/*
 *  PicoRV32 -- A Small RISC-V (RV32I) Processor Core
 *
 *  Copyright (C) 2015  Clifford Wolf <clifford@clifford.at>
 *  
 *  Permission to use, copy, modify, and/or distribute this software for any
 *  purpose with or without fee is hereby granted, provided that the above
 *  copyright notice and this permission notice appear in all copies.
 *  
 *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */

`timescale 1 ns / 1 ps
// `define DEBUG


/***************************************************************
 * picorv32
 ***************************************************************/

module picorv32 #(
	parameter ENABLE_COUNTERS = 1,
	parameter ENABLE_REGS_16_31 = 1
) (
	input clk, resetn,
	output reg trap,

	output reg        mem_valid,
	output reg        mem_instr,
	input             mem_ready,

	output reg [31:0] mem_addr,
	output reg [31:0] mem_wdata,
	output reg [ 3:0] mem_wstrb,
	input      [31:0] mem_rdata
);
	localparam integer regfile_size = ENABLE_REGS_16_31 ? 32 : 16;
	localparam integer regindex_bits = ENABLE_REGS_16_31 ? 5 : 4;

	reg [63:0] count_cycle, count_instr;
	reg [31:0] reg_pc, reg_op1, reg_op2, reg_out;
	reg [31:0] cpuregs [0:regfile_size-1];
	reg [4:0] reg_sh;

	wire reg_out_0 = reg_out[0];


	// Memory Interface

	reg [1:0] mem_state;
	reg [1:0] mem_wordsize;
	reg [31:0] mem_buffer;
	reg mem_do_prefetch;
	reg mem_do_rinst;
	reg mem_do_rdata;
	reg mem_do_wdata;
	reg mem_done;

	wire mem_busy = |{mem_do_prefetch, mem_do_rinst, mem_do_rdata, mem_do_wdata};

	always @(posedge clk) begin
		mem_done <= 0;
		if (!resetn) begin
			mem_state <= 0;
			mem_valid <= 0;
		end else case (mem_state)
			0: begin
				if (mem_do_rinst || mem_do_prefetch) begin
					mem_valid <= 1;
					mem_addr <= mem_do_prefetch ? reg_pc + 4 : reg_pc;
					mem_instr <= 1;
					mem_wstrb <= 0;
					mem_state <= 1;
				end
				if (mem_do_rdata) begin
					mem_valid <= 1;
					mem_addr <= {reg_op1[31:2], 2'b00};
					mem_instr <= 0;
					mem_wstrb <= 0;
					mem_state <= 1;
				end
				if (mem_do_wdata) begin
					mem_valid <= 1;
					mem_addr <= {reg_op1[31:2], 2'b00};
					mem_instr <= 0;
					(* full_case *)
					case (mem_wordsize)
						0: begin
							mem_wdata <= reg_op2;
							mem_wstrb <= 4'b1111;
						end
						1: begin
							mem_wdata <= {2{reg_op2[15:0]}};
							mem_wstrb <= reg_op1[1] ? 4'b1100 : 4'b0011;
						end
						2: begin
							mem_wdata <= {4{reg_op2[7:0]}};
							mem_wstrb <= 4'b0001 << reg_op1[1:0];
						end
					endcase
					mem_state <= 2;
				end
			end
			1: begin
				if (mem_ready) begin
					(* full_case *)
					case (mem_wordsize)
						0: begin
							mem_buffer <= mem_rdata;
						end
						1: begin
							case (reg_op1[1])
								1'b0: mem_buffer <= mem_rdata[15: 0];
								1'b1: mem_buffer <= mem_rdata[31:16];
							endcase
						end
						2: begin
							case (reg_op1[1:0])
								2'b00: mem_buffer <= mem_rdata[ 7: 0];
								2'b01: mem_buffer <= mem_rdata[15: 8];
								2'b10: mem_buffer <= mem_rdata[23:16];
								2'b11: mem_buffer <= mem_rdata[31:24];
							endcase
						end
					endcase
					mem_valid <= 0;
					mem_state <= 3;
					mem_done <= mem_do_rinst || mem_do_rdata;
				end
			end
			2: begin
				if (mem_ready) begin
					mem_valid <= 0;
					mem_state <= 3;
					mem_done <= 1;
				end
			end
			3: begin
				if (mem_done)
					mem_state <= 0;
				else if (mem_do_rinst || mem_do_rdata)
					mem_done <= 1;
			end
		endcase
	end


