bpo-44313: generate LOAD_ATTR/CALL_FUNCTION for top-level imported objects (GH-26677)

Author: isidentical

Include/internal/pycore_symtable.h

@@ -72,6 +72,7 @@ extern PyTypeObject PySTEntry_Type;
 
 #define PySTEntry_Check(op) Py_IS_TYPE(op, &PySTEntry_Type)
 
+extern long _PyST_GetSymbol(PySTEntryObject *, PyObject *);
 extern int _PyST_GetScope(PySTEntryObject *, PyObject *);
 
 extern struct symtable* _PySymtable_Build(

Lib/importlib/_bootstrap_external.py

@@ -360,6 +360,7 @@ def _write_atomic(path, data, mode=0o666):
 #     Python 3.11a1 3455 (add MAKE_CELL bpo-43693)
 #     Python 3.11a1 3456 (interleave cell args bpo-43693)
 #     Python 3.11a1 3457 (Change localsplus to a bytes object bpo-43693)
+#     Python 3.11a1 3458 (imported objects now don't use LOAD_METHOD/CALL_METHOD)
 
 #
 # MAGIC must change whenever the bytecode emitted by the compiler may no

Lib/test/test_compile.py

@@ -6,6 +6,7 @@
 import _ast
 import tempfile
 import types
+import textwrap
 from test import support
 from test.support import script_helper
 from test.support.os_helper import FakePath
@@ -791,6 +792,41 @@ def or_false(x):
                 self.assertIn('LOAD_', opcodes[0].opname)
                 self.assertEqual('RETURN_VALUE', opcodes[1].opname)
 
+    def test_imported_load_method(self):
+        sources = [
+            """\
+            import os
+            def foo():
+                return os.uname()
+            """,
+            """\
+            import os as operating_system
+            def foo():
+                return operating_system.uname()
+            """,
+            """\
+            from os import path
+            def foo(x):
+                return path.join(x)
+            """,
+            """\
+            from os import path as os_path
+            def foo(x):
+                return os_path.join(x)
+            """
+        ]
+        for source in sources:
+            namespace = {}
+            exec(textwrap.dedent(source), namespace)
+            func = namespace['foo']
+            with self.subTest(func=func.__name__):
+                opcodes = list(dis.get_instructions(func))
+                instructions = [opcode.opname for opcode in opcodes]
+                self.assertNotIn('LOAD_METHOD', instructions)
+                self.assertNotIn('CALL_METHOD', instructions)
+                self.assertIn('LOAD_ATTR', instructions)
+                self.assertIn('CALL_FUNCTION', instructions)
+
     def test_lineno_procedure_call(self):
         def call():
             (

Misc/NEWS.d/next/Core and Builtins/2021-06-10-16-10-39.bpo-44313.34RjI8.rst

@@ -0,0 +1,4 @@
+Directly imported objects and modules (through import and from import
+statements) don't generate ``LOAD_METHOD``/``CALL_METHOD`` for directly
+accessed objects on their namespace. They now use the regular
+``LOAD_ATTR``/``CALL_FUNCTION``.

Programs/test_frozenmain.h

@@ -4278,6 +4278,23 @@ check_index(struct compiler *c, expr_ty e, expr_ty s)
     }
 }
 
+static int
+is_import_originated(struct compiler *c, expr_ty e)
+{
+    /* Check whether the global scope has an import named
+     e, if it is a Name object. For not traversing all the
+     scope stack every time this function is called, it will
+     only check the global scope to determine whether something
+     is imported or not. */
+
+    if (e->kind != Name_kind) {
+        return 0;
+    }
+
+    long flags = _PyST_GetSymbol(c->c_st->st_top, e->v.Name.id);
+    return flags & DEF_IMPORT;
+}
+
 // Return 1 if the method call was optimized, -1 if not, and 0 on error.
 static int
 maybe_optimize_method_call(struct compiler *c, expr_ty e)
@@ -4291,6 +4308,12 @@ maybe_optimize_method_call(struct compiler *c, expr_ty e)
     if (meth->kind != Attribute_kind || meth->v.Attribute.ctx != Load) {
         return -1;
     }
+
+    /* Check that the base object is not something that is imported */
+    if (is_import_originated(c, meth->v.Attribute.value)) {
+        return -1;
+    }
+
     /* Check that there aren't too many arguments */
     argsl = asdl_seq_LEN(args);
     kwdsl = asdl_seq_LEN(kwds);