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Re: Vector subregs

From: Jakub Jelinek <jakub at redhat dot com>
To: Alexandre Oliva <aoliva at redhat dot com>
Cc: Dale Johannesen <dalej at apple dot com>, gcc-patches at gcc dot gnu dot org, gcc at gcc dot gnu dot org
Date: Fri, 14 Dec 2001 14:09:32 -0500
Subject: Re: Vector subregs
References: <93A5FF64-F0C2-11D5-86F6-003065C86F94@apple.com> <orheqt4oh0.fsf@free.redhat.lsd.ic.unicamp.br>
Reply-to: Jakub Jelinek <jakub at redhat dot com>

On Fri, Dec 14, 2001 at 04:59:39PM -0200, Alexandre Oliva wrote:
> On Dec 14, 2001, Dale Johannesen <dalej@apple.com> wrote:
> 
> > Subreg's of vectors don't have a register implementation on any
> > hardware AFAIK, so there is no reason to support them.
> 
> Hmm...  The SH4 can use 4 FP registers as a V4SF unit for some
> operations, as well as 4 of these sets as a 4x4 SF matrix.  I suppose
> it would be reasonable to be able to use subregs to refer to
> individual registers that compose such vectors and matrices, wouldn't
> it?

Similarly on SPARC, e.g. for V2SI register you can access the 32-bit subregs
individually.

	Jakub

References:
- Vector subregs
  - From: Dale Johannesen
- Re: Vector subregs
  - From: Alexandre Oliva

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