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Topic starter 01/09/2025 12:09 am
```verilog
// CISC CPU - High Performance Multi-threaded and Single-threaded
module cisc_cpu (
input wire clk,
input wire rst_n,
input wire [31:0] instruction_fetch,
input wire [31:0] data_read,
output reg [31:0] instruction_output,
output reg [31:0] data_write,
output reg mem_we,
output reg mem_re,
output reg [31:0] pc_out
);
// CPU State Machine
reg [2:0] cpu_state;
localparam IDLE = 3'b000;
localparam FETCH = 3'b001;
localparam DECODE = 3'b010;
localparam EXECUTE = 3'b011;
localparam MEMORY = 3'b100;
localparam WRITEBACK = 3'b101;
localparam THREAD_SWITCH = 3'b110;
// Thread Management
reg [1:0] current_thread;
reg [1:0] next_thread;
reg thread_active[0:3];
reg thread_context_switch[0:3];
reg [31:0] thread_pc[0:3];
reg [31:0] thread_regs[0:3][15:0]; // 16 registers per thread
reg [31:0] thread_flags[0:3];
// Core Registers
reg [31:0] pc;
reg [31:0] instruction;
reg [31:0] operand1, operand2, result;
reg [31:0] stack_ptr;
reg [31:0] program_counter;
reg [31:0] base_pointer;
reg [31:0] accumulator;
// Control signals
reg [3:0] alu_op;
reg [3:0] memory_op;
reg [3:0] branch_cond;
reg [3:0] reg_write_enable;
reg [3:0] mem_read_enable;
reg [3:0] mem_write_enable;
reg [1:0] thread_select;
// Status flags
reg zero_flag;
reg carry_flag;
reg sign_flag;
reg overflow_flag;
// Performance counters
reg [31:0] instruction_count;
reg [31:0] cycle_count;
reg [31:0] thread_switch_count;
// Instruction decode signals
reg is_branch;
reg is_jump;
reg is_call;
reg is_return;
reg is_load;
reg is_store;
reg is_arithmetic;
reg is_logic;
reg is_shift;
// Multi-threading control
reg multi_threading_enabled;
reg thread_scheduler_active;
reg [3:0] active_threads;
// ALU Operations
localparam ALU_ADD = 4'b0000;
localparam ALU_SUB = 4'b0001;
localparam ALU_MUL = 4'b0010;
localparam ALU_DIV = 4'b0011;
localparam ALU_AND = 4'b0100;
localparam ALU_OR = 4'b0101;
localparam ALU_XOR = 4'b0110;
localparam ALU_SHL = 4'b0111;
localparam ALU_SHR = 4'b1000;
localparam ALU_CMP = 4'b1001;
// Memory operations
localparam MEM_READ = 4'b0001;
localparam MEM_WRITE = 4'b0010;
localparam MEM_INC = 4'b0100;
localparam MEM_DEC = 4'b1000;
// Branch conditions
localparam BRANCH_EQ = 4'b0001;
localparam BRANCH_NE = 4'b0010;
localparam BRANCH_LT = 4'b0100;
localparam BRANCH_GT = 4'b1000;
// Thread context structure
reg [31:0] thread_context[0:3][16:0]; // PC + 16 registers
// Pipeline stages
reg [31:0] fetch_stage_pc;
reg [31:0] decode_stage_instruction;
reg [31:0] execute_stage_result;
reg [31:0] memory_stage_address;
reg [31:0] writeback_stage_data;
// Performance optimization flags
reg pipeline_flush;
reg branch_prediction_valid;
reg branch_prediction_taken;
reg [31:0] branch_prediction_target;
// Instruction cache for performance
reg [31:0] instruction_cache[0:255];
reg instruction_cache_valid[0:255];
reg [7:0] cache_index;
// Main CPU process
always @(posedge clk or negedge rst_n) begin
if (!rst_n) begin
// Reset all registers
cpu_state <= IDLE;
pc <= 32'h00000000;
instruction <= 32'h00000000;
operand1 <= 32'h00000000;
operand2 <= 32'h00000000;
result <= 32'h00000000;
// Initialize thread management
current_thread <= 2'b00;
next_thread <= 2'b00;
multi_threading_enabled <= 1'b1;
active_threads <= 4'b0001;
// Initialize threads
for (int i = 0; i < 4; i = i + 1) begin
thread_active[i] <= 1'b0;
thread_context_switch[i] <= 1'b0;
thread_pc[i] <= 32'h00000000;
end
// Initialize performance counters
instruction_count <= 32'h00000000;
cycle_count <= 32'h00000000;
thread_switch_count <= 32'h00000000;
// Initialize flags
zero_flag <= 1'b0;
carry_flag <= 1'b0;
sign_flag <= 1'b0;
overflow_flag <= 1'b0;
// Initialize control signals
alu_op <= 4'b0000;
memory_op <= 4'b0000;
branch_cond <= 4'b0000;
reg_write_enable <= 4'b0000;
mem_read_enable <= 4'b0000;
mem_write_enable <= 4'b0000;
// Initialize pipeline registers
