X-Git-Url: http://git.joshuawise.com/firearm.git/blobdiff_plain/732b7730ab749590dcf0e05b3c9a0669bfd24418..793482e95432866affeec1c87c4d9e94caed8934:/Execute.v

diff --git a/Execute.v b/Execute.v
index ac759bb..3a21968 100644
--- a/Execute.v
+++ b/Execute.v
@@ -62,6 +62,10 @@ module Execute(
 		end
 	end
 
+	reg prevstall = 0;
+	always @(posedge clk)
+		prevstall <= outstall;
+
 	always @(*)
 	begin
 		outstall = stall;
@@ -71,13 +75,34 @@ module Execute(
 		next_write_num = 4'hx;
 		next_write_data = 32'hxxxxxxxx;
 	
+		mult_start = 0;
+		mult_acc0 = 32'hxxxxxxxx;
+		mult_in0 = 32'hxxxxxxxx;
+		mult_in1 = 32'hxxxxxxxx;
+	
 		alu_in0 = 32'hxxxxxxxx;
 		alu_in1 = 32'hxxxxxxxx;
 		alu_op = 4'hx;	/* hax! */
 		alu_setflags = 1'bx;
 		
 		casez (insn)
-		`DECODE_ALU_MULT,	/* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
+		`DECODE_ALU_MULT:	/* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
+		begin
+			if (!prevstall && !inbubble)
+			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
+			outstall = stall | ((!prevstall | !mult_done) && !inbubble);
+			next_outbubble = inbubble | !mult_done | !prevstall;
+			next_outcpsr = insn[20] /* S */ ? {mult_result[31] /* N */, mult_result == 0 /* Z */, 1'b0 /* C */, cpsr[28] /* V */, cpsr[27:0]} : cpsr;
+			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_MUL_LONG,	/* Multiply long */
 		`DECODE_ALU_MRS,	/* MRS (Transfer PSR to register) */
 		`DECODE_ALU_MSR,	/* MSR (Transfer register to PSR) */
@@ -154,7 +179,6 @@ module Multiplier(
 	end
 endmodule
 
-/* XXX is the interface correct? */
 module ALU(
 	input clk,
 	input Nrst,	/* XXX not used yet */
@@ -173,12 +197,15 @@ module ALU(
 	wire [31:0] res;
 	wire flag_n, flag_z, flag_c, flag_v, setres;
 	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 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;
@@ -197,26 +224,32 @@ module ALU(
 		end
 		`ALU_SUB: begin
 			{flag_c, result} = diff;
+			flag_v = diff_v;
 			setres = 1'b1;
 		end
 		`ALU_RSB: begin
 			{flag_c, result} = rdiff;
+			flag_v = rdiff_v;
 			setres = 1'b1;
 		end
 		`ALU_ADD: begin
 			{flag_c, result} = sum;
+			flag_v = sum_v;
 			setres = 1'b1;
 		end
 		`ALU_ADC: begin
 			{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, result} = diff - {32'b0, (~cpsr[`CPSR_C])};
+			flag_v = diff_v | (diff[31] & ~result[31]);
 			setres = 1'b1;
 		end
 		`ALU_RSC: begin
 			{flag_c, result} = rdiff - {32'b0, (~cpsr[`CPSR_C])};
+			flag_v = rdiff_v | (rdiff[31] & ~result[31]);
 			setres = 1'b1;
 		end
 		`ALU_TST: begin
@@ -231,10 +264,12 @@ module ALU(
 		end
 		`ALU_CMP: begin
 			{flag_c, result} = diff;
+			flag_v = diff_v;
 			setres = 1'b0;
 		end
 		`ALU_CMN: begin
 			{flag_c, result} = sum;
+			flag_v = sum_v;
 			setres = 1'b0;
 		end
 		`ALU_ORR: begin