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Re: [tree-ssa] New regressions as of 2003-11-04
- From: Michael Matz <matz at suse dot de>
- To: Andrew MacLeod <amacleod at redhat dot com>
- Cc: Jan Hubicka <jh at suse dot cz>, Jeff Law <law at redhat dot com>,Diego Novillo <dnovillo at redhat dot com>,Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>,Daniel Berlin <dberlin at dberlin dot org>,gcc mailing list <gcc at gcc dot gnu dot org>
- Date: Wed, 5 Nov 2003 16:33:08 +0100 (CET)
- Subject: Re: [tree-ssa] New regressions as of 2003-11-04
Hi,
On 5 Nov 2003, Andrew MacLeod wrote:
> > The point is that we *want* to create temporary registers so unless
> > there is good reason to do so, we don't want single register to be set
> > two times. That confuses RTL.
> >
>
> Setting a single register more than once confuses RTL? Im not sure I
> follow.
It doesn't strictly confuse anything, but makes the work for RTL
optimizers harder. So much that some of the optimizers give up one some
possible improvements if disconnected live ranges are using the same REG.
> The register allocator ought to be smart enough to tell when two
> disjoint live ranges use the same register, and rename one of the
> registers to something else to allow them to prevent artifical
The new one is, the old one not, for instance.
Ciao,
Michael.