[firearm.git] / Decode.v

`include "ARM_Constants.v"

module Decode(
	input clk,
	input [31:0] insn,
	input [31:0] inpc,
	input [31:0] cps_in,
	output reg [31:0] op0,
	output reg [31:0] op1,
	output reg [31:0] op2,
	output reg [31:0] cps_out,

	output [3:0] regsel0,
	output [3:0] regsel1,
	output [3:0] regsel2,
	input [31:0] iregs0,
	input [31:0] iregs1,
	input [31:0] iregs2
	);

	wire [31:0] regs0, regs1, regs2, rpc;
	wire [31:0] op1_res, new_cps;

	/* shifter stuff */
	wire [31:0] shift_oper;
	wire [31:0] shift_res;
	wire shift_cflag_out;

	assign regs0 = (regsel0 == 4'b1111) ? rpc : iregs0;
	assign regs1 = (regsel1 == 4'b1111) ? rpc : iregs1;
	assign regs2 = iregs2; /* use regs2 for things that cannot be r15 */

	IHATEARMSHIFT blowme(.insn(insn),
	                     .operand(regs1),
	                     .reg_amt(regs2),
	                     .cflag_in(cps_in[`CPSR_C]),
	                     .res(shift_res),
	                     .cflag_out(shift_cflag_out));
	
	always @(*)
		casez (insn)
		32'b????000000??????????????1001????,	/* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
//		32'b????00001???????????????1001????,	/* Multiply long */
		32'b????00010?001111????000000000000,	/* MRS (Transfer PSR to register) */
		32'b????00010?101001111100000000????,	/* MSR (Transfer register to PSR) */
		32'b????00?10?1010001111????????????,	/* MSR (Transfer register or immediate to PSR, flag bits only) */
		32'b????00010?00????????00001001????,	/* Atomic swap */
		32'b????000100101111111111110001????,	/* Branch */
		32'b????000??0??????????00001??1????,	/* Halfword transfer - register offset */
		32'b????000??1??????????00001??1????,	/* Halfword transfer - register offset */
		32'b????011????????????????????1????,	/* Undefined. I hate ARM */
		32'b????01??????????????????????????,	/* Single data transfer */
		32'b????100?????????????????????????,	/* Block data transfer */
		32'b????101?????????????????????????,	/* Branch */
		32'b????110?????????????????????????,	/* Coprocessor data transfer */
		32'b????1110???????????????????0????,	/* Coprocessor data op */
		32'b????1110???????????????????1????,	/* Coprocessor register transfer */
		32'b????1111????????????????????????:	/* SWI */
			rpc = inpc - 8;
		32'b????00??????????????????????????:	/* ALU */
			rpc = inpc - (insn[25] ? 8 : (insn[4] ? 12 : 8));
		default:				/* X everything else out */
			rpc = 32'hxxxxxxxx;
		endcase

