richard Earnshaw wrote:
>
> > Is it safe to write assembler functions which don't save r12 (and
> > call them from C compiled with both gcc and armcc) ?? Or will
> > things eventually all go horribly wrong if I don't save r12 ?? :-)
> >
>
> If you look more carefully you will find that r12 is first set to a
> copy of the stack pointer before it is saved. This is done to
> simplify the register saving process.
>
> So both are correct.
>
OK, after looking again, I can see you are absolutely right. Thanks.
I do have one other question however:
When using -fomit-frame-pointer with arm-elf-gcc v2.95.2, it seems
that r11 doesn't get used at all ??
Is this correct ? (If so why ?) Or have I missed something again :-)
Andre
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