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Re: [tree-ssa] PATCH to improve optimization@ssa rewrite time
- From: Steven Bosscher <s dot bosscher at student dot tudelft dot nl>
- To: Daniel Berlin <dberlin at dberlin dot org>
- Cc: Jason Merrill <jason at redhat dot com>, gcc-patches at gcc dot gnu dot org
- Date: 13 May 2003 21:31:18 +0200
- Subject: Re: [tree-ssa] PATCH to improve optimization@ssa rewrite time
- References: <C411EE92-8578-11D7-901D-000A95A34564@dberlin.org>
Op di 13-05-2003, om 21:26 schreef Daniel Berlin:
> > This is very useful in conjunction with expression temporaries, which
> > produce a lot of redundant statements.
> Actually, as I pointed out to Diego privately, doing all these
> redundancy eliminations is really screwing up PRE.
> I've come up with tons of cases where we'd be able to eliminate the
> entire function if we didn't do these optimizations when going into SSA
> (because PRE would enable CCP to constant convert everything), but we
> are left with computations because we did.
> As soon as PRE is on by default, i'm going to be looking@switching
> off some of these into-SSA optimizations.
At what level will PRE be enabled by default, at -O1 or at -O2+?? if
the latter, would it make sense to keep these little into-ssa enabled at