3 files changed, 104 insertions, 0 deletions
diff --git a/tests/opt/opt_merge_init.ys b/tests/opt/opt_merge_init.ys
index a29c29df6..0176f09c7 100644
--- a/tests/opt/opt_merge_init.ys
+++ b/tests/opt/opt_merge_init.ys
@@ -20,6 +20,7 @@ endmodule
 EOT
 
 opt_merge
+select -assert-count 1 t:$dff
 select -assert-count 1 a:init=1'0
 
 
@@ -46,4 +47,31 @@ endmodule
 EOT
 
 opt_merge
+select -assert-count 1 t:$dff
 select -assert-count 1 a:init=2'bx1
+
+
+design -reset
+read_verilog -icells <<EOT
+module top(input clk, i, (* init = 1'b0 *) output o, /* NB: no init here! */ output p);
+  \$dff  #(
+    .CLK_POLARITY(1'h1),
+    .WIDTH(32'd1)
+  ) ffo  (
+    .CLK(clk),
+    .D(i),
+    .Q(o)
+  );
+  \$dff  #(
+    .CLK_POLARITY(1'h1),
+    .WIDTH(32'd1)
+  ) ffp  (
+    .CLK(clk),
+    .D(i),
+    .Q(p)
+  );
+endmodule
+EOT
+
+opt_merge
+select -assert-count 2 t:$dff
diff --git a/tests/opt/opt_merge_keep.ys b/tests/opt/opt_merge_keep.ys
new file mode 100644
index 000000000..2a9202901
--- /dev/null
+++ b/tests/opt/opt_merge_keep.ys
@@ -0,0 +1,64 @@
+read_verilog -icells <<EOT
+module top(input clk, i, output o, p);
+  (* keep *)
+  \$_DFF_P_ ffo  (
+    .C(clk),
+    .D(i),
+    .Q(o)
+  );
+  \$_DFF_P_ ffp  (
+    .C(clk),
+    .D(i),
+    .Q(p)
+  );
+endmodule
+EOT
+
+opt_merge
+select -assert-count 1 t:$_DFF_P_
+select -assert-count 1 a:keep
+
+
+design -reset
+read_verilog -icells <<EOT
+module top(input clk, i, output o, p);
+  \$_DFF_P_ ffo  (
+    .C(clk),
+    .D(i),
+    .Q(o)
+  );
+  (* keep *)
+  \$_DFF_P_ ffp  (
+    .C(clk),
+    .D(i),
+    .Q(p)
+  );
+endmodule
+EOT
+
+opt_merge
+select -assert-count 1 t:$_DFF_P_
+select -assert-count 1 a:keep
+
+
+design -reset
+read_verilog -icells <<EOT
+module top(input clk, i, output o, p);
+  (* keep *)
+  \$_DFF_P_ ffo  (
+    .C(clk),
+    .D(i),
+    .Q(o)
+  );
+  (* keep *)
+  \$_DFF_P_ ffp  (
+    .C(clk),
+    .D(i),
+    .Q(p)
+  );
+endmodule
+EOT
+
+opt_merge
+select -assert-count 2 t:$_DFF_P_
+select -assert-count 2 a:keep
diff --git a/tests/simple/dynslice.v b/tests/simple/dynslice.v
new file mode 100644
index 000000000..7236ac3a5
--- /dev/null
+++ b/tests/simple/dynslice.v
@@ -0,0 +1,12 @@
+module dynslice (
+    input clk ,
+    input [9:0] ctrl ,
+    input [15:0] din ,
+    input [3:0] sel ,
+    output reg [127:0] dout
+);
+always @(posedge clk)
+begin
+    dout[ctrl*sel+:16] <= din ;
+end
+endmodule