Added LO to ICESTORM_LC for LUT cascade route.

techlibs/ice40/cells_sim.v

@@ -661,7 +661,7 @@ endmodule
 
 module ICESTORM_LC (
 	input I0, I1, I2, I3, CIN, CLK, CEN, SR,
-	output O, COUT
+	output LO, O, COUT
 );
 	parameter [15:0] LUT_INIT = 0;
 
@@ -678,6 +678,8 @@ module ICESTORM_LC (
 	wire [1:0] lut_s1 = I1 ?   lut_s2[ 3:2] :   lut_s2[1:0];
 	wire       lut_o  = I0 ?   lut_s1[   1] :   lut_s1[  0];
 
+	assign LO = lut_o;
+
 	wire polarized_clk;
 	assign polarized_clk = CLK ^ NEG_CLK;