Address review: skip the fast path for a comprehension that is not inlined

Instead of copying a shared set in make_frozenset(), don't use the
frozenset() fast path for a set comprehension that is not inlined.
Only such a comprehension returns its set from a call, where a trace
function can keep it, so make_frozenset() keeps its assumption that
the set is uniquely referenced and other uses pay for no extra check.

Author: fedonman

Python/codegen.c

@@ -4029,6 +4029,20 @@ maybe_optimize_function_call(compiler *c, expr_ty e, jump_target_label end)
 
     if (_PyUnicode_EqualToASCIIString(func->v.Name.id, "frozenset")
         && (arg_expr->kind == Set_kind || arg_expr->kind == SetComp_kind)) {
+        if (arg_expr->kind == SetComp_kind) {
+            /* A comprehension that is not inlined returns its set from a
+               call, so a trace function may still hold a reference to it. */
+            PySTEntryObject *entry = _PySymtable_Lookup(SYMTABLE(c),
+                                                        (void *)arg_expr);
+            if (entry == NULL) {
+                return ERROR;
+            }
+            int is_inlined = (entry->ste_type == InlinedComprehensionBlock);
+            Py_DECREF(entry);
+            if (!is_inlined) {
+                return 0;
+            }
+        }
         NEW_JUMP_TARGET_LABEL(c, skip_optimization);
 
         ADDOP_I(c, loc, COPY, 1);

Python/intrinsics.c

@@ -212,9 +212,7 @@ static PyObject *
 make_frozenset(PyThreadState* Py_UNUSED(ignored), PyObject *set)
 {
     assert(PySet_CheckExact(set));
-    if (!_PyObject_IsUniquelyReferenced(set)) {
-        return PyFrozenSet_New(set);
-    }
+    assert(_PyObject_IsUniquelyReferenced(set));
     return _PySet_Freeze(set);
 }