Re: Question about IPA-PTA and build_alias

[Richard Biener <richard.guenther@gmail.com>]

On Mon, Aug 17, 2020 at 3:22 PM Erick Ochoa
<erick.ochoa@theobroma-systems.com> wrote:
>
> Hello,
>
> I'm looking to understand better the points-to analysis (IPA-PTA) and
> the alias analysis (build_alias).
>
> How is the information produced by IPA-PTA consumed?
>
> Are alias sets in build_alias computed by the intersections of the
> points_to_set(s) (computed by IPA-PTA)?
>
> My intuition tells me that it could be relatively simple to move
> build_alias to be an SIMPLE_IPA_PASS performed just after IPA-PTA, but I
> do not have enough experience in GCC to tell if this is correct. What
> could be some difficulties which I am not seeing? (Either move, or
> create a new IPA-ALIAS SIMPLE_IPA_PASS.) This pass would have the same
> sensitivity as IPA-PTA { flow-insensitive, context-insensitive,
> field-sensitive } because the alias sets could be computed by the
> intersection of points-to-sets.

Both IPA-PTA and build_alias do the same, they build PTA constraint
sets, solve them and attach points-to info to SSA names.  Just IPA-PTA
does this for the whole TU while build_alias does it for a function at a time.

So I guess I do not understand your question.

Richard.

>
> Thanks!