mirror of
https://gitlab.com/brendanhaines/cpu.git
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547 lines
19 KiB
Verilog
547 lines
19 KiB
Verilog
module core(
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input clk,
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input reset,
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// Memory - instruction
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output reg [31:0] mem_inst_addr,
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input [31:0] mem_inst_data,
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// // Memory - data
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output reg [31:0] mem_data_addr,
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input [31:0] mem_data_rdata,
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output reg [31:0] mem_data_wdata,
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output reg [(32/8)-1:0] mem_data_wmask,
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output reg mem_data_we,
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// output reg [31:0] mem_data_waddr,
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// output reg [31:0] mem_data_wdata,
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// output reg [3:0] mem_data_wmask,
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// output reg mem_data_wvalid,
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// input wire mem_data_wready,
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// output reg [31:0] mem_data_raddr,
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// output reg mem_data_raddr_valid,
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// input wire mem_data_raddr_ready,
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// input wire [31:0] mem_data_rdata,
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// input wire mem_data_rdata_valid,
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// output reg mem_data_rdata_ready,
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// // instruction memory
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// output axi_inst_ACLK,
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// output axi_inst_ARESETn,
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// output axi_inst_AWVALID,
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// output axi_inst_AWADDR,
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// output [2:0] axi_inst_AWPROT,
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// input axi_inst_AWREADY,
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// output axi_inst_WVALID,
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// output [DATA_WIDTH-1:0] axi_inst_WDATA,
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// output [(DATA_WIDTH/8)-1:0] axi_inst_WSTRB,
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// input axi_inst_WREADY,
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// input axi_inst_BVALID,
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// output axi_inst_BREADY,
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// input [1:0] axi_inst_BRESP,
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// output axi_inst_ARVALID,
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// output axi_inst_ARADDR,
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// output [2:0] axi_inst_ARPROT,
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// input axi_inst_ARREADY,
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// input axi_inst_RVALID,
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// input [DATA_WIDTH-1:0] axi_inst_RDATA,
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// input [1:0] axi_inst_RRESP,
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// output axi_inst_RREADY,
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// data memory
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// output axi_data_ACLK,
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// output axi_data_ARESETn,
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// output axi_data_AWVALID,
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// output axi_data_AWADDR,
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// output [2:0] axi_data_AWPROT,
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// input axi_data_AWREADY,
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// output axi_data_WVALID,
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// output [DATA_WIDTH-1:0] axi_data_WDATA,
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// output [(DATA_WIDTH/8)-1:0] axi_data_WSTRB,
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// input axi_data_WREADY,
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// input axi_data_BVALID,
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// output axi_data_BREADY,
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// input [1:0] axi_data_BRESP,
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// output axi_data_ARVALID,
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// output axi_data_ARADDR,
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// output [2:0] axi_data_ARPROT,
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// input axi_data_ARREADY,
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// input axi_data_RVALID,
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// input [DATA_WIDTH-1:0] axi_data_RDATA,
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// input [1:0] axi_data_RRESP,
