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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/97474] [8/9/10/11 Regression] produces wrong code with
 references to another field
Date: Tue, 20 Oct 2020 06:47:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97474

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org,
                   |                            |mpolacek at gcc dot gnu.or=
g,
                   |                            |ppalka at gcc dot gnu.org

--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I think the place in the C++ FE that adds restrict here is:
tree
type_passed_as (tree type)
{
  /* Pass classes with copy ctors by invisible reference.  */
  if (TREE_ADDRESSABLE (type))
    {
      type =3D build_reference_type (type);
      /* There are no other pointers to this temporary.  */
      type =3D cp_build_qualified_type (type, TYPE_QUAL_RESTRICT);
    }

So, the options are either not to do it for types that contain any
pointers/references among its members, or do some extra analysis as to whet=
her
even if it contains some pointers/references if those are guaranteed not to
point to anything within the structure (e.g. because of TBAA rules), or usi=
ng
that analysis decide if it can use normal restrict or needs to use a weaker
restrict, etc.=