[Patch Ping] [RFC] Alias export patch

[Richard Guenther]

On 6/5/06, Andrey Belevantsev <abel@ispras.ru> wrote:
> Richard Guenther wrote:
> > I wonder how/if you deal with the problem that the tree loop optimizers
> > (ivopts mostly) generate new pointers as induction variables but we don't
> > run may_alias after them, so possibly all interesting (performance wise)
> > pointers do not have updated points-to information?  Do your numbers
> > (not performance) improve if you specify -fno-tree-loop-optimize?
>
> Since the patch was created, we wanted to insert an additional
> pass_may_alias before going out of ssa to cope with this problem.
> However, as ivopts does not keep the points-to information updated, this
> does not work -- gcc ICEs in verify_ssa.  We've tried several times to
> turn off pass_loop_optimize and insert an extra may alias pass, and that
> didn't change much performance wise.  Now I've tried that once again.
> It gives the following (for x86):
>
>     before (with ivopts)       after (no ivopts, extra alias pass)
> bootstrap       SPEC         bootstrap       SPEC
> C = 433         C = 26       C = 435         C = 32
> O = 523         O = 52       O = 523         O = 49
> a = 10563       a = 11691    a = 10607       a = 45750
> x = 1954        x = 1035     x = 2148        x = 1200
>
> C  --- add_coalesce is called for pointers with different points-to sets
> O  --- add_coalesce is called when one pointer has a points-to set and
> the other has not
> a  --- new disambiguations from extended alias sets when
> alias_sets_conflict_p is called
> x  --- new disambiguations from saved points-to sets when *_dependence
> is called

Can you add base numbers here, i.e. how many disambiguations are
there in total for a and x?

Thanks,
Richard.