fetch_stage_pc <= 32'h00000000;
decode_stage_instruction <= 32'h00000000;
execute_stage_result <= 32'h00000000;
memory_stage_address <= 32'h00000000;
writeback_stage_data <= 32'h00000000;
// Initialize pipeline control
pipeline_flush <= 1'b0;
branch_prediction_valid <= 1'b0;
branch_prediction_taken <= 1'b0;
branch_prediction_target <= 32'h00000000;
// Clear cache
for (int i = 0; i < 256; i = i + 1) begin
instruction_cache_valid[i] <= 1'b0;
end
pc_out <= 32'h00000000;
end else begin
// Update cycle counter
cycle_count <= cycle_count + 1;
// Pipeline control
case (cpu_state)
IDLE: begin
if (multi_threading_enabled && active_threads > 1) begin
cpu_state <= THREAD_SWITCH;
end else begin
cpu_state <= FETCH;
end
end
FETCH: begin
fetch_stage_pc <= pc;
instruction <= instruction_fetch;
decode_stage_instruction <= instruction_fetch;
cpu_state <= DECODE;
end
DECODE: begin
// Decode instruction and set up control signals
decode_instruction();
cpu_state <= EXECUTE;
end
EXECUTE: begin
execute_operation();
cpu_state <= MEMORY;
end
MEMORY: begin
memory_operation();
cpu_state <= WRITEBACK;
end
WRITEBACK: begin
writeback_operation();
cpu_state <= IDLE;
// Increment instruction counter
instruction_count <= instruction_count + 1;
// Update PC for next instruction
pc <= pc + 4;
end
THREAD_SWITCH: begin
thread_switch_operation();
cpu_state <= FETCH;
end
default: cpu_state <= IDLE;
endcase
// Update PC output
pc_out <= pc;
// Update instruction output for debugging
instruction_output <= instruction;
// Update data write output
data_write <= execute_stage_result;
end
end
// Instruction decode logic
task decode_instruction();
begin
// Simple instruction decoding for CISC
case (instruction[31:24])
8'h00: begin // NOP
is_branch <= 1'b0;
is_jump <= 1'b0;
is_load <= 1'b0;
is_store <= 1'b0;
is_arithmetic <= 1'b0;
alu_op <= ALU_ADD;
end
8'h01: begin // MOV
is_branch <= 1'b0;
is_jump <= 1'b0;
is_load <= 1'b0;
is_store <= 1'b0;
is_arithmetic <= 1'b0;
alu_op <= ALU_ADD; // Simple move operation
end
8'h02: begin // ADD
is_branch <= 1'b0;
is_jump <= 1'b0;
is_load <= 1'b0;
is_store <= 1'b0;
is_arithmetic <= 1'b1;
alu_op <= ALU_ADD;
end
8'h03: begin // SUB
is_branch <= 1'b0;
is_jump <= 1'b0;
is_load <= 1'b0;
is_store <= 1'b0;
is_arithmetic <= 1'b1;
alu_op <= ALU_SUB;
end
8'h04: begin // MUL
is_branch <= 1'b0;
is_jump <= 1'b0;
is_load <= 1'b0;
is_store <= 1'b0;
is_arithmetic <= 1'b1;
alu_op <= ALU_MUL;
end
8'h05: begin // DIV
is_branch <= 1'b0;
is_jump <= 1'b0;
is_load <= 1'b0;
is_store <= 1'b0;
is_arithmetic <= 1'b1;
alu_op <= ALU_DIV;
end
8'h06: begin // AND
is_branch <= 1'b0;
is_jump <= 1'b0;
is_load <= 1'b0;
is_store <= 1'b0;
is_logic <= 1'b1;
alu_op <= ALU_AND;
end
8'h07: begin // OR
is_branch <= 1'b0;
is_jump <= 1'b0;
is_load <= 1'b0;
is_store <= 1'b0;
is_logic <= 1'b1;
alu_op <= ALU_OR;
end
8'h08: begin // XOR
is_branch <= 1'b0;
is_jump <= 1'b0;
is_load <= 1'b0;
is_store <= 1'b0;
is_logic <= 1'b1;
alu_op <= ALU_XOR;
end
8'h09: begin // JMP
is_branch <= 1'b0;
is_jump <= 1'b1;
is_load <= 1'b0;
is_store <= 1'b0;
is_arithmetic <= 1'b0;
alu_op <= ALU_ADD; // Jump operation
end
8'h0A: begin // CALL
is_branch <= 1'b0;
is_jump <= 1'b0;
is_call <= 1'b1;
is_load <= 1'b0;
is_store <= 1'b0;
is_arithmetic <= 1'b0;
alu_op <= ALU_ADD; // Call operation
end
8'h0B: begin // RET
is_branch <= 1'b0;
is_jump <= 1'b0;
is_return <= 1'b1;
is_load <= 1'b0;
is_store <= 1'b0;
is_arithmetic <= 1'b0;
alu_op <= ALU_ADD; // Return operation
end
8'h0C: begin // CMP
is_branch <= 1'b0;
is_jump <= 1'b0;
is_load <= 1'b0;
is_store <= 1'b0;
is_arithmetic <= 1'b1;
alu_op <= ALU_CMP;
end
default: begin
is_branch <= 1'b0;
is_jump <= 1'b0;
is_load <= 1'b0;
is_store <= 1'b0;
is_arithmetic <= 1'b0;
alu_op <= ALU_ADD;
end
endcase
end
endtask
// Execute operation logic
task execute_operation();
begin
// Perform ALU operations based on instruction type
case (alu_op)
