[Bug tree-optimization/25737] ACATS c974001 c974013 hang with struct aliasing

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

------- Comment #36 from dberlin at gcc dot gnu dot org  2006-09-22 12:55 -------
Subject: Re:  ACATS c974001 c974013 hang with struct aliasing

On 21 Sep 2006 16:53:49 -0000, ebotcazou at gcc dot gnu dot org
<gcc-bugzilla@gcc.gnu.org> wrote:
>
>
> ------- Comment #35 from ebotcazou at gcc dot gnu dot org  2006-09-21 16:53 -------
> > I suspect the reality is there is some fundamental misunderstanding of
> > how aliasing or addressability works on the part of the Ada folks (no
> > offense to them, it's just the arguments they keep offering are, well,
> > strange to anyone who understands aliasing).
>
> I suspect that we were simply not on the same page, you being at a general
> level about aliasing/addressability and I being at the implementation level
> about DECL_NONADDRESSABLE_P and TYPE_NONALIASED_COMPONENT.
>

No, really, you don't seem to understand.
If you respect these DECL_NONADDRESSABLE_P or
TYPE_NONALIASED_COMPONENT flags, you are going to make them unaliased.
Your whole bug report is that they are not aliased and should be, and
that the loads and stores currently don't interfere but should.

This is what everyone has told you so far. I've copied Diego, and I
expect he will tell you the same thing.

Diego, the short summary is that Eric has some Ada testcases where we
end up with less V_MAY_DEF's than he thinks should.  He believes that
respecting these flags, which specify you cannot form the address of a
certain component, etc, will somehow cause him to end up with more
aliasing and fix his testcase by anything other than luck.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25737