Add regression tests for constant recursive functions

Check that constant recursive functions are supported. Check both Verilog
style using assignments to the implicit function return signal and
SystemVerilog style using `return`.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

ivtest/gold/recursive_func_const.gold

@@ -0,0 +1,3 @@
+factorial 3 = 6
+factorial 4 = 24
+factorial 5 = 120

ivtest/ivltests/recursive_func_const1.v

@@ -0,0 +1,25 @@
+// Check that constant recursive functions are supported.
+
+module recursive_func();
+
+function automatic [15:0] factorial;
+
+input [15:0] n;
+
+begin
+  factorial = (n > 1) ? factorial(n - 1) * n : n;
+end
+
+endfunction
+
+localparam F3 = factorial(3);
+localparam F4 = factorial(4);
+localparam F5 = factorial(5);
+
+initial begin
+  $display("factorial 3 = %0d", F3);
+  $display("factorial 4 = %0d", F4);
+  $display("factorial 5 = %0d", F5);
+end
+
+endmodule

ivtest/ivltests/recursive_func_const2.v

@@ -0,0 +1,23 @@
+// Check that constant recursive functions are supported when the `return`
+// statement is used.
+
+module recursive_func();
+
+function automatic [15:0] factorial(input [15:0] n);
+  if (n > 1) begin
+    return factorial(n - 1) * n;
+  end
+  return n;
+endfunction
+
+localparam F3 = factorial(3);
+localparam F4 = factorial(4);
+localparam F5 = factorial(5);
+
+initial begin
+  $display("factorial 3 = %0d", F3);
+  $display("factorial 4 = %0d", F4);
+  $display("factorial 5 = %0d", F5);
+end
+
+endmodule

ivtest/regress-sv.list

@@ -403,6 +403,7 @@ program5b		CE,-g2009		ivltests
 program_hello		normal,-g2009		ivltests
 program_hello2		CE,-g2009		ivltests
 recursive_func2		normal,-g2005-sv	ivltests gold=recursive_func.gold
+recursive_func_const2	normal,-g2005-sv	ivltests gold=recursive_func_const.gold
 sbyte_test		normal,-g2005-sv	ivltests
 scalar_vector		normal,-g2005-sv	ivltests
 sf_countbits		normal,-g2012		ivltests

ivtest/regress-vlg.list

@@ -1470,6 +1470,7 @@ real_invalid_ops	CE			ivltests gold=real_invalid_ops.gold
 real_logical		normal			ivltests
 real_reg_force_rel	normal			ivltests
 recursive_func1		normal			ivltests gold=recursive_func.gold
+recursive_func_const1	normal			ivltests gold=recursive_func_const.gold
 recursive_task		normal			ivltests gold=recursive_task.gold
 redef_net_error 	CE			ivltests
 redef_reg_error 	CE			ivltests

ivtest/regress-vlog95.list

@@ -92,6 +92,8 @@ pr2929913		CE			ivltests
 real_events		CE			ivltests
 recursive_func1		CE			ivltests
 recursive_func2		CE			ivltests
+recursive_func_const1	CE			ivltests
+recursive_func_const2	CE			ivltests
 recursive_task		CE			ivltests
 task_init_var1		CE,-pallowsigned=1	ivltests
 task_init_var2		CE,-pallowsigned=1	ivltests