X-Git-Url: http://git.joshuawise.com/firearm.git/blobdiff_plain/879a3986d6c3aeb3b51a0209069d15c37bfac3dc..dfddccfb552a24c60589696269a5325ec267c46d:/Execute.v

diff --git a/Execute.v b/Execute.v
index 4865aa3..c1049ba 100644
--- a/Execute.v
+++ b/Execute.v
@@ -9,6 +9,7 @@ module Execute(
 	input [31:0] pc,
 	input [31:0] insn,
 	input [31:0] cpsr,
+	input [31:0] spsr,
 	input [31:0] op0,
 	input [31:0] op1,
 	input [31:0] op2,
@@ -16,9 +17,17 @@ module Execute(
 	
 	output reg outstall = 0,
 	output reg outbubble = 1,
+	output reg [31:0] outcpsr = 0,
+	output reg [31:0] outspsr = 0,
+	output reg outcpsrup = 0,
 	output reg write_reg = 1'bx,
 	output reg [3:0] write_num = 4'bxxxx,
-	output reg [31:0] write_data = 32'hxxxxxxxx
+	output reg [31:0] write_data = 32'hxxxxxxxx,
+	output reg [31:0] jmppc,
+	output reg jmp,
+	output reg [31:0] outpc,
+	output reg [31:0] outinsn,
+	output reg [31:0] outop0, outop1, outop2
 	);
 	
 	reg mult_start;
@@ -26,10 +35,220 @@ module Execute(
 	wire mult_done;
 	wire [31:0] mult_result;
 	
