Support standalone 'this' in classes (#3675) (#2594) (#3248)

src/V3AstNodeMath.h

@@ -1273,6 +1273,22 @@ public:
     bool cleanOut() const override { return true; }
     bool same(const AstNode* /*samep*/) const override { return true; }
 };
+class AstThisRef final : public AstNodeMath {
+    // Reference to 'this'.
+    // @astgen op1 := childDTypep : Optional[AstClassRefDType] // dtype of the node
+public:
+    explicit AstThisRef(FileLine* fl, AstClassRefDType* dtypep)
+        : ASTGEN_SUPER_ThisRef(fl) {
+        childDTypep(dtypep);
+    }
+    ASTGEN_MEMBERS_AstThisRef;
+    string emitC() override { return "this"; }
+    string emitVerilog() override { return "this"; }
+    bool same(const AstNode* /*samep*/) const override { return true; }
+    bool cleanOut() const override { return true; }
+    AstNodeDType* getChildDTypep() const override { return childDTypep(); }
+    virtual AstNodeDType* subDTypep() const { return dtypep() ? dtypep() : childDTypep(); }
+};
 class AstUCFunc final : public AstNodeMath {
     // User's $c function
     // Perhaps this should be an AstNodeListop; but there's only one list math right now

src/V3EmitCFunc.h

@@ -1168,6 +1168,12 @@ public:
             emitConstant(nodep, nullptr, "");
         }
     }
+    void visit(AstThisRef* nodep) override {
+        putbs(nodep->dtypep()->cType("", false, false));
+        puts("{");
+        puts(m_useSelfForThis ? "vlSelf" : "this");
+        puts("}");
+    }
 
     //
     void visit(AstMTaskBody* nodep) override {

src/V3LinkDot.cpp

@@ -2054,6 +2054,13 @@ private:
         }
         return false;
     }
+    VSymEnt* getThisClassSymp() {
+        VSymEnt* classSymp = m_ds.m_dotSymp;
+        do {
+            classSymp = classSymp->parentp();
+        } while (classSymp && !VN_IS(classSymp->nodep(), Class));
+        return classSymp;
+    }
 
     // VISITs
     void visit(AstNetlist* nodep) override {
@@ -2201,10 +2208,7 @@ private:
             m_ds.m_dotPos = DP_SCOPE;
 
             if (VN_IS(nodep->lhsp(), ParseRef) && nodep->lhsp()->name() == "this") {
-                VSymEnt* classSymp = m_ds.m_dotSymp;
-                do {
-                    classSymp = classSymp->parentp();
-                } while (classSymp && !VN_IS(classSymp->nodep(), Class));
+                VSymEnt* classSymp = getThisClassSymp();
                 if (!classSymp) {
                     nodep->v3error("'this' used outside class (IEEE 1800-2017 8.11)");
                     m_ds.m_dotErr = true;
@@ -2213,10 +2217,7 @@ private:
                     UINFO(8, "     this. " << m_ds.ascii() << endl);
                 }
             } else if (VN_IS(nodep->lhsp(), ParseRef) && nodep->lhsp()->name() == "super") {
-                const VSymEnt* classSymp = m_ds.m_dotSymp;
-                do {
-                    classSymp = classSymp->parentp();
-                } while (classSymp && !VN_IS(classSymp->nodep(), Class));
+                const VSymEnt* classSymp = getThisClassSymp();
                 if (!classSymp) {
                     nodep->v3error("'super' used outside class (IEEE 1800-2017 8.15)");
                     m_ds.m_dotErr = true;
@@ -2310,6 +2311,22 @@ private:
             nodep->v3warn(E_UNSUPPORTED, "Unsupported: super");
             m_ds.m_dotErr = true;
         }
+        if (nodep->name() == "this") {
+            iterateChildren(nodep);
+            if (m_statep->forPrimary()) return;  // The class might be parametrized somewhere
+            const VSymEnt* classSymp = getThisClassSymp();
+            if (!classSymp) {
+                nodep->v3error("'this' used outside class (IEEE 1800-2017 8.11)");
+                return;
+            }
+            AstClass* const classp = VN_AS(classSymp->nodep(), Class);
+            AstClassRefDType* const dtypep
+                = new AstClassRefDType{nodep->fileline(), classp, nullptr};
+            AstThisRef* const newp = new AstThisRef{nodep->fileline(), dtypep};
+            nodep->replaceWith(newp);
+            VL_DO_DANGLING(pushDeletep(nodep), nodep);
+            return;
+        }
         if (m_ds.m_dotPos == DP_FINAL && VN_IS(m_ds.m_unlinkedScopep, LambdaArgRef)
             && nodep->name() == "index") {
             // 'with' statement's 'item.index'

src/V3Width.cpp

@@ -2465,6 +2465,10 @@ private:
         userIterateChildren(nodep, nullptr);  // First size all members
         nodep->repairCache();
     }
+    void visit(AstThisRef* nodep) override {
+        if (nodep->didWidthAndSet()) return;
+        nodep->dtypep(iterateEditMoveDTypep(nodep, nodep->childDTypep()));
+    }
     void visit(AstClassRefDType* nodep) override {
         if (nodep->didWidthAndSet()) return;
         // TODO this maybe eventually required to properly resolve members,

test_regress/t/t_class_uses_this.v

@@ -11,13 +11,25 @@ class Cls;
      this.addr = addr;
    end : body
    endfunction
+   function void set2(bit [3:0] addr);
+   begin : body
+     Cls c2 = this;
+     c2.addr = addr;
+   end : body
+   endfunction
    extern function void setext(bit [3:0] addr);
+   extern function void setext2(bit [3:0] addr);
 endclass
 
 function void Cls::setext(bit [3:0] addr);
    this.addr = addr;
 endfunction
 
+function void Cls::setext2(bit [3:0] addr);
+   Cls c2 = this;
+   c2.addr = addr;
+endfunction
+
 module t(/*AUTOARG*/
    // Inputs
    clk
@@ -34,8 +46,12 @@ module t(/*AUTOARG*/
       $display(baz.addr);
 `endif
       if (bar.addr != 4) $stop;
+      bar.set2(1);
+      if (bar.addr != 1) $stop;
       bar.setext(2);
       if (bar.addr != 2) $stop;
+      bar.setext2(3);
+      if (bar.addr != 3) $stop;
       $write("*-* All Finished *-*\n");
       $finish;
    end