[Bug middle-end/33330] [4.3 Regression] Wrong alias for accessing scalar through array

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2007-09-07 10:06 -------
The problem is that DCE2 deletes the my_char = 121; store because aliasing
thinks the array reference doesn't alias the scalar:

;; Function sub0 (sub0)

sub0 ()
{
  char[1:1] & my_char_ref;
  char D.874;
  char my_char;

<bb 2>:
  # my_char_4 = VDEF <my_char_3(D)>
  my_char = 121;
  my_char_ref_1 = (char[1:1] &) &my_char;
  # VUSE <NMT.30_5(D)>
  D.874_2 = (*my_char_ref_1)[1]{lb: 1 sz: 1};
  if (D.874_2 != 121)
    goto <bb 3>;
  else
    goto <bb 4>;

<bb 3>:
  _gfortran_abort ();

<bb 4>:
  return;

}

aliasing has similar problems where references are not combined completely
in some places like

  my_char_ref_1 = (char[1:1] &) &my_char;
  # VUSE <NMT.30_5(D)>
  D.874_2 = (*my_char_ref_1)[1]{lb: 1 sz: 1};

we might be able to work around this by properly doing the propagation.

Finally a nice small testcase though ;)


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dberlin at gcc dot gnu dot
                   |                            |org, rguenth at gcc dot gnu
                   |                            |dot org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |alias, wrong-code
   Last reconfirmed|0000-00-00 00:00:00         |2007-09-07 10:06:13
               date|                            |
            Summary|[gfortran] inlining problem |[4.3 Regression] Wrong alias
                   |                            |for accessing scalar through
                   |                            |array
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33330