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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/111003] [14 Regression] Dead Code Elimination
 Regression at -O3 since r14-2161-g237e83e2158
Date: Mon, 14 Aug 2023 08:03:50 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111003

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|rguenther at suse dot de           |rguenth at gcc dot =
gnu.org

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
So the only additional hoisting is in LIM4

Moving statement
_60 =3D _13 ^ iftmp.9_18;
(cost 1) out of loop 1.

Moving statement
_62 =3D _60 =3D=3D 10;
(cost 21) out of loop 1.


@@ -239,6 +279,8 @@
   goto <bb 31>; [100.00%]

   <bb 50> [local count: 477815112]:
+  _60 =3D _13 ^ iftmp.9_18;
+  _62 =3D _60 =3D=3D 10;

   <bb 7> [local count: 4343774241]:
   _9 =3D a ();
@@ -296,8 +338,6 @@
   goto <bb 15>; [100.00%]

   <bb 14> [local count: 14585209535]:
-  _60 =3D _13 ^ iftmp.9_18;
-  _62 =3D _60 =3D=3D 10;

   <bb 15> [local count: 35145083376]:
   # prephitmp_63 =3D PHI <0(73), _62(14), 0(74)>

and -fdisable-tree-lim4 restores the missed optimization.  The difference
is then in CCP4 which is able to remove the call to foo() when not hoisting
the compare.  When not hoisting the global range of _60 is stricter:

-  # RANGE [irange] unsigned int [0, 511] MASK 0x1c7 VALUE 0x0
-  _60 =3D _13 ^ iftmp.9_18;
+  # RANGE [irange] unsigned int [0, 16383] MASK 0x3fff VALUE 0x0
+  _60 =3D _13 ^ iftmp.9_18;=