[mypyc] Add primitive for <type>.__name__ (#19683)

This seems quite common in real-world code, including in
performance-critical functions. Python 3.11 added a C API function for
this, which we use here.

The primitive works for arbtirary objects, but only type objects have a
specialized code path. Other use cases of `__name__` seem typically less
performance-sensitive.

This PR makes this micro-benchmark 2.0x faster on Python 3.13:
```
from typing import Iterator

class FooBar: pass

def foo(x: type[object], n: int) -> str:
    for a in range(n):
        s = x.__name__
    return s

def bench(n: int) -> None:
    for i in range(n):
        foo(FooBar, 1000)

from time import time
bench(50 * 1000)
t0 = time()
bench(50 * 1000)
print(time() - t0)
```

Author: JukkaL

mypyc/irbuild/expression.py

@@ -76,6 +76,7 @@
     is_int_rprimitive,
     is_list_rprimitive,
     is_none_rprimitive,
+    is_object_rprimitive,
     object_rprimitive,
     set_rprimitive,
 )
@@ -98,7 +99,7 @@
 from mypyc.irbuild.specialize import apply_function_specialization, apply_method_specialization
 from mypyc.primitives.bytes_ops import bytes_slice_op
 from mypyc.primitives.dict_ops import dict_get_item_op, dict_new_op, exact_dict_set_item_op
-from mypyc.primitives.generic_ops import iter_op
+from mypyc.primitives.generic_ops import iter_op, name_op
 from mypyc.primitives.list_ops import list_append_op, list_extend_op, list_slice_op
 from mypyc.primitives.misc_ops import ellipsis_op, get_module_dict_op, new_slice_op, type_op
 from mypyc.primitives.registry import builtin_names
@@ -218,6 +219,13 @@ def transform_member_expr(builder: IRBuilder, expr: MemberExpr) -> Value:
     obj = builder.accept(expr.expr, can_borrow=can_borrow)
     rtype = builder.node_type(expr)
 
+    if (
+        is_object_rprimitive(obj.type)
+        and expr.name == "__name__"
+        and builder.options.capi_version >= (3, 11)
+    ):
+        return builder.primitive_op(name_op, [obj], expr.line)
+
     # Special case: for named tuples transform attribute access to faster index access.
     typ = get_proper_type(builder.types.get(expr.expr))
     if isinstance(typ, TupleType) and typ.partial_fallback.type.is_named_tuple:

mypyc/lib-rt/CPy.h

@@ -931,6 +931,10 @@ PyObject *CPy_GetANext(PyObject *aiter);
 void CPy_SetTypeAliasTypeComputeFunction(PyObject *alias, PyObject *compute_value);
 void CPyTrace_LogEvent(const char *location, const char *line, const char *op, const char *details);
 
+#if CPY_3_11_FEATURES
+PyObject *CPy_GetName(PyObject *obj);
+#endif
+
 #if CPY_3_14_FEATURES
 void CPy_SetImmortal(PyObject *obj);
 #endif

mypyc/lib-rt/misc_ops.c

@@ -1045,6 +1045,20 @@ PyObject *CPy_GetANext(PyObject *aiter)
     return NULL;
 }
 
+#if CPY_3_11_FEATURES
+
+// Return obj.__name__ (specialized to type objects, which are the most common target).
+PyObject *CPy_GetName(PyObject *obj) {
+    if (PyType_Check(obj)) {
+        return PyType_GetName((PyTypeObject *)obj);
+    }
+    _Py_IDENTIFIER(__name__);
+    PyObject *name = _PyUnicode_FromId(&PyId___name__); /* borrowed */
+    return PyObject_GetAttr(obj, name);
+}
+
+#endif
+
 #ifdef MYPYC_LOG_TRACE
 
 // This is only compiled in if trace logging is enabled by user

mypyc/lib-rt/mypyc_util.h

@@ -140,6 +140,7 @@ static inline CPyTagged CPyTagged_ShortFromSsize_t(Py_ssize_t x) {
 }
 
 // Are we targeting Python 3.X or newer?
+#define CPY_3_11_FEATURES (PY_VERSION_HEX >= 0x030b0000)
 #define CPY_3_12_FEATURES (PY_VERSION_HEX >= 0x030c0000)
 #define CPY_3_14_FEATURES (PY_VERSION_HEX >= 0x030e0000)
 

mypyc/primitives/generic_ops.py

@@ -26,6 +26,7 @@
     ERR_NEG_INT,
     binary_op,
     custom_op,
+    custom_primitive_op,
     function_op,
     method_op,
     unary_op,
@@ -382,3 +383,12 @@
     c_function_name="CPy_GetANext",
     error_kind=ERR_MAGIC,
 )
+
+# x.__name__ (requires Python 3.11+)
+name_op = custom_primitive_op(
+    name="__name__",
+    arg_types=[object_rprimitive],
+    return_type=object_rprimitive,
+    c_function_name="CPy_GetName",
+    error_kind=ERR_MAGIC,
+)

mypyc/test-data/irbuild-classes.test

@@ -1468,3 +1468,51 @@ L1:
 L2:
     r2 = self == r0
     return r2
+
+[case testTypeObjectName_python3_11]
+from typing import Any
+
+class C: pass
+class D(C): pass
+
+def n1(t: type[object]) -> str:
+    return t.__name__
+
+def n2(t: Any) -> str:
+    return t.__name__
+
+def n3() -> str:
+    return C.__name__
+
+def n4(t: type[C]) -> str:
+    return t.__name__
+[out]
+def n1(t):
+    t, r0 :: object
+    r1 :: str
+L0:
+    r0 = CPy_GetName(t)
+    r1 = cast(str, r0)
+    return r1
+def n2(t):
+    t, r0 :: object
+    r1 :: str
+L0:
+    r0 = CPy_GetName(t)
+    r1 = cast(str, r0)
+    return r1
+def n3():
+    r0, r1 :: object
+    r2 :: str
+L0:
+    r0 = __main__.C :: type
+    r1 = CPy_GetName(r0)
+    r2 = cast(str, r1)
+    return r2
+def n4(t):
+    t, r0 :: object
+    r1 :: str
+L0:
+    r0 = CPy_GetName(t)
+    r1 = cast(str, r0)
+    return r1

mypyc/test-data/run-classes.test

@@ -3115,3 +3115,51 @@ f(C(1, "yes"))
 [out]
 B 1
 C yes
+
+[case testTypeObjectName]
+from typing import Any
+import re
+
+from dynamic import E, foo, Thing
+
+class C: pass
+class D(C): pass
+
+def type_name(t: type[object]) -> str:
+    return t.__name__
+
+def any_name(x: Any) -> str:
+    return x.__name__
+
+def assert_type_name(x: Any) -> None:
+    assert type_name(x) == getattr(x, "__name__")
+    assert any_name(x) == getattr(x, "__name__")
+
+def assert_any_name(x: Any) -> None:
+    assert any_name(x) == getattr(x, "__name__")
+
+def test_type_name() -> None:
+    assert_type_name(C)
+    assert_type_name(D)
+    assert_type_name(int)
+    assert_type_name(E)
+    assert_type_name(re.Pattern)
+
+def test_module_name() -> None:
+    assert_any_name(re)
+
+def test_function_name() -> None:
+    assert_any_name(any_name)
+    assert_any_name(foo)
+
+def test_obj_name() -> None:
+    assert_any_name(Thing())
+
+[file dynamic.py]
+class E: pass
+
+def foo(): pass
+
+class Thing:
+    def __init__(self):
+        self.__name__ = "xyz"