Re: [PATCH 04/17] MIPS: o32: provide ta0..ta3 register definitions

[Denis Orlov <denorl2009@gmail.com>]

On Tue, 6 Jun 2023 at 11:13, Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
>
> On 05.06.23 22:10, Denis Orlov wrote:
> > This allows to write generic assembly code that will compile under both
> > o32 and n64 ABIs, as otherwise the register definitions would conflict.
> >
> > Taken from Linux kernel sources, commit 'MIPS: O32: Provide definition
> > of registers ta0 .. ta3.' (3ba1e543ab4b02640d396098f2f6a199560d5f2d).
> >
> > Signed-off-by: Denis Orlov <denorl2009@gmail.com>
>
> Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
>
> I must say, this file looks odd though. _MIPS_SIM is apparently
> defined by the compiler and it's compared against _MIPS_SIM_ABI32,
> which barebox defines...

AFAICS, the compiler defines _MIPS_SIM with the value of some number,
_MIPS_SIM_ABI32, on the other hand, gives a symbolic representation
(as another define) for this number. This just adds more sense to what
we are actually comparing against. But this header also seems to be
quite old, maybe nowadays there is a better way to check for those.

Regards,
Denis

>
> > ---
> >  arch/mips/include/asm/regdef.h | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/arch/mips/include/asm/regdef.h b/arch/mips/include/asm/regdef.h
> > index 1300251661..df87582e8e 100644
> > --- a/arch/mips/include/asm/regdef.h
> > +++ b/arch/mips/include/asm/regdef.h
> > @@ -3,6 +3,8 @@
> >   * Copyright (C) 1985 MIPS Computer Systems, Inc.
> >   * Copyright (C) 1994, 95, 99, 2003 by Ralf Baechle
> >   * Copyright (C) 1990 - 1992, 1999 Silicon Graphics, Inc.
> > + * Copyright (C) 2011 Wind River Systems,
> > + *   written by Ralf Baechle <ralf@linux-mips.org>
> >   */
> >  #ifndef _ASM_REGDEF_H
> >  #define _ASM_REGDEF_H
> > @@ -27,9 +29,13 @@
> >  #define t2      $10
> >  #define t3      $11
> >  #define t4      $12
> > +#define ta0     $12
> >  #define t5      $13
> > +#define ta1     $13
> >  #define t6      $14
> > +#define ta2     $14
> >  #define t7      $15
> > +#define ta3     $15
> >  #define s0      $16     /* callee saved */
> >  #define s1      $17
> >  #define s2      $18
>
> --
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