Skip to content

Commit

Permalink
gh-91248: Optimize PyFrame_GetVar() (#99252)
Browse files Browse the repository at this point in the history 
PyFrame_GetVar() no longer creates a temporary dictionary to get a
variable.
  • Loading branch information
@vstinner
vstinner committed Nov 13, 2022
1 parent 57be545 commit 6788303
Show file tree
Hide file tree
Showing 3 changed files with 144 additions and 95 deletions.
2 changes: 2 additions & 0 deletions Doc/c-api/frame.rst
View file
Expand Up @@ -87,6 +87,8 @@ See also :ref:`Reflection <reflection>`.
* Raise :exc:`NameError` and return ``NULL`` if the variable does not exist.
* Raise an exception and return ``NULL`` on error.
*name* type must be a :class:`str`.
.. versionadded:: 3.12
Expand Down
6 changes: 6 additions & 0 deletions Lib/test/test_frame.py
View file
Expand Up @@ -352,6 +352,12 @@ def test_getvar(self):
with self.assertRaises(NameError):
_testcapi.frame_getvarstring(current_frame, b"y")

# wrong name type
with self.assertRaises(TypeError):
_testcapi.frame_getvar(current_frame, b'x')
with self.assertRaises(TypeError):
_testcapi.frame_getvar(current_frame, 123)

def getgenframe(self):
yield sys._getframe()

Expand Down
231 changes: 136 additions & 95 deletions Objects/frameobject.c
View file
Expand Up @@ -1109,81 +1109,106 @@ _PyFrame_OpAlreadyRan(_PyInterpreterFrame *frame, int opcode, int oparg)
return 0;
}


// Initialize frame free variables if needed
static void
frame_init_get_vars(_PyInterpreterFrame *frame)
{
// COPY_FREE_VARS has no quickened forms, so no need to use _PyOpcode_Deopt
// here:
PyCodeObject *co = frame->f_code;
int lasti = _PyInterpreterFrame_LASTI(frame);
if (!(lasti < 0 && _Py_OPCODE(_PyCode_CODE(co)[0]) == COPY_FREE_VARS
&& PyFunction_Check(frame->f_funcobj)))
{
/* Free vars are initialized */
return;
}

/* Free vars have not been initialized -- Do that */
PyObject *closure = ((PyFunctionObject *)frame->f_funcobj)->func_closure;
int offset = co->co_nlocals + co->co_nplaincellvars;
for (int i = 0; i < co->co_nfreevars; ++i) {
PyObject *o = PyTuple_GET_ITEM(closure, i);
frame->localsplus[offset + i] = Py_NewRef(o);
}
// COPY_FREE_VARS doesn't have inline CACHEs, either:
frame->prev_instr = _PyCode_CODE(frame->f_code);
}


static int
frame_get_var(_PyInterpreterFrame *frame, PyCodeObject *co, int i,
PyObject **pvalue)
{
_PyLocals_Kind kind = _PyLocals_GetKind(co->co_localspluskinds, i);

/* If the namespace is unoptimized, then one of the
following cases applies:
1. It does not contain free variables, because it
uses import * or is a top-level namespace.
2. It is a class namespace.
We don't want to accidentally copy free variables
into the locals dict used by the class.
*/
if (kind & CO_FAST_FREE && !(co->co_flags & CO_OPTIMIZED)) {
return 0;
}

PyObject *value = frame->localsplus[i];
if (frame->stacktop) {
if (kind & CO_FAST_FREE) {
// The cell was set by COPY_FREE_VARS.
assert(value != NULL && PyCell_Check(value));
value = PyCell_GET(value);
}
else if (kind & CO_FAST_CELL) {
// Note that no *_DEREF ops can happen before MAKE_CELL
// executes. So there's no need to duplicate the work
// that MAKE_CELL would otherwise do later, if it hasn't
// run yet.
if (value != NULL) {
if (PyCell_Check(value) &&
_PyFrame_OpAlreadyRan(frame, MAKE_CELL, i)) {
// (likely) MAKE_CELL must have executed already.
value = PyCell_GET(value);
}
// (likely) Otherwise it it is an arg (kind & CO_FAST_LOCAL),
// with the initial value set when the frame was created...
// (unlikely) ...or it was set to some initial value by
// an earlier call to PyFrame_LocalsToFast().
}
}
}
else {
assert(value == NULL);
}
*pvalue = value;
return 1;
}

int
_PyFrame_FastToLocalsWithError(_PyInterpreterFrame *frame) {
_PyFrame_FastToLocalsWithError(_PyInterpreterFrame *frame)
{
/* Merge fast locals into f->f_locals */
PyObject *locals;
PyObject **fast;
PyCodeObject *co;
locals = frame->f_locals;
PyObject *locals = frame->f_locals;
if (locals == NULL) {
locals = frame->f_locals = PyDict_New();
if (locals == NULL)
if (locals == NULL) {
return -1;
}
co = frame->f_code;
fast = _PyFrame_GetLocalsArray(frame);
// COPY_FREE_VARS has no quickened forms, so no need to use _PyOpcode_Deopt
// here:
int lasti = _PyInterpreterFrame_LASTI(frame);
if (lasti < 0 && _Py_OPCODE(_PyCode_CODE(co)[0]) == COPY_FREE_VARS
&& PyFunction_Check(frame->f_funcobj))
{
/* Free vars have not been initialized -- Do that */
PyCodeObject *co = frame->f_code;
PyObject *closure = ((PyFunctionObject *)frame->f_funcobj)->func_closure;
int offset = co->co_nlocals + co->co_nplaincellvars;
for (int i = 0; i < co->co_nfreevars; ++i) {
PyObject *o = PyTuple_GET_ITEM(closure, i);
frame->localsplus[offset + i] = Py_NewRef(o);
}
// COPY_FREE_VARS doesn't have inline CACHEs, either:
frame->prev_instr = _PyCode_CODE(frame->f_code);
}
for (int i = 0; i < co->co_nlocalsplus; i++) {
_PyLocals_Kind kind = _PyLocals_GetKind(co->co_localspluskinds, i);

