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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/101326] std::optional returns forced through stack
Date: Tue, 06 Jul 2021 06:38:14 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101326

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
I think the issue is simply that RTL expansion forces the object to memory
since that is what GIMPLE does:

struct optional foo ()
{
  struct optional D.12374;

  <bb 2> [local count: 1073741824]:
  MEM <long int> [(struct optional *)&D.12374] =3D 0;
  MEM <unsigned char> [(struct optional *)&D.12374 + 8B] =3D 1;
  return D.12374;
}

and yes, if it would have had TImode we could expand it to a register pair
but it has BLKmode because it's TYPE_NEEDS_CONSTRUCTING(?), the type
isn't TREE_ADDRESSABLE for me.=