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[Bug tree-optimization/39201] [meta-bug] ivopts metabug
- From: "bonzini at gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 16 Feb 2009 09:56:19 -0000
- Subject: [Bug tree-optimization/39201] [meta-bug] ivopts metabug
- References: <bug-39201-7849@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #3 from bonzini at gnu dot org 2009-02-16 09:56 -------
Subject: Re: [meta-bug] ivopts metabug
> I'm adding PR 34163 in the hope that ivopts pass will someday know how to
> handle x[n] = f (x[n-1]) from "... very tight loops that calculate x[n] from
> the value x[n-1], where x[n-1] is the result of a previous step."
>
> This is especially important for unrolled loops, see PR 34163, comment #8
Isn't what you want simply load PRE? That looks like a pass ordering
problem...
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39201