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Re: [Bug rtl-optimization/19078] [4.0 Regression] Poor qualitycode after loop unrolling.
- From: Jeffrey A Law <law at redhat dot com>
- To: Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>
- Cc: steven at gcc dot gnu dot org <gcc-bugzilla at gcc dot gnu dot org>, gcc at gcc dot gnu dot org
- Date: Thu, 10 Feb 2005 10:59:22 -0700
- Subject: Re: [Bug rtl-optimization/19078] [4.0 Regression] Poor qualitycode after loop unrolling.
- Organization: Red Hat, Inc
- References: <20041219105831.19078.chris@bubblescope.net> <20050210110254.14455.qmail@sourceware.org> <20050210111202.GA26395@atrey.karlin.mff.cuni.cz>
- Reply-to: law at redhat dot com
On Thu, 2005-02-10 at 12:12 +0100, Zdenek Dvorak wrote:
> > In comment #3 Zdenek said "Possibly even better would be to add generation of
> > autoincrements to loop optimizer, but this would require fixing cse so that it
> > handles them correctly." Zdenek, can you elaborate on why CSE needs fixing?
>
> cse does not handle autoincrements. I have no idea what's the problem
> there, it is just what I was told when I asked for the possibility to
> move the autoinc creation pass last time. Anyone has more precise
> information about the nature of the problem?
It's been about a decade since I looked at cse vs autoincrements, so
the details have faded from memory. [The original context I found the
problem was in an attempt to run cse after reload. ]
Anyway, from a 30 second look at CSE the first thing that jumps out at
me is I don't think we would invalidate objects in the hash table which
are auto-incremented.
Jeff