// This declares the decoder.
decoder RiscV32I {
  // The namespace in which code will be generated.
  namespace mpact::sim::codelab;
  // The name (including any namespace qualifiers) of the opcode enum type.
  opcode_enum = "OpcodeEnum";
  // Include files specific to this decoder.
  includes {
    #include "riscv_isa_decoder/solution/riscv32i_decoder.h"
  }
  // Instruction groups for which to generate decode functions.
  RiscVInst32;
};

// The generic RiscV 32 bit instruction format.
format Inst32Format[32] {
  fields:
    unsigned bits[25];
    unsigned opcode[7];
};

// Exercise 2 format.
// End of Exercise 2 format.

// RiscV 32 bit instruction format used by a number of instructions
// needing a 12 bit immediate, including CSR instructions.
format IType[32] : Inst32Format {
  fields:
    signed imm12[12];
    unsigned rs1[5];
    unsigned func3[3];
    unsigned rd[5];
    unsigned opcode[7];
};

// Exercise 3 format.
// End of Exercise 3 format.

// Exercise 4 formats.
// End of Exercise 4 formats.

// Exercise 5 format.
// End of Exercise 5 format.

// Exercise 6 format.
// End of Exercise 6 format.

// RiscV instruction format used by fence instructions.
format Fence[32] : Inst32Format {
  fields:
    unsigned fm[4];
    unsigned pred[4];
    unsigned succ[4];
    unsigned rs1[5];
    unsigned func3[3];
    unsigned rd[5];
    unsigned opcode[7];
};

// This defines the RiscVInst32 instruction group which defines the encoding
// of the RiscV instructions we care about.
instruction group RiscVInst32[32] : Inst32Format {
  // Exercise 2 instructions.
  // End Exercise 2 instructions.

  // Exercise 3 instructions.
  // End of Exercise 3 instructions.

  // Exercise 4 instructions.
  // End of Exercise 4 instructions.

  // Exercise 5 instructions.
  // End of Exercise 5 instructions.

  // Exercise 6 instructions.
  // End of Exercise 6 instructions.

  fence   : Fence  : func3 == 0b000, opcode == 0b000'1111;
  csrs    : IType  : func3 == 0b010, rs1 != 0, opcode == 0b111'0011;
  csrw_nr : IType  : func3 == 0b001, rd == 0,  opcode == 0b111'0011;
  csrs_nw : IType  : func3 == 0b010, rs1 == 0, opcode == 0b111'0011;
};