Micro-optimize list index range checks (GH-9784)
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@ -208,6 +208,19 @@ PyList_Size(PyObject *op)
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return Py_SIZE(op);
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}
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static inline int
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valid_index(Py_ssize_t i, Py_ssize_t limit)
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{
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/* The cast to size_t lets us use just a single comparison
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to check whether i is in the range: 0 <= i < limit.
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See: Section 14.2 "Bounds Checking" in the Agner Fog
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optimization manual found at:
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https://www.agner.org/optimize/optimizing_cpp.pdf
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*/
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return (size_t) i < (size_t) limit;
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}
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static PyObject *indexerr = NULL;
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PyObject *
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@ -217,7 +230,7 @@ PyList_GetItem(PyObject *op, Py_ssize_t i)
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PyErr_BadInternalCall();
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return NULL;
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}
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if (i < 0 || i >= Py_SIZE(op)) {
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if (!valid_index(i, Py_SIZE(op))) {
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if (indexerr == NULL) {
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indexerr = PyUnicode_FromString(
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"list index out of range");
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@ -240,7 +253,7 @@ PyList_SetItem(PyObject *op, Py_ssize_t i,
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PyErr_BadInternalCall();
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return -1;
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}
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if (i < 0 || i >= Py_SIZE(op)) {
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if (!valid_index(i, Py_SIZE(op))) {
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Py_XDECREF(newitem);
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PyErr_SetString(PyExc_IndexError,
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"list assignment index out of range");
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@ -426,7 +439,7 @@ list_contains(PyListObject *a, PyObject *el)
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static PyObject *
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list_item(PyListObject *a, Py_ssize_t i)
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{
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if (i < 0 || i >= Py_SIZE(a)) {
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if (!valid_index(i, Py_SIZE(a))) {
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if (indexerr == NULL) {
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indexerr = PyUnicode_FromString(
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"list index out of range");
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@ -749,7 +762,7 @@ list_inplace_repeat(PyListObject *self, Py_ssize_t n)
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static int
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list_ass_item(PyListObject *a, Py_ssize_t i, PyObject *v)
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{
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if (i < 0 || i >= Py_SIZE(a)) {
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if (!valid_index(i, Py_SIZE(a))) {
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PyErr_SetString(PyExc_IndexError,
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"list assignment index out of range");
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return -1;
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@ -996,7 +1009,7 @@ list_pop_impl(PyListObject *self, Py_ssize_t index)
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}
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if (index < 0)
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index += Py_SIZE(self);
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if (index < 0 || index >= Py_SIZE(self)) {
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if (!valid_index(index, Py_SIZE(self))) {
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PyErr_SetString(PyExc_IndexError, "pop index out of range");
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return NULL;
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}
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