require_extension(EXT_ZCA);
if (insn.rvc_rd() == 2) { // c.addi16sp
  require(insn.rvc_addi16sp_imm() != 0);
  WRITE_REG(X_SP, sext_xlen(RVC_SP + insn.rvc_addi16sp_imm()));
} else {
  require(insn.rvc_imm() != 0);
  WRITE_RD(insn.rvc_imm() << 12);
}
