Support 'this' (#2585).

Changes

@@ -9,6 +9,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 ****  Support # as a comment in -f files (#2497). [phantom-killua]
 
+****  Support 'this' (#2585). [Rafal Kapuscik]
+
 ****  Fix -G dropping public indication (#2561). [Andrew Goessling]
 
 ****  Fix $urandom_range passed variable (#2563). [nanduraj1]

docs/CONTRIBUTORS

@@ -53,6 +53,7 @@ Philipp Wagner
 Pieter Kapsenberg
 Piotr Binkowski
 Qingyao Sun
+Rafal Kapuscik
 Richard Myers
 Rupert Swarbrick
 Sean Cross

include/verilated_threads.h

@@ -28,7 +28,7 @@
 // VL_THREADED.
 // Alternatively it is always safe but may harm performance to always
 // define VL_THREADED for all compiles.
-# error "verilated_threads.h/cpp expected VL_THREADED (from verilator --threads)"
+#error "verilated_threads.h/cpp expected VL_THREADED (from verilator --threads)"
 #endif
 
 #include <condition_variable>

src/V3AstNodes.h

@@ -2359,7 +2359,9 @@ public:
         if (varScopep()) {
             return (varScopep() == samep->varScopep());
         } else {
-            return (hiername() == samep->hiername() && varp()->name() == samep->varp()->name());
+            return (hiername() == samep->hiername()
+                    && (hiername() != "" || samep->hiername() != "")
+                    && varp()->name() == samep->varp()->name());
         }
     }
     virtual int instrCount() const override {

src/V3LinkDot.cpp

@@ -1961,8 +1961,18 @@ private:
             m_ds.m_dotp = nodep;  // Always, not just at start
             m_ds.m_dotPos = DP_SCOPE;
 
-            // m_ds.m_dotText communicates the cell prefix between stages
-            if (VN_IS(nodep->lhsp(), ClassOrPackageRef)) {
+            if (VN_IS(nodep->lhsp(), ParseRef) && nodep->lhsp()->name() == "this") {
+                VSymEnt* classSymp = m_ds.m_dotSymp;
+                do {
+                    classSymp = classSymp->fallbackp();
+                } while (classSymp && !VN_IS(classSymp->nodep(), Class));
+                m_ds.m_dotSymp = classSymp;
+                if (!classSymp) {
+                    nodep->v3error("'this' used outside class");
+                    m_ds.m_dotErr = true;
+                }
+            } else if (VN_IS(nodep->lhsp(), ClassOrPackageRef)) {
+                // m_ds.m_dotText communicates the cell prefix between stages
                 // if (!start) { nodep->lhsp()->v3error("Package reference may not be embedded in
                 // dotted reference"); m_ds.m_dotErr=true; }
                 m_ds.m_dotPos = DP_PACKAGE;
@@ -2019,21 +2029,14 @@ private:
         // Generally resolved during Primay, but might be at param time under AstUnlinkedRef
         UASSERT_OBJ(m_statep->forPrimary() || m_statep->forPrearray(), nodep,
                     "ParseRefs should no longer exist");
-        if (nodep->name() == "this") {
-            nodep->v3warn(E_UNSUPPORTED, "Unsupported: this");
-        } else if (nodep->name() == "super") {
-            nodep->v3warn(E_UNSUPPORTED, "Unsupported: super");
-        }
+        if (nodep->name() == "super") { nodep->v3warn(E_UNSUPPORTED, "Unsupported: super"); }
         DotStates lastStates = m_ds;
         bool start = (m_ds.m_dotPos == DP_NONE);  // Save, as m_dotp will be changed
         if (start) {
             m_ds.init(m_curSymp);
             // Note m_ds.m_dot remains nullptr; this is a reference not under a dot
         }
-        if (nodep->name() == "this") {
-            nodep->v3warn(E_UNSUPPORTED, "Unsupported: this");
-            m_ds.m_dotErr = true;
-        } else if (nodep->name() == "super") {
+        if (nodep->name() == "super") {
             nodep->v3warn(E_UNSUPPORTED, "Unsupported: super");
             m_ds.m_dotErr = true;
         }

