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From: "law at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/103771] [12 Regression] Missed vectorization under
 -mavx512f -mavx512vl after r12-5489
Date: Tue, 01 Feb 2022 16:13:22 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103771

--- Comment #34 from Jeffrey A. Law <law at gcc dot gnu.org> ---
I've always wanted to see us be able to push something like those matched
conversions down through the PHI.

That would make the code look like:

  if (x.1_1 > 255)
    goto <bb 3>; [INV]
  else
    goto <bb 4>; [INV]

  <bb 3> :
  _2 =3D -x_5(D);
  _3 =3D _2 >> 31;
  goto <bb 5>; [INV]

  <bb 4> :

  <bb 5> :
  # tmp =3D PHI <_3, x_5(4)>
  iftmp.0_4 =3D (uint8_t) tmp

And presumably we'd clean up the empty bb4 which would in turn unblock other
optimizations.

Is that what you're working on?=