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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/98854] [11 Regression] cray benchmark is
 about 15% slower since r11-4428-g4a369d199bf2f34e
Date: Wed, 27 Jan 2021 15:17:30 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98854

--- Comment #8 from rguenther at suse dot de <rguenther at suse dot de> ---
On Wed, 27 Jan 2021, marxin at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98854
>=20
> --- Comment #7 from Martin Li=C5=A1ka <marxin at gcc dot gnu.org> ---
> > I used -O3 but -O2 -ftree-slp-vectorize also vectorizes it.
>=20
> I must be blind, but I see for the current master:
>=20
> gcc pr98854.c -c -O2 -ftree-slp-vectorize -fdump-tree-optimized=3D/dev/st=
dout
>=20
> foo (int n)
> {
>   unsigned long ivtmp.8;
>   double y;
>   double x;
>   double _6;
>   double _8;
>   double _9;
>   double _11;
>   int _14;
>   void * _29;
>   unsigned long _31;
>=20
>   <bb 2>:
>   ivtmp.8_28 =3D (unsigned long) &MEM[(void *)&a + 8184B];
>   _31 =3D (unsigned long) &a;
>=20
>   <bb 3>:
>   # x_1 =3D PHI <0.0(2), x_10(5)>
>   # y_2 =3D PHI <0.0(2), y_12(5)>
>   # ivtmp.8_18 =3D PHI <ivtmp.8_28(2), ivtmp.8_27(5)>
>   _29 =3D (void *) ivtmp.8_18;
>   _6 =3D MEM[base: _29, offset: 0B];
>   _8 =3D MEM[base: _29, offset: 8B];
>   _9 =3D _6 + _8;
>   x_10 =3D _9 + x_1;
>   _11 =3D _6 / _8;
>   y_12 =3D _11 + y_2;
>   _14 =3D bar ();
>   if (_14 !=3D 0)
>     goto <bb 4>;
>   else
>     goto <bb 5>;
>=20
>   <bb 4>:
>   a[0] =3D x_10;
>   a[1] =3D y_12;
>   return;
>=20
>   <bb 5>:
>   ivtmp.8_27 =3D ivtmp.8_18 - 8;
>   if (ivtmp.8_27 !=3D _31)
>     goto <bb 3>;
>   else
>     goto <bb 4>;
>=20
> }

Hmm, maybe my dev tree has related adjustments to SLP ... at least
the posted patch fixes the regression for me.=