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From: "luoxhu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/22326] promotions (from float to double) are
 not removed when they should be able to
Date: Fri, 27 Nov 2020 06:27:40 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D22326

--- Comment #14 from luoxhu at gcc dot gnu.org ---
(In reply to luoxhu from comment #13)
>=20
> 2)  mad2.c
>=20
> float foo (double x, float y, float z)
> {
>    return ( y * fabs (x) + z );=20
> }
>=20
>=20
> mad2.c.098t.cunrolli:
>=20
> foo (double x, float y, float z)
> {
>   double _1;
>   double _2;
>   double _3;
>   double _4;
>   double _5;
>   float _9;
>=20
>   <bb 2> [local count: 1073741824]:
>   _1 =3D (double) y_6(D);
>   _2 =3D ABS_EXPR <x_7(D)>;
>   _3 =3D _1 * _2;
>   _4 =3D (double) z_8(D);
>   _5 =3D _3 + _4;
>   _9 =3D (float) _5;
>   return _9;
>=20
> }
>=20

Maybe should use forward propagation here to save [_1, _2, _3 ... _9] to m_=
vars
and set ignore_convert status in usage_info if rhs of the expression could
remove double conversion, for stmt which has two rhs, need intersect status
with AND operation of rhs1 ignore_convert and rhs2 ignore_convert, also cle=
ar
the ignore_convert status if any of it is false.  Not sure whether this wor=
ks,
also a bit more complicated then expected...=