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Re: [PATCH] Make alias_sets_conflict_p less conservative
- From: Michael Matz <matz at suse dot de>
- To: Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>
- Cc: dberlin at dberlin dot org, gcc at gcc dot gnu dot org, joseph at codesourcery dot com, rguenther at suse dot de
- Date: Wed, 5 Mar 2008 22:40:18 +0100 (CET)
- Subject: Re: [PATCH] Make alias_sets_conflict_p less conservative
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On Wed, 5 Mar 2008, Richard Kenner wrote:
> > alias_sets_conflict_p() is used to determine if an addressable variable
> > and a type conflict also from the tree-ssa alias machinery (in effect to
> > determine which virtual variables need to be clobbered). It just isn't
> > feed COMPONENT_REFs, that's what you found very wrong, and I explained the
> > reasons for not doing so. If we were to do that (and hence become more
> > precise) we would have to increase memory use as just explained. You were
> > asking how feeding COMPONENT_REFs would be connected with memory use, and
> > I explained it.
> Why can't you keep the vops as they are now, but when you call
> alias_sets_conflict_p, pass the actual reference from the op, not the vop?
Because as explained already, making use of whatever alias_sets_conflict_p
would tell us when given COMPONENT_REFs would require blowing up our
explicit dependency representation. It's not the case that we inherently
can't call alias_sets_conflict_p() with the COMPONENT_REF if we have one.
We could. But we have no way to express the resulting dependencies
without needing much more memory.