ALU_ADD: result <= operand1 + operand2;
ALU_SUB: result <= operand1 - operand2;
ALU_MUL: result <= operand1 * operand2;
ALU_DIV: result <= operand2 != 0 ? operand1 / operand2 : 32'h00000000;
ALU_AND: result <= operand1 & operand2;
ALU_OR: result <= operand1 | operand2;
ALU_XOR: result <= operand1 ^ operand2;
ALU_SHL: result <= operand1 << operand2[4:0];
ALU_SHR: result <= operand1 >> operand2[4:0];
ALU_CMP: begin
result <= operand1 - operand2;
zero_flag <= (result == 32'h00000000);
sign_flag <= result[31];
// Set carry and overflow flags as needed
end
default: result <= operand1;
endcase
execute_stage_result <= result;
end
endtask
// Memory operation logic
task memory_operation();
begin
if (is_load) begin
mem_re <= 1'b1;
mem_we <= 1'b0;
memory_stage_address <= result;
end else if (is_store) begin
mem_re <= 1'b0;
mem_we <= 1'b1;
memory_stage_address <= result;
end else begin
mem_re <= 1'b0;
mem_we <= 1'b0;
end
end
endtask
// Writeback operation logic
task writeback_operation();
begin
// Handle register writes based on instruction type
if (reg_write_enable != 4'b0000) begin
// Write result to appropriate register
thread_regs[current_thread][0] <= result; // Example: write to R0
end
// Handle memory operations
if (mem_write_enable != 4'b0000 && mem_we) begin
// Memory write operation would be handled by memory controller
end
end
endtask
// Thread switching logic
task thread_switch_operation();
begin
if (multi_threading_enabled && active_threads > 1) begin
// Simple round-robin thread switching
next_thread <= (current_thread + 1) % 4;
// Switch to next thread
current_thread <= next_thread;
// Update PC for new thread
pc <= thread_pc[next_thread];
// Increment thread switch counter
thread_switch_count <= thread_switch_count + 1;
end else begin
cpu_state <= FETCH;
end
end
endtask
// Multi-threading control logic
always @(posedge clk or negedge rst_n) begin
if (!rst_n) begin
thread_scheduler_active <= 1'b0;
active_threads <= 4'b0001;
end else begin
// Simple thread scheduler logic
if (multi_threading_enabled) begin
thread_scheduler_active <= 1'b1;
// Update active threads based on some scheduling criteria
// This is a simplified example - in reality, this would be more complex
active_threads <= active_threads | 4'b0001; // Always keep at least one thread active
end else begin
thread_scheduler_active <= 1'b0;
end
end
end
// Performance optimization logic
always @(posedge clk or negedge rst_n) begin
if (!rst_n) begin
pipeline_flush <= 1'b0;
branch_prediction_valid <= 1'b0;
branch_prediction_taken <= 1'b0;
end else begin
// Simple branch prediction
if (is_branch && branch_prediction_valid) begin
if (branch_prediction_taken) begin
pc <= branch_prediction_target;
end
end
// Flush pipeline on certain conditions
if (pipeline_flush) begin
pipeline_flush <= 1'b0;
// Clear pipeline registers
end
end
end
// Instruction cache logic
always @(posedge clk or negedge rst_n) begin
if (!rst_n) begin
cache_index <= 8'h00;
end else begin
// Simple instruction cache update logic
if (cpu_state == FETCH) begin
cache_index <= pc[7:0]; // Use PC low bits as cache index
instruction_cache[cache_index] <= instruction;
instruction_cache_valid[cache_index] <= 1'b1;
end
end
end
// Performance monitoring
always @(posedge clk or negedge rst_n) begin
if (!rst_n) begin
// Reset performance counters
end else begin
// Monitor and report performance statistics
// This would be expanded in a real implementation
end
end
// Output assignments
assign mem_we = mem_write_enable[0];
assign mem_re = mem_read_enable[0];
endmodule
// Example usage of the CPU module
/*
module test_cpu;
reg clk, rst_n;
wire [31:0] pc_out;
wire [31:0] instruction_output;
wire [31:0] data_write;
wire mem_we, mem_re;
cpu_inst uut (
.clk(clk),
.rst_n(rst_n),
.pc_out(pc_out),
.instruction_output(instruction_output),
.data_write(data_write),
.mem_we(mem_we),
.mem_re(mem_re)
);
// Testbench code would go here
endmodule
*/
