[Bug tree-optimization/29680] [4.3 Regression] Misscompilation of spec2006 gcc

["rakdver at atrey dot karlin dot mff dot cuni dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #26 from rakdver at atrey dot karlin dot mff dot cuni dot cz  2006-11-09 18:03 -------
Subject: Re:  [4.3 Regression] Misscompilation of spec2006 gcc

> > Right, but the difference is, In the scheme i propose, you'd never
> > have overlapping live ranges of vuse/vdefs, and in mem-ssa, you do.
> > IE we wouldn't run into all the problems mem-ssa is going to bring in
> > this regard.
> 
> No, that's not right.  Overlapping live-ranges are not a problem until 
> you hit a PHI node.  That's where currently mem-ssa is having 
> difficulties with.

well, in any case, Daniel's proposal has advantage that it is much less
intrusive than mem-ssa -- does not need to change ssa renaming at all,
probably needs much less changes to operand scanning, and does not need
any changes to optimizations that assume vops are in FUD form (i.e.,
that the life ranges of vops do not overlap).  If he could create (or help
someone create) a working prototype in reasonable time (few weeks?),
I would very much like to see it compared with mem-ssa before mem-ssa
branch is merged.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29680