Fix ++/-- tree fix in case statements (#3346) (#3349).

docs/CONTRIBUTORS

@@ -18,6 +18,7 @@ David Horton
 David Metz
 David Stanford
 David Turner
+Drew Ranck
 Drew Taussig
 Driss Hafdi
 Edgar E. Iglesias

src/V3LinkInc.cpp

@@ -134,6 +134,16 @@ private:
         iterateAndNextNull(nodep->elsesp());
         m_insStmtp = nullptr;
     }
+    virtual void visit(AstCaseItem* nodep) override {
+        m_insMode = IM_BEFORE;
+        {
+            VL_RESTORER(m_unsupportedHere);
+            m_unsupportedHere = true;
+            iterateAndNextNull(nodep->condsp());
+        }
+        m_insStmtp = nullptr;  // Next thing should be new statement
+        iterateAndNextNull(nodep->bodysp());
+    }
     virtual void visit(AstNodeFor* nodep) override {  // LCOV_EXCL_LINE
         nodep->v3fatalSrc(
             "For statements should have been converted to while statements in V3Begin.cpp");

test_regress/t/t_case_incrdecr.pl

@@ -0,0 +1,22 @@
+#!/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(simulator => 1);
+
+compile(
+    verilator_flags2 => ["--trace --Os -x-assign 0"],
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_case_incrdecr.v

@@ -0,0 +1,156 @@
+module t
+  (/*AUTOARG*/
+   // Inputs
+   clk
+   );
+
+  input clk;
+
+  int   cyc = 0;
+
+  logic [1:0] case_sel;
+
+  always @ (posedge clk) begin : main
+    cyc <= cyc + 1;
+
+    case_sel <= 2'($urandom);
+
+    if (cyc > 100) begin
+      $write("*-* All Finished *-*\n");
+      $finish();
+    end
+  end
+
+
+  // -------------------------
+  // Simple case-stmt with ++/--
+
+  logic [3:0] count_d;
+  logic [3:0] count_q = '0;
+
+  logic [3:0] want_count_d;
+  logic [3:0] want_count_q = '0;
+
+  always_ff @(posedge clk) begin : flops
+    count_q      <= count_d;
+    want_count_q <= want_count_d;
+  end
+
+  always @(posedge clk) begin : simple_check
+    if (cyc > 0) begin
+      if (count_q !== want_count_q) begin
+        $error("%m: Checks cyc=%0d, count_q (%0d) !== want_count_q (%0d)",
+               cyc, count_q, want_count_q);
+        $stop; // don't finish to fail the test.
+      end
+    end
+  end
+
+  always_comb begin : update_golden_counts
+    want_count_d = want_count_q;
+    if (case_sel == 2'b10)
+      want_count_d++;
+    else if (case_sel == 2'b01)
+      want_count_d--;
+  end
+
+  // Make sure the ++ and -- operators are handled correctly in case stmts.
+  // Test for https://github.com/verilator/verilator/issues/3346
+  always_comb begin : update_counts
+    count_d = count_q;
+    case (case_sel)
+    2'b10: count_d++;
+    2'b01: count_d--;
+    default : ;
+    endcase // case (case_sel)
+  end
+
+  // -------------------------
+  // FSM with ++/--
+  // A more elaborate case statement, with if-else, for loops, etc
+  // to confirm that ++/-- is handled by V3LinkInc.cpp
+  logic [3:0] state_d, state_q;
+  initial state_q = '0;
+  logic [3:0] state_counter_d, state_counter_q;
+  always_ff @(posedge clk) begin
+    state_q         <= state_d;
+    state_counter_q <= state_counter_d;
+  end
+
+
+  always_comb begin : update_state
+    state_d = state_q;
+    state_counter_d = state_counter_q;
+    case (state_q)
+
+    // state 0, no begin/end, goes to state 1
+    4'd0: state_d = 4'd1;
+
+    // state 1, clears state_counter_d, goes to state 2
+    4'd1: begin
+      state_d = 4'd2;
+      state_counter_d = '0;
+    end
+
+    // state 2, wait until state_counter_d increments to 4.
+    4'd2: begin
+      state_counter_d++;
+      if (state_counter_q == 4) begin
+        state_d = 4'd3;
+      end
+    end
+    // state 3, decrements state_counter_d from 5 to 0.
+    4'd3: begin
+      state_counter_d--;
+      if (state_counter_q == 1) begin
+        state_d = 4'd4;
+      end
+    end
+
+    4'd4: begin
+      // add 4 with for-loop and ++.
+      for (int unsigned i = 0; i < 4; i++) begin
+        state_counter_d++;
+      end
+
+      if (state_counter_q == 12) begin
+        state_counter_d = '0;
+        state_d = 4'd5;
+      end
+    end
+
+    4'd5: begin
+      // add 8 with a while loop and go to state 6.
+      while (state_counter_d <= 7) begin
+        state_counter_d++;
+      end
+
+      if (state_counter_d == 8) begin
+        state_d = 4'd15;
+      end
+    end
+    4'd15 : begin
+      // success, stay here.
+      state_counter_d = 4'd7; // pick and hold some success number.
+    end
+    default: ;
+    endcase // case (state_q)
+
+  end // block: state
+
+  always @(posedge clk) begin : simple_state_check
+    //$display("%m: debug, cyc=%0d, state_q=%0d, state_counter_q=%0d",
+    //           cyc, state_q, state_counter_q);
+    if (cyc >= 90) begin
+      // the above FSM should finish before 90 cycles.
+      // Make sure we made it to state 4'd15.
+      if (state_q !== 4'd15 ||
+          state_counter_q !== 4'd7) begin
+        $error("%m: EOT checks, cyc=%0d, state_q=%0d (want 15), state_counter_q=%0d (want 7)",
+               cyc, state_q, state_counter_q);
+        $stop; // don't finish to fail the test.
+      end
+    end
+  end
+
+endmodule : t

test_regress/t/t_incr_void.pl

@@ -0,0 +1,22 @@
+#!/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(simulator => 1);
+
+compile(
+    verilator_flags2 => ["--Os -x-assign 0"],
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_incr_void.v

@@ -0,0 +1,55 @@
+module t
+  (/*AUTOARG*/
+   // Inputs
+   clk
+   );
+
+  input clk;
+
+  int   cyc = 0;
+
+  always @ (posedge clk) begin : main
+    cyc <= cyc + 1;
+
+    if (cyc > 100) begin
+      $write("*-* All Finished *-*\n");
+      $finish();
+    end
+  end
+
+
+
+  logic [3:0] count_d;
+  logic [3:0] count_q = '0;
+
+  logic [3:0] want_count_d;
+  logic [3:0] want_count_q = '0;
+
+  always_ff @(posedge clk) begin : flops
+    count_q        <= count_d;
+    want_count_q   <= want_count_d;
+  end
+
+  always @(posedge clk) begin : simple_check
+    if (cyc > 0) begin
+      if (count_q !== want_count_q) begin
+        $error("%m: cyc=%0d, count_q (%0d) !== want_count_q (%0d)",
+               cyc, count_q, want_count_q);
+        $stop; // don't finish to fail the test.
+      end
+    end
+  end
+
+  always_comb begin : update_golden_counts
+    want_count_d = want_count_q;
+    want_count_d += 1'b1;
+  end
+
+  // make sure an implicit void cast on n++ works as expected.
+  always_comb begin : update_counts
+    count_d = count_q;
+    count_d++;
+  end
+
+
+endmodule