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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug rtl-optimization/99305] [11 Regression] range condition
 simplification after inlining
Date: Mon, 01 Mar 2021 09:22:54 +0000
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X-Bugzilla-Keywords: missed-optimization, needs-bisection
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99305

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization,
                   |                            |needs-bisection
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Target Milestone|---                         |11.0
   Last reconfirmed|                            |2021-03-01

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  Some forwprop/match.pd prevents phiopt to trigger:

GCC 10 (forwprop->phiopt):

   <bb 2> [local count: 1073741824]:
   _7 =3D (unsigned char) c_2(D);
   _8 =3D _7 + 208;
-  if (_8 <=3D 9)
-    goto <bb 3>; [50.00%]
-  else
-    goto <bb 4>; [50.00%]
-
-  <bb 3> [local count: 536870913]:
-
-  <bb 4> [local count: 1073741824]:
-  # iftmp.1_1 =3D PHI <1(3), 0(2)>
-  return iftmp.1_1;
+  _9 =3D _8 <=3D 9;
+  return _9;

forwprop difference GCC 10/11:

-  Replaced '_9 !=3D 0' with '_8 <=3D 9'
-bar (char c)
+bool bar (char c)
 {
   bool iftmp.1_1;
-  unsigned char _7;
-  unsigned char _8;
+  unsigned char c.0_4;
+  unsigned char _5;
+  bool _6;
+  bool _7;

   <bb 2> [local count: 1073741824]:
-  _7 =3D (unsigned char) c_2(D);
-  _8 =3D _7 + 208;
-  if (_8 <=3D 9)
+  if (c_2(D) !=3D 0)
     goto <bb 3>; [50.00%]
   else
     goto <bb 4>; [50.00%]

   <bb 3> [local count: 536870913]:
+  c.0_4 =3D (unsigned char) c_2(D);
+  _5 =3D c.0_4 + 208;
+  _6 =3D _5 <=3D 9;
+  _7 =3D -_6;

   <bb 4> [local count: 1073741824]:
-  # iftmp.1_1 =3D PHI <1(3), 0(2)>
+  # iftmp.1_1 =3D PHI <_7(3), 0(2)>
   return iftmp.1_1;=