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From: "amacleod at redhat dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/106063] [13 Regression] ICE: in
 gimple_expand_vec_cond_expr, at gimple-isel.cc:281 with -O2
 -fno-tree-forwprop --param=evrp-mode=legacy-first
Date: Thu, 23 Jun 2022 14:22:13 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106063

Andrew Macleod <amacleod at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amacleod at redhat dot com

--- Comment #1 from Andrew Macleod <amacleod at redhat dot com> ---
That option enables legacy EVRP, and will be going away soon.  however, loo=
king
at the IL, the difference out of EVRP is that legacy doesnt touch the code.=
 The
IL is:

  vector(1) __int128 _1;
  vector(1) <signed-boolean:128> _2;
  V _4;

  <bb 2> :
  _1 =3D v_3(D) & { 15 };
  _2 =3D v_3(D) =3D=3D _1;
  _4 =3D VEC_COND_EXPR <_2, { -1 }, { 0 }>;
  return _4;


Ranger ends up triggering a simplification :

Folding statement: _2 =3D v_3(D) =3D=3D _1;
gimple_simplified to _6 =3D v_3(D) & { -16 };
_2 =3D _6 =3D=3D { 0 };
Folded into: _2 =3D _6 =3D=3D { 0 };

producing:

    _1 =3D v_3(D) & { 15 };
    _6 =3D v_3(D) & { -16 };
    _2 =3D _6 =3D=3D { 0 };
    _4 =3D VEC_COND_EXPR <_2, { -1 }, { 0 }>;
    return _4;

Which ends up not causing the ICE seen in this PR.

However, if we completely disable EVRP, we also get the trap.

   -O2 -fno-tree-forwprop --disable-tree-evrp

So it would seem the problem probably lies with vector expansion?=