Collect stats for UNPACK_SEQUENCE. (GH-31105)

Author: markshannon

Python/ceval.c

@@ -2792,6 +2792,12 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, InterpreterFrame *frame, int thr
         TARGET(UNPACK_SEQUENCE) {
             PREDICTED(UNPACK_SEQUENCE);
             PyObject *seq = POP(), *item, **items;
+#ifdef Py_STATS
+            extern int _PySpecialization_ClassifySequence(PyObject *);
+            _py_stats.opcode_stats[UNPACK_SEQUENCE].specialization.failure++;
+            _py_stats.opcode_stats[UNPACK_SEQUENCE].specialization.
+                failure_kinds[_PySpecialization_ClassifySequence(seq)]++;
+#endif
             if (PyTuple_CheckExact(seq) &&
                 PyTuple_GET_SIZE(seq) == oparg) {
                 items = ((PyTupleObject *)seq)->ob_item;

Python/specialize.c

@@ -572,6 +572,10 @@ initial_counter_value(void) {
 #define SPEC_FAIL_ITER_DICT_VALUES 22
 #define SPEC_FAIL_ITER_ENUMERATE 23
 
+/* UNPACK_SEQUENCE */
+#define SPEC_FAIL_TUPLE 10
+#define SPEC_FAIL_LIST 11
+
 
 static int
 specialize_module_load_attr(
@@ -1880,7 +1884,6 @@ _Py_Specialize_CompareOp(PyObject *lhs, PyObject *rhs,
     adaptive->counter = initial_counter_value();
 }
 
-
 int
  _PySpecialization_ClassifyIterator(PyObject *iter)
 {
@@ -1930,3 +1933,15 @@ int
     }
     return SPEC_FAIL_OTHER;
 }
+
+int
+_PySpecialization_ClassifySequence(PyObject *seq)
+{
+    if (PyTuple_CheckExact(seq)) {
+        return SPEC_FAIL_TUPLE;
+    }
+    if (PyList_CheckExact(seq)) {
+        return SPEC_FAIL_LIST;
+    }
+    return SPEC_FAIL_OTHER;
+}