	// Instruction Decoder

	reg instr_lui, instr_auipc, instr_jal, instr_jalr;
	reg instr_beq, instr_bne, instr_blt, instr_bge, instr_bltu, instr_bgeu;
	reg instr_lb, instr_lh, instr_lw, instr_lbu, instr_lhu, instr_sb, instr_sh, instr_sw;
	reg instr_addi, instr_slti, instr_sltiu, instr_xori, instr_ori, instr_andi, instr_slli, instr_srli, instr_srai;
	reg instr_add, instr_sub, instr_sll, instr_slt, instr_sltu, instr_xor, instr_srl, instr_sra, instr_or, instr_and;
	reg instr_fence, instr_rdcycle, instr_rdcycleh, instr_rdinstr, instr_rdinstrh;
	wire instr_trap;

	reg [regindex_bits-1:0] decoded_rd, decoded_rs1, decoded_rs2;
	reg [31:0] decoded_imm;
	reg decoder_trigger;

	wire [31:0] decoded_imm_uj;
	assign { decoded_imm_uj[31:20], decoded_imm_uj[10:1], decoded_imm_uj[11], decoded_imm_uj[19:12], decoded_imm_uj[0] } = $signed({mem_buffer[31:12], 1'b0});

	reg is_lui_auipc_jal;
	reg is_lb_lh_lw_lbu_lhu;
	reg is_slli_srli_srai;
	reg is_jalr_addi_slti_sltiu_xori_ori_andi;
	reg is_sb_sh_sw;
	reg is_sll_srl_sra;
	reg is_lui_auipc_jal_jalr_addi_add;
	reg is_slti_blt_slt;
	reg is_sltiu_bltu_sltu;
	reg is_beq_bne_blt_bge_bltu_bgeu;
	reg is_lbu_lhu_lw;

	always @(posedge clk) begin
		is_lui_auipc_jal <= |{instr_lui, instr_auipc, instr_jal};
		is_lb_lh_lw_lbu_lhu <= |{instr_lb, instr_lh, instr_lw, instr_lbu, instr_lhu};
		is_slli_srli_srai <= |{instr_slli, instr_srli, instr_srai};
		is_jalr_addi_slti_sltiu_xori_ori_andi <= |{instr_jalr, instr_addi, instr_slti, instr_sltiu, instr_xori, instr_ori, instr_andi};
		is_sb_sh_sw <= |{instr_sb, instr_sh, instr_sw};
		is_sll_srl_sra <= |{instr_sll, instr_srl, instr_sra};
		is_lui_auipc_jal_jalr_addi_add <= |{instr_lui, instr_auipc, instr_jal, instr_jalr, instr_addi, instr_add};
		is_slti_blt_slt <= |{instr_slti, instr_blt, instr_slt};
		is_sltiu_bltu_sltu <= |{instr_sltiu, instr_bltu, instr_sltu};
		is_beq_bne_blt_bge_bltu_bgeu <= |{instr_beq, instr_bne, instr_blt, instr_bge, instr_bltu, instr_bgeu};
		is_lbu_lhu_lw <= |{instr_lbu, instr_lhu, instr_lw};
	end

	assign instr_trap = ~|{instr_lui, instr_auipc, instr_jal, instr_jalr,
			instr_beq, instr_bne, instr_blt, instr_bge, instr_bltu, instr_bgeu,
			instr_lb, instr_lh, instr_lw, instr_lbu, instr_lhu, instr_sb, instr_sh, instr_sw,
			instr_addi, instr_slti, instr_sltiu, instr_xori, instr_ori, instr_andi, instr_slli, instr_srli, instr_srai,
			instr_add, instr_sub, instr_sll, instr_slt, instr_sltu, instr_xor, instr_srl, instr_sra, instr_or, instr_and,
			instr_fence, instr_rdcycle, instr_rdcycleh, instr_rdinstr, instr_rdinstrh};
	
	reg [63:0] instruction;

	always @* begin
		instruction = 'bx;
		if (instr_lui)      instruction = "lui";
		if (instr_auipc)    instruction = "auipc";
		if (instr_jal)      instruction = "jal";
		if (instr_jalr)     instruction = "jalr";

		if (instr_beq)      instruction = "beq";
		if (instr_bne)      instruction = "bne";
		if (instr_blt)      instruction = "blt";
		if (instr_bge)      instruction = "bge";
		if (instr_bltu)     instruction = "bltu";
		if (instr_bgeu)     instruction = "bgeu";

		if (instr_lb)       instruction = "lb";
		if (instr_lh)       instruction = "lh";
		if (instr_lw)       instruction = "lw";
		if (instr_lbu)      instruction = "lbu";
		if (instr_lhu)      instruction = "lhu";
		if (instr_sb)       instruction = "sb";
		if (instr_sh)       instruction = "sh";
		if (instr_sw)       instruction = "sw";

