Internals: Change AstAssignVarScope into AstAliasScope (#6280) (#6512)

Rename and make it derive from AstNode instead of AstNodeAssign.

Small step towards #6280. No functional change.

src/V3AstNodeOther.h

@@ -450,7 +450,7 @@ public:
     inline bool hasCombo() const;
 };
 class AstAlias final : public AstNode {
-    // Alias statement
+    // Alias construct - Used for source level net alias, and also for variable aliases internally
     // @astgen op1 := itemsp : List[AstNodeExpr]  // Alias operands
 public:
     AstAlias(FileLine* fl, AstNodeExpr* itemsp)
@@ -459,6 +459,18 @@ public:
     }
     ASTGEN_MEMBERS_AstAlias;
 };
+class AstAliasScope final : public AstNode {
+    // Like AstAlias, but aliases two scopes instead of nets/variables
+    // @astgen op1 := rhsp : AstNodeExpr
+    // @astgen op2 := lhsp : AstNodeExpr
+public:
+    AstAliasScope(FileLine* fl, AstNodeExpr* lhsp, AstNodeExpr* rhsp)
+        : ASTGEN_SUPER_AliasScope(fl) {
+        this->lhsp(lhsp);
+        this->rhsp(rhsp);
+    }
+    ASTGEN_MEMBERS_AstAliasScope;
+};
 class AstBind final : public AstNode {
     // Parents: MODULE
     // Children: CELL

src/V3AstNodeStmt.h

@@ -68,7 +68,6 @@ public:
     bool sameNode(const AstNode*) const override { return true; }
     string verilogKwd() const override { return "="; }
     bool isTimingControl() const override { return timingControlp(); }
-    virtual bool brokeLhsMustBeLvalue() const = 0;
 };
 class AstNodeBlock VL_NOT_FINAL : public AstNodeStmt {
     // A Begin/fork block
@@ -1119,7 +1118,6 @@ public:
         AstNode* const controlp = timingControlp() ? timingControlp()->cloneTree(false) : nullptr;
         return new AstAssign{fileline(), lhsp, rhsp, controlp};
     }
-    bool brokeLhsMustBeLvalue() const override { return true; }
 };
 class AstAssignDly final : public AstNodeAssign {
 public:
@@ -1133,7 +1131,6 @@ public:
     }
     bool isGateOptimizable() const override { return false; }
     string verilogKwd() const override { return "<="; }
-    bool brokeLhsMustBeLvalue() const override { return true; }
 };
 class AstAssignForce final : public AstNodeAssign {
     // Procedural 'force' statement
@@ -1144,20 +1141,6 @@ public:
     AstNodeAssign* cloneType(AstNodeExpr* lhsp, AstNodeExpr* rhsp) override {
         return new AstAssignForce{fileline(), lhsp, rhsp};
     }
-    bool brokeLhsMustBeLvalue() const override { return true; }
-};
-class AstAssignVarScope final : public AstNodeAssign {
-    // Assign two VarScopes to each other
-public:
-    AstAssignVarScope(FileLine* fl, AstNodeExpr* lhsp, AstNodeExpr* rhsp)
-        : ASTGEN_SUPER_AssignVarScope(fl, lhsp, rhsp) {
-        dtypeFrom(rhsp);
-    }
-    ASTGEN_MEMBERS_AstAssignVarScope;
-    AstNodeAssign* cloneType(AstNodeExpr* lhsp, AstNodeExpr* rhsp) override {
-        return new AstAssignVarScope{fileline(), lhsp, rhsp};
-    }
-    bool brokeLhsMustBeLvalue() const override { return false; }
 };
 class AstAssignW final : public AstNodeAssign {
     // Like assign, but wire/assign's in verilog, the only setting of the specified variable
@@ -1176,7 +1159,6 @@ public:
             return refp->access().isWriteOrRW() && refp->varp()->delayp();
         });
     }
-    bool brokeLhsMustBeLvalue() const override { return true; }
     AstDelay* getLhsNetDelay() const;
     AstAlways* convertToAlways();
 };

src/V3Broken.cpp

@@ -225,8 +225,7 @@ private:
     // VISITORS
     void visit(AstNodeAssign* nodep) override {
         processAndIterate(nodep);
-        UASSERT_OBJ(!(v3Global.assertDTypesResolved() && nodep->brokeLhsMustBeLvalue()
+        UASSERT_OBJ(!(v3Global.assertDTypesResolved() && VN_IS(nodep->lhsp(), NodeVarRef)
-                      && VN_IS(nodep->lhsp(), NodeVarRef)
                       && !VN_AS(nodep->lhsp(), NodeVarRef)->access().isWriteOrRW()),
                     nodep, "Assignment LHS is not an lvalue");
     }

src/V3Const.cpp

@@ -3244,8 +3244,8 @@ class ConstVisitor final : public VNVisitor {
     void visit(AstAlias* nodep) override {
         // Don't perform any optimizations, keep the alias around
     }
-    void visit(AstAssignVarScope* nodep) override {
+    void visit(AstAliasScope* nodep) override {
-        // Don't perform any optimizations, the node won't be linked yet
+        // Don't perform any optimizations, keep the alias around
     }
     void visit(AstAssignW* nodep) override {
         iterateChildren(nodep);

