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[3.8] bpo-37233: optimize method_vectorcall in case of totalargs == 0 (GH-14550) #14574

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Merged
merged 1 commit into from
Jul 3, 2019
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[3.8] bpo-37233: optimize method_vectorcall in case of totalargs == 0 (GH-14550) #14574

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bpo-37233: optimize method_vectorcall in case of totalargs == 0 (GH-1… 
…4550)

(cherry picked from commit 53c2143)

Co-authored-by: Jeroen Demeyer <J.Demeyer@UGent.be>
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@jdemeyer @miss-islington
jdemeyer authored and miss-islington committed Jul 3, 2019
commit 03cf5f291abf40e322b35a0fc67fb668acc3bb1b
16 changes: 10 additions & 6 deletions Objects/classobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -62,9 +62,13 @@ method_vectorcall(PyObject *method, PyObject *const *args,
}
else {
Py_ssize_t nkwargs = (kwnames == NULL) ? 0 : PyTuple_GET_SIZE(kwnames);
PyObject **newargs;
Py_ssize_t totalargs = nargs + nkwargs;
if (totalargs == 0) {
return _PyObject_Vectorcall(func, &self, 1, NULL);
}

PyObject *newargs_stack[_PY_FASTCALL_SMALL_STACK];
PyObject **newargs;
if (totalargs <= (Py_ssize_t)Py_ARRAY_LENGTH(newargs_stack) - 1) {
newargs = newargs_stack;
}
Expand All @@ -77,11 +81,11 @@ method_vectorcall(PyObject *method, PyObject *const *args,
}
/* use borrowed references */
newargs[0] = self;
if (totalargs) { /* bpo-37138: if totalargs == 0, then args may be
* NULL and calling memcpy() with a NULL pointer
* is undefined behaviour. */
memcpy(newargs + 1, args, totalargs * sizeof(PyObject *));
}
/* bpo-37138: since totalargs > 0, it's impossible that args is NULL.
* We need this, since calling memcpy() with a NULL pointer is
* undefined behaviour. */
assert(args != NULL);
memcpy(newargs + 1, args, totalargs * sizeof(PyObject *));
result = _PyObject_Vectorcall(func, newargs, nargs+1, kwnames);
if (newargs != newargs_stack) {
PyMem_Free(newargs);
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