performance: use vectorcall for call0 and call_method0

CHANGELOG.md

@@ -20,7 +20,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Add context.h functions (`PyContext_New`, etc) to FFI. [#1259](https://github.com/PyO3/pyo3/pull/1259)
 - Add `PyAny::is_instance()` method. [#1276](https://github.com/PyO3/pyo3/pull/1276)
 - Add support for conversion between `char` and `PyString`. [#1282](https://github.com/PyO3/pyo3/pull/1282)
-- Add FFI definitions for `PyBuffer_SizeFromFormat`, `PyObject_LengthHint`, `PyObject_CallNoArgs`, `PyObject_CallOneArg`, `PyObject_CallMethodNoArgs`, `PyObject_CallMethodOneArg`, `PyObject_VectorcallDict`, and `PyObject_VectorcallMethod`. [#1285](https://github.com/PyO3/pyo3/pull/1285)
+- Add FFI definitions for `PyBuffer_SizeFromFormat`, `PyObject_LengthHint`, `PyObject_CallNoArgs`, `PyObject_CallOneArg`, `PyObject_CallMethodNoArgs`, `PyObject_CallMethodOneArg`, `PyObject_VectorcallDict`, and `PyObject_VectorcallMethod`. [#1287](https://github.com/PyO3/pyo3/pull/1287)
 
 ### Changed
 - Change return type `PyType::name()` from `Cow<str>` to `PyResult<&str>`. [#1152](https://github.com/PyO3/pyo3/pull/1152)
@@ -30,6 +30,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Change `Debug` and `Display` impls for `PyException` to be consistent with `PyAny`. [#1275](https://github.com/PyO3/pyo3/pull/1275)
 - Change `Debug` impl of `PyErr` to output more helpful information (acquiring the GIL if necessary). [#1275](https://github.com/PyO3/pyo3/pull/1275)
 - Rename `PyTypeInfo::is_instance` and `PyTypeInfo::is_exact_instance` to `PyTypeInfo::is_type_of` and `PyTypeInfo::is_exact_type_of`. [#1278](https://github.com/PyO3/pyo3/pull/1278)
+- Optimize `PyAny::call0`, `Py::call0` and `PyAny::call_method0` and `Py::call_method0` on Python 3.9 and up. [#1287](https://github.com/PyO3/pyo3/pull/1285)
 - Deprecate `Python::is_instance`, `Python::is_subclass`, `Python::release`, and `Python::xdecref`. [#1292](https://github.com/PyO3/pyo3/pull/1292)
 
 ### Removed
@@ -39,8 +40,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Fixed
 - Fix missing field in `PyCodeObject` struct (`co_posonlyargcount`) - caused invalid access to other fields in Python >3.7. [#1260](https://github.com/PyO3/pyo3/pull/1260)
 - Fix building for `x86_64-unknown-linux-musl` target from `x86_65-unknown-linux-gnu` host. [#1267](https://github.com/PyO3/pyo3/pull/1267)
-- Fix FFI definitions for `PyObject_Vectorcall` and `PyVectorcall_Call`. [#1285](https://github.com/PyO3/pyo3/pull/1285)
 - Fix `#[text_signature]` interacting badly with rust `r#raw_identifiers`. [#1286](https://github.com/PyO3/pyo3/pull/1286)
+- Fix FFI definitions for `PyObject_Vectorcall` and `PyVectorcall_Call`. [#1287](https://github.com/PyO3/pyo3/pull/1285)
 - Fix building with Anaconda python inside a virtualenv. [#1290](https://github.com/PyO3/pyo3/pull/1290)
 
 ## [0.12.3] - 2020-10-12

Cargo.toml

@@ -15,6 +15,7 @@ build = "build.rs"
 edition = "2018"
 
 [dependencies]
+cfg-if = { version = "1.0" }
 ctor = { version = "0.1", optional = true }
 indoc = { version = "1.0.3", optional = true }
 inventory = { version = "0.1.4", optional = true }

src/instance.rs

@@ -272,7 +272,18 @@ impl<T> Py<T> {
     ///
     /// This is equivalent to the Python expression `self()`.
     pub fn call0(&self, py: Python) -> PyResult<PyObject> {
-        self.call(py, (), None)
+        cfg_if::cfg_if! {
+            // TODO: Use PyObject_CallNoArgs instead after https://bugs.python.org/issue42415.
+            // Once the issue is resolved, we can enable this optimization for limited API.
+            if #[cfg(all(Py_3_9, not(Py_LIMITED_API)))] {
+                // Optimized path on python 3.9+
+                unsafe {
+                    PyObject::from_owned_ptr_or_err(py, ffi::_PyObject_CallNoArg(self.as_ptr()))
+                }
+            } else {
+                self.call(py, (), None)
+            }
+        }
     }
 