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// output axi_data_RREADY,
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output dummy_out
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);
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parameter PIPELINED = 1;
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localparam INST_NOP = 32'h00000013; // nop
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// Register File
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reg [31:0] regfile [0:31];
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initial begin : init_regfile
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integer i;
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for (i=0; i<32; i=i+1) begin
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regfile[i] = 32'h00000000;
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end
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end
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// Registers
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reg [31:0] r_if_pc = 0, r_id_pc, r_ex_pc, r_mem_pc, r_wb_pc;
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reg [31:0] r_id_inst, r_ex_inst, r_mem_inst, r_wb_inst;
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reg r_id_valid=0, r_ex_valid=0, r_mem_valid=0, r_wb_valid=0;
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reg [4:0] r_ex_rs1, r_mem_rs1, r_wb_rs1;
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reg [4:0] r_ex_rs2, r_mem_rs2, r_wb_rs2;
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reg [4:0] r_ex_rd, r_mem_rd, r_wb_rd;
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reg [3:0] r_ex_aluop;
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reg [31:0] r_ex_s1, r_mem_s1;
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reg [31:0] r_ex_s2, r_mem_s2;
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reg [31:0] r_mem_alu_out, r_wb_alu_out;
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reg r_mem_alu_zero;
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reg r_ex_jump, r_mem_jump, r_wb_jump;
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reg r_ex_store, r_mem_store;
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reg r_ex_load, r_mem_load, r_wb_load;
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reg [31:0] r_mem_wdata, r_wb_wdata;
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reg r_ex_branch_pol;
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reg r_ex_branch, r_mem_branch, r_wb_branch;
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reg [31:0] r_ex_immed_btype;
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reg [31:0] r_mem_ra, r_wb_ra;
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reg [31:0] r_wb_load_data;
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// IF
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reg s_if_stall = 0;
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reg [31:0] s_if_next_pc;
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reg [31:0] s_if_inst;
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always @(*) begin
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s_if_stall = s_id_stall;
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if (s_ex_take_branch) begin
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s_if_next_pc = s_ex_branch_addr;
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end else begin
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s_if_next_pc = r_if_pc + 4;
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end
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mem_inst_addr = r_if_pc;
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s_if_inst = mem_inst_data;
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end
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// ID
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reg s_id_stall;
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reg [6:0] s_id_opcode;
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reg [2:0] s_id_funct3;
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reg [6:0] s_id_funct7;
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reg [4:0] s_id_rd, s_id_rs1, s_id_rs2;
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reg [31:0] s_id_immed_itype, s_id_immed_stype, s_id_immed_utype, s_id_immed_btype, s_id_immed_jtype;
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reg [31:0] s_id_s1, s_id_s2;
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reg [3:0] s_id_aluop;
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reg s_id_invalid;
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reg s_id_jump, s_id_branch;
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reg s_id_store, s_id_load;
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reg s_id_branch_pol;
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// RV32I / RV64I / RV32M
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localparam OP_LUI = 7'b0110111,
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OP_AUIPC = 7'b0010111,
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OP_JAL = 7'b1101111,
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OP_JALR = 7'b1100111,
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OP_BRANCH = 7'b1100011,
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OP_LOAD = 7'b0000011,
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OP_STORE = 7'b0100011,
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OP_IMM = 7'b0010011,
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OP_ALU = 7'b0110011,
