message: replace some ssa nodes with register nodes
diff: @@ -96,6 +96,12 @@ impl<'a> CASTDataGraph<'a> {
  return;
  }
  self.seen.insert(ret_node);
  + let regs = self.ssa.registers(ret_node);
  + if regs.len() > 0 {
  + let ast_node = ast.constant(&regs[0], None);
  + self.var_map.insert(ret_node, ast_node);
  + return;
  + }
  let ops = self.ssa.operands_of(ret_node);
  radeco_trace!("CASTBuilder::update_values opcode: {:?}", self.ssa.opcode(ret_node));
  @@ -166,17 +172,11 @@ impl<'a> CASTDataGraph<'a> {
  }
  fn prepare_regs(&mut self, ast: &mut SimpleCAST) {
  - let entry_node = self.ssa.entry_node();
  - if entry_node.is_none() {
  - radeco_warn!("Entry node not found");
  - return;
  - }
  for walk_node in self.ssa.inorder_walk() {
  // TODO avoid unwrap
  let reg_state = self.ssa.registers_in(walk_node);
  if reg_state.is_none() {
  - radeco_warn!("RegisterState not found");
  - return;
  + continue;
  }
  let reg_map = utils::register_state_info(reg_state.unwrap(), self.ssa);
  for (idx, (node, vt)) in reg_map.into_iter() {
  