The way to choose how to declare your signal is not by how it will be physically instantiated, but by how you will syntactically assign its value.
If the signal is driven by assignments in a procedural block (a block beginning with
initial), then it must be declared as
If the signal is driven by continuous assignment (an
assign statement) or is the output of a module instance, then it must be declared as
wire (or one of its variants like
wand), or as an output without the
reg signal might be physically the output of either a latch or a flip-flop or of combinatorial logic (for example, there's a very common way of inferring a combinatorial multiplexer using an
always block). A
wire might be physically the output of a latch or a flip-flop or combinatorial logic (for example if the flip-flop is within a submodule).