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OP_FENCE = 7'b0001111,
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OP_SYSTEM = 7'b1110011;
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// RV64M
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// localparam OP_???????? = 7'b0111011;
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// RV32A / RV64A
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// localparam OP_ATOMIC = 7'b0101111;
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// TODO: add opcodes for other extensions
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// ALU OPCODES
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localparam ALUOP_ADD = 4'b0000,
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ALUOP_SUB = 4'b0001,
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ALUOP_XOR = 4'b0010,
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ALUOP_OR = 4'b0011,
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ALUOP_AND = 4'b0100,
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ALUOP_SL = 4'b0101,
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ALUOP_SRL = 4'b0110,
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ALUOP_SRA = 4'b0111,
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ALUOP_SLT = 4'b1000,
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ALUOP_SLTU = 4'b1001;
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always @(*) begin
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s_id_invalid = 0;
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s_id_store = 0;
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s_id_load = 0;
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s_id_opcode = r_id_inst[6:0];
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s_id_rd = r_id_inst[11:7];
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s_id_rs1 = r_id_inst[19:15];
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s_id_rs2 = r_id_inst[24:20];
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s_id_funct3 = r_id_inst[14:12];
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s_id_funct7 = r_id_inst[31:25];
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s_id_immed_itype = {{20{r_id_inst[31]}}, r_id_inst[31:20]};
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s_id_immed_stype = {{20{r_id_inst[31]}}, r_id_inst[31:25], r_id_inst[11:7]};
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s_id_immed_utype = {r_id_inst[31:12], 12'b0};
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s_id_immed_btype = {{19{r_id_inst[31]}}, r_id_inst[31], r_id_inst[7], r_id_inst[30:25], r_id_inst[11:8], 1'b0};
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s_id_immed_jtype = {{11{r_id_inst[31]}}, r_id_inst[31], r_id_inst[19:12], r_id_inst[20], r_id_inst[30:21], 1'b0};
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// default values
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s_id_s1 = 32'hxxxxxxxx;
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s_id_s2 = 32'hxxxxxxxx;
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s_id_jump = 0;
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s_id_branch = 0;
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s_id_branch_pol = 1'bx;
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case (s_id_opcode)
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OP_LUI: begin // LUI
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s_id_s1 = 32'h00000000;
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s_id_s2 = s_id_immed_utype;
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s_id_aluop = ALUOP_ADD;
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end
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OP_AUIPC: begin // AUIPC
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s_id_s1 = r_id_pc;
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s_id_s2 = s_id_immed_utype;
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s_id_aluop = ALUOP_ADD;
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end
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OP_JAL: begin // JAL
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s_id_s1 = r_id_pc;
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s_id_s2 = s_id_immed_jtype;
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s_id_aluop = ALUOP_ADD;
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s_id_jump = 1;
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end
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OP_JALR: begin // JALR
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s_id_s1 = regfile[s_id_rs1];
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s_id_s2 = s_id_immed_itype;
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s_id_aluop = ALUOP_ADD;
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s_id_jump = 1;
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end
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OP_BRANCH: begin
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s_id_s1 = regfile[s_id_rs1];
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s_id_s2 = regfile[s_id_rs2];
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s_id_branch = 1;
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case (s_id_funct3)
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3'b000: begin // BEQ
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s_id_aluop = ALUOP_SUB;
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s_id_branch_pol = 0;
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end
