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Re: [3.3 PATCH] fix PHI insertion for RTL SSA-CCP
- From: Jeffrey A Law <law at redhat dot com>
- To: Steven Bosscher <stevenb at suse dot de>
- Cc: gcc-patches at gcc dot gnu dot org, matz at suse dot de, Gabriel Dos Reis <gdr at integrable-solutions dot net>
- Date: Tue, 24 Aug 2004 13:56:38 -0600
- Subject: Re: [3.3 PATCH] fix PHI insertion for RTL SSA-CCP
- Organization: Red Hat, Inc
- References: <200408242150.21085.stevenb@suse.de>
- Reply-to: law at redhat dot com
On Tue, 2004-08-24 at 13:50, Steven Bosscher wrote:
> Hello,
>
> This is a fix for a part of GCC 3.3 based compiler that is
> used probably by no-one at all.
>
> Like I have nothing better to do...
>
> But I wanted to see if RTL SSA really is as poor as everyone
> always claims it to be, and I need it in more-or-less working
> shape for that purpose (it now "only" fails with a bunch of
> unrecognizable insns that all look alike -- it actually looks
> like that may be a "real" bug...).
There's lots of stuff lurking.
libcalls cause major problems
subregs cause major problems
That's a start.
However, I _do_ think that we'll one day be at a point where we can
push SSA formalism into the RTL passes. One of the things we have
learned from tree-ssa is that we do not have to put every object into
SSA form. We can (and should) use that knowledge for RTL-SSA as well.
Jeff