	always @ (*) begin
		casez (insn)
		32'b????000000??????????????1001????: begin /* Multiply */
			regsel0 = insn[15:12]; /* Rn */
			regsel1 = insn[3:0];   /* Rm */
			regsel2 = insn[11:8];  /* Rs */
			op1_res = regs1;
			new_cps = cps_in;
		end
/*
		32'b????00001???????????????1001????: begin * Multiply long *
			regsel0 = insn[11:8]; * Rn *
			regsel1 = insn[3:0];  * Rm *
			regsel2 = 4'b0;       * anyus *
			op1_res = regs1;
		end
*/
		32'b????00010?001111????000000000000: begin /* MRS (Transfer PSR to register) */
			new_cps = cps_in;
		end
        	32'b????00010?101001111100000000????: begin /* MSR (Transfer register to PSR) */
			new_cps = cps_in;
        	end
                32'b????00?10?1010001111????????????: begin /* MSR (Transfer register or immediate to PSR, flag bits onry) */
			new_cps = cps_in;
                end
		32'b????00??????????????????????????: begin /* ALU */
			regsel0 = insn[19:16]; /* Rn */
			regsel1 = insn[3:0];   /* Rm */
			regsel2 = insn[11:8];  /* Rs for shift */
			if(insn[25]) begin     /* the constant case */
				new_cps = cps_in;
				op1_res = ({24'b0, insn[7:0]} >> {insn[11:8], 1'b0}) | ({24'b0, insn[7:0]} << (5'b0 - {insn[11:8], 1'b0}));
			end else begin
				new_cps = {cps_in[31:30], shift_cflag_out, cps_in[28:0]};
				op1_res = shift_res;
			end
		end
		32'b????00010?00????????00001001????: begin /* Atomic swap */
			regsel0 = insn[19:16]; /* Rn */
			regsel1 = insn[3:0];   /* Rm */
			regsel2 = 4'b0;        /* anyus */
			op1_res = regs1;
		end
		32'b????000100101111111111110001????: begin /* Branch and exchange */
			regsel0 = insn[3:0];   /* Rn */
			new_cps = cps_in;
		end
		32'b????000??0??????????00001??1????: begin /* Halfword transfer - register offset */
			regsel0 = insn[19:16];
			regsel1 = insn[3:0];
			regsel2 = 4'b0;
			op1_res = regs1;
			new_cps = cps_in;
		end
		32'b????000??1??????????00001??1????: begin /* Halfword transfer - immediate offset */
			regsel0 = insn[19:16];
			regsel1 = insn[3:0];
			op1_res = {24'b0, insn[11:8], insn[3:0]};
			new_cps = cps_in;
		end
		32'b????011????????????????????1????: begin /* Undefined. I hate ARM */
			/* eat shit */
		end
		32'b????01??????????????????????????: begin /* Single data transfer */
			regsel0 = insn[19:16]; /* Rn */
			regsel1 = insn[3:0];   /* Rm */
			if(insn[25]) begin
				op1_res = {20'b0, insn[11:0]};
				new_cps = cps_in;
			end else begin
				op1_res = shift_res;
				new_cps = {cps_in[31:30], shift_cflag_out, cps_in[28:0]};
			end
		end
		32'b????100?????????????????????????: begin /* Block data transfer */
			regsel0 = insn[19:16];
			op1_res = {16'b0, insn[15:0]};
			new_cps = cps_in;
		end
		32'b????101?????????????????????????: begin /* Branch */
			op1_res = {{6{insn[23]}}, insn[23:0], 2'b0};
			new_cps = cps_in;
		end
		32'b????110?????????????????????????: begin /* Coprocessor data transfer */
			regsel0 = insn[19:16];
			op1_res = {24'b0, insn[7:0]};
			new_cps = cps_in;
		end
		32'b????1110???????????????????0????: begin /* Coprocessor data op */
			new_cps = cps_in;
		end
		32'b????1110???????????????????1????: begin /* Coprocessor register transfer */
			new_cps = cps_in;
		end
		32'b????1111????????????????????????: begin /* SWI */
			new_cps = cps_in;
		end
		default: begin end
		endcase
	end

	always @ (posedge clk) begin
		op0 <= regs0;   /* Rn - always */
		op1 <= op1_res; /* 'operand 2' - Rm */
		op2 <= regs2;   /* thirdedge - Rs */
		cps_out <= new_cps;
	end

endmodule

module IHATEARMSHIFT(
	input [31:0] insn,
	input [31:0] operand,
	input [31:0] reg_amt,
	input cflag_in,
	output [31:0] res,
	output cflag_out
);
	wire [5:0] shift_amt;
	wire elanus;