     /// Calls a method on the object.
@@ -316,7 +327,17 @@ impl<T> Py<T> {
     ///
     /// This is equivalent to the Python expression `self.name()`.
     pub fn call_method0(&self, py: Python, name: &str) -> PyResult<PyObject> {
-        self.call_method(py, name, (), None)
+        cfg_if::cfg_if! {
+            if #[cfg(all(Py_3_9, not(Py_LIMITED_API)))] {
+                // Optimized path on python 3.9+
+                unsafe {
+                    let name = name.into_py(py);
+                    PyObject::from_owned_ptr_or_err(py, ffi::PyObject_CallMethodNoArgs(self.as_ptr(), name.as_ptr()))
+                }
+            } else {
+                self.call_method(py, name, (), None)
+            }
+        }
     }
 
     /// Create a `Py<T>` instance by taking ownership of the given FFI pointer.

src/types/any.rs

@@ -226,7 +226,18 @@ impl PyAny {
     ///
     /// This is equivalent to the Python expression `self()`.
     pub fn call0(&self) -> PyResult<&PyAny> {
-        self.call((), None)
+        cfg_if::cfg_if! {
+            // TODO: Use PyObject_CallNoArgs instead after https://bugs.python.org/issue42415.
+            // Once the issue is resolved, we can enable this optimization for limited API.
+            if #[cfg(all(Py_3_9, not(Py_LIMITED_API)))] {
+                // Optimized path on python 3.9+
+                unsafe {
+                    self.py().from_owned_ptr_or_err(ffi::_PyObject_CallNoArg(self.as_ptr()))
+                }
+            } else {
+                self.call((), None)
+            }
+        }
     }
 
     /// Calls the object with only positional arguments.
@@ -283,7 +294,17 @@ impl PyAny {
     ///
     /// This is equivalent to the Python expression `self.name()`.
     pub fn call_method0(&self, name: &str) -> PyResult<&PyAny> {
-        self.call_method(name, (), None)
+        cfg_if::cfg_if! {
+            if #[cfg(all(Py_3_9, not(Py_LIMITED_API)))] {
+                // Optimized path on python 3.9+
+                unsafe {
+                    let name = name.into_py(self.py());
+            self.py().from_owned_ptr_or_err(ffi::PyObject_CallMethodNoArgs(self.as_ptr(), name.as_ptr()))
+                }
+            } else {
+                self.call_method(name, (), None)
+            }
+        }
     }
 
     /// Calls a method on the object with only positional arguments.
@@ -464,8 +485,17 @@ impl PyAny {
 
 #[cfg(test)]
 mod test {
-    use crate::types::{IntoPyDict, PyList, PyLong};
-    use crate::{Python, ToPyObject};
+    use crate::{
+        types::{IntoPyDict, PyList, PyLong, PyModule},
+        Python, ToPyObject,
+    };
+
+    macro_rules! test_module {
+        ($py:ident, $code:literal) => {
+            PyModule::from_code($py, indoc::indoc!($code), file!(), "test_module")
+                .expect("module creation failed")
+        };
+    }
 
     #[test]
     fn test_call_for_non_existing_method() {
@@ -488,6 +518,30 @@ mod test {
         assert_eq!(list.extract::<Vec<i32>>(py).unwrap(), vec![7, 6, 5, 4, 3]);
     }
 
+    #[test]
+    fn test_call_method0() {
+        Python::with_gil(|py| {
+            let module = test_module!(
+                py,
+                r#"
+                class SimpleClass:
+                    def foo(self):
+                        return 42
+            "#
+            );
+
+            let simple_class = module.getattr("SimpleClass").unwrap().call0().unwrap();
+            assert_eq!(
+                simple_class
+                    .call_method0("foo")
+                    .unwrap()
+                    .extract::<u32>()
+                    .unwrap(),
+                42
+            );
+        })
+    }
+
     #[test]
     fn test_type() {
         let gil = Python::acquire_gil();