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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/53100] Optimize __int128 with range information
Date: Fri, 06 Aug 2021 00:33:27 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D53100

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|middle-end                  |tree-optimization
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2021-08-06
           Keywords|                            |missed-optimization
     Ever confirmed|0                           |1

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So in the #if 0 case we get:
  x_13 =3D (long int) a_12(D);
  y_15 =3D (long int) b_14(D);
  z_17 =3D (long int) c_16(D);
  t_19 =3D (long int) d_18(D);
  u_21 =3D (long int) e_20(D);
  v_23 =3D (long int) f_22(D);
  _1 =3D z_17 - x_13;
  _3 =3D v_23 - y_15;
  _5 =3D _1 w* _3;

Notice the w*

While with the original case we get:
  x_9 =3D (__int128) a_8(D);
  y_11 =3D (__int128) b_10(D);
  z_13 =3D (__int128) c_12(D);
  t_15 =3D (__int128) d_14(D);
  u_17 =3D (__int128) e_16(D);
  v_19 =3D (__int128) f_18(D);
  _1 =3D z_13 - x_9;
  _2 =3D v_19 - y_11;
  _3 =3D _1 * _2;

If we had simplified/shortened: ((__int128) c_12(D)) - ((__int128) a_8(D))
to
(__int128)(long)((unsigned long) c_12(D)) - ((unsigned long) a_8(D))
We might have optimized this.
There might be another bug about having some PLUS_EXPR which has WRAPPING
effects rather than undefined OVERFLOW which will help the casting issue.=