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3'b001: begin // BNE
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s_id_aluop = ALUOP_SUB;
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s_id_branch_pol = 1;
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end
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3'b100: begin // BLT
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s_id_aluop = ALUOP_SLT;
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s_id_branch_pol = 1;
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end
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3'b101: begin // BGE
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s_id_aluop = ALUOP_SLT;
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s_id_branch_pol = 0;
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end
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3'b110: begin // BLTU
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s_id_aluop = ALUOP_SLTU;
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s_id_branch_pol = 1;
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end
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3'b111: begin // BGEU
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s_id_aluop = ALUOP_SLTU;
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s_id_branch_pol = 0;
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end
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default: s_id_invalid = 1;
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endcase
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end
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OP_LOAD: begin
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s_id_load = 1;
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s_id_s1 = regfile[s_id_rs1];
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s_id_s2 = s_id_immed_itype;
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// TODO: finish parsing (byte vs word. For now always assume word)
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end
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OP_STORE: begin
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s_id_store = 1;
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s_id_s1 = regfile[s_id_rs1];
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s_id_s2 = s_id_immed_stype;
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// TODO: finish parsing (byte vs word. For now always assume word)
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end
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OP_IMM: begin
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s_id_s1 = regfile[s_id_rs1];
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s_id_s2 = s_id_immed_itype;
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casex ({s_id_funct3, s_id_funct7})
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10'b000xxxxxxx: s_id_aluop = ALUOP_ADD; // ADDI
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10'b010xxxxxxx: s_id_aluop = ALUOP_SLT; // SLTI
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10'b011xxxxxxx: s_id_aluop = ALUOP_SLTU; // SLTIU
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10'b100xxxxxxx: s_id_aluop = ALUOP_XOR; // XORI
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10'b110xxxxxxx: s_id_aluop = ALUOP_OR; // ORI
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10'b111xxxxxxx: s_id_aluop = ALUOP_AND; // ANDI
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10'b001000000x: s_id_aluop = ALUOP_SL; // SLLI // NOTE: technically s_id_funct7[0] must be 0 however GCC allows shifts of up to 63b despite assembling for 32b. I can tolerate this deviation from ISA spec at essentially no cost
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10'b101000000x: s_id_aluop = ALUOP_SRL; // SRLI // NOTE: technically s_id_funct7[0] must be 0 however GCC allows shifts of up to 63b despite assembling for 32b. I can tolerate this deviation from ISA spec at essentially no cost
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10'b101010000x: s_id_aluop = ALUOP_SRA; // SRAI // NOTE: technically s_id_funct7[0] must be 0 however GCC allows shifts of up to 63b despite assembling for 32b. I can tolerate this deviation from ISA spec at essentially no cost
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default: s_id_invalid = 1;
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endcase
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end
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OP_ALU: begin
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s_id_s1 = regfile[s_id_rs1];
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s_id_s2 = regfile[s_id_rs2];
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case ({s_id_funct3, s_id_funct7})
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10'b0000000000: s_id_aluop = ALUOP_ADD; // ADD
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10'b0000100000: s_id_aluop = ALUOP_SUB; // SUB
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10'b0010000000: s_id_aluop = ALUOP_SL; // SLL
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10'b0100000000: s_id_aluop = ALUOP_SLT; // SLT
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10'b0110000000: s_id_aluop = ALUOP_SLTU; // SLTU
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10'b1000000000: s_id_aluop = ALUOP_XOR; // XOR
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10'b1100000000: s_id_aluop = ALUOP_OR; // OR
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10'b1110000000: s_id_aluop = ALUOP_AND; // AND
