Added header guards to prevent errors from double-inclusions

modules/asu.sv

@@ -1,3 +1,6 @@
+`ifndef ASU_H_SV
+`define ASU_H_SV
+
 module asu #(parameter width = 2)(
 	input logic [0:0] op,
 	input logic[2**width-1:0] A, input logic[2**width-1:0] B,
@@ -15,3 +18,5 @@ module asu #(parameter width = 2)(
     // Cin for final bit in adder to later be xor'ed with COUT to determine if a signed overflow occured for the MIPS architecture
     assign OUT_CIN = A[2**width-1] ^ operand[2**width-1] ^ OUT_1[2**width-1];
 endmodule
+
+`endif