yosys/tests/simple/muxtree.v

// test case generated from IWLS 2005 usb_phy core
// (triggered a bug in opt_muxtree pass)

module usb_tx_phy(clk, rst, DataOut_i, TxValid_i, hold_reg);

input		clk;
input		rst;
input		DataOut_i;
input		TxValid_i;
output reg	hold_reg;

reg		state, next_state;
reg		ld_sop_d;
reg		ld_data_d;

always @(posedge clk)
	if(ld_sop_d)
		hold_reg <= 0;
	else
		hold_reg <= DataOut_i;

always @(posedge clk)
	if(!rst)	state <= 0;
	else		state <= next_state;

always @(state or TxValid_i)
   begin
	next_state = state;

	ld_sop_d = 1'b0;
	ld_data_d = 1'b0;

	case(state)	// synopsys full_case parallel_case
	   0:
			if(TxValid_i)
			   begin
				ld_sop_d = 1'b1;
				next_state = 1;
			   end
	   1:
			if(TxValid_i)
			   begin
				ld_data_d = 1'b1;
				next_state = 0;
			   end
	endcase
   end

endmodule


// test case inspired by softusb_navre code:
// default not as last case

module default_cases(a, y);

input [2:0] a;
output reg [3:0] y;

always @* begin
	case (a)
		3'b000, 3'b111: y <= 0;
		default: y <= 4;
		3'b001: y <= 1;
		3'b010: y <= 2;
		3'b100: y <= 3;
	endcase
end

endmodule


// test case for muxtree with select on leaves

module select_leaves(input R, C, D, output reg Q);
	always @(posedge C)
		if (!R)
			Q <= R;
		else
			Q <= Q ? Q : D ? D : Q;
endmodule