Add comment with expected behavior for latches,tribuf tests;Update adffs test

tests/xilinx/adffs.v

@@ -22,30 +22,26 @@ module adffn
             q <= d;
 endmodule
 
-module dffsr
+module dffs
     ( input d, clk, pre, clr, output reg q );
     initial begin
       q = 0;
     end
-	always @( posedge clk, posedge pre, posedge clr )
-		if ( clr )
-			q <= 1'b0;
-		else if ( pre )
+	always @( posedge clk )
+		if ( pre )
 			q <= 1'b1;
 		else
             q <= d;
 endmodule
 
-module ndffnsnr
+module ndffnr
     ( input d, clk, pre, clr, output reg q );
     initial begin
       q = 0;
     end
-	always @( negedge clk, negedge pre, negedge clr )
+	always @( negedge clk )
 		if ( !clr )
 			q <= 1'b0;
-		else if ( !pre )
-			q <= 1'b1;
 		else
             q <= d;
 endmodule
@@ -58,7 +54,7 @@ input a,
 output b,b1,b2,b3
 );
 
-dffsr u_dffsr (
+dffs u_dffs (
         .clk (clk ),
         .clr (clr),
         .pre (pre),
@@ -66,7 +62,7 @@ dffsr u_dffsr (
         .q (b )
     );
 
-ndffnsnr u_ndffnsnr (
+ndffnr u_ndffnr (
         .clk (clk ),
         .clr (clr),
         .pre (pre),

tests/xilinx/adffs.ys

@@ -9,6 +9,5 @@ cd top # Constrain all select calls below inside the top module
 select -assert-count 1 t:BUFG
 select -assert-count 3 t:FDRE
 select -assert-count 1 t:FDRE_1
-select -assert-count 4 t:LUT2
-select -assert-count 4 t:LUT3
-select -assert-none t:BUFG t:FDRE t:FDRE_1 t:LUT2 t:LUT3 %% t:* %D
+select -assert-count 5 t:LUT2
+select -assert-none t:BUFG t:FDRE t:FDRE_1 t:LUT2 %% t:* %D

tests/xilinx/latches.ys

@@ -15,5 +15,6 @@ flatten
 cd top
 select -assert-count 1 t:LUT1
 select -assert-count 2 t:LUT3
+#Xilinx Vivado synthesizes LDCE cell for this case. Need support it.
 select -assert-count 3 t:$_DLATCH_P_
 select -assert-none t:LUT1 t:LUT3 t:$_DLATCH_P_ %% t:* %D

tests/xilinx/tribuf.ys

@@ -7,5 +7,6 @@ synth
 equiv_opt -assert -map +/xilinx/cells_sim.v -map +/simcells.v synth_xilinx # equivalency check
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd top # Constrain all select calls below inside the top module
+#Xilinx Vivado synthesizes OBUFT cell for this case. Need support it.
 select -assert-count 1 t:$_TBUF_
 select -assert-none t:$_TBUF_ %% t:* %D