ir.IRStage = OPT_IR.MIR; ir.MIRInfo = new OPT_MIRInfo(ir);
    public final void perform (OPT_IR ir) {      OPT_ComplexLIR2MIRExpansion.convert(ir);      // ir now contains well formed MIR.      ir.IRStage = OPT_IR.MIR;      ir.MIRInfo = new OPT_MIRInfo(ir);    }