Support empty queue assignment to delete queue

src/V3Ast.cpp

@@ -1264,12 +1264,15 @@ AstNodeDType* AstNode::findBitRangeDType(const VNumRange& range, int widthMin,
 AstBasicDType* AstNode::findInsertSameDType(AstBasicDType* nodep) {
     return v3Global.rootp()->typeTablep()->findInsertSameDType(nodep);
 }
-AstNodeDType* AstNode::findVoidDType() const {
-    return v3Global.rootp()->typeTablep()->findVoidDType(fileline());
+AstNodeDType* AstNode::findEmptyQueueDType() const {
+    return v3Global.rootp()->typeTablep()->findEmptyQueueDType(fileline());
 }
 AstNodeDType* AstNode::findQueueIndexDType() const {
     return v3Global.rootp()->typeTablep()->findQueueIndexDType(fileline());
 }
+AstNodeDType* AstNode::findVoidDType() const {
+    return v3Global.rootp()->typeTablep()->findVoidDType(fileline());
+}
 
 //######################################################################
 // AstNVisitor

src/V3Ast.h

@@ -1698,6 +1698,7 @@ public:
     void dtypeSetSigned32() { dtypep(findSigned32DType()); }
     void dtypeSetUInt32() { dtypep(findUInt32DType()); }  // Twostate
     void dtypeSetUInt64() { dtypep(findUInt64DType()); }  // Twostate
+    void dtypeSetEmptyQueue() { dtypep(findEmptyQueueDType()); }
     void dtypeSetVoid() { dtypep(findVoidDType()); }
 
     // Data type locators
@@ -1708,6 +1709,7 @@ public:
     AstNodeDType* findUInt32DType() { return findBasicDType(AstBasicDTypeKwd::UINT32); }
     AstNodeDType* findUInt64DType() { return findBasicDType(AstBasicDTypeKwd::UINT64); }
     AstNodeDType* findCHandleDType() { return findBasicDType(AstBasicDTypeKwd::CHANDLE); }
+    AstNodeDType* findEmptyQueueDType() const;
     AstNodeDType* findVoidDType() const;
     AstNodeDType* findQueueIndexDType() const;
     AstNodeDType* findBitDType(int width, int widthMin, VSigning numeric) const;

src/V3AstNodes.cpp

@@ -932,9 +932,18 @@ void AstTypeTable::repairCache() {
     }
 }
 
+AstEmptyQueueDType* AstTypeTable::findEmptyQueueDType(FileLine* fl) {
+    if (VL_UNLIKELY(!m_emptyQueuep)) {
+        AstEmptyQueueDType* newp = new AstEmptyQueueDType{fl};
+        addTypesp(newp);
+        m_emptyQueuep = newp;
+    }
+    return m_emptyQueuep;
+}
+
 AstVoidDType* AstTypeTable::findVoidDType(FileLine* fl) {
     if (VL_UNLIKELY(!m_voidp)) {
-        AstVoidDType* newp = new AstVoidDType(fl);
+        AstVoidDType* newp = new AstVoidDType{fl};
         addTypesp(newp);
         m_voidp = newp;
     }
@@ -1642,6 +1651,10 @@ void AstUnsizedArrayDType::dumpSmall(std::ostream& str) const {
     this->AstNodeDType::dumpSmall(str);
     str << "[]";
 }
+void AstEmptyQueueDType::dumpSmall(std::ostream& str) const {
+    this->AstNodeDType::dumpSmall(str);
+    str << "emptyq";
+}
 void AstVoidDType::dumpSmall(std::ostream& str) const {
     this->AstNodeDType::dumpSmall(str);
     str << "void";

src/V3AstNodes.h

@@ -183,6 +183,17 @@ public:
     static AstConst* parseParamLiteral(FileLine* fl, const string& literal);
 };
 
+class AstEmptyQueue final : public AstNodeMath {
+public:
+    AstEmptyQueue(FileLine* fl)
+        : ASTGEN_SUPER_EmptyQueue(fl) {}
+    ASTNODE_NODE_FUNCS(EmptyQueue)
+    virtual string emitC() { V3ERROR_NA_RETURN(""); }
+    virtual string emitVerilog() { return "{}"; }
+    virtual bool same(const AstNode* samep) const override { return true; }
+    virtual bool cleanOut() const { return true; }
+};
+
 class AstRange final : public AstNodeRange {
     // Range specification, for use under variables and cells
 public:
@@ -1354,6 +1365,33 @@ public:
     }
 };
 
