[Bug middle-end/26899] New: Fold does not fold (i0 > i1 + 1) || (i1 < i0 - 1)

[rguenth at gcc dot gnu dot org]

Fold currently does not fold a lot of TRUTH_AND/OR_EXPRs created by
tree-ssa-loop-niter.c:tree_simplify_using_condition_1.  Like for the testcase

int foo0(int i0, int i1)
{
  int i, j = 0;
  for (i=i0; i<=i1+1; ++i)
    ++j;
  return j;
}

with PR26898 fixed.  We there get

  i0D.1520_4 > i1D.1521_6 + 1  ||  i1D.1521_6 < i0D.1520_4 - 1

(which is false) and

  i0D.1520_4 <= i1D.1521_6 + 1  &&  i1D.1521_6 < i0D.1520_4 - 1

(which is also false and would make us figure out # iterations for the loop).


-- 
           Summary: Fold does not fold (i0 > i1 + 1) || (i1 < i0 - 1)
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26899