if you want to implement clock forwarding, so that you can output your global clock to a pin, then use an ODDR2 as follows:
ODDR2 #(
.DDR_ALIGNMENT("C0"), // Sets output alignment to "NONE", "C0" or "C1"
.INIT(1'b0), // Sets initial state of the Q output to 1'b0 or 1'b1
.SRTYPE("ASYNC") // Specifies "SYNC" or "ASYNC" set/reset
)
ODDR2_0 (
.Q(clock_out), // 1-bit DDR output data
.C0(global_clock), // 1-bit clock input
.C1(~global_clock), // 1-bit clock input
.CE(1'b1), // 1-bit clock enable input
.D0(1'b1), // 1-bit data input (associated with C0)
.D1(1'b0), // 1-bit data input (associated with C1)
.R(reset), // 1-bit reset input active high
.S(1'b0) // 1-bit set input
);