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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/103300] [12 Regression] wrong code at -O3 on
 x86_64-linux-gnu
Date: Wed, 17 Nov 2021 22:32:11 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103300

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to hubicka from comment #2)
> Needs -O2  -floop-unroll-and-jam   --param early-inlining-insns=3D14
> to fail, so I guess it may be issue with unrol-and-jam.

The major difference I see between GCC 11 and GCC 12 is how tree-loop-im
handles the load/store of a and c. In GCC 11, it was an unconditional move =
of
the store of a and c while in GCC 12 we get some interesting branches:
  <bb 9> [local count: 35059055]:
  # a_lsm.21_25 =3D PHI <_20(D)(6), _15(8)>
  # a_lsm_flag.22_8 =3D PHI <0(6), 1(8)>
  # c_lsm.23_22 =3D PHI <0(6), _5(8)>
  if (c_lsm.23_22 <=3D 2)
    goto <bb 17>; [94.50%]
  else
    goto <bb 10>; [5.50%]

  <bb 10> [local count: 1928248]:
  # a_lsm_flag.22_14 =3D PHI <a_lsm_flag.22_8(9)>
  # a_lsm.21_28 =3D PHI <a_lsm.21_25(9)>
  c_lsm.23_27 =3D 3;
  if (a_lsm_flag.22_14 !=3D 0)
    goto <bb 11>; [66.67%]
  else
    goto <bb 12>; [33.33%]

  <bb 11> [local count: 1285499]:
  c =3D c_lsm.23_27;

  <bb 12> [local count: 1285499]:
  if (a_lsm_flag.22_14 !=3D 0)
    goto <bb 13>; [66.67%]
  else
    goto <bb 14>; [33.33%]

  <bb 13> [local count: 856999]:
  a =3D a_lsm.21_28;

  <bb 14> [local count: 1928248]:=