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Re: [PATCH] Fix PR middle-end/28690, indexed load/store performance + reload bug
- From: "Ulrich Weigand" <uweigand at de dot ibm dot com>
- To: matz at suse dot de (Michael Matz)
- Cc: bergner at vnet dot ibm dot com (Peter Bergner), pinskia at gmail dot com (Andrew Pinski), gcc-patches at gcc dot gnu dot org
- Date: Mon, 11 Dec 2006 20:33:54 +0100 (CET)
- Subject: Re: [PATCH] Fix PR middle-end/28690, indexed load/store performance + reload bug
Michael Matz wrote:
> That is a correct choice. The alternate class is not necessarily a set of
> registers acceptable in all operands (which would be the intersection),
> but a superset. The alternate class is the biggest class containing
> only registers which are cheaper than memory. If guess on PPC all
> registers are cheaper than MEMs, so that's ALL_REGS for all alternate
> classes then.
Hmm. I would have expected regclass to ensure its selection results in
instructions that are at least valid in the non-strict sense (i.e. satisfy
the predicates).
If this is not the case, then I guess the question becomes what is the
point of rejecting particular registers in predicate in the first place?
Does this make sense at all then?
Bye,
Ulrich
--
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE
Ulrich.Weigand@de.ibm.com