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Re: Feature request: ability to describe x86 register halves as contraints.
- To: Joern Rennecke <amylaar at cygnus dot co dot uk>
- Subject: Re: Feature request: ability to describe x86 register halves as contraints.
- From: Jeffrey A Law <law at cygnus dot com>
- Date: Tue, 30 Jun 1998 11:01:32 -0600
- cc: ak at muc dot de, egcs at cygnus dot com
- Reply-To: law at cygnus dot com
In message <199806301655.RAA04324@phal.cygnus.co.uk>you write:
> > > Is it possible to add such an extension to the constraints language?
> > > Hopefully only minimal changes should be needed for this.
> > First there'd have to be a way to describe hi/lo halves of registers
> > in RTL. I'm not aware of any such mechanism.
>
> I think we should change SUBREG to count addressable units instead of
> 'words'. This would also fix some brokenness when there are
> varying register sizes (E.g. floating point wider than integer...)
I'm not sure I'd recommend changing the meaning of SUBREG -- we might
be better off with a new RTX for this kindof thing.
jeff