Add error when constant function under a generate (#3103).

Changes

@@ -23,6 +23,7 @@ Verilator 4.211 devel
 * Parameter values are now emitted as 'static constexpr' instead of enum.
   C++ direct references to parameters might require updating (#3077). [Geza Lore]
 * Refactored Verilated include files; include verilated.h not verilated_heavy.h.
+* Add error when constant function under a generate (#3103). [Don Owen]
 * Fix -G to treat simple integer literals as signed (#3060). [Anikin1610]
 * Fix emitted string array initializers (#2895). [Iztok Jeras]
 * Fix bitop tree optimization dropping necessary & operator (#3096). [Flavien Solt]

src/V3Ast.h

@@ -2682,6 +2682,7 @@ private:
     bool m_isHideProtected : 1;  // Verilog protected
     bool m_pure : 1;  // DPI import pure (vs. virtual pure)
     bool m_pureVirtual : 1;  // Pure virtual
+    bool m_underGenerate : 1;  // Under generate (for warning)
     bool m_virtual : 1;  // Virtual method in class
     VLifetime m_lifetime;  // Lifetime
 protected:
@@ -2704,6 +2705,7 @@ protected:
         , m_isHideProtected{false}
         , m_pure{false}
         , m_pureVirtual{false}
+        , m_underGenerate{false}
         , m_virtual{false} {
         addNOp3p(stmtsp);
         cname(name);  // Might be overridden by dpi import/export
@@ -2770,6 +2772,8 @@ public:
     bool pure() const { return m_pure; }
     void pureVirtual(bool flag) { m_pureVirtual = flag; }
     bool pureVirtual() const { return m_pureVirtual; }
+    void underGenerate(bool flag) { m_underGenerate = flag; }
+    bool underGenerate() const { return m_underGenerate; }
     void isVirtual(bool flag) { m_virtual = flag; }
     bool isVirtual() const { return m_virtual; }
     void lifetime(const VLifetime& flag) { m_lifetime = flag; }

src/V3LinkResolve.cpp

@@ -52,6 +52,7 @@ private:
     AstNodeFTask* m_ftaskp = nullptr;  // Function or task we're inside
     AstNodeCoverOrAssert* m_assertp = nullptr;  // Current assertion
     int m_senitemCvtNum = 0;  // Temporary signal counter
+    bool m_underGenerate = false;  // Under GenFor/GenIf
 
     // METHODS
     VL_DEBUG_FUNC;  // Declare debug()
@@ -111,6 +112,7 @@ private:
 
     virtual void visit(AstNodeFTask* nodep) override {
         // NodeTask: Remember its name for later resolution
+        if (m_underGenerate) nodep->underGenerate(true);
         // Remember the existing symbol table scope
         if (m_classp) {
             if (nodep->name() == "pre_randomize" || nodep->name() == "post_randomize") {
@@ -520,6 +522,17 @@ private:
     // virtual void visit(AstModport* nodep) override { ... }
     // We keep Modport's themselves around for XML dump purposes
 
+    virtual void visit(AstGenFor* nodep) override {
+        VL_RESTORER(m_underGenerate);
+        m_underGenerate = true;
+        iterateChildren(nodep);
+    }
+    virtual void visit(AstGenIf* nodep) override {
+        VL_RESTORER(m_underGenerate);
+        m_underGenerate = true;
+        iterateChildren(nodep);
+    }
+
     virtual void visit(AstNode* nodep) override { iterateChildren(nodep); }
 
 public:

src/V3Simulate.h

@@ -484,8 +484,16 @@ private:
             return;
         }
         if (nodep->dpiImport()) {
+            if (m_params) {
+                nodep->v3error("Constant function may not be DPI import (IEEE 1800-2017 13.4.3)");
+            }
             clearOptimizable(nodep, "DPI import functions aren't simulatable");
         }
+        if (nodep->underGenerate()) {
+            nodep->v3error(
+                "Constant function may not be declared under generate (IEEE 1800-2017 13.4.3)");
+            clearOptimizable(nodep, "Constant function called under generate");
+        }
         checkNodeInfo(nodep);
         iterateChildren(nodep);
     }

test_regress/t/t_lint_const_func_dpi_bad.out

@@ -0,0 +1,11 @@
+%Error: t/t_lint_const_func_dpi_bad.v:8:32: Constant function may not be DPI import (IEEE 1800-2017 13.4.3)
+                                          : ... In instance t
+    8 |    import "DPI-C" function int dpiFunc();
+      |                                ^~~~~~~
+%Error: t/t_lint_const_func_dpi_bad.v:9:23: Expecting expression to be constant, but can't determine constant for FUNCREF 'dpiFunc'
+                                          : ... In instance t
+        t/t_lint_const_func_dpi_bad.v:8:32: ... Location of non-constant FUNC 'dpiFunc': DPI import functions aren't simulatable
+        t/t_lint_const_func_dpi_bad.v:9:23: ... Called from dpiFunc() with parameters:
+    9 |    localparam PARAM = dpiFunc();
+      |                       ^~~~~~~
+%Error: Exiting due to

test_regress/t/t_lint_const_func_dpi_bad.pl

@@ -0,0 +1,19 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2008 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(vlt => 1);
+
+lint(
+    fails => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_lint_const_func_dpi_bad.v

@@ -0,0 +1,10 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2021 by Donald Owen.
+// SPDX-License-Identifier: CC0-1.0
+
+module t ();
+   import "DPI-C" function int dpiFunc();
+   localparam PARAM = dpiFunc();
+endmodule

test_regress/t/t_lint_const_func_gen_bad.out

@@ -0,0 +1,11 @@
+%Error: t/t_lint_const_func_gen_bad.v:11:30: Constant function may not be declared under generate (IEEE 1800-2017 13.4.3)
+                                           : ... In instance t
+   11 |       function automatic bit constFunc();
+      |                              ^~~~~~~~~
+%Error: t/t_lint_const_func_gen_bad.v:15:26: Expecting expression to be constant, but can't determine constant for FUNCREF 'constFunc'
+                                           : ... In instance t
+        t/t_lint_const_func_gen_bad.v:11:30: ... Location of non-constant FUNC 'constFunc': Constant function called under generate
+        t/t_lint_const_func_gen_bad.v:15:26: ... Called from constFunc() with parameters:
+   15 |       localparam PARAM = constFunc();
+      |                          ^~~~~~~~~
+%Error: Exiting due to

test_regress/t/t_lint_const_func_gen_bad.pl

@@ -0,0 +1,19 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2008 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(vlt => 1);
+
+lint(
+    fails => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_lint_const_func_gen_bad.v

@@ -0,0 +1,17 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2021 by Donald Owen.
+// SPDX-License-Identifier: CC0-1.0
+
+module t ();
+   if (1) begin: GenConstFunc
+      // IEEE 1800-2017 13.4.3, constant functions shall not be declared inside a
+      //generate block
+      function automatic bit constFunc();
+         constFunc = 1'b1;
+      endfunction
+
+      localparam PARAM = constFunc();
+    end
+endmodule