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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/103723] zero extend not moved out of the loop
 after IV-OPTS
Date: Wed, 15 Dec 2021 11:45:28 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103723

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Actually this is more complex, I had missed the original add too.
the full loop:
 <bb 3> [local count: 958878296]:
  _18 =3D (unsigned int) ivtmp.7_15;
  len_test_12 =3D _18 + 1;
  ivtmp.7_7 =3D ivtmp.7_15 + 1;
  if (ivtmp.7_7 !=3D _21)
    goto <bb 7>; [94.50%]
  else
    goto <bb 9>; [5.50%]

  <bb 9> [local count: 52738306]:
  # len_test_17 =3D PHI <len_test_12(3)>
  goto <bb 5>; [100.00%]

  <bb 7> [local count: 906139990]:

  <bb 4> [local count: 1014686026]:
  # ivtmp.7_15 =3D PHI <ivtmp.7_7(7), 2(6)>
  _4 =3D (unsigned int) ivtmp.7_15;
  len_test_13 =3D _4;
  _3 =3D MEM[(const uint8_t *)buf_9(D) + ivtmp.7_15 * 1];
  _6 =3D MEM[(const uint8_t *)buf_back_11(D) + ivtmp.7_15 * 1];
  if (_3 =3D=3D _6)
    goto <bb 3>; [94.50%]
  else
    goto <bb 10>; [5.50%]

  <bb 10> [local count: 55807731]:
  # len_test_16 =3D PHI <len_test_13(4)>

We can't just sink the cast though as that would violate the closed-loop-SS=
A.
We would need to sink also:
  _18 =3D (unsigned int) ivtmp.7_15;
  len_test_12 =3D _18 + 1;

Which we do at the RTL level ....=