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From: "amacleod at redhat dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/105346] [11/12 Regression] -Wno-free-nonheap-object
 false positive (on Bison-generated grammar code)
Date: Tue, 26 Apr 2022 13:53:00 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105346

--- Comment #11 from Andrew Macleod <amacleod at redhat dot com> ---
(In reply to Richard Biener from comment #6)

>=20
>   <bb 2> :
>   bufp_2 =3D &buf;
>   if (&buf !=3D bufp_2)
>     goto <bb 3>; [INV]
>   else
>     goto <bb 4>; [INV]
>=20
>   <bb 3> :
>   __builtin_free (bufp_2);
>=20
> and for the stmt __builtin_free (bufp_2) I'd like to ask if we know
> that bufp_2 is !=3D &buf (I'd expect a 'true' answer).  I think the
> relation oracle should be able to answer this but I can't find the
> appropriate API to use for this?

- The relation oracle currently only works with ssa-names.
- Ranger also doesn't currently track that sort of symbolic equivalence with
irange.
- the VRP passes have a pointer tracking mechanism as part of the dom walk,=
 and
the call to rvrp_folder::value_of_expr (bufp_2) would give us &buf.  I also
think we also would fold the stmt in VRP.  This could in theory be extended=
 to
any pass doing a dom walk.  however:
- I believe the upcoming prange extension for pointer ranges in stage 1 will
make this happen naturally with rangers query system. range_of_stmt ( if <.=
.>)
would then produce bool [0, 0].  I would also expect that prange will have =
an
easy way to ask what its base/equivalence(s) are.=