merging changes from OPAE branch making this branch

old_rtl/VX_generic_stack.v

@@ -0,0 +1,38 @@
+module VX_generic_stack
+	#(
+		parameter WIDTH = 40,
+		parameter DEPTH = 2
+	)
+	(
+	input  wire              clk,
+	input  wire              reset,
+	input  wire              push,
+	input  wire              pop,
+	input  reg [WIDTH - 1:0] q1,
+	input  reg [WIDTH - 1:0] q2,
+	output wire[WIDTH - 1:0] d
+	);
+
+
+	reg [DEPTH - 1:0] ptr;
+	reg [WIDTH - 1:0] stack [0:(1 << DEPTH) - 1];
+
+	integer i;
+	always @(posedge clk) begin
+		if (reset) begin
+			ptr <= 0;
+			for (i = 0; i < (1 << DEPTH); i=i+1) stack[i] <= 0;
+		end else if (push) begin
+			stack[ptr]   <= q1;
+			stack[ptr+1] <= q2;
+			ptr          <= ptr + 2;
+		end else if (pop) begin
+			ptr <= ptr - 1;
+		end
+
+	end
+
+
+	assign d = stack[ptr - 1];
+
+endmodule