		if (instr_addi)     instruction = "addi";
		if (instr_slti)     instruction = "slti";
		if (instr_sltiu)    instruction = "sltiu";
		if (instr_xori)     instruction = "xori";
		if (instr_ori)      instruction = "ori";
		if (instr_andi)     instruction = "andi";
		if (instr_slli)     instruction = "slli";
		if (instr_srli)     instruction = "srli";
		if (instr_srai)     instruction = "srai";

		if (instr_add)      instruction = "add";
		if (instr_sub)      instruction = "sub";
		if (instr_sll)      instruction = "sll";
		if (instr_slt)      instruction = "slt";
		if (instr_sltu)     instruction = "sltu";
		if (instr_xor)      instruction = "xor";
		if (instr_srl)      instruction = "srl";
		if (instr_sra)      instruction = "sra";
		if (instr_or)       instruction = "or";
		if (instr_and)      instruction = "and";

		if (instr_fence)    instruction = "fence";
		if (instr_rdcycle)  instruction = "rdcycle";
		if (instr_rdcycleh) instruction = "rdcycleh";
		if (instr_rdinstr)  instruction = "rdinstr";
		if (instr_rdinstrh) instruction = "rdinstrh";
	end

	always @(posedge clk) begin
		decoder_trigger <= 0;

		if (mem_do_rinst && mem_done) begin
			instr_lui   <= mem_buffer[6:0] == 7'b0110111;
			instr_auipc <= mem_buffer[6:0] == 7'b0010111;

			instr_jal   <= mem_buffer[6:0] == 7'b1101111;
			instr_jalr  <= mem_buffer[6:0] == 7'b1100111;

			instr_beq   <= mem_buffer[6:0] == 7'b1100011 && mem_buffer[14:12] == 3'b000;
			instr_bne   <= mem_buffer[6:0] == 7'b1100011 && mem_buffer[14:12] == 3'b001;
			instr_blt   <= mem_buffer[6:0] == 7'b1100011 && mem_buffer[14:12] == 3'b100;
			instr_bge   <= mem_buffer[6:0] == 7'b1100011 && mem_buffer[14:12] == 3'b101;
			instr_bltu  <= mem_buffer[6:0] == 7'b1100011 && mem_buffer[14:12] == 3'b110;
			instr_bgeu  <= mem_buffer[6:0] == 7'b1100011 && mem_buffer[14:12] == 3'b111;

			instr_lb    <= mem_buffer[6:0] == 7'b0000011 && mem_buffer[14:12] == 3'b000;
			instr_lh    <= mem_buffer[6:0] == 7'b0000011 && mem_buffer[14:12] == 3'b001;
			instr_lw    <= mem_buffer[6:0] == 7'b0000011 && mem_buffer[14:12] == 3'b010;
			instr_lbu   <= mem_buffer[6:0] == 7'b0000011 && mem_buffer[14:12] == 3'b100;
			instr_lhu   <= mem_buffer[6:0] == 7'b0000011 && mem_buffer[14:12] == 3'b101;

			instr_sb    <= mem_buffer[6:0] == 7'b0100011 && mem_buffer[14:12] == 3'b000;
			instr_sh    <= mem_buffer[6:0] == 7'b0100011 && mem_buffer[14:12] == 3'b001;
			instr_sw    <= mem_buffer[6:0] == 7'b0100011 && mem_buffer[14:12] == 3'b010;

			instr_addi  <= mem_buffer[6:0] == 7'b0010011 && mem_buffer[14:12] == 3'b000;
			instr_slti  <= mem_buffer[6:0] == 7'b0010011 && mem_buffer[14:12] == 3'b010;
			instr_sltiu <= mem_buffer[6:0] == 7'b0010011 && mem_buffer[14:12] == 3'b011;
			instr_xori  <= mem_buffer[6:0] == 7'b0010011 && mem_buffer[14:12] == 3'b100;
			instr_ori   <= mem_buffer[6:0] == 7'b0010011 && mem_buffer[14:12] == 3'b110;
			instr_andi  <= mem_buffer[6:0] == 7'b0010011 && mem_buffer[14:12] == 3'b111;

			instr_slli  <= mem_buffer[6:0] == 7'b0010011 && mem_buffer[14:12] == 3'b001 && mem_buffer[31:25] == 7'b0000000;
			instr_srli  <= mem_buffer[6:0] == 7'b0010011 && mem_buffer[14:12] == 3'b101 && mem_buffer[31:25] == 7'b0000000;
			instr_srai  <= mem_buffer[6:0] == 7'b0010011 && mem_buffer[14:12] == 3'b101 && mem_buffer[31:25] == 7'b0100000;

