[Bug rtl-optimization/19078] [4.0 Regression] Poor quality code after loop unrolling.

["law at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From law at redhat dot com  2005-02-10 18:01 -------
Subject: Re:  [4.0 Regression] Poor quality
	code after loop unrolling.

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



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19078