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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/111718] Missed optimization of '(a+a)/a'
Date: Sun, 08 Oct 2023 04:00:07 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111718

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |missed-optimization
   Last reconfirmed|                            |2023-10-08

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #3)
> For comment #2 from EVRP:
> Folding statement: _3 =3D _2 / a_5(D);
> Applying pattern match.pd:934, gimple-match-4.cc:2021
> gimple_simplified to _3 =3D 2;
>=20
> Which corresponds to the match pattern:
> /* Simplify (t * 2) / 2) -> t.  */
> (for div (trunc_div ceil_div floor_div round_div exact_div)
>  (simplify
>   (div (mult:c @0 @1) @1)
>   (if (ANY_INTEGRAL_TYPE_P (type))
>    (if (TYPE_OVERFLOW_UNDEFINED (type))
>     @0
> #if GIMPLE
>     (with {value_range vr0, vr1;}
>      (if (INTEGRAL_TYPE_P (type)
> 	  && get_range_query (cfun)->range_of_expr (vr0, @0)
> 	  && get_range_query (cfun)->range_of_expr (vr1, @1)
> 	  && range_op_handler (MULT_EXPR).overflow_free_p (vr0, vr1))
>       @0))
> #endif
>    ))))

Which was improved on the trunk by r14-4082-g55b22a6f630e (and then by
r14-4191-gd946fc1c71bd). I don't know why the original testcase is not caus=
ing
the above pattern to match though, maybe because a*2 is used twice ...=