[patch] Lno branch merge part 12 -- induction variable optimizations

Zdenek Dvorak rakdver@atrey.karlin.mff.cuni.cz
Mon Aug 30 19:42:00 GMT 2004


Hello,

> >So far I've "solved" those problems by punting and waiting for
> >DCE to clean things up.  That's been pretty consistent with the
> >design decisions we've made regarding isolation of optimizations.
> >
> >Is there some reason why that model is not appropriate?  For example,
> >does leaving these dead statements in the IL until the next DCE
> >pass actually inhibit optimizations or cause correctness issues?
> >
> >
> >[ While I sometimes lean towards having dead code automatically go
> >  away when the last use of the statement's LHS goes away, I'm
> >  very leery of going that direction because of our past experiences
> >  of doing this kind of thing at the RTL level. ]
> 
> In my loops to memset optimization, I do punt almost everything to
> DCE except for the memory access which I transform to the memset
> call.  So I remove the memory store as it is not removed by DCE.
> Also we don't remove loops on later passes which hurt performance.
> 
> Can anyone say when we are going to remove empty loops even without
> -funroll-loops?

after my patch to do it is reviewed?  I posted it sometimes in the
July, IIRC.

Zdenek



More information about the Gcc-patches mailing list