	/* might want to write our own damn shifter that does arithmetic/logical efficiently and stuff */
	always @ (*) begin
		if(insn[4]) begin
			shift_amt = {|reg_amt[7:5], reg_amt[4:0]};
			elanus = 1'b1;
		end else begin
			shift_amt = {insn[11:7] == 5'b0, insn[11:7]};
			elanus = 1'b0;
		end

		case (insn[6:5]) /* shift type */
		`SHIFT_LSL: begin
			{cflag_out, res} = {cflag_in, operand} << {elanus & shift_amt[5], shift_amt[4:0]};
		end
		`SHIFT_LSR: begin
			{res, cflag_out} = {operand, cflag_in} >> shift_amt;
		end
		`SHIFT_ASR: begin
			{res, cflag_out} = {operand, cflag_in} >> shift_amt | (operand[31] ? ~(33'h1FFFFFFFF >> shift_amt) : 33'b0);
		end
		`SHIFT_ROR: begin
			if(!elanus && shift_amt[4:0] == 5'b0) begin /* RRX x.x */
				res = {cflag_in, operand[31:1]};
				cflag_out = operand[0];
			end else if(shift_amt == 6'b0) begin
				res = operand;
				cflag_out = cflag_in;
			end else begin
				res = operand >> shift_amt[4:0] | operand << (5'b0 - shift_amt[4:0]);
				cflag_out = operand[shift_amt[4:0] - 5'b1];
			end
		end
		endcase
	end
endmodule
Commit	Line	Data
26049339 CL	1	`include "ARM_Constants.v"
26049339 CL	2
bae77231 CL	3	module Decode(
bae77231 CL	4	input clk,
be64a9df	5	input [31:0] insn,
bae77231 CL	6	input [31:0] inpc,
	7	input [31:0] cps_in,
	8	output reg [31:0] op0,
	9	output reg [31:0] op1,
	10	output reg [31:0] op2,
	11	output reg [31:0] cps_out,
	12
	13	output [3:0] regsel0,
	14	output [3:0] regsel1,
	15	output [3:0] regsel2,
	16	input [31:0] iregs0,
	17	input [31:0] iregs1,
	18	input [31:0] iregs2
	19	);
	20
	21	wire [31:0] regs0, regs1, regs2, rpc;
	22	wire [31:0] op1_res, new_cps;
	23
	24	/* shifter stuff */
	25	wire [31:0] shift_oper;
	26	wire [31:0] shift_res;
	27	wire shift_cflag_out;
	28
	29	assign regs0 = (regsel0 == 4'b1111) ? rpc : iregs0;
	30	assign regs1 = (regsel1 == 4'b1111) ? rpc : iregs1;
	31	assign regs2 = iregs2; /* use regs2 for things that cannot be r15 */
	32
be64a9df	33	IHATEARMSHIFT blowme(.insn(insn),
26049339 CL	34	.operand(regs1),
	35	.reg_amt(regs2),
	36	.cflag_in(cps_in[`CPSR_C]),
	37	.res(shift_res),
	38	.cflag_out(shift_cflag_out));
be64a9df JW	39
	40	always @(*)
	41	casez (insn)
	42	32'b????000000??????????????1001????, /* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
	43	// 32'b????00001???????????????1001????, /* Multiply long */
	44	32'b????00010?001111????000000000000, /* MRS (Transfer PSR to register) */
	45	32'b????00010?101001111100000000????, /* MSR (Transfer register to PSR) */
	46	32'b????00?10?1010001111????????????, /* MSR (Transfer register or immediate to PSR, flag bits only) */
	47	32'b????00010?00????????00001001????, /* Atomic swap */
	48	32'b????000100101111111111110001????, /* Branch */
	49	32'b????000??0??????????00001??1????, /* Halfword transfer - register offset */
	50	32'b????000??1??????????00001??1????, /* Halfword transfer - register offset */
	51	32'b????011????????????????????1????, /* Undefined. I hate ARM */
	52	32'b????01??????????????????????????, /* Single data transfer */
	53	32'b????100?????????????????????????, /* Block data transfer */
