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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/113134] gcc does not version loops with early
 break conditions that don't have side-effects
Date: Mon, 08 Jan 2024 08:11:54 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113134

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hubicka at gcc dot gnu.org

--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
The loop is rotated by header copying and the "combined" exit test looks li=
ke

  if (i_21 =3D=3D 1001)
    goto <bb 5>; [1.00%]
  else
    goto <bb 4>; [99.00%]

  <bb 4> [local count: 1004539166]:
  i_18 =3D i_21 + 1;
  if (N_13(D) > i_18)
    goto <bb 3>; [94.50%]
  else
    goto <bb 5>; [5.50%]

this could be rewritten to use min(1002, N_13(D)) with the knowledge how
'i' evolves.  We get i_21 !=3D 1001 || N_13(D) > (i_21 + 1) for the iterati=
on
condition which I think we cannot combine in general.

The "easiest" way would be to have loop splitting split the loop on the
i_21 =3D=3D 1001 condition I think.=