[turbofan] Properly implement %_ClassOf intrinsic.

src/compiler/js-generic-lowering.cc

Index: src/compiler/js-generic-lowering.cc
diff --git a/src/compiler/js-generic-lowering.cc b/src/compiler/js-generic-lowering.cc
index 13ea668e7693d4ef526235a9a3b511fc2d58a25e..bc36c64f27c8a55b39699654b4c4dfed1635106a 100644
--- a/src/compiler/js-generic-lowering.cc
+++ b/src/compiler/js-generic-lowering.cc
@@ -143,6 +143,15 @@ void JSGenericLowering::LowerJSToBoolean(Node* node) {
                       Operator::kEliminatable);
 }
 
+void JSGenericLowering::LowerJSClassOf(Node* node) {
+  // The %_ClassOf intrinsic doesn't need the current context.
+  NodeProperties::ReplaceContextInput(node, jsgraph()->NoContextConstant());
+  Callable callable = CodeFactory::ClassOf(isolate());
+  node->AppendInput(zone(), graph()->start());
+  ReplaceWithStubCall(node, callable, CallDescriptor::kNoAllocate,
+                      Operator::kEliminatable);
+}
+
 void JSGenericLowering::LowerJSTypeOf(Node* node) {
   // The typeof operator doesn't need the current context.
   NodeProperties::ReplaceContextInput(node, jsgraph()->NoContextConstant());