Fix constant function return of function var, bug1467.

Changes

@@ -36,6 +36,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 ****  Fix --savable invalid C++ on packed arrays, bug1465. [Alex Chadwick]
 
+****  Fix constant function return of function var, bug1467. [Roman Popov]
+
 
 * Verilator 4.014 2019-05-08
 

src/V3Number.cpp

@@ -1658,13 +1658,17 @@ V3Number& V3Number::opBufIf1(const V3Number& ens, const V3Number& if1s) {
 }
 
 V3Number& V3Number::opAssign(const V3Number& lhs) {
-    // Note may be a width change during the assign
-    setZero();
-    if (isString()) {
-        m_stringVal = lhs.m_stringVal;
-    } else {
-        for (int bit=0; bit<this->width(); bit++) {
-            setBit(bit, lhs.bitIs(bit));
+    // Note may be a width change during the assign.
+    // Special case: opAssign unlike other ops, allows this an assignment
+    // to itself; V3Simulate does this when hits "foo=foo;"
+    if (this != &lhs) {
+        setZero();
+        if (isString()) {
+            m_stringVal = lhs.m_stringVal;
+        } else {
+            for (int bit=0; bit<this->width(); bit++) {
+                setBit(bit, lhs.bitIs(bit));
+            }
         }
     }
     return *this;

test_regress/t/t_gen_self_return.pl

@@ -0,0 +1,20 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2019 by Wilson Snyder. This program is free software; you can
+# redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+
+scenarios(simulator => 1);
+
+compile(
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_gen_self_return.v

@@ -0,0 +1,54 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2019 by Roman Popov.
+
+module dut
+  #(
+    parameter DEPTH = 16,
+    parameter WIDTH = 32,
+    parameter RAM_SPLIT_WIDTH = 16
+    )
+   (
+    output logic [WIDTH-1:0] ram_dataout
+    );
+
+   localparam RAM_ADDR_WIDTH = $clog2(DEPTH);  // = 4
+   localparam NUM_RAM_BLOCKS = (WIDTH/RAM_SPLIT_WIDTH) + {31'h0, ((WIDTH % RAM_SPLIT_WIDTH) > 0)};  // = 2
+   typedef logic [NUM_RAM_BLOCKS:0][31:0] block_index_t;  // width 96
+
+   function automatic block_index_t index_calc(input int WIDTH, NUM_RAM_BLOCKS);
+      index_calc[0] = '0;
+      for(int i = 0; i < NUM_RAM_BLOCKS; i++) index_calc[i+1] = WIDTH/NUM_RAM_BLOCKS + {31'h0, (i < (WIDTH%NUM_RAM_BLOCKS))};
+      for(int i = 0; i < NUM_RAM_BLOCKS; i++) index_calc[i+1] = index_calc[i+1] + index_calc[i];
+      // bug1467 was this return
+      return index_calc;
+   endfunction
+
+   localparam block_index_t RAM_BLOCK_INDEX = index_calc(WIDTH, NUM_RAM_BLOCKS);
+
+   generate
+      begin : ram_dataout_gen
+         for (genvar i = 0; i < NUM_RAM_BLOCKS; i++) begin
+            always_comb ram_dataout[RAM_BLOCK_INDEX[i+1]-1:RAM_BLOCK_INDEX[i]] = 0;
+         end
+      end
+   endgenerate
+
+   initial begin
+      if (RAM_BLOCK_INDEX != {32'd32, 32'd16, 32'd0}) $stop;
+      $write("*-* All Finished *-*\n");
+      $finish;
+   end
+
+endmodule
+
+module t
+  (
+   input               clk,
+   output logic [31:0] ram_dataout
+   );
+
+   dut dut0(.*);
+
+endmodule