[tree-ssa] PATCH to improve optimization@ssa rewrite time

Steven Bosscher s.bosscher@student.tudelft.nl
Tue May 13 19:32:00 GMT 2003


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
-O1?

Gr.
Steven





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