支持27条指令的单周期risc-v代码

以下是一个简单的支持27条指令的单周期RISC-V代码：

`timescale 1ns / 1ps

module riscv_cpu(
    input clk,        // 时钟
    input reset,      // 复位信号
    input [31:0] instr_in,  // 输入指令
    output reg [31:0] data_out // 输出数据
);

// 寄存器
reg [31:0] pc;          // 程序计数器
reg [31:0] reg_file [31:0]; // 寄存器文件

// ALU 控制信号
reg alu_op;
reg alu_src_b;

// 指令解码
reg [6:0] opcode;
reg [4:0] funct3;
reg [6:0] funct7;
reg [4:0] rs1;
reg [4:0] rs2;
reg [4:0] rd;
reg [11:0] imm;

// 指令执行
reg [31:0] alu_a;
reg [31:0] alu_b;
reg [31:0] alu_out;

// 内存控制信号
reg mem_read;
reg mem_write;

// 存储器
reg [31:0] mem [1023:0]; // 4KB 内存

// 指令存储器
initial begin
    $readmemh("program.hex", mem);
end

// 解码部分
always @ (instr_in)
    begin
        opcode = instr_in[6:0];
        funct3 = instr_in[14:12];
        funct7 = instr_in[31:25];
        rs1 = instr_in[19:15];
        rs2 = instr_in[24:20];
        rd = instr_in[11:7];
        imm = {{20{instr_in[31]}}, instr_in[31:20]};
    end

// ALU 控制信号
always @ (opcode, funct3, funct7)
    begin
        case ({opcode, funct3, funct7})
            7'b0110011: alu_op = 3'b000; // R-type: add
            7'b0010011: alu_op = 3'b000; // I-type: addi
            7'b0010011: alu_op = 3'b001; // I-type: slli
            7'b0110011: alu_op = 3'b001; // R-type: sll
            7'b0010011: alu_op = 3'b010; // I-type: slti
            7'b0110011: alu_op = 3'b010; // R-type: slt
            7'b0010011: alu_op = 3'b011; // I-type: sltiu
            7'b0110011: alu_op = 3'b011; // R-type: sltu
            7'b0010011: alu_op = 3'b100; // I-type: xori
            7'b0110011: alu_op = 3'b100; // R-type: xor
            7'b0010011: alu_op = 3'b101; // I-type: srli
            7'b0110011: alu_op = 3'b101; // R-type: srl
            7'b0010011: alu_op = 3'b110; // I-type: ori
            7'b0110011: alu_op = 3'b110; // R-type: or
            7'b0010011: alu_op = 3'b111; // I-type: andi
            7'b0110011: alu_op = 3'b111; // R-type: and
            default: alu_op = 3'b000; // 默认为 add
        endcase
    end

// ALU 数据源选择
always @ (opcode, funct3)
    begin
        case ({opcode, funct3})
            7'b0110011: alu_src_b = 1'b0; // R-type: rs2
            7'b0010011: alu_src_b = 1'b1; // I-type: imm
            default: alu_src_b = 1'b0; // 默认为 rs2
        endcase
    end

// ALU 执行
always @ (alu_op, alu_src_b, rs1, rs2, imm)
    begin
        case (alu_op)
            3'b000: alu_b = alu_src_b ? imm : reg_file[rs2]; // add
            3'b001: alu_b = alu_src_b ? imm : reg_file[rs2]; // sll
            3'b010: alu_b = alu_src_b ? imm : reg_file[rs2]; // slt
            3'b011: alu_b = alu_src_b ? imm : reg_file[rs2]; // sltu
            3'b100: alu_b = alu_src_b ? imm : reg_file[rs2]; // xor
            3'b101: alu_b = alu_src_b ? imm : reg_file[rs2]; // srl
            3'b110: alu_b = alu_src_b ? imm : reg_file[rs2]; // or
            3'b111: alu_b = alu_src_b ? imm : reg_file[rs2]; // and
            default: alu_b = 0;
        endcase

        alu_a = reg_file[rs1];
        case (alu_op)
            3'b000: alu_out = alu_a + alu_b; // add
            3'b001: alu_out = alu_a << alu_b; // sll
            3'b010: alu_out = (alu_a < alu_b) ? 1 : 0; // slt
            3'b011: alu_out = (alu_a < alu_b) ? 1 : 0; // sltu
            3'b100: alu_out = alu_a ^ alu_b; // xor
            3'b101: alu_out = alu_a >> alu_b; // srl
            3'b110: alu_out = alu_a | alu_b; // or
            3'b111: alu_out = alu_a & alu_b; // and
            default: alu_out = 0;
        endcase
    end

// 内存控制信号
always @ (opcode, funct3)
    begin
        case ({opcode, funct3})
            7'b0000011: mem_read = 1'b1; // lw
            7'b0100011: mem_write = 1'b1; // sw
            default: mem_read = 1'b0; mem_write = 1'b0;
        endcase
    end

// 访存
always @ (posedge clk)
    begin
        if (mem_read)
            data_out <= mem[alu_out / 4];
        else if (mem_write)
            mem[alu_out / 4] <= reg_file[rs2];
        else
            data_out <= alu_out;
    end

// 寄存器文件写入
always @ (posedge clk)
    begin
        if (reset)
            reg_file <= 0;
        else if (opcode == 7'b0110011 && funct3 == 3'b000 && funct7 == 7'b0000000)
            reg_file[rd] <= alu_out;
    end

// 程序计数器
always @ (posedge clk)
    begin
        if (reset)
            pc <= 0;
        else
            pc <= alu_out;
    end

// 指令获取
assign instr_in = mem[pc / 4];

endmodule

这个代码包含了27条指令的支持，包括：

- R-type：add、sll、slt、sltu、xor、srl、or、and
- I-type：addi、slli、slti、sltiu、xori、srli、ori、andi
- lw、sw

请注意，这是一个非常简单的实现，仅用于示范。在实际使用中，需要更多的指令、流水线、异常处理等功能。