[Bug middle-end/27132] New: Fold does not canonicalize i - -1

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

Fold does not canonicalize i - -1 to i + 1 where allowed.  It has

        /* A - B -> A + (-B) if B is easily negatable.  */
        if (negate_expr_p (arg1)
          && ((FLOAT_TYPE_P (type)
                 /* Avoid this transformation if B is a positive REAL_CST.  */
               && (TREE_CODE (arg1) != REAL_CST
                   ||  REAL_VALUE_NEGATIVE (TREE_REAL_CST (arg1))))
              || (INTEGRAL_TYPE_P (type) && flag_wrapv && !flag_trapv)))
        return fold_build2 (PLUS_EXPR, type,
                            fold_convert (type, arg0),
                            fold_convert (type, negate_expr (arg1)));

but that doesn't trigger if !flag_wrapv.


-- 
           Summary: Fold does not canonicalize i - -1
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          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=27132