[Bug tree-optimization/23286] missed fully redundant expression

["pinskia at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-08-08 18:42 -------
Confirmed, for some reason the following is caught though:
  unsigned short f(unsigned short a)
  {
    unsigned short b = a <<1;
    if (a & 0x8000)
      a <<= 1, a = a ^ 0x1021;
    else
      a = b;

    return a;
  }
as a<<1 is caught being redundant.  FRE catches the above on the mainline.

Hmm there is only one VH for the expression:
Created value VH.0 for a_2
Created value VH.1 for (short int) VH.0
Created value VH.2 for VH.0 << 1
Created value VH.3 for VH.2 ^ 4129
Created value VH.4 for a_1
Created value VH.5 for (int) VH.4
Created value VH.6 for <retval>_5
exp_gen[-1] := {  }
tmp_gen[-1] := { a_2 (VH.0)  }
avail_out[-1] := { a_2 (VH.0)  }
exp_gen[0] := { a_2 (VH.0) , (short int) VH.0 (VH.1)  }
tmp_gen[0] := { a.0_3 (VH.1)  }
avail_out[0] := { a_2 (VH.0) , a.0_3 (VH.1)  }
exp_gen[1] := { a_2 (VH.0) , VH.0 << 1 (VH.2) , VH.2 ^ 4129 (VH.3)  }
tmp_gen[1] := { a_7 (VH.2) , a_8 (VH.3)  }
avail_out[1] := { a_2 (VH.0) , a.0_3 (VH.1) , a_7 (VH.2) , a_8 (VH.3)  }
exp_gen[2] := { a_2 (VH.0) , VH.0 << 1 (VH.2)  }
tmp_gen[2] := { a_6 (VH.2)  }
avail_out[2] := { a_2 (VH.0) , a.0_3 (VH.1) , a_6 (VH.2)  }
exp_gen[3] := { a_1 (VH.4) , (int) VH.4 (VH.5)  }
tmp_gen[3] := { D.1280_4 (VH.5) , <retval>_5 (VH.6)  }
avail_out[3] := { a_1 (VH.4) , a_2 (VH.0) , a.0_3 (VH.1) , D.1280_4 (VH.5) , <retval>_5 (VH.6)  }
exp_gen[-2] := {  }
tmp_gen[-2] := {  }
avail_out[-2] := {  }


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dberlin at gcc dot gnu dot
                   |                            |org
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-08-08 18:42:33
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23286