[PATCH] Fix PR38826 and PR38477

Richard Guenther rguenther@suse.de
Wed Jan 14 20:57:00 GMT 2009


On Wed, 14 Jan 2009, Daniel Berlin wrote:

> On Wed, Jan 14, 2009 at 4:19 AM, Richard Guenther <rguenther@suse.de> wrote:
> > On Tue, 13 Jan 2009, Daniel Berlin wrote:
> >
> >> How is this not going to become the same problem with IPA mode?
> >> ISTM we should probably move the computation of call clobbering to be
> >> more independent of the rest of PTA.
> >
> > You cannot decouple them, as a call may clobber (and thus affects
> > the points-to sets) of all reachable memory.
> 
> True, but you can assume that all address taken pointers are included in that :)
> IE there is a conservatively correct set of things you can use.

Sure.  This is what alias-improvements branch uses for the call-clobber
solution until we do PTA.

> >  Unless you mark all
> > memory that had its address taken as pointing to anything after each call,
> > of course.
> 
> Right.
> MOD/REF depends on aliasing info, aliasing info does not depend on MOD/REF.

Right.  But you weaken both by doing them separately, and MOD/REF is an
IPA thing and we do PTA only locally.  So I think its good to do it like
we do now.

Richard.



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