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C++ Object life cycle through SV DPI

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Hi all,

I have a C++ Object life cycle through SV DPI problem.

For example, I have a C++ reference model class named ALU.  Only one public function revealed to client (e.g. ALU::ALU_EXEC) and was encapsulated in DPI(ALU_EXEC_DPI) . And there are two types of ALU commands was entered to ALU::ALU_EXEC. One is setup ALU parameters (i.e. setup the ALU class private member) , the other is calculating the result.
 
The question is when I leave DPI, the ALU object is eliminated and all the setup parameter is cleared, right? So can I keep a C++ Object even after I leave DPI (i.e. is the C++ Object life cycle only as long as DPI call life cycle).

My friend suggest me to return all the ALU parameter out to SV and re-enter these parameters to ALU through ALU_EXEC_DPI when I call the ALU reference model. But it may break the model encapsulation :(

May be my question is not very clear and any suggestions are welcome!
Davy




Originally posted in cdnusers.org by davyzhu
Parents

  • Hi Vivek,

    I will try to describe the situation I encounter comprehensively. Please point it out if you think it is ambiguous.

    First, I want to re-use a C++ model as the reference model. It contains a class, ALU. The ALU class have one public function ALU_exec (opcode,src,result). I will keep them untouched.

    Then, if I encapsulate the class ALU with DPI function like
    ALU_exec_DPI (opcode,src, result) {
    ALU::ALU();
    ALU::ALU_exec (opcode,src,result).
    ALU::~ALU();
    }

    But as you see, when the DPI function return, the ALU object is eliminated (But I want to keep the ALU object alive until the simulation end for there are some status information stored in the ALU object), and there will be a new ALU object when I re-enter the DPI function.

    At last, I turn to youi for help, and you suggest to use DPI task.
    I guess if I use DPI task, I can generate the ALU object ALU::ALU(); when I enter the simulation ( or I get the first instruction)
    , while ALU::ALU_exec (opcode,src,result) is always running on the same ALU object through the whole simulation time
    , and ALU::~ALU(); to eliminate the ALU object when I exit the simulation.

    And what do you mean by call task in always loop?
    //---SV file
    import “DPI” task alu_run(...);
    always @(clk, a, b, opcode)
    alu_run(clk, opcode,a, b, result,$realtime);
    //---

    BTW, "$realtime" is copied from Sutherland's example and I don't think it is a must :)

    Any suggestions are welcome!

    Best regards,
    Davy


    Originally posted in cdnusers.org by davyzhu
Reply

  • Hi Vivek,

    I will try to describe the situation I encounter comprehensively. Please point it out if you think it is ambiguous.

    First, I want to re-use a C++ model as the reference model. It contains a class, ALU. The ALU class have one public function ALU_exec (opcode,src,result). I will keep them untouched.

    Then, if I encapsulate the class ALU with DPI function like
    ALU_exec_DPI (opcode,src, result) {
    ALU::ALU();
    ALU::ALU_exec (opcode,src,result).
    ALU::~ALU();
    }

    But as you see, when the DPI function return, the ALU object is eliminated (But I want to keep the ALU object alive until the simulation end for there are some status information stored in the ALU object), and there will be a new ALU object when I re-enter the DPI function.

    At last, I turn to youi for help, and you suggest to use DPI task.
    I guess if I use DPI task, I can generate the ALU object ALU::ALU(); when I enter the simulation ( or I get the first instruction)
    , while ALU::ALU_exec (opcode,src,result) is always running on the same ALU object through the whole simulation time
    , and ALU::~ALU(); to eliminate the ALU object when I exit the simulation.

    And what do you mean by call task in always loop?
    //---SV file
    import “DPI” task alu_run(...);
    always @(clk, a, b, opcode)
    alu_run(clk, opcode,a, b, result,$realtime);
    //---

    BTW, "$realtime" is copied from Sutherland's example and I don't think it is a must :)

    Any suggestions are welcome!

    Best regards,
    Davy


    Originally posted in cdnusers.org by davyzhu
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