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Re: Sharing hard registers


> At 4:27 PM -0600 6/13/02, law@redhat.com wrote:
> >In message <200206132203.g5DM3lv24315@potter.sfbay.redhat.com>, 
> >"Eric Christoph
> >er" writes:
> > > On Thu, 13 Jun 2002 13:27:39 -0700, law wrote:
> > >
> > >
> > > > It may be necessary to back out the last patch which makes gen_rtx_REG
> > > > share hard registers in some circumstances.
> > > >
> 
> 	The porting guide's "Structure Sharing Assumptions" needs to 
> be updated to
> 	explicitly indicate that hard registers are "shared".  Right 
> now, it just says
> 	that pseudos are always shared.

Pseudo registers are always shared.  We are speaking abou hard registers
here and I believe it has been always documented in a way that they can
be shared or not.  At least that way gcc worked for a while.

Honza
> 
> 	Also, I'm curious about the issue of a hard-register with 
> more than one mode.
> 	How does that work if R1 can be a SF or a SI mode value???
> 
> 	Doesn't the mode get in the way of sharing the hard register? 
> Or is this cached
> 	by (mode,regno).?
> 
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