+	reg [31:0] alu_in0, alu_in1;
+	reg [3:0] alu_op;
+	reg alu_setflags;
+	wire [31:0] alu_result, alu_outcpsr;
+	wire alu_setres;
+	
+	reg next_outbubble;
+	reg [31:0] next_outcpsr, next_outspsr;
+	reg next_outcpsrup;
+	reg next_write_reg;
+	reg [3:0] next_write_num;
+
+	reg [31:0] next_write_data;
+
 	Multiplier multiplier(
 		.clk(clk), .Nrst(Nrst),
 		.start(mult_start), .acc0(mult_acc0), .in0(mult_in0),
 		.in1(mult_in1), .done(mult_done), .result(mult_result));
+	
+	ALU alu(
+		.clk(clk), .Nrst(Nrst),
+		.in0(alu_in0), .in1(alu_in1), .cpsr(cpsr), .op(alu_op),
+		.setflags(alu_setflags), .shifter_carry(carry),
+		.result(alu_result), .cpsr_out(alu_outcpsr), .setres(alu_setres));
+
+	always @(posedge clk)
+	begin
+		if (!stall)
+		begin
+			outbubble <= next_outbubble;
+			outcpsr <= next_outcpsr;
+			outspsr <= next_outspsr;
+			outcpsrup <= next_outcpsrup;
+			write_reg <= next_write_reg;
+			write_num <= next_write_num;
+			write_data <= next_write_data;
+			outpc <= pc;
+			outinsn <= insn;
+			outop0 <= op0;
+			outop1 <= op1;
+			outop2 <= op2;
+		end
+	end
+	
+	reg delayedflush = 0;
+	always @(posedge clk)
+		if (flush && outstall /* halp! I can't do it now, maybe later? */)
+			delayedflush <= 1;
+		else if (!outstall /* anything has been handled this time around */)
+			delayedflush <= 0;
+
+	reg prevstall = 0;
+	always @(posedge clk)
+		prevstall <= outstall;
+	
+	always @(*)
+	begin
+		outstall = stall;
+		
+		casez (insn)
+		`DECODE_ALU_MULT:	/* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
+			outstall = outstall | ((!prevstall | !mult_done) && !inbubble);
+		endcase
+	end
+	
+	/* ALU inputs */
+	always @(*)
+	begin
+		alu_in0 = op0;
+		alu_in1 = op1;
+		alu_op = insn[24:21];
+		alu_setflags = insn[20] /* S */;
+	end
+	
+	/* Register outputs */
+	always @(*)
+	begin
+		next_outcpsr = cpsr;
+		next_outspsr = spsr;
+		next_outcpsrup = 0;
+		next_write_reg = 0;
+		next_write_num = 4'hx;
+		next_write_data = 32'hxxxxxxxx;
+		
+		casez(insn)
+		`DECODE_ALU_MULT:	/* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
+		begin
+			next_outcpsr = insn[20] /* S */ ? {mult_result[31] /* N */, mult_result == 0 /* Z */, 1'b0 /* C */, cpsr[28] /* V */, cpsr[27:0]} : cpsr;
+			next_outcpsrup = insn[20] /* S */;
+			next_write_reg = 1;
+			next_write_num = insn[19:16] /* Rd -- why the fuck isn't this the same place as ALU */;
+			next_write_data = mult_result;
+		end
+		`DECODE_ALU_MRS:	/* MRS (Transfer PSR to register) */
+		begin
+			next_write_reg = 1;
+			next_write_num = insn[15:12];
+			if (insn[22] /* Ps */)
+				next_write_data = spsr;
+			else
+				next_write_data = cpsr;
+		end
+		`DECODE_ALU_MSR,	/* MSR (Transfer register to PSR) */
+		`DECODE_ALU_MSR_FLAGS:	/* MSR (Transfer register or immediate to PSR, flag bits only) */
+		begin
+			if ((cpsr[4:0] == `MODE_USR) || (insn[16] /* that random bit */ == 1'b0))	/* flags only */
+			begin
+				if (insn[22] /* Ps */)
+					next_outspsr = {op0[31:29], spsr[28:0]};
+				else
+					next_outcpsr = {op0[31:29], cpsr[28:0]};
+			end else begin
+				if (insn[22] /* Ps */)
+					next_outspsr = op0;
+				else
+					next_outcpsr = op0;
+			end
+			next_outcpsrup = 1;
+		end
+		`DECODE_ALU_SWP,	/* Atomic swap */
+		`DECODE_ALU_BX,		/* Branch */
+		`DECODE_ALU_HDATA_REG,	/* Halfword transfer - register offset */
+		`DECODE_ALU_HDATA_IMM:	/* Halfword transfer - immediate offset */
+		begin end
+		`DECODE_ALU:		/* ALU */
+		begin
+			if (alu_setres) begin
+				next_write_reg = 1;
+				next_write_num = insn[15:12] /* Rd */;
+				next_write_data = alu_result;
+			end
+			
+			if (insn[20] /* S */) begin
+				next_outcpsrup = 1;
+				next_outcpsr = ((insn[15:12] == 4'b1111) && insn[20]) ? spsr : alu_outcpsr;
+			end
+		end
+		`DECODE_LDRSTR_UNDEFINED,	/* Undefined. I hate ARM */
+		`DECODE_LDRSTR,		/* Single data transfer */
+		`DECODE_LDMSTM:		/* Block data transfer */
+		begin end
+		`DECODE_BRANCH:		/* Branch */
+		begin
+			if(insn[24] /* L */) begin
+				next_write_reg = 1;
+				next_write_num = 4'hE; /* link register */
+				next_write_data = pc + 32'h4;
+			end
+		end
+		endcase
+	end
+	
+	/* Multiplier inputs */
+	always @(*)
+	begin
+		mult_start = 0;
+		mult_acc0 = 32'hxxxxxxxx;
+		mult_in0 = 32'hxxxxxxxx;
+		mult_in1 = 32'hxxxxxxxx;
+		
+		casez(insn)
+		`DECODE_ALU_MULT:
+		begin
+			if (!prevstall /* i.e., this is a new one */ && !inbubble /* i.e., this is a real one */)
+			begin
+				mult_start = 1;
+				mult_acc0 = insn[21] /* A */ ? op0 /* Rn */ : 32'h0;
+				mult_in0 = op1 /* Rm */;
+				mult_in1 = op2 /* Rs */;
+				$display("New MUL instruction");
+			end
+		end
+		endcase
+	end
+
+	/* Miscellaneous cleanup. */
+	always @(*)
+	begin
+		next_outbubble = inbubble | flush | delayedflush;
+
+		jmp = 1'b0;
+		jmppc = 32'h00000000;
+
+		casez (insn)
+		`DECODE_ALU_MULT:	/* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
+			next_outbubble = next_outbubble | !mult_done | !prevstall;
+		`DECODE_ALU_MRS,	/* MRS (Transfer PSR to register) */
+		`DECODE_ALU_MSR,	/* MSR (Transfer register to PSR) */
+		`DECODE_ALU_MSR_FLAGS,	/* MSR (Transfer register or immediate to PSR, flag bits only) */
+		`DECODE_ALU_SWP,	/* Atomic swap */
+		`DECODE_ALU_BX,		/* Branch */
+		`DECODE_ALU_HDATA_REG,	/* Halfword transfer - register offset */
+		`DECODE_ALU_HDATA_IMM,	/* Halfword transfer - immediate offset */
+		`DECODE_ALU,		/* ALU */
+		`DECODE_LDRSTR_UNDEFINED,	/* Undefined. I hate ARM */
+		`DECODE_LDRSTR,		/* Single data transfer */
+		`DECODE_LDMSTM:		/* Block data transfer */
+		begin end
+		`DECODE_BRANCH:
+		begin
+			if(!inbubble && !flush && !delayedflush && !outstall /* Let someone else take precedence. */) begin
+				jmppc = pc + op0 + 32'h8;
+				jmp = 1'b1;
+			end
+		end                     /* Branch */
+		`DECODE_LDCSTC,		/* Coprocessor data transfer */
+		`DECODE_CDP,		/* Coprocessor data op */
+		`DECODE_MRCMCR,		/* Coprocessor register transfer */
+		`DECODE_SWI:		/* SWI */
+		begin end
+		default:		/* X everything else out */
+		begin end
+		endcase
+	end
 endmodule
 