			instr_add   <= mem_buffer[6:0] == 7'b0110011 && mem_buffer[14:12] == 3'b000 && mem_buffer[31:25] == 7'b0000000;
			instr_sub   <= mem_buffer[6:0] == 7'b0110011 && mem_buffer[14:12] == 3'b000 && mem_buffer[31:25] == 7'b0100000;
			instr_sll   <= mem_buffer[6:0] == 7'b0110011 && mem_buffer[14:12] == 3'b001 && mem_buffer[31:25] == 7'b0000000;
			instr_slt   <= mem_buffer[6:0] == 7'b0110011 && mem_buffer[14:12] == 3'b010 && mem_buffer[31:25] == 7'b0000000;
			instr_sltu  <= mem_buffer[6:0] == 7'b0110011 && mem_buffer[14:12] == 3'b011 && mem_buffer[31:25] == 7'b0000000;
			instr_xor   <= mem_buffer[6:0] == 7'b0110011 && mem_buffer[14:12] == 3'b100 && mem_buffer[31:25] == 7'b0000000;
			instr_srl   <= mem_buffer[6:0] == 7'b0110011 && mem_buffer[14:12] == 3'b101 && mem_buffer[31:25] == 7'b0000000;
			instr_sra   <= mem_buffer[6:0] == 7'b0110011 && mem_buffer[14:12] == 3'b101 && mem_buffer[31:25] == 7'b0100000;
			instr_or    <= mem_buffer[6:0] == 7'b0110011 && mem_buffer[14:12] == 3'b110 && mem_buffer[31:25] == 7'b0000000;
			instr_and   <= mem_buffer[6:0] == 7'b0110011 && mem_buffer[14:12] == 3'b111 && mem_buffer[31:25] == 7'b0000000;

			instr_fence <= (mem_buffer[6:0] == 7'b0001111 && mem_buffer[19:12] == 0 && mem_buffer[31:28] == 4'b0000) ||
			               (mem_buffer[6:0] == 7'b0001111 && mem_buffer[31:12] == 1);

			instr_rdcycle  <= ((mem_buffer[6:0] == 7'b1110011 && mem_buffer[31:12] == 'b11000000000000000010) ||
			                   (mem_buffer[6:0] == 7'b1110011 && mem_buffer[31:12] == 'b11000000000100000010)) && ENABLE_COUNTERS;
			instr_rdcycleh <= ((mem_buffer[6:0] == 7'b1110011 && mem_buffer[31:12] == 'b11001000000000000010) ||
			                   (mem_buffer[6:0] == 7'b1110011 && mem_buffer[31:12] == 'b11001000000100000010)) && ENABLE_COUNTERS;
			instr_rdinstr  <= (mem_buffer[6:0] == 7'b1110011 && mem_buffer[31:12] == 'b11000000001000000010) && ENABLE_COUNTERS;
			instr_rdinstrh <= (mem_buffer[6:0] == 7'b1110011 && mem_buffer[31:12] == 'b11001000001000000010) && ENABLE_COUNTERS;

			decoded_rd <= mem_buffer[11:7];
			decoded_rs1 <= mem_buffer[19:15];
			decoded_rs2 <= mem_buffer[24:20];

			decoder_trigger <= 1;
		end

		if (decoder_trigger) begin
			(* parallel_case *)
			case (1'b1)
				|{instr_lui, instr_auipc}:
					decoded_imm <= mem_buffer[31:12] << 12;
				instr_jal:
					decoded_imm <= decoded_imm_uj;
				instr_jalr:
					decoded_imm <= $signed(mem_buffer[31:20]);
				|{instr_beq, instr_bne, instr_blt, instr_bge, instr_bltu, instr_bgeu}:
					decoded_imm <= $signed({mem_buffer[31], mem_buffer[7], mem_buffer[30:25], mem_buffer[11:8], 1'b0});
				|{instr_lb, instr_lh, instr_lw, instr_lbu, instr_lhu}:
					decoded_imm <= $signed(mem_buffer[31:20]);
				|{instr_sb, instr_sh, instr_sw}:
					decoded_imm <= $signed({mem_buffer[31:25], mem_buffer[11:7]});
				|{instr_addi, instr_slti, instr_sltiu, instr_xori, instr_ori, instr_andi}:
					decoded_imm <= $signed(mem_buffer[31:20]);
				default:
					decoded_imm <= 1'bx;
			endcase
		end
	end


