[Bug middle-end/26898] New: Fold does not fold signed +- CST CMP signed +- CST

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

Fold at the moment does not fold comparisons involving signed variables with
a constant offset.  Like we get from number-of-iterations analysis for

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

where niter->may_be_zero ends up as i0 + 1 < i1 + 2 which can be folded
to i0 < i1 + 1 because signed overflow is undefined.

And I have a patch for this.


-- 
           Summary: Fold does not fold signed +- CST CMP signed +- CST
           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=26898