+class AstEmptyQueueDType final : public AstNodeDType {
+    // For EmptyQueue
+public:
+    explicit AstEmptyQueueDType(FileLine* fl)
+        : ASTGEN_SUPER_EmptyQueueDType(fl) {
+        dtypep(this);
+    }
+    ASTNODE_NODE_FUNCS(EmptyQueueDType)
+    virtual void dumpSmall(std::ostream& str) const override;
+    virtual bool hasDType() const override { return true; }
+    virtual bool maybePointedTo() const override { return true; }
+    virtual AstNodeDType* subDTypep() const override { return nullptr; }
+    virtual AstNodeDType* virtRefDTypep() const override { return nullptr; }
+    virtual void virtRefDTypep(AstNodeDType* nodep) override {}
+    virtual bool similarDType(AstNodeDType* samep) const override { return this == samep; }
+    virtual AstBasicDType* basicp() const override { return nullptr; }
+    // cppcheck-suppress csyleCast
+    virtual AstNodeDType* skipRefp() const override { return (AstNodeDType*)this; }
+    // cppcheck-suppress csyleCast
+    virtual AstNodeDType* skipRefToConstp() const override { return (AstNodeDType*)this; }
+    // cppcheck-suppress csyleCast
+    virtual AstNodeDType* skipRefToEnump() const override { return (AstNodeDType*)this; }
+    virtual int widthAlignBytes() const override { return 1; }
+    virtual int widthTotalBytes() const override { return 1; }
+    virtual bool isCompound() const override { return false; }
+};
+
 class AstVoidDType final : public AstNodeDType {
     // For e.g. a function returning void
 public:
@@ -9088,8 +9126,9 @@ public:
 class AstTypeTable final : public AstNode {
     // Container for hash of standard data types
     // Children:  NODEDTYPEs
-    AstVoidDType* m_voidp = nullptr;
+    AstEmptyQueueDType* m_emptyQueuep = nullptr;
     AstQueueDType* m_queueIndexp = nullptr;
+    AstVoidDType* m_voidp = nullptr;
     AstBasicDType* m_basicps[AstBasicDTypeKwd::_ENUM_MAX];
     //
     using DetailedMap = std::map<VBasicTypeKey, AstBasicDType*>;
@@ -9100,14 +9139,15 @@ public:
     ASTNODE_NODE_FUNCS(TypeTable)
     AstNodeDType* typesp() const { return VN_CAST(op1p(), NodeDType); }  // op1 = List of dtypes
     void addTypesp(AstNodeDType* nodep) { addOp1p(nodep); }
-    AstVoidDType* findVoidDType(FileLine* fl);
-    AstQueueDType* findQueueIndexDType(FileLine* fl);
     AstBasicDType* findBasicDType(FileLine* fl, AstBasicDTypeKwd kwd);
     AstBasicDType* findLogicBitDType(FileLine* fl, AstBasicDTypeKwd kwd, int width, int widthMin,
                                      VSigning numeric);
     AstBasicDType* findLogicBitDType(FileLine* fl, AstBasicDTypeKwd kwd, const VNumRange& range,
                                      int widthMin, VSigning numeric);
     AstBasicDType* findInsertSameDType(AstBasicDType* nodep);
+    AstEmptyQueueDType* findEmptyQueueDType(FileLine* fl);
+    AstQueueDType* findQueueIndexDType(FileLine* fl);
+    AstVoidDType* findVoidDType(FileLine* fl);
     void clearCache();
     void repairCache();
     virtual void dump(std::ostream& str = std::cout) const override;