	// Main State Machine

	localparam cpu_state_fetch  = 0;
	localparam cpu_state_ld_rs1 = 1;
	localparam cpu_state_ld_rs2 = 2;
	localparam cpu_state_exec   = 3;
	localparam cpu_state_shift  = 4;
	localparam cpu_state_store  = 5;
	localparam cpu_state_stmem  = 6;
	localparam cpu_state_ldmem  = 7;
	reg [2:0] cpu_state;

	reg force_mem_do_rinst;
	reg force_mem_do_rdata;
	reg force_mem_do_wdata;
	reg mask_decoder_trigger;
	reg force_decoder_trigger;

	reg latched_is_lu;
	reg latched_is_lh;
	reg latched_is_lb;
	reg [regindex_bits-1:0] latched_rd;

	always @(posedge clk) begin
		reg_sh <= 'bx;
		reg_out <= 'bx;
		force_mem_do_rinst = 0;
		force_mem_do_rdata = 0;
		force_mem_do_wdata = 0;
		mask_decoder_trigger <= 0;
		force_decoder_trigger <= 0;

		if (ENABLE_COUNTERS)
			count_cycle <= resetn ? count_cycle + 1 : 0;

		if (!resetn) begin
			trap <= 0;
			reg_pc <= 0;
			reg_op1 <= 'bx;
			reg_op2 <= 'bx;
			if (ENABLE_COUNTERS)
				count_instr <= 0;
			latched_is_lu <= 0;
			latched_is_lh <= 0;
			latched_is_lb <= 0;
			cpu_state <= cpu_state_fetch;
		end else
		(* parallel_case, full_case *)
		case (cpu_state)
			cpu_state_fetch: begin
				mem_do_rinst <= (!decoder_trigger || mask_decoder_trigger) && !trap && !force_decoder_trigger;
				mem_do_prefetch <= 0;
				mem_wordsize <= 0;

				if (latched_is_lu || latched_is_lh || latched_is_lb) begin
`ifdef DEBUG
					$display("ST_RD:  %2d 0x%08x", latched_rd, reg_out);
`endif
					cpuregs[latched_rd] <= reg_out;
				end

				latched_is_lu <= 0;
				latched_is_lh <= 0;
				latched_is_lb <= 0;

