add __iter__ runtime IC

from_cpython/Include/object.h

@@ -456,7 +456,7 @@ struct _typeobject {
 
     void* _hcls;
     void* _hcattrs;
-    char _ics[32];
+    char _ics[40];
     void* _gcvisit_func;
     int _attrs_offset;
     char _flags[7]; // These are bools in C++

src/runtime/list.cpp

@@ -1273,7 +1273,6 @@ void setupList() {
     static PyMappingMethods list_as_mapping;
     list_cls->tp_as_mapping = &list_as_mapping;
 
-    list_cls->tp_iter = listIter;
     list_iterator_cls = BoxedClass::create(type_cls, object_cls, &BoxedListIterator::gcHandler, 0, 0,
                                            sizeof(BoxedListIterator), false, "listiterator");
     list_reverse_iterator_cls = BoxedClass::create(type_cls, object_cls, &BoxedListIterator::gcHandler, 0, 0,
@@ -1356,6 +1355,7 @@ void setupList() {
 
     list_cls->giveAttr("__hash__", None);
     list_cls->freeze();
+    list_cls->tp_iter = listIter;
 
     list_cls->tp_as_sequence->sq_length = list_length;
     list_cls->tp_as_sequence->sq_concat = (binaryfunc)list_concat;

src/runtime/objmodel.cpp

@@ -5728,8 +5728,7 @@ Box* getiter(Box* o) {
     if (PyType_HasFeature(type, Py_TPFLAGS_HAVE_ITER) && type->tp_iter != slot_tp_iter && type->tp_iter) {
         r = type->tp_iter(o);
     } else {
-        static BoxedString* iter_str = internStringImmortal("__iter__");
-        r = callattrInternal0<CXX, NOT_REWRITABLE>(o, iter_str, LookupScope::CLASS_ONLY, NULL, ArgPassSpec(0));
+        r = type->callIterIC(o);
     }
     if (r) {
         if (!PyIter_Check(r)) {

src/runtime/types.cpp

@@ -290,6 +290,20 @@ Box* BoxedClass::callReprIC(Box* obj) {
     return ic->call(obj, repr_str, callattr_flags, nullptr, nullptr, nullptr, nullptr, nullptr);
 }
 
+Box* BoxedClass::callIterIC(Box* obj) {
+    assert(obj->cls == this);
+
+    auto ic = iter_ic.get();
+    if (!ic) {
+        ic = new CallattrIC();
+        iter_ic.reset(ic);
+    }
+
+    static BoxedString* iter_str = internStringImmortal("__iter__");
+    CallattrFlags callattr_flags{.cls_only = true, .null_on_nonexistent = true, .argspec = ArgPassSpec(0) };
+    return ic->call(obj, iter_str, callattr_flags, nullptr, nullptr, nullptr, nullptr, nullptr);
+}
+
 bool BoxedClass::callNonzeroIC(Box* obj) {
     assert(obj->cls == this);
 

src/runtime/types.h

@@ -194,11 +194,12 @@ public:
 
     // TODO: these don't actually get deallocated right now
     std::unique_ptr<CallattrCapiIC> next_ic;
-    std::unique_ptr<CallattrIC> hasnext_ic, repr_ic;
+    std::unique_ptr<CallattrIC> hasnext_ic, repr_ic, iter_ic;
     std::unique_ptr<NonzeroIC> nonzero_ic;
     Box* callHasnextIC(Box* obj, bool null_on_nonexistent);
     Box* call_nextIC(Box* obj) noexcept;
     Box* callReprIC(Box* obj);
+    Box* callIterIC(Box* obj);
     bool callNonzeroIC(Box* obj);
 
     gcvisit_func gc_visit;