 module Multiplier(
@@ -69,7 +288,6 @@ module Multiplier(
 	end
 endmodule
 
-/* XXX is the interface correct? */
 module ALU(
 	input clk,
 	input Nrst,	/* XXX not used yet */
@@ -83,17 +301,20 @@ module ALU(
 
 	output reg [31:0] result,
 	output reg [31:0] cpsr_out,
-	output reg set
+	output reg setres
 );
-	wire [31:0] res;
-	wire flag_n, flag_z, flag_c, flag_v, setres;
+	reg [31:0] res;
+	reg flag_n, flag_z, flag_c, flag_v;
 	wire [32:0] sum, diff, rdiff;
+	wire sum_v, diff_v, rdiff_v;
 
 	assign sum = {1'b0, in0} + {1'b0, in1};
 	assign diff = {1'b0, in0} - {1'b0, in1};
-	assign rdiff = {1'b0, in1} + {1'b0, in0};
+	assign rdiff = {1'b0, in1} - {1'b0, in0};
+	assign sum_v = (in0[31] ^~ in1[31]) & (sum[31] ^ in0[31]);
+	assign diff_v = (in0[31] ^ in1[31]) & (diff[31] ^ in0[31]);
+	assign rdiff_v = (in0[31] ^ in1[31]) & (rdiff[31] ^ in1[31]);
 