				if ((decoder_trigger && !mask_decoder_trigger) || force_decoder_trigger) begin
`ifdef DEBUG
					$display("DECODE: 0x%08x %-s", reg_pc, instruction);
`endif
					if (instr_trap) begin
						trap <= 1;
					end else if (instr_fence) begin
						mem_do_rinst <= 1;
						reg_pc <= reg_pc + 4;
						cpu_state <= cpu_state_fetch;
					end else if (instr_jal) begin
						mem_do_rinst <= 1;
						reg_out <= reg_pc + 4;
						if (latched_is_lu || latched_is_lh || latched_is_lb)
							reg_pc <= reg_pc + decoded_imm;
						else
							reg_pc <= reg_pc + decoded_imm_uj;
						latched_rd <= decoded_rd;
						cpu_state <= cpu_state_store;
					end else if (|{instr_rdcycle, instr_rdcycleh, instr_rdinstr, instr_rdinstrh}) begin
						(* parallel_case, full_case *)
						case (1'b1)
							instr_rdcycle:
								reg_out <= count_cycle[31:0];
							instr_rdcycleh:
								reg_out <= count_cycle[63:32];
							instr_rdinstr:
								reg_out <= count_instr[31:0];
							instr_rdinstrh:
								reg_out <= count_instr[63:32];
						endcase
						latched_rd <= decoded_rd;
						cpu_state <= cpu_state_store;
					end else begin
						mem_do_prefetch <= !instr_jalr;
						cpu_state <= cpu_state_ld_rs1;
					end
					if (ENABLE_COUNTERS)
						count_instr <= count_instr + 1;
				end
			end
			cpu_state_ld_rs1: begin
				if (is_lui_auipc_jal) begin
					reg_op1 <= instr_lui ? 0 : reg_pc;
					reg_op2 <= decoded_imm;
					mem_do_rinst <= mem_do_prefetch;
					cpu_state <= cpu_state_exec;
				end else begin
`ifdef DEBUG
					$display("LD_RS1: %2d 0x%08x", decoded_rs1, decoded_rs1 ? cpuregs[decoded_rs1] : 0);
`endif
					reg_op1 <= decoded_rs1 ? cpuregs[decoded_rs1] : 0;
					if (is_lb_lh_lw_lbu_lhu) begin
						cpu_state <= cpu_state_ldmem;
						mem_do_rinst <= 1;
					end else if (is_slli_srli_srai) begin
						reg_sh <= decoded_rs2;
						cpu_state <= cpu_state_shift;
					end else if (is_jalr_addi_slti_sltiu_xori_ori_andi) begin
						reg_op2 <= decoded_imm;
						mem_do_rinst <= mem_do_prefetch;
						cpu_state <= cpu_state_exec;
					end else
						cpu_state <= cpu_state_ld_rs2;
				end
			end
			cpu_state_ld_rs2: begin
`ifdef DEBUG
				$display("LD_RS2: %2d 0x%08x", decoded_rs2, decoded_rs2 ? cpuregs[decoded_rs2] : 0);
`endif
				reg_op2 <= decoded_rs2 ? cpuregs[decoded_rs2] : 0;
				if (is_sb_sh_sw) begin
					cpu_state <= cpu_state_stmem;
					mem_do_rinst <= 1;
				end else if (is_sll_srl_sra) begin
					reg_sh <= decoded_rs2 ? cpuregs[decoded_rs2] : 0;
					cpu_state <= cpu_state_shift;
				end else begin
					mem_do_rinst <= mem_do_prefetch;
					cpu_state <= cpu_state_exec;
				end
			end
			cpu_state_exec: begin
				(* parallel_case, full_case *)
				case (1'b1)
					is_lui_auipc_jal_jalr_addi_add:
						reg_out <= reg_op1 + reg_op2;
					instr_sub:
						reg_out <= reg_op1 - reg_op2;
					instr_beq:
						reg_out <= {31'bx, reg_op1 == reg_op2};
					instr_bne:
						reg_out <= {31'bx, reg_op1 != reg_op2};
					instr_bge:
						reg_out <= {31'bx, $signed(reg_op1) >= $signed(reg_op2)};
					instr_bgeu:
						reg_out <= {31'bx, reg_op1 >= reg_op2};
					is_slti_blt_slt:
						reg_out <= $signed(reg_op1) < $signed(reg_op2);
					is_sltiu_bltu_sltu:
						reg_out <= reg_op1 < reg_op2;
					instr_xori || instr_xor:
						reg_out <= reg_op1 ^ reg_op2;
					instr_ori || instr_or:
						reg_out <= reg_op1 | reg_op2;
					instr_andi || instr_and:
						reg_out <= reg_op1 & reg_op2;
				endcase
				latched_rd <= decoded_rd;
				cpu_state <= cpu_state_store;
			end
			cpu_state_shift: begin
				if (reg_sh == 0) begin
					reg_out <= reg_op1;
					mem_do_rinst <= mem_do_prefetch;
					latched_rd <= decoded_rd;
					cpu_state <= cpu_state_store;
				end else if (reg_sh >= 4) begin
					(* parallel_case, full_case *)
					case (1'b1)
						instr_slli || instr_sll: reg_op1 <= reg_op1 << 4;
						instr_srli || instr_srl: reg_op1 <= reg_op1 >> 4;
						instr_srai || instr_sra: reg_op1 <= $signed(reg_op1) >>> 4;
					endcase
					reg_sh <= reg_sh - 4;
				end else begin
					(* parallel_case, full_case *)
					case (1'b1)
						instr_slli || instr_sll: reg_op1 <= reg_op1 << 1;
						instr_srli || instr_srl: reg_op1 <= reg_op1 >> 1;
						instr_srai || instr_sra: reg_op1 <= $signed(reg_op1) >>> 1;
					endcase
					reg_sh <= reg_sh - 1;
				end
			end
			cpu_state_store: begin
				mem_do_rinst <= mem_do_prefetch || mem_do_rinst;
				cpu_state <= cpu_state_fetch;
				if (instr_jal) begin
`ifdef DEBUG
					$display("ST_RD:  %2d 0x%08x", latched_rd, reg_out);
`endif
					cpuregs[latched_rd] <= reg_out;
				end else if (instr_jalr) begin
`ifdef DEBUG
					$display("ST_RD:  %2d 0x%08x", latched_rd, reg_pc + 4);
`endif
					cpuregs[latched_rd] <= reg_pc + 4;
					reg_pc <= reg_out;
				end else if (is_beq_bne_blt_bge_bltu_bgeu) begin
					if (reg_out_0) begin
						if (mem_done) begin
							force_mem_do_rinst = 1;
							mask_decoder_trigger <= 1;
							reg_pc <= reg_pc + decoded_imm;
						end else begin
							/* waiting for mem_done */
							cpu_state <= cpu_state_store;
							reg_out[0] <= reg_out_0;
						end
					end else
						reg_pc <= reg_pc + 4;
				end else begin
`ifdef DEBUG
					$display("ST_RD:  %2d 0x%08x", latched_rd, reg_out);
`endif
					cpuregs[latched_rd] <= reg_out;
					reg_pc <= reg_pc + 4;
				end
			end
			cpu_state_stmem: begin
				if (!mem_do_prefetch || mem_done) begin
					if (!mem_do_wdata) begin
						(* parallel_case, full_case *)
						case (1'b1)
							instr_sb: mem_wordsize <= 2;
							instr_sh: mem_wordsize <= 1;
							instr_sw: mem_wordsize <= 0;
						endcase
						reg_op1 <= reg_op1 + decoded_imm;
						force_mem_do_wdata = 1;
					end
					if (!mem_do_prefetch && mem_done) begin
						reg_pc <= reg_pc + 4;
						cpu_state <= cpu_state_fetch;
						force_decoder_trigger <= 1;
					end
				end
			end
			cpu_state_ldmem: begin
				if (!mem_do_prefetch || mem_done) begin
					if (!mem_do_rdata) begin
						(* parallel_case, full_case *)
						case (1'b1)
							instr_lb || instr_lbu: mem_wordsize <= 2;
							instr_lh || instr_lhu: mem_wordsize <= 1;
							instr_lw: mem_wordsize <= 0;
						endcase
						latched_is_lu <= is_lbu_lhu_lw;
						latched_is_lh <= instr_lh;
						latched_is_lb <= instr_lb;
						latched_rd <= decoded_rd;
						reg_op1 <= reg_op1 + decoded_imm;
						force_mem_do_rdata = 1;
					end
					if (!mem_do_prefetch && mem_done) begin
						(* parallel_case, full_case *)
						case (1'b1)
							latched_is_lu: reg_out <= mem_buffer;
							latched_is_lh: reg_out <= $signed(mem_buffer[15:0]);
							latched_is_lb: reg_out <= $signed(mem_buffer[7:0]);
						endcase
						reg_pc <= reg_pc + 4;
						force_decoder_trigger <= 1;
						cpu_state <= cpu_state_fetch;
					end
				end
			end
		endcase

