[Bug tree-optimization/67530] Failure to eliminate dead code produced by vector lowering

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67530

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-09-14
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
The relevant pass is lower_vector_ssa which runs way before the last cd_cde. 
The issue is that

  _6 = {_11, _14, _17, _20, _23, _26, _29, _32};
  _7 = BIT_FIELD_REF <_6, 32, 64>;
  _8 = (long int) _7;
  return _8;

is only resolved very late in the forwprop pass _after_ the last DCE.  I
suppose
vector lowering could be changed to fold all stmts that have vector operands
(it doesn't touch _7 = BIT_FIELD_REF <_6, 32, 64> otherwise).