src/V3Inline.cpp

@@ -499,7 +499,7 @@ void connectPort(AstNodeModule* modp, AstVar* nodep, AstNodeExpr* pinExprp) {
         UINFO(6, "Inlning port variable: " << nodep);
         if (nodep->isIfaceRef()) {
             modp->addStmtsp(
-                new AstAssignVarScope{flp, portRef(VAccess::WRITE), pinRef(VAccess::READ)});
+                new AstAliasScope{flp, portRef(VAccess::WRITE), pinRef(VAccess::READ)});
         } else {
             AstVarRef* const aliasArgsp = portRef(VAccess::WRITE);
             aliasArgsp->addNext(pinRef(VAccess::READ));
@@ -633,7 +633,7 @@ void process(AstNetlist* netlistp, ModuleStateUser1Allocator& moduleStates) {
     // Clean up AstIfaceRefDType references
     // If the cell has been removed let's make sure we don't leave a
     // reference to it. This dtype may still be in use by the
-    // AstAssignVarScope created earlier but that'll get cleared up later
+    // AstAliasScope created earlier but that'll get cleared up later
     netlistp->typeTablep()->foreach([](AstIfaceRefDType* nodep) {
         if (nodep->user1()) nodep->cellp(nullptr);
     });

src/V3Inst.cpp

@@ -90,7 +90,7 @@ class InstVisitor final : public VNVisitor {
                                         ->subDTypep()
                                         ->skipRefp(),
                                     IfaceRefDType))) {
-                // Create an AstAssignVarScope for Vars to Cells so we can
+                // Create an AstAliasScope for Vars to Cells so we can
                 // link with their scope later
                 AstNodeExpr* const lhsp = new AstVarXRef{exprp->fileline(), nodep->modVarp(),
                                                          m_cellp->name(), VAccess::READ};
@@ -98,9 +98,7 @@ class InstVisitor final : public VNVisitor {
                 const AstVarXRef* const xrefp = VN_CAST(exprp, VarXRef);
                 UASSERT_OBJ(refp || xrefp, exprp,
                             "Interfaces: Pin is not connected to a VarRef or VarXRef");
-                AstAssignVarScope* const assp
+                m_cellp->addNextHere(new AstAliasScope{exprp->fileline(), lhsp, exprp});
-                    = new AstAssignVarScope{exprp->fileline(), lhsp, exprp};
-                m_cellp->addNextHere(assp);
             } else {
                 nodep->v3error("Assigned pin is neither input nor output");
             }

src/V3Interface.cpp

@@ -70,7 +70,7 @@ class InlineIntfRefVisitor final : public VNVisitor {
 
         iterateChildren(modp);
     }
-    void visit(AstAssignVarScope* nodep) override {
+    void visit(AstAliasScope* nodep) override {
         // Reference
         const AstVarRef* const reflp = VN_CAST(nodep->lhsp(), VarRef);
         // What the reference refers to

src/V3LinkDot.cpp

@@ -2326,8 +2326,8 @@ private:
         iterateChildren(nodep);
         pushDeletep(nodep->unlinkFrBack());
     }
-    void visit(AstAssignVarScope* nodep) override {  // ScopeVisitor::
+    void visit(AstAliasScope* nodep) override {  // ScopeVisitor::
-        UINFO(5, "ASSIGNVARSCOPE  " << nodep);
+        UINFO(5, "ALIASSCOPE  " << nodep);
         UINFOTREE(9, nodep, "", "avs");
         VSymEnt* rhsSymp;
         {

src/V3Scope.cpp

@@ -216,7 +216,7 @@ class ScopeVisitor final : public VNVisitor {
         m_scopep->addBlocksp(clonep);
         iterateChildren(clonep);  // We iterate under the *clone*
     }
-    void visit(AstAssignVarScope* nodep) override {
+    void visit(AstAliasScope* nodep) override {
         // Copy under the scope but don't recurse
         UINFO(4, "    Move " << nodep);
         AstNode* const clonep = nodep->cloneTree(false);
@@ -354,7 +354,7 @@ class ScopeCleanupVisitor final : public VNVisitor {
 
     void visit(AstNodeProcedure* nodep) override { movedDeleteOrIterate(nodep); }
     void visit(AstAlias* nodep) override { movedDeleteOrIterate(nodep); }
-    void visit(AstAssignVarScope* nodep) override { movedDeleteOrIterate(nodep); }
+    void visit(AstAliasScope* nodep) override { movedDeleteOrIterate(nodep); }
     void visit(AstAssignW* nodep) override { movedDeleteOrIterate(nodep); }
     void visit(AstCoverToggle* nodep) override { movedDeleteOrIterate(nodep); }
     void visit(AstNodeFTask* nodep) override { movedDeleteOrIterate(nodep); }