When I synthesize the following test code in Webpack 5.1 I get the following warnings. Am I misunderstanding something here? Note that the code below is a silly example as I tried to simplify my actual code to understand the warning by removing parts that don't cause the error.
WARNING:Xst:646 - Signal is assigned but never used. WARNING:Xst:646 - Signal is assigned but never used. WARNING:Xst:646 - Signal is assigned but never used. WARNING:Xst:646 - Signal is assigned but never used.
module test(a,b,c,d); input [1:0] a, b; output c, d;
reg c, d; reg e, f, g, h;
always@ (a or b) begin e = a[1]; f = a[0]; g = b[1]; h = b[0];
c = e ^ g; d = f ^ h; end
endmodule