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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/108358] [13 Regression] Dead Code Elimination
 Regression at -Os since r13-3378-gf6c168f8c06047
Date: Mon, 27 Mar 2023 11:56:32 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108358

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Both -O2 and -O1 can optimize away the call to foo.  For -Os we end up with

  <bb 2> [local count: 118111600]:
  l =3D *.LC0;
  goto <bb 4>; [100.00%]

  <bb 3> [local count: 955630225]:
  bar31_ ();
  i.0_1 =3D i;
  _2 =3D i.0_1 + 1;
  i =3D _2;

  <bb 4> [local count: 1073741824]:
  i.1_3 =3D i;
  if (i.1_3 !=3D 0)
    goto <bb 3>; [89.00%]
  else
    goto <bb 5>; [11.00%]

  <bb 5> [local count: 118111600]:
  j =3D l;
  m$h$b_18 =3D j.h.b;
  if (m$h$b_18 !=3D 0)
    goto <bb 7>; [67.00%]
  else
    goto <bb 6>; [33.00%]

  <bb 6> [local count: 38976828]:
  foo ();

but FREs looking through the j =3D l copy causes us to fail disambiguating
against the cycle because of 'abort_on_visited' which I think is a bit
overeager here.=