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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/100923] wrong code at -O2 and above on
 x86_64-linux-gnu
Date: Sun, 06 Jun 2021 20:57:59 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100923

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|wrong code at -Os and above |wrong code at -O2 and above
                   |on x86_64-linux-gnu         |on x86_64-linux-gnu
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-06-06
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |alias, wrong-code

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
- working (-O2 -fno-strict-aliasing)
+ not working (-O2 -fstrict-aliasing)

-  l.1_3 =3D l;
-  e.2_5 =3D e;
-  f.3_6 =3D f;
-  *e.2_5 =3D f.3_6;
-  _7 =3D *l.1_3;
-  if (_7 !=3D 0)

+  l.1_4 =3D l;
+  _5 =3D *l.1_4;
+  e.2_6 =3D e;
+  f.3_7 =3D f;
+  *e.2_6 =3D f.3_7;
+  if (_5 !=3D 0)

So we swapped around the store to *e and the load from *l.=