[Bug tree-optimization/110451] New: LIM fails to hoist comparisons

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110451

            Bug ID: 110451
           Summary: LIM fails to hoist comparisons
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

For SPEC bwaves or gfortran.dg/pr81303.f we interchange the loop nest which
produces a conditional in the innermost loop like the following to handle
a reduction with invariant initialization:

  <bb 14> [local count: 955630226]:
  # l_93 = PHI <l_94(21), 1(13)>
  # ivtmp_58 = PHI <ivtmp_84(21), _85(13)>
  _30 = (integer(kind=8)) l_93;
  _31 = _29 + _30;
  y__I_lsm.120_22 = (*y_139(D))[_31];
  _23 = m_95 != 1;
  y__I_lsm.120_33 = _23 ? y__I_lsm.120_22 : 0.0;
  _42 = _30 + _41;
  _43 = (*a_141(D))[_42];

currently the LIM cost modeling finds it not profitable to hoist the
invariant m_95 != 1 compare.  This causes vectorization to choose
a larger vectorization factor to accomodate vectorizing this compare.