Throw warning if static variable is declared in a loop (#4018)

Signed-off-by: Ryszard Rozak <rrozak@antmicro.com>

src/V3LinkParse.cpp

@@ -65,6 +65,7 @@ private:
     int m_genblkAbove = 0;  // Begin block number of if/case/for above
     int m_genblkNum = 0;  // Begin block number, 0=none seen
     VLifetime m_lifetime = VLifetime::STATIC;  // Propagating lifetime
+    bool m_insideLoop = false;  // True if the node is inside a loop
 
     // METHODS
     void cleanFileline(AstNode* nodep) {
@@ -222,6 +223,9 @@ private:
 
     void visit(AstVar* nodep) override {
         cleanFileline(nodep);
+        if (nodep->lifetime().isStatic() && m_insideLoop) {
+            nodep->v3warn(E_UNSUPPORTED, "Unsupported: Static variable inside a loop");
+        }
         if (nodep->lifetime().isNone() && nodep->varType() != VVarType::PORT) {
             nodep->lifetime(m_lifetime);
         }
@@ -459,6 +463,8 @@ private:
         //   2. ASTSELBIT(first, var0))
         //   3. ASTSELLOOPVARS(first, var0..var1))
         //   4. DOT(DOT(first, second), ASTSELBIT(third, var0))
+        VL_RESTORER(m_insideLoop);
+        m_insideLoop = true;
         AstNode* bracketp = nodep->arrayp();
         while (AstDot* dotp = VN_CAST(bracketp, Dot)) bracketp = dotp->rhsp();
         if (AstSelBit* const selp = VN_CAST(bracketp, SelBit)) {
@@ -471,14 +477,34 @@ private:
         } else if (VN_IS(bracketp, SelLoopVars)) {
             // Ok
         } else {
-            nodep->v3error(
-                "Syntax error; foreach missing bracketed loop variable (IEEE 1800-2017 12.7.3)");
+            nodep->v3error("Syntax error; foreach missing bracketed loop variable (IEEE "
+                           "1800-2017 12.7.3)");
             VL_DO_DANGLING(nodep->unlinkFrBack()->deleteTree(), nodep);
             return;
         }
         iterateChildren(nodep);
     }
-
+    void visit(AstRepeat* nodep) override {
+        VL_RESTORER(m_insideLoop);
+        {
+            m_insideLoop = true;
+            iterateChildren(nodep);
+        }
+    }
+    void visit(AstDoWhile* nodep) override {
+        VL_RESTORER(m_insideLoop);
+        {
+            m_insideLoop = true;
+            iterateChildren(nodep);
+        }
+    }
+    void visit(AstWhile* nodep) override {
+        VL_RESTORER(m_insideLoop);
+        {
+            m_insideLoop = true;
+            iterateChildren(nodep);
+        }
+    }
     void visit(AstNodeModule* nodep) override {
         V3Config::applyModule(nodep);
 

test_regress/t/t_static_in_loop_unsup.out

@@ -0,0 +1,5 @@
+%Error-UNSUPPORTED: t/t_static_in_loop_unsup.v:14:24: Unsupported: Static variable inside a loop
+   14 |             static int a = 0;
+      |                        ^
+                    ... For error description see https://verilator.org/warn/UNSUPPORTED?v=latest
+%Error: Exiting due to

test_regress/t/t_static_in_loop_unsup.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 2003 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_static_in_loop_unsup.v

@@ -0,0 +1,26 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2023 by Antmicro Ltd.
+// SPDX-License-Identifier: CC0-1.0
+
+
+module t;
+   initial begin
+      int x = 0;
+      while (x < 10) begin : outer_loop
+         int y = 0;
+         while (y < x) begin : inner_loop
+            static int a = 0;
+            a++;
+            y++;
+         end
+         x++;
+      end
+      if (outer_loop.inner_loop.a != 45) $stop;
+
+      $write("*-* All Finished *-*\n");
+      $finish;
+   end
+
+endmodule