diff --git a/frontends/ast/ast.cc b/frontends/ast/ast.cc
index 431f7b4f8..fbfa77a18 100644
--- a/frontends/ast/ast.cc
+++ b/frontends/ast/ast.cc
@@ -248,6 +248,9 @@ AstNode::AstNode(AstNodeType type, AstNode *child1, AstNode *child2, AstNode *ch
 		children.push_back(child4);
 
 	fixup_hierarchy_flags();
+#ifdef ASTNODE_GC
+	Tagger::get().reg(this);
+#endif
 }
 
 // create a (deep recursive) copy of a node
@@ -283,12 +286,28 @@ void AstNode::cloneInto(AstNode *other) const
 // delete all children in this node
 void AstNode::delete_children()
 {
+#ifdef ASTNODE_GC
+	for (auto &it : children)
+		if (Tagger::get().nodes.count(it))
+			delete it;
+		else
+			log("skip child %p\n", it);
+#else
 	for (auto &it : children)
 		delete it;
+#endif
 	children.clear();
 
+#ifdef ASTNODE_GC
+	for (auto &it : attributes)
+		if (Tagger::get().nodes.count(it.second))
+			delete it.second;
+		else
+			log("skip attr %p\n", it.second);
+#else
 	for (auto &it : attributes)
 		delete it.second;
+#endif
 	attributes.clear();
 }
 
@@ -296,7 +315,14 @@ void AstNode::delete_children()
 AstNode::~AstNode()
 {
 	astnodes--;
+#ifdef ASTNODE_GC
+	Tagger::get().unreg(this);
+#endif
 	delete_children();
+	if (yosys_xtrace) {
+		log("DESTR %X %p\n", hashidx_, this);
+		log_backtrace("", yosys_xtrace-1);
+	}
 }
 
 // create a nice text representation of the node
diff --git a/frontends/ast/ast.h b/frontends/ast/ast.h
index 2c2d408ce..923594a3c 100644
--- a/frontends/ast/ast.h
+++ b/frontends/ast/ast.h
@@ -467,6 +467,72 @@ namespace AST_INTERNAL
 	                           AST::AstNode *original_ast = nullptr);
 }
 
+#undef ASTNODE_GC
+#ifdef ASTNODE_GC
+struct Tagger {
+	std::set<AST::AstNode*> nodes;
+	std::set<AST::AstNode*> tagged;
+	static Tagger& get() {
+		static Tagger instance;
+		return instance;
+	}
+	void reg(AST::AstNode* p) {
+		if (!p)
+			return;
+		log_assert(!nodes.count(p));
+		nodes.insert(p);
+	}
+	void unreg(AST::AstNode* p) {
+		if (!p || !nodes.count(p))
+			return;
+		nodes.erase(p);
+	}
+	void tag(AST::AstNode* p) {
+		if (!p)
+			return;
+		tagged.insert(p);
+		for (AST::AstNode* c : p->children)
+			tag(c);
+		for (auto x : p->attributes)
+			tag(x.second);
+		tag(p->id2ast);
+	}
+	void clear() {
+		tagged.clear();
+	}
+	void dump_untagged() {
+		Yosys::log("Dumping untagged:\n");
+		for (auto p : nodes) {
+			if (!tagged.count(p)) {
+				Yosys::log(">> %p\n", p);
+				p->dumpAst(stdout, "");
+			}
+		}
+	}
+	void shadow_kill(AST::AstNode* p) {
+		if (!p || !nodes.count(p))
+			return;
+		for (AST::AstNode* c : p->children)
+			shadow_kill(c);
+		for (auto x : p->attributes)
+			shadow_kill(x.second);
+		shadow_kill(p->id2ast);
+		delete p;
+	}
+	void kill_untagged() {
+		auto copy = nodes;
+		while (!copy.empty()) {
+			AST::AstNode* p = *(copy.begin());
+			copy.erase(p);
+			fflush(stdout);
+			if (!tagged.count(p)) {
+				shadow_kill(p);
+			}
+		}
+	}
+};
+#endif // ASTNODE_GC
+
 YOSYS_NAMESPACE_END
 
 #endif
diff --git a/frontends/verilog/verilog_frontend.cc b/frontends/verilog/verilog_frontend.cc
index 14a0f16c0..2e4ea9859 100644
--- a/frontends/verilog/verilog_frontend.cc
+++ b/frontends/verilog/verilog_frontend.cc
@@ -39,6 +39,7 @@
 YOSYS_NAMESPACE_BEGIN
 using namespace VERILOG_FRONTEND;
 
+
 // use the Verilog bison/flex parser to generate an AST and use AST::process() to convert it to RTLIL
 
 static std::vector<std::string> verilog_defaults;
@@ -528,7 +529,15 @@ struct VerilogFrontend : public Frontend {
 
 		AST::process(design, current_ast, flag_nodisplay, flag_dump_ast1, flag_dump_ast2, flag_no_dump_ptr, flag_dump_vlog1, flag_dump_vlog2, flag_dump_rtlil, flag_nolatches,
 				flag_nomeminit, flag_nomem2reg, flag_mem2reg, flag_noblackbox, lib_mode, flag_nowb, flag_noopt, flag_icells, flag_pwires, flag_nooverwrite, flag_overwrite, flag_defer, default_nettype_wire);
+#ifdef ASTNODE_GC
+		Tagger::get().clear();
+		Tagger::get().tag(current_ast);
+		for (RTLIL::Module* m : design->modules())
+			if (AST::AstModule* am = dynamic_cast<AST::AstModule*>(m))
+				Tagger::get().tag(am->ast);
 
+		Tagger::get().dump_untagged();
+#endif
 
 		if (!flag_nopp)
 			delete lexin;
@@ -539,6 +548,9 @@ struct VerilogFrontend : public Frontend {
 
 		delete current_ast;
 		current_ast = NULL;
+#ifdef ASTNODE_GC
+		Tagger::get().kill_untagged();
+#endif
 
 		log("Successfully finished Verilog frontend.\n");
 	}