https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117222
--- Comment #8 from Andrew Macleod <amacleod at redhat dot com> --- pointer_diff depends on range_operator::fold_range to do the generic fold, which invokes wi_fold on subranges. It also in turn invokes op1_op2_relation_effect. This worked fine when pointers were implemented with irange, but when the transition to prange was made, a new version of fold_range is invoked by dispatch which uses prange operators. The default fold_range for prange does nothing, expecting the few operators which need it to implement their own fold_range. As a result all calls to fold_range for pointer_diff were returning false, which translates to VARYING. This PR demonstrates a dependency on knowing the relation between the operands is VREL_NE, in which case pointer_diff should return a non-zero result instead of varying. The upcoming patch implements the pointer_diff version of fold_range which then invokes the appropriate op1_op2_relation_effect () routine. This will in turn will cause the result to be non-zero as expected.