-	/* TODO XXX flag_v not set correctly */
 	always @(*) begin
 		res = 32'hxxxxxxxx;
 		setres = 1'bx;
@@ -101,89 +322,95 @@ module ALU(
 		flag_v = cpsr[`CPSR_V];
 		case(op)
 		`ALU_AND: begin
-			res = in0 & in1;
+			result = in0 & in1;
 			flag_c = shifter_carry;
 			setres = 1'b1;
 		end
 		`ALU_EOR: begin
-			res = in0 ^ in1;
+			result = in0 ^ in1;
 			flag_c = shifter_carry;
 			setres = 1'b1;
 		end
 		`ALU_SUB: begin
-			{flag_c, res} = diff;
+			{flag_c, result} = diff;
+			flag_c = !flag_c;
+			flag_v = diff_v;
 			setres = 1'b1;
 		end
 		`ALU_RSB: begin
-			{flag_c, res} = rdiff;
+			{flag_c, result} = rdiff;
+			flag_c = !flag_c;
+			flag_v = rdiff_v;
 			setres = 1'b1;
 		end
 		`ALU_ADD: begin
-			{flag_c, res} = sum;
+			{flag_c, result} = sum;
+			flag_v = sum_v;
 			setres = 1'b1;
 		end
 		`ALU_ADC: begin
-			{flag_c, res} = sum + cpsr[`CPSR_C];
+			{flag_c, result} = sum + {32'b0, cpsr[`CPSR_C]};
+			flag_v = sum_v | (~sum[31] & result[31]);
 			setres = 1'b1;
 		end
 		`ALU_SBC: begin
-			{flag_c, res} = diff - (~cpsr[`CPSR_C]);
+			{flag_c, result} = diff - {32'b0, (~cpsr[`CPSR_C])};
+			flag_c = !flag_c;
+			flag_v = diff_v | (diff[31] & ~result[31]);
 			setres = 1'b1;
 		end
 		`ALU_RSC: begin
-			{flag_c, res} = rdiff - (~cpsr[`CPSR_C]);
+			{flag_c, result} = rdiff - {32'b0, (~cpsr[`CPSR_C])};
+			flag_c = !flag_c;
+			flag_v = rdiff_v | (rdiff[31] & ~result[31]);
 			setres = 1'b1;
 		end
 		`ALU_TST: begin
-			res = in0 & in1;
+			result = in0 & in1;
 			flag_c = shifter_carry;
 			setres = 1'b0;
 		end
 		`ALU_TEQ: begin
-			res = in0 ^ in1;
+			result = in0 ^ in1;
 			flag_c = shifter_carry;
 			setres = 1'b0;
 		end
 		`ALU_CMP: begin
-			{flag_c, res} = diff;
+			{flag_c, result} = diff;
+			flag_c = !flag_c;
+			flag_v = diff_v;
 			setres = 1'b0;
 		end
 		`ALU_CMN: begin
-			{flag_c, res} = sum;
+			{flag_c, result} = sum;
+			flag_v = sum_v;
 			setres = 1'b0;
 		end
 		`ALU_ORR: begin
-			res = in0 | in1;
+			result = in0 | in1;
 			flag_c = shifter_carry;
 			setres = 1'b1;
 		end
 		`ALU_MOV: begin
-			res = in1;
+			result = in1;
 			flag_c = shifter_carry;
 			setres = 1'b1;
 		end
 		`ALU_BIC: begin
-			res = in0 & (~in1);
+			result = in0 & (~in1);
 			flag_c = shifter_carry;
 			setres = 1'b1;
 		end
 		`ALU_MVN: begin
-			res = ~in1;
+			result = ~in1;
 			flag_c = shifter_carry;
 			setres = 1'b1;
 		end
 		endcase
+		
+		flag_z = (result == 0);
+		flag_n = result[31];
+		
+		cpsr_out = setflags ? {flag_n, flag_z, flag_c, flag_v, cpsr[27:0]} : cpsr;
 	end
-
-	always @(*) begin
-		flag_z = (res == 0);
-		flag_n = res[31];
-	end
-
-	always @(posedge clk) begin
-		result <= res;
-		cpsr_out <= setflags ? {flag_n, flag_z, flag_c, flag_v, cpsr[27:0]} : cpsr;
-		set <= setres;
-	end
-
 endmodule