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Subject: [Bug tree-optimization/39999] gcc 4.4.0 compiles in infinite loop
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------- Comment #3 from rguenth at gcc dot gnu dot org  2009-05-02 10:19 -------
Confirmed.  I hit

#ifdef ENABLE_CHECKING
      /* Theoretically possible, but *highly* unlikely.  */
      gcc_assert (num_iterations < 500);
#endif

on trunk.

We seem to oscillate

....
ANTIC_IN[12] := { A1_1 (0001), A2_2 (0002), {pointer_plus_expr,A1_1,-4} (0026),
{pointer_plus_expr,A2_2,-4} (0046) }
ANTIC_IN[12] := { A1_1 (0001), A2_2 (0002), {pointer_plus_expr,A2_2,-4} (0025),
{pointer_plus_expr,A2_2,-4} (0046) }
ANTIC_IN[12] := { A1_1 (0001), A2_2 (0002), {pointer_plus_expr,A1_1,-4} (0026),
{pointer_plus_expr,A2_2,-4} (0046) }
ANTIC_IN[12] := { A1_1 (0001), A2_2 (0002), {pointer_plus_expr,A2_2,-4} (0025),
{pointer_plus_expr,A2_2,-4} (0046) }
ANTIC_IN[12] := { A1_1 (0001), A2_2 (0002), {pointer_plus_expr,A1_1,-4} (0026),
{pointer_plus_expr,A2_2,-4} (0046) }
ANTIC_IN[12] := { A1_1 (0001), A2_2 (0002), {pointer_plus_expr,A2_2,-4} (0025),
{pointer_plus_expr,A2_2,-4} (0046) }

Maybe we get confused by the degenerate PHIs

<bb 22>:

<bb 14>:
  # A1_17 = PHI <A1_1(22)>
  # A2_18 = PHI <A2_2(22)>
  C_29 = MMAPMON (p_8(D), A2_18);
  D.1783_30 = A2_18 + -4;
  free (D.1783_30);
  D.1784_31 = A1_17 + -4;


-- 

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
          Component|middle-end                  |tree-optimization
     Ever Confirmed|0                           |1
           Keywords|                            |ice-on-valid-code
   Last reconfirmed|0000-00-00 00:00:00         |2009-05-02 10:19:57
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39999