		if (resetn && (mem_do_rdata || mem_do_wdata)) begin
			if (mem_wordsize == 0 && reg_op1[1:0] != 0) begin
`ifdef DEBUG
				$display("MISALIGNED WORD: 0x%08x", reg_op1);
`endif
				trap <= 1;
			end
			if (mem_wordsize == 1 && reg_op1[0] != 0) begin
`ifdef DEBUG
				$display("MISALIGNED HALFWORD: 0x%08x", reg_op1);
`endif
				trap <= 1;
			end
		end
		if (resetn && mem_do_rinst && reg_pc[1:0] != 0) begin
`ifdef DEBUG
			$display("MISALIGNED INSTRUCTION: 0x%08x", reg_pc);
`endif
			trap <= 1;
		end

		if (!resetn || mem_done) begin
			mem_do_prefetch <= 0;
			mem_do_rinst <= 0;
			mem_do_rdata <= 0;
			mem_do_wdata <= 0;
		end

		if (force_mem_do_rinst)
			mem_do_rinst <= 1;
		if (force_mem_do_rdata)
			mem_do_rdata <= 1;
		if (force_mem_do_wdata)
			mem_do_wdata <= 1;

		// optimize for 32bit instr alignment
		reg_pc[1:0] <= 0;
	end
endmodule


/***************************************************************
 * picorv32_axi
 ***************************************************************/

module picorv32_axi #(
	parameter ENABLE_COUNTERS = 1,
	parameter ENABLE_REGS_16_31 = 1
) (
	input clk, resetn,
	output trap,

	// AXI4-lite master memory interface

	output        mem_axi_awvalid,
	input         mem_axi_awready,
	output [31:0] mem_axi_awaddr,
	output [ 2:0] mem_axi_awprot,

	output        mem_axi_wvalid,
	input         mem_axi_wready,
	output [31:0] mem_axi_wdata,
	output [ 3:0] mem_axi_wstrb,

	input         mem_axi_bvalid,
	output        mem_axi_bready,

	output        mem_axi_arvalid,
	input         mem_axi_arready,
	output [31:0] mem_axi_araddr,
	output [ 2:0] mem_axi_arprot,

	input         mem_axi_rvalid,
	output        mem_axi_rready,
	input  [31:0] mem_axi_rdata
);
	wire        mem_valid;
	wire [31:0] mem_addr;
	wire [31:0] mem_wdata;
	wire [ 3:0] mem_wstrb;
	wire        mem_instr;
	wire        mem_ready;
	wire [31:0] mem_rdata;

