* @param insn {@code non-null;} instruction to scrutinize
*/
private static void addConstants(HashSet<Constant> result,
DalvInsn insn) {
if (insn instanceof CstInsn) {
Constant cst = ((CstInsn) insn).getConstant();
result.add(cst);
} else if (insn instanceof LocalSnapshot) {
RegisterSpecSet specs = ((LocalSnapshot) insn).getLocals();
int size = specs.size();
for (int i = 0; i < size; i++) {