	54	32'b????101?????????????????????????, /* Branch */
	55	32'b????110?????????????????????????, /* Coprocessor data transfer */
	56	32'b????1110???????????????????0????, /* Coprocessor data op */
	57	32'b????1110???????????????????1????, /* Coprocessor register transfer */
	58	32'b????1111????????????????????????: /* SWI */
	59	rpc = inpc - 8;
	60	32'b????00??????????????????????????: /* ALU */
	61	rpc = inpc - (insn[25] ? 8 : (insn[4] ? 12 : 8));
	62	default: /* X everything else out */
	63	rpc = 32'hxxxxxxxx;
	64	endcase
bae77231 CL	65
bae77231 CL	66	always @ (*) begin
be64a9df	67	casez (insn)
bae77231	68	32'b????000000??????????????1001????: begin /* Multiply */
be64a9df JW	69	regsel0 = insn[15:12]; /* Rn */
	70	regsel1 = insn[3:0]; /* Rm */
	71	regsel2 = insn[11:8]; /* Rs */
bae77231 CL	72	op1_res = regs1;
	73	new_cps = cps_in;
	74	end
	75	/*
	76	32'b????00001???????????????1001????: begin * Multiply long *
be64a9df JW	77	regsel0 = insn[11:8]; * Rn *
be64a9df JW	78	regsel1 = insn[3:0]; * Rm *
bae77231 CL	79	regsel2 = 4'b0; * anyus *
	80	op1_res = regs1;
	81	end
	82	*/
	83	32'b????00010?001111????000000000000: begin /* MRS (Transfer PSR to register) */
bae77231 CL	84	new_cps = cps_in;
	85	end
	86	32'b????00010?101001111100000000????: begin /* MSR (Transfer register to PSR) */
bae77231 CL	87	new_cps = cps_in;
	88	end
	89	32'b????00?10?1010001111????????????: begin /* MSR (Transfer register or immediate to PSR, flag bits onry) */
bae77231 CL	90	new_cps = cps_in;
	91	end
	92	32'b????00??????????????????????????: begin /* ALU */
be64a9df JW	93	regsel0 = insn[19:16]; /* Rn */
	94	regsel1 = insn[3:0]; /* Rm */
	95	regsel2 = insn[11:8]; /* Rs for shift */
	96	if(insn[25]) begin /* the constant case */
bae77231	97	new_cps = cps_in;
be64a9df	98	op1_res = ({24'b0, insn[7:0]} >> {insn[11:8], 1'b0}) \| ({24'b0, insn[7:0]} << (5'b0 - {insn[11:8], 1'b0}));
bae77231	99	end else begin
26049339	100	new_cps = {cps_in[31:30], shift_cflag_out, cps_in[28:0]};
bae77231 CL	101	op1_res = shift_res;
	102	end
	103	end
	104	32'b????00010?00????????00001001????: begin /* Atomic swap */
be64a9df JW	105	regsel0 = insn[19:16]; /* Rn */
be64a9df JW	106	regsel1 = insn[3:0]; /* Rm */
bae77231 CL	107	regsel2 = 4'b0; /* anyus */
	108	op1_res = regs1;
	109	end
	110	32'b????000100101111111111110001????: begin /* Branch and exchange */
be64a9df	111	regsel0 = insn[3:0]; /* Rn */
bae77231 CL	112	new_cps = cps_in;
	113	end
	114	32'b????000??0??????????00001??1????: begin /* Halfword transfer - register offset */
be64a9df JW	115	regsel0 = insn[19:16];
be64a9df JW	116	regsel1 = insn[3:0];
bae77231 CL	117	regsel2 = 4'b0;
	118	op1_res = regs1;
	119	new_cps = cps_in;
	120	end
	121	32'b????000??1??????????00001??1????: begin /* Halfword transfer - immediate offset */
be64a9df JW	122	regsel0 = insn[19:16];
	123	regsel1 = insn[3:0];
	124	op1_res = {24'b0, insn[11:8], insn[3:0]};
bae77231 CL	125	new_cps = cps_in;
	126	end
	127	32'b????011????????????????????1????: begin /* Undefined. I hate ARM */
	128	/* eat shit */
	129	end