/* If the namespace is unoptimized, then one of the
following cases applies:
1. It does not contain free variables, because it
uses import * or is a top-level namespace.
2. It is a class namespace.
We don't want to accidentally copy free variables
into the locals dict used by the class.
*/
if (kind & CO_FAST_FREE && !(co->co_flags & CO_OPTIMIZED)) {
frame_init_get_vars(frame);

PyCodeObject *co = frame->f_code;
for (int i = 0; i < co->co_nlocalsplus; i++) {
PyObject *value; // borrowed reference
if (!frame_get_var(frame, co, i, &value)) {
continue;
}

PyObject *name = PyTuple_GET_ITEM(co->co_localsplusnames, i);
PyObject *value = fast[i];
if (frame->stacktop) {
if (kind & CO_FAST_FREE) {
// The cell was set by COPY_FREE_VARS.
assert(value != NULL && PyCell_Check(value));
value = PyCell_GET(value);
}
else if (kind & CO_FAST_CELL) {
// Note that no *_DEREF ops can happen before MAKE_CELL
// executes. So there's no need to duplicate the work
// that MAKE_CELL would otherwise do later, if it hasn't
// run yet.
if (value != NULL) {
if (PyCell_Check(value) &&
_PyFrame_OpAlreadyRan(frame, MAKE_CELL, i)) {
// (likely) MAKE_CELL must have executed already.
value = PyCell_GET(value);
}
// (likely) Otherwise it it is an arg (kind & CO_FAST_LOCAL),
// with the initial value set when the frame was created...
// (unlikely) ...or it was set to some initial value by
// an earlier call to PyFrame_LocalsToFast().
}
}
}
else {
assert(value == NULL);
}
if (value == NULL) {
if (PyObject_DelItem(locals, name) != 0) {
if (PyErr_ExceptionMatches(PyExc_KeyError)) {
Expand All @@ -1203,6 +1228,54 @@ _PyFrame_FastToLocalsWithError(_PyInterpreterFrame *frame) {
return 0;
}


PyObject *
PyFrame_GetVar(PyFrameObject *frame_obj, PyObject *name)
{
if (!PyUnicode_Check(name)) {
PyErr_Format(PyExc_TypeError, "name must be str, not %s",
Py_TYPE(name)->tp_name);
return NULL;
}

_PyInterpreterFrame *frame = frame_obj->f_frame;
frame_init_get_vars(frame);

PyCodeObject *co = frame->f_code;
for (int i = 0; i < co->co_nlocalsplus; i++) {
PyObject *var_name = PyTuple_GET_ITEM(co->co_localsplusnames, i);
if (!_PyUnicode_Equal(var_name, name)) {
continue;
}

PyObject *value; // borrowed reference
if (!frame_get_var(frame, co, i, &value)) {
break;
}
if (value == NULL) {
break;
}
return Py_NewRef(value);
}

PyErr_Format(PyExc_NameError, "variable %R does not exist", name);
return NULL;
}


PyObject *
PyFrame_GetVarString(PyFrameObject *frame, const char *name)
{
PyObject *name_obj = PyUnicode_FromString(name);
if (name_obj == NULL) {
return NULL;
}
PyObject *value = PyFrame_GetVar(frame, name_obj);
Py_DECREF(name_obj);
return value;
}


int
PyFrame_FastToLocalsWithError(PyFrameObject *f)
{
Expand Down Expand Up @@ -1413,35 +1486,3 @@ _PyEval_BuiltinsFromGlobals(PyThreadState *tstate, PyObject *globals)

return _PyEval_GetBuiltins(tstate);
}

PyObject *
PyFrame_GetVar(PyFrameObject *frame, PyObject *name)
{
PyObject *locals = PyFrame_GetLocals(frame);
if (locals == NULL) {
return NULL;
}
PyObject *value = PyDict_GetItemWithError(locals, name);
Py_DECREF(locals);

if (value == NULL) {
if (PyErr_Occurred()) {
return NULL;
}
PyErr_Format(PyExc_NameError, "variable %R does not exist", name);
return NULL;
}
return Py_NewRef(value);
}

PyObject *
PyFrame_GetVarString(PyFrameObject *frame, const char *name)
{
PyObject *name_obj = PyUnicode_FromString(name);
if (name_obj == NULL) {
return NULL;
}
PyObject *value = PyFrame_GetVar(frame, name_obj);
Py_DECREF(name_obj);
return value;
}

0 comments on commit 6788303

Please sign in to comment.