namely [0, n) where n is the width of type a. (Or better type a's mode to be safe). Look at infer_value_range().
-- Summary: VRP can infer a range for b in a >> b and a << b Product: gcc Version: 4.3.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: enhancement Priority: P3 Component: tree-optimization AssignedTo: rguenth at gcc dot gnu dot org ReportedBy: rguenth at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31178