	picorv32_axi_adapter axi_adapter (
		.clk            (clk            ),
		.resetn         (resetn         ),
		.mem_axi_awvalid(mem_axi_awvalid),
		.mem_axi_awready(mem_axi_awready),
		.mem_axi_awaddr (mem_axi_awaddr ),
		.mem_axi_awprot (mem_axi_awprot ),
		.mem_axi_wvalid (mem_axi_wvalid ),
		.mem_axi_wready (mem_axi_wready ),
		.mem_axi_wdata  (mem_axi_wdata  ),
		.mem_axi_wstrb  (mem_axi_wstrb  ),
		.mem_axi_bvalid (mem_axi_bvalid ),
		.mem_axi_bready (mem_axi_bready ),
		.mem_axi_arvalid(mem_axi_arvalid),
		.mem_axi_arready(mem_axi_arready),
		.mem_axi_araddr (mem_axi_araddr ),
		.mem_axi_arprot (mem_axi_arprot ),
		.mem_axi_rvalid (mem_axi_rvalid ),
		.mem_axi_rready (mem_axi_rready ),
		.mem_axi_rdata  (mem_axi_rdata  ),
		.mem_valid      (mem_valid      ),
		.mem_instr      (mem_instr      ),
		.mem_ready      (mem_ready      ),
		.mem_addr       (mem_addr       ),
		.mem_wdata      (mem_wdata      ),
		.mem_wstrb      (mem_wstrb      ),
		.mem_rdata      (mem_rdata      )
	);

	picorv32 #(
		.ENABLE_COUNTERS  (ENABLE_COUNTERS  ),
		.ENABLE_REGS_16_31(ENABLE_REGS_16_31)
	) picorv32_core (
		.clk      (clk      ),
		.resetn   (resetn   ),
		.trap     (trap     ),
		.mem_valid(mem_valid),
		.mem_addr (mem_addr ),
		.mem_wdata(mem_wdata),
		.mem_wstrb(mem_wstrb),
		.mem_instr(mem_instr),
		.mem_ready(mem_ready),
		.mem_rdata(mem_rdata)
	);
endmodule


/***************************************************************
 * picorv32_axi_adapter
 ***************************************************************/

module picorv32_axi_adapter (
	input clk, resetn,

	// AXI4-lite master memory interface

	output        mem_axi_awvalid,
	input         mem_axi_awready,
	output [31:0] mem_axi_awaddr,
	output [ 2:0] mem_axi_awprot,

	output        mem_axi_wvalid,
	input         mem_axi_wready,
	output [31:0] mem_axi_wdata,
	output [ 3:0] mem_axi_wstrb,

	input         mem_axi_bvalid,
	output        mem_axi_bready,

	output        mem_axi_arvalid,
	input         mem_axi_arready,
	output [31:0] mem_axi_araddr,
	output [ 2:0] mem_axi_arprot,

	input         mem_axi_rvalid,
	output        mem_axi_rready,
	input  [31:0] mem_axi_rdata,

	// Native PicoRV32 memory interface

	input         mem_valid,
	input         mem_instr,
	output        mem_ready,
	input  [31:0] mem_addr,
	input  [31:0] mem_wdata,
	input  [ 3:0] mem_wstrb,
	output [31:0] mem_rdata
);
	reg ack_awvalid;
	reg ack_arvalid;
	reg ack_wvalid;

	assign mem_axi_awvalid = mem_valid && |mem_wstrb && !ack_awvalid;
	assign mem_axi_awaddr = mem_addr;
	assign mem_axi_awprot = 0;

	assign mem_axi_arvalid = mem_valid && ~|mem_wstrb && !ack_arvalid;
	assign mem_axi_araddr = mem_addr;
	assign mem_axi_arprot = mem_instr ? 3'b100 : 3'b000;

	assign mem_axi_wvalid = mem_valid && |mem_wstrb && !ack_wvalid;
	assign mem_axi_wdata = mem_wdata;
	assign mem_axi_wstrb = mem_wstrb;

	assign mem_ready = mem_axi_bvalid || mem_axi_rvalid;
	assign mem_axi_bready = mem_valid && |mem_wstrb;
	assign mem_axi_rready = mem_valid && !mem_wstrb;
	assign mem_rdata = mem_axi_rdata;

	always @(posedge clk) begin
		if (!resetn) begin
			ack_awvalid <= 0;
		end else begin
			if (mem_axi_awready && mem_axi_awvalid)
				ack_awvalid <= 1;
			if (mem_axi_arready && mem_axi_arvalid)
				ack_arvalid <= 1;
			if (mem_axi_wready && mem_axi_wvalid)
				ack_wvalid <= 1;
			if (!mem_valid) begin
				ack_awvalid <= 0;
				ack_arvalid <= 0;
				ack_wvalid <= 0;
			end
		end
	end
endmodule