[Bug tree-optimization/56625] After if-conversion vectorizer doesn't recognize similar loads

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56625

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
            Summary|After if-conversion         |After if-conversion
                   |vectorizer doesn't          |vectorizer doesn't
                   |recognize similar stores    |recognize similar loads

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-15 12:29:50 UTC ---
Oh, it's about the loads!

  <bb 3>:
  # i_22 = PHI <i_19(4), 0(2)>
  # ivtmp_28 = PHI <ivtmp_24(4), 100(2)>
  _5 = (long unsigned int) i_22;
  _6 = _5 * 8;
  _8 = a_7(D) + _6;
  _9 = *_8;
  _11 = b_10(D) + _6;
  _12 = *_11;
  _13 = _12 * 4.0e+0;
  _15 = b_10(D) + _6;
  _16 = *_15;
  _17 = _16 * 3.0e+0;
  cstore_18 = _9 == 0.0 ? _13 : _17;
  *_8 = cstore_18;

and

t.c:4: note: versioning for alias required: can't determine dependence between
*_11 and *_8
t.c:4: note: mark for run-time aliasing test between *_11 and *_8
t.c:4: note: versioning for alias required: can't determine dependence between
*_15 and *_8
t.c:4: note: mark for run-time aliasing test between *_15 and *_8

Creating dr for *_11
analyze_innermost: success.
        base_address: b_10(D)
        offset from base address: 0
        constant offset from base address: 0
        step: 8
        aligned to: 128
        base_object: *b_10(D)
        Access function 0: {0B, +, 8}_1
Creating dr for *_15
analyze_innermost: success.
        base_address: b_10(D)
        offset from base address: 0
        constant offset from base address: 0
        step: 8
        aligned to: 128
        base_object: *b_10(D)
        Access function 0: {0B, +, 8}_1

somehow the equality test (which we have!) doesn't work here.