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10'b1010000000: s_id_aluop = ALUOP_SRL; // SRL
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10'b1010100000: s_id_aluop = ALUOP_SRA; // SRA
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default: s_id_invalid = 1;
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endcase
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end
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// OP_FENCE: begin
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// end
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// OP_SYSTEM: begin
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// end
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default: begin
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s_id_invalid = 1;
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end
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endcase
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s_id_stall = s_ex_stall ||
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(r_ex_valid && (s_ex_take_branch == 0) &&
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(((r_ex_rd == s_id_rs1) && (s_id_rs1 != 0)) ||
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((r_ex_rd == s_id_rs2) && (s_id_rs2 != 0)))) ||
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(r_mem_valid &&
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(((r_mem_rd == s_id_rs1) && (s_id_rs1 != 0)) ||
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((r_mem_rd == s_id_rs2) && (s_id_rs2 != 0)))) ||
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(r_wb_valid &&
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(((r_wb_rd == s_id_rs1) && (s_id_rs1 != 0)) ||
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((r_wb_rd == s_id_rs2) && (s_id_rs2 != 0))));
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if (s_id_invalid & r_id_valid) begin
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$display("%0t:\tInvalid instruction at PC=0x%h", $time, r_id_pc);
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s_id_aluop = 3'hx;
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end
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end
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// EX
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reg s_ex_stall = 0;
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reg [31:0] s_ex_data1, s_ex_data2;
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reg [31:0] s_ex_alu_out;
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reg s_ex_alu_zero;
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reg s_ex_take_branch;
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reg [31:0] s_ex_branch_addr;
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reg [31:0] s_ex_ra;
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always @(*) begin
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s_ex_stall = s_mem_stall;
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// NOTE: s_ex_data* exist for adding data paths bypassing regfile in the future
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s_ex_data1 = r_ex_s1;
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s_ex_data2 = r_ex_s2;
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case (r_ex_aluop)
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ALUOP_ADD: begin
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s_ex_alu_out = s_ex_data1 + s_ex_data2;
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end
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ALUOP_SUB: begin
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s_ex_alu_out = s_ex_data1 - s_ex_data2;
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end
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ALUOP_XOR: begin
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s_ex_alu_out = s_ex_data1 ^ s_ex_data2;
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end
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ALUOP_OR: begin
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s_ex_alu_out = s_ex_data1 | s_ex_data2;
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end
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ALUOP_AND: begin
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s_ex_alu_out = s_ex_data1 & s_ex_data2;
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end
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ALUOP_SL: begin
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s_ex_alu_out = s_ex_data1 << s_ex_data2[4:0];
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end
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ALUOP_SRL: begin
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s_ex_alu_out = s_ex_data1 >> s_ex_data2[4:0];
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end
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ALUOP_SRA: begin
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s_ex_alu_out = $signed(s_ex_data1) >>> s_ex_data2[4:0];
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end
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ALUOP_SLT: begin
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s_ex_alu_out = $signed(s_ex_data1) < $signed(s_ex_data2);
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end
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ALUOP_SLTU: begin
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s_ex_alu_out = s_ex_data1 < s_ex_data2;
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end
