Randomize CSR in main

[predator-111]

riscv-dv initializes floating point CSRs frm using init_floating_point_gpr(). I want to add randomization to certain CSRs in the main function without breaking the existing setup. Kindly suggest any way to achieve this effectively.

[zeeshanrafique23]

Not sure, if this is helpful to you: https://htmlpreview.github.io/?https://github.com/google/riscv-dv/blob/master/docs/build/singlehtml/index.html#setup-privileged-csr-description-optional

[MikeOpenHWGroup]

You can extend riscv_asm_program_gen and overload the init_floating_point_gpr() method:

class my_riscv_asm_program_gen extends riscv_asm_program_gen;

  // my implementation of init_floating_point_gpr()
  virtual function void init_floating_point_gpr();
    int int_gpr;
    string str;
    for(int i = 0; i < NUM_FLOAT_GPR; i++) begin
      // your code goes here...
    end
    // Initialize rounding mode of FCSR
    str = $sformatf("%0sfsrmi %0d", indent, cfg.fcsr_rm);
    instr_stream.push_back(str);
  endfunction

endclass: my_riscv_asm_program_gen

You will also need to create your own build script(s) to add the new class to the manifest.

Warning! I have based the above on what we have done in the past, and the above code has not been exposed to a SystemVerilog compiler. :stuck_out_tongue_closed_eyes:

[predator-111]

This would add the instructions that I want in the initialization section of the program. What I want to achieve is the CSR instructions appearing randomly in the main section of the program, not just in the initialization section

[MikeOpenHWGroup]

You can apply the same strategy to any class (and thereby class function/task) in riscv-dv.

[predator-111]

When I am trying to extend a particular class and trying to accommodate fsrmi instruction (or any particular CSR instruction), the types of queues there are of the riscv_instr_t, and this riscv_instr_t does not support CSR instructions, as those instructions can not be casted into that type (that is why those CSR instructions are hardcoded as a string and used in riscv_asm_program_gen.sv, the queue type being there is string, hence any string can be pushed, but only in the initialization section of the program). Hence, I can not push those CSR instructions in the main part of the program by extending any class.

[MikeOpenHWGroup]

Hence, I can not push those CSR instructions in the main part of the program by extending any class.

Ah, now I get it. I'll bet ChipsAlliance would look favourably upon a pull-request to update riscv_instr_t. (Disclaimer, I am not a member of CA.)