	130	32'b????01??????????????????????????: begin /* Single data transfer */
be64a9df JW	131	regsel0 = insn[19:16]; /* Rn */
	132	regsel1 = insn[3:0]; /* Rm */
	133	if(insn[25]) begin
	134	op1_res = {20'b0, insn[11:0]};
bae77231 CL	135	new_cps = cps_in;
	136	end else begin
	137	op1_res = shift_res;
26049339	138	new_cps = {cps_in[31:30], shift_cflag_out, cps_in[28:0]};
bae77231 CL	139	end
	140	end
	141	32'b????100?????????????????????????: begin /* Block data transfer */
be64a9df JW	142	regsel0 = insn[19:16];
be64a9df JW	143	op1_res = {16'b0, insn[15:0]};
bae77231 CL	144	new_cps = cps_in;
	145	end
	146	32'b????101?????????????????????????: begin /* Branch */
be64a9df	147	op1_res = {{6{insn[23]}}, insn[23:0], 2'b0};
bae77231 CL	148	new_cps = cps_in;
	149	end
	150	32'b????110?????????????????????????: begin /* Coprocessor data transfer */
be64a9df JW	151	regsel0 = insn[19:16];
be64a9df JW	152	op1_res = {24'b0, insn[7:0]};
bae77231 CL	153	new_cps = cps_in;
	154	end
	155	32'b????1110???????????????????0????: begin /* Coprocessor data op */
bae77231 CL	156	new_cps = cps_in;
	157	end
	158	32'b????1110???????????????????1????: begin /* Coprocessor register transfer */
bae77231 CL	159	new_cps = cps_in;
	160	end
	161	32'b????1111????????????????????????: begin /* SWI */
bae77231 CL	162	new_cps = cps_in;
bae77231 CL	163	end
26049339	164	default: begin end
bae77231 CL	165	endcase
	166	end
	167
	168	always @ (posedge clk) begin
	169	op0 <= regs0; /* Rn - always */
	170	op1 <= op1_res; /* 'operand 2' - Rm */
	171	op2 <= regs2; /* thirdedge - Rs */
	172	cps_out <= new_cps;
	173	end
	174
	175	endmodule
	176
	177	module IHATEARMSHIFT(
	178	input [31:0] insn,
	179	input [31:0] operand,
	180	input [31:0] reg_amt,
	181	input cflag_in,
	182	output [31:0] res,
	183	output cflag_out
	184	);
bae77231 CL	185	wire [5:0] shift_amt;
	186	wire elanus;
	187
bae77231 CL	188
	189	/* might want to write our own damn shifter that does arithmetic/logical efficiently and stuff */
	190	always @ (*) begin
26049339 CL	191	if(insn[4]) begin
	192	shift_amt = {\|reg_amt[7:5], reg_amt[4:0]};
	193	elanus = 1'b1;
	194	end else begin
	195	shift_amt = {insn[11:7] == 5'b0, insn[11:7]};
	196	elanus = 1'b0;
	197	end
	198
	199	case (insn[6:5]) /* shift type */
bae77231 CL	200	`SHIFT_LSL: begin
	201	{cflag_out, res} = {cflag_in, operand} << {elanus & shift_amt[5], shift_amt[4:0]};
	202	end
	203	`SHIFT_LSR: begin
	204	{res, cflag_out} = {operand, cflag_in} >> shift_amt;
	205	end
	206	`SHIFT_ASR: begin
	207	{res, cflag_out} = {operand, cflag_in} >> shift_amt \| (operand[31] ? ~(33'h1FFFFFFFF >> shift_amt) : 33'b0);
	208	end
	209	`SHIFT_ROR: begin
	210	if(!elanus && shift_amt[4:0] == 5'b0) begin /* RRX x.x */
	211	res = {cflag_in, operand[31:1]};
	212	cflag_out = operand[0];
26049339	213	end else if(shift_amt == 6'b0) begin
bae77231 CL	214	res = operand;
	215	cflag_out = cflag_in;
	216	end else begin
	217	res = operand >> shift_amt[4:0] \| operand << (5'b0 - shift_amt[4:0]);
	218	cflag_out = operand[shift_amt[4:0] - 5'b1];
	219	end
	220	end
26049339	221	endcase
bae77231 CL	222	end
bae77231 CL	223	endmodule