[Bug tree-optimization/23659] Should able to add dereferencing (statements with VUSE) without rerunning may_alias

["dnovillo at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #5 from dnovillo at gcc dot gnu dot org  2006-03-01 14:30 -------
(In reply to comment #4)

> are you still working on this PR?
> 
Yes.  In fact, it's one of the kind of manipulations that drove the design
decisions in memory SSA.

> I think something similar to the attached patch should fix the problem -- it
> makes us remember alias class --> TMT mapping globally, and uses it to set up
> TMT's for the new pointers.  Could you please comment on whether you consider
> this the right approach, or propose an alternative one?
> 
Whenever a new pointer symbol is introduced, it should receive a type tag. 
This type tag is then assigned a set of aliases (or not, depending on context).
 In fact, my plan is for these manually added type tags to be marked so that
subsequent alias passes don't affect them.  This should help the vectorizer and
other passes introduce a pointer symbol with a specific set of points-to
aliases that the aliaser may not have a chance of compute so accurately
otherwise.

> On a side note, things like this might become even more difficult with the new
> memory ssa approach.
> 
Huh.  What makes you think that?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23659