src/V3SymTable.h

@@ -108,6 +108,7 @@ public:
     void operator delete(void* objp, size_t size) {}
 #endif
     void fallbackp(VSymEnt* entp) { m_fallbackp = entp; }
+    VSymEnt* fallbackp() const { return m_fallbackp; }
     void parentp(VSymEnt* entp) { m_parentp = entp; }
     VSymEnt* parentp() const { return m_parentp; }
     void packagep(AstNodeModule* entp) { m_packagep = entp; }

test_regress/t/t_class_extends_this.out

@@ -1,15 +1,3 @@
-%Error-UNSUPPORTED: t/t_class_extends_this.v:13:11: Unsupported: this
-   13 |       if (this.value != 1) $stop;
-      |           ^~~~
-%Error: t/t_class_extends_this.v:13:11: Can't find definition of scope/variable: 'this'
-   13 |       if (this.value != 1) $stop;
-      |           ^~~~
-%Error-UNSUPPORTED: t/t_class_extends_this.v:21:11: Unsupported: this
-   21 |       if (this.value != 2) $stop;
-      |           ^~~~
-%Error: t/t_class_extends_this.v:21:11: Can't find definition of scope/variable: 'this'
-   21 |       if (this.value != 2) $stop;
-      |           ^~~~
 %Error-UNSUPPORTED: t/t_class_extends_this.v:22:11: Unsupported: super
    22 |       if (super.value != 1) $stop;
       |           ^~~~~
@@ -28,12 +16,6 @@
 %Error: t/t_class_extends_this.v:24:7: Can't find definition of scope/variable: 'super'
    24 |       super.value = 10;
       |       ^~~~~
-%Error-UNSUPPORTED: t/t_class_extends_this.v:25:7: Unsupported: this
-   25 |       this.value = 20;
-      |       ^~~~
-%Error: t/t_class_extends_this.v:25:7: Can't find definition of scope/variable: 'this'
-   25 |       this.value = 20;
-      |       ^~~~
 %Error-UNSUPPORTED: t/t_class_extends_this.v:26:11: Unsupported: super
    26 |       if (super.value != 10) $stop;
       |           ^~~~~

test_regress/t/t_class_uses_this.pl

@@ -0,0 +1,21 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2020 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.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(simulator => 1);
+
+compile(
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_class_uses_this.v

@@ -0,0 +1,34 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2020 Rafal Kapuscik
+// SPDX-License-Identifier: CC0-1.0
+//
+class foo;
+   bit [3:0] addr;
+   function void set (bit [3:0] addr);
+   begin : body
+     this.addr = addr;
+   end : body
+   endfunction
+endclass
+
+module t(/*AUTOARG*/
+   // Inputs
+   clk
+   );
+   input clk;
+   foo bar;
+   foo baz;
+   initial begin
+       bar = new();
+       baz = new();
+       bar.set(4);
+`ifdef TEST_VERBOSE
+       $display(bar.addr);
+       $display(baz.addr);
+`endif
+       $write("*-* All Finished *-*\n");
+       $finish;
+   end
+endmodule

test_regress/t/t_class_uses_this_bad.out

@@ -0,0 +1,4 @@
+%Error: t/t_class_uses_this_bad.v:15:12: 'this' used outside class
+   15 |        this.addr = 2;
+      |            ^
+%Error: Exiting due to

test_regress/t/t_class_uses_this_bad.pl

@@ -0,0 +1,23 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2020 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.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(simulator => 1);
+
+compile(
+    fails => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+#execute(
+#    check_finished => 1,
+#    );
+
+ok(1);
+1;

test_regress/t/t_class_uses_this_bad.v

@@ -0,0 +1,19 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2020 Rafal Kapuscik
+// SPDX-License-Identifier: CC0-1.0
+//
+
+module t(/*AUTOARG*/
+   // Inputs
+   clk
+   );
+   input clk;
+   bit [3:0] addr;
+   initial begin
+       this.addr = 2;
+       $write("*-* All Finished *-*\n");
+       $finish;
+   end
+endmodule