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default: begin
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s_ex_alu_out = 32'hxxxxxxxx;
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end
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endcase
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s_ex_alu_zero = (s_ex_alu_out == 0);
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s_ex_take_branch = r_ex_valid && (r_ex_jump || (r_ex_branch && (s_ex_alu_zero ^ r_ex_branch_pol)));
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s_ex_ra = r_ex_pc + 4;
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if (r_ex_jump) begin
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s_ex_branch_addr = s_ex_alu_out;
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end else begin
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s_ex_branch_addr = r_ex_pc + r_ex_immed_btype;
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end
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end
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// MEM
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reg s_mem_stall = 0;
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reg s_mem_bp;
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reg [31:0] s_mem_load_data;
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always @(*) begin
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s_mem_stall = 0; // TODO: add stall logic when actually reading/writing
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s_mem_bp = 0;
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mem_data_addr = r_mem_alu_out;
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mem_data_wdata = regfile[r_mem_rs2];
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mem_data_wmask = 4'b1111; // TODO: implement smaller writes
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mem_data_we = r_mem_store && r_mem_valid;
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s_mem_load_data = mem_data_rdata; // TODO: implement smaller reads
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end
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// WB
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reg [31:0] s_wb_data;
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reg s_wb_write;
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always @(*) begin
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// load instructions do not use output of alu in wb
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if (r_wb_jump) begin
|
|
s_wb_data = r_wb_ra;
|
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end else if (r_wb_load) begin
|
|
s_wb_data = r_wb_load_data;
|
|
end else begin
|
|
s_wb_data = r_wb_alu_out;
|
|
end
|
|
|
|
// FIXME: always writes!!!
|
|
s_wb_write = (r_wb_branch == 0);
|
|
end
|
|
|
|
// SYS
|
|
|
|
// Register update
|
|
always @(posedge clk) begin: pipeline_update
|
|
integer i;
|
|
if (reset) begin
|
|
r_if_pc <= 32'h00000000;
|
|
|
|
r_id_pc <= 0;
|
|
r_id_inst <= INST_NOP;
|
|
|
|
r_ex_pc <= 0;
|
|
r_ex_inst <= INST_NOP;
|
|
r_ex_rd <= 0;
|
|
r_ex_s1 <= 0;
|
|
r_ex_s2 <= 0;
|
|
r_ex_aluop <= 0;
|
|
r_ex_jump <= 0;
|
|
r_ex_store <= 0;
|
|
r_ex_load <= 0;
|
|
|
|
r_mem_pc <= 0;
|
|
r_mem_inst <= INST_NOP;
|
|
r_mem_rd <= 0;
|
|
r_mem_s1 <= 0;
|
|
r_mem_s2 <= 0;
|
|
r_mem_alu_out <= 0;
|
|
r_mem_alu_zero <= 0;
|
|
r_mem_store <= 0;
|
|
r_mem_load <= 0;
|
|
|
|
r_wb_pc <= 0;
|
|
r_wb_inst <= INST_NOP;
|
|
r_wb_rd <= 0;
|
|
|
|
for (i=1; i<32; i=i+1) begin
|
|
regfile[i] <= 0;
|
|
end
|
|
|
|
end else begin
|
|
// IF
|
|
if (!s_if_stall) begin
|
|
r_if_pc <= s_if_next_pc;
|
|
end
|
|
|
|
// ID
|
|
if (!s_id_stall) begin
|
|
r_id_pc <= r_if_pc;
|
|
r_id_inst <= s_if_inst;
|
|
r_id_valid <= ~(s_ex_take_branch && r_ex_valid);
|
|
end
|
|
|
|
// EX
|
|
if (!s_ex_stall) begin
|
|
r_ex_pc <= r_id_pc;
|
|
r_ex_inst <= r_id_inst;
|
|
r_ex_rs1 <= s_id_rs1;
|
|
r_ex_rs2 <= s_id_rs2;
|
|
r_ex_rd <= s_id_rd;
|
|
r_ex_s1 <= s_id_s1;
|
|
r_ex_s2 <= s_id_s2;
|
|
r_ex_aluop <= s_id_aluop;
|
|
r_ex_jump <= s_id_jump;
|
|
r_ex_branch <= s_id_branch;
|
|
r_ex_store <= s_id_store;
|
|
r_ex_load <= s_id_load;
|
|
r_ex_valid <= r_id_valid && ~(s_ex_take_branch && r_ex_valid) && ~(s_id_stall && r_id_valid);
|
|
r_ex_branch_pol <= s_id_branch_pol;
|
|
r_ex_immed_btype <= s_id_immed_btype;
|
|
end
|
|
|
|
|
|
// MEM
|
|
if (!s_mem_stall) begin
|
|
r_mem_pc <= r_ex_pc;
|
|
r_mem_inst <= r_ex_inst;
|
|
r_mem_rs1 <= r_ex_rs1;
|
|
r_mem_rs2 <= r_ex_rs2;
|
|
r_mem_rd <= r_ex_rd;
|
|
r_mem_s1 <= r_ex_s1;
|
|
r_mem_s2 <= r_ex_s2;
|
|
r_mem_alu_out <= s_ex_alu_out;
|
|
r_mem_alu_zero <= s_ex_alu_zero;
|
|
r_mem_store <= r_ex_store;
|
|
r_mem_load <= r_ex_load;
|
|
r_mem_valid <= r_ex_valid;
|
|
r_mem_branch <= r_ex_branch;
|
|
r_mem_ra <= s_ex_ra;
|
|
r_mem_jump <= r_ex_jump;
|
|
end
|
|
|
|
// WB
|
|
if (1) begin
|
|
r_wb_pc <= r_mem_pc;
|
|
r_wb_inst <= r_mem_inst;
|
|
r_wb_rs1 <= r_mem_rs1;
|
|
r_wb_rs2 <= r_mem_rs2;
|
|
r_wb_rd <= r_mem_rd;
|
|
r_wb_alu_out <= r_mem_alu_out;
|
|
r_wb_valid <= r_mem_valid;
|
|
r_wb_branch <= r_mem_branch;
|
|
r_wb_ra <= r_mem_ra;
|
|
r_wb_jump <= r_mem_jump;
|
|
r_wb_load <= r_mem_load;
|
|
r_wb_load_data <= s_mem_load_data;
|
|
end
|
|
|
|
// Register File
|
|
// TODO: should I write if s_wb_stall=1?
|
|
if (r_wb_rd != 0 && s_wb_write && r_wb_valid) begin
|
|
regfile[r_wb_rd] <= s_wb_data;
|
|
$display("%0t:\tPC=0x%h\tx%02d=0x%h", $time, r_id_pc, r_wb_rd, s_wb_data);
|
|
end
|
|
end
|
|
end
|
|
|
|
assign dummy_out = s_wb_data[0];
|
|
|
|
endmodule |