generic: Add support for post-PnR simulation

Signed-off-by: David Shah <dave@ds0.me>

1 files changed, 11 insertions, 2 deletions

diff --git a/generic/synth/prims.v b/generic/synth/prims.v
index 1148041c..ca445e6e 100644
--- a/generic/synth/prims.v
+++ b/generic/synth/prims.v
@@ -2,18 +2,27 @@
 
 module LUT #(
 	parameter K = 4,
-	parameter [2**K-1:0] INIT = 0,
+	parameter [2**K-1:0] INIT = 0
 ) (
 	input [K-1:0] I,
 	output Q
 );
-	assign Q = INIT[I];
+	wire [K-1:0] I_pd;
+
+	genvar ii;
+	generate
+		for (ii = 0; ii < K; ii = ii + 1'b1)
+			assign I_pd[ii] = (I[ii] === 1'bz) ? 1'b0 : I[ii];
+	endgenerate
+
+	assign Q = INIT[I_pd];
 endmodule
 
 module DFF (
 	input CLK, D,
 	output reg Q
 );
+	initial Q = 1'b0;
 	always @(posedge CLK)
 		Q <= D;
 endmodule