src/V3Width.cpp

@@ -1078,6 +1078,12 @@ private:
         // We don't size the constant until we commit the widths, as need parameters
         // to remain unsized, and numbers to remain unsized to avoid backp() warnings
     }
+    virtual void visit(AstEmptyQueue* nodep) override {
+        nodep->dtypeSetEmptyQueue();
+        if (!VN_IS(nodep->backp(), Assign))
+            nodep->v3warn(E_UNSUPPORTED,
+                          "Unsupported/Illegal: empty queue ('{}') in this context");
+    }
     virtual void visit(AstFell* nodep) override {
         if (m_vup->prelim()) {
             iterateCheckSizedSelf(nodep, "LHS", nodep->exprp(), SELF, BOTH);
@@ -1173,6 +1179,7 @@ private:
                 return;
             }
         }
+        nodep->backp()->dumpTree(cout, "-FIXME-tr ");
         nodep->v3warn(E_UNSUPPORTED, "Unsupported/illegal unbounded ('$') in this context.");
     }
     virtual void visit(AstIsUnbounded* nodep) override {
@@ -3761,6 +3768,23 @@ private:
                 nodep->v3warn(E_UNSUPPORTED, "Unsupported: assignment of event data type");
             }
         }
+        if (VN_IS(nodep->rhsp(), EmptyQueue)) {
+            UINFO(9, "= {} -> .delete(): " << nodep);
+            if (!VN_IS(nodep->lhsp()->dtypep()->skipRefp(), QueueDType)) {
+                nodep->v3warn(E_UNSUPPORTED,
+                              "Unsupported/Illegal: empty queue ('{}') in this assign context");
+                VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
+                return;
+            }
+            AstMethodCall* const newp = new AstMethodCall{
+                nodep->fileline(), nodep->lhsp()->unlinkFrBack(), "delete", nullptr};
+            newp->makeStatement();
+            nodep->replaceWith(newp);
+            VL_DO_DANGLING(pushDeletep(nodep), nodep);
+            // Need to now convert it
+            visit(newp);
+            return;
+        }
         if (AstNewDynamic* dynp = VN_CAST(nodep->rhsp(), NewDynamic)) {
             UINFO(9, "= new[] -> .resize(): " << nodep);
             AstCMethodHard* newp;
@@ -3777,6 +3801,7 @@ private:
             newp->makeStatement();
             nodep->replaceWith(newp);
             VL_DO_DANGLING(pushDeletep(nodep), nodep);
+            // return;
         }
     }
 

src/verilog.y

@@ -4268,8 +4268,7 @@ expr<nodep>:			// IEEE: part of expression/constant_expression/primary
 	//			// IEEE: "... hierarchical_identifier select"  see below
 	//
 	//			// IEEE: empty_queue (IEEE 1800-2017 empty_unpacked_array_concatenation)
-	|	'{' '}'					{ $$ = new AstConst($1, AstConst::BitFalse());
-							  BBUNSUP($<fl>1, "Unsupported: empty queues (\"{ }\")"); }
+	|	'{' '}'					{ $$ = new AstEmptyQueue($1); }
 	//
 	//			// IEEE: concatenation/constant_concatenation
 	//			// Part of exprOkLvalue below

test_regress/t/t_queue_empty_bad.out

@@ -0,0 +1,10 @@
+%Error-UNSUPPORTED: t/t_queue_empty_bad.v:11:11: Unsupported/Illegal: empty queue ('{}') in this context
+                                               : ... In instance t
+   11 |       i = {} + 1;
+      |           ^
+                    ... For error description see https://verilator.org/warn/UNSUPPORTED?v=latest
+%Error-UNSUPPORTED: t/t_queue_empty_bad.v:13:9: Unsupported/Illegal: empty queue ('{}') in this assign context
+                                              : ... In instance t
+   13 |       i = {};
+      |         ^
+%Error: Exiting due to

test_regress/t/t_queue_empty_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 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_queue_empty_bad.v

@@ -0,0 +1,18 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2019 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module t (/*AUTOARG*/);
+   initial begin
+      int i;
+
+      i = {} + 1;
+
+      i = {};
+
+      $write("*-* All Finished *-*\n");
+      $finish;
+   end
+endmodule

test_regress/t/t_queue_slice.v

@@ -26,6 +26,9 @@ module t (/*AUTOARG*/);
       q = '{"q"};
       v = $sformatf("%p", q); `checks(v, "'{\"q\"} ");
 
+      q = {};
+      i = q.size(); `checkh(i, 0);
+
       q = '{"q", "b", "c", "d", "e", "f"};
       if (q[0] !== "q") $stop;
       v = $sformatf("%p", q); `checks(v, "'{\"q\", \"b\", \"c\", \"d\", \"e\", \"f\"} ");