bpo-46702: Specialize UNPACK_SEQUENCE

Include/internal/pycore_code.h

@@ -276,6 +276,8 @@ int _Py_Specialize_CallNoKw(PyObject *callable, _Py_CODEUNIT *instr, int nargs,
 void _Py_Specialize_BinaryOp(PyObject *lhs, PyObject *rhs, _Py_CODEUNIT *instr,
                              SpecializedCacheEntry *cache);
 void _Py_Specialize_CompareOp(PyObject *lhs, PyObject *rhs, _Py_CODEUNIT *instr, SpecializedCacheEntry *cache);
+void _Py_Specialize_UnpackSequence(PyObject *seq, _Py_CODEUNIT *instr,
+                                   SpecializedCacheEntry *cache);
 
 /* Deallocator function for static codeobjects used in deepfreeze.py */
 void _PyStaticCode_Dealloc(PyCodeObject *co);

Lib/opcode.py

@@ -283,6 +283,10 @@ def jabs_op(name, op):
     "STORE_ATTR_INSTANCE_VALUE",
     "STORE_ATTR_SLOT",
     "STORE_ATTR_WITH_HINT",
+    "UNPACK_SEQUENCE_ADAPTIVE",
+    "UNPACK_SEQUENCE_LIST",
+    "UNPACK_SEQUENCE_TUPLE",
+    "UNPACK_SEQUENCE_TWO_TUPLE",
     # Super instructions
     "LOAD_FAST__LOAD_FAST",
     "STORE_FAST__LOAD_FAST",

Misc/NEWS.d/next/Core and Builtins/2022-02-09-16-36-11.bpo-46702.LcaEuC.rst

@@ -0,0 +1,2 @@
+Specialize :opcode:`UNPACK_SEQUENCE` for :class:`tuple` and :class:`list`
+unpackings.

Python/ceval.c

@@ -2738,52 +2738,84 @@ _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 *, int);
-            _py_stats.opcode_stats[UNPACK_SEQUENCE].specialization.failure++;
-            _py_stats.opcode_stats[UNPACK_SEQUENCE].specialization.
-                failure_kinds[_PySpecialization_ClassifySequence(seq, oparg)]++;
-#endif
-            if (PyTuple_CheckExact(seq) &&
-                PyTuple_GET_SIZE(seq) == oparg) {
-                items = ((PyTupleObject *)seq)->ob_item;
-                while (oparg--) {
-                    item = items[oparg];
-                    Py_INCREF(item);
-                    PUSH(item);
-                }
-            } else if (PyList_CheckExact(seq) &&
-                       PyList_GET_SIZE(seq) == oparg) {
-                items = ((PyListObject *)seq)->ob_item;
-                while (oparg--) {
-                    item = items[oparg];
-                    Py_INCREF(item);
-                    PUSH(item);
-                }
-            } else if (unpack_iterable(tstate, seq, oparg, -1,
-                                       stack_pointer + oparg)) {
-                STACK_GROW(oparg);
-            } else {
-                /* unpack_iterable() raised an exception */
+            PyObject *seq = POP();
+            PyObject **top = stack_pointer + oparg;
+            if (!unpack_iterable(tstate, seq, oparg, -1, top)) {
                 Py_DECREF(seq);
                 goto error;
             }
+            STACK_GROW(oparg);
             Py_DECREF(seq);
             DISPATCH();
         }
 
+        TARGET(UNPACK_SEQUENCE_ADAPTIVE) {
+            assert(cframe.use_tracing == 0);
+            SpecializedCacheEntry *cache = GET_CACHE();
+            if (cache->adaptive.counter == 0) {
+                PyObject *seq = TOP();
+                next_instr--;
+                _Py_Specialize_UnpackSequence(seq, next_instr, cache);
+                DISPATCH();
+            }
+            else {
+                STAT_INC(UNPACK_SEQUENCE, deferred);
+                cache->adaptive.counter--;
+                oparg = cache->adaptive.original_oparg;
+                JUMP_TO_INSTRUCTION(UNPACK_SEQUENCE);
+            }
+        }
+
+        TARGET(UNPACK_SEQUENCE_TWO_TUPLE) {
+            PyObject *seq = TOP();
+            DEOPT_IF(!PyTuple_CheckExact(seq), UNPACK_SEQUENCE);
+            DEOPT_IF(PyTuple_GET_SIZE(seq) != 2, UNPACK_SEQUENCE);
+            STAT_INC(UNPACK_SEQUENCE, hit);
+            SET_TOP(Py_NewRef(PyTuple_GET_ITEM(seq, 1)));
+            PUSH(Py_NewRef(PyTuple_GET_ITEM(seq, 0)));
+            Py_DECREF(seq);
+            NOTRACE_DISPATCH();
+        }
+
+        TARGET(UNPACK_SEQUENCE_TUPLE) {
+            PyObject *seq = TOP();
+            int len = GET_CACHE()->adaptive.original_oparg;
+            DEOPT_IF(!PyTuple_CheckExact(seq), UNPACK_SEQUENCE);
+            DEOPT_IF(PyTuple_GET_SIZE(seq) != len, UNPACK_SEQUENCE);
+            STAT_INC(UNPACK_SEQUENCE, hit);
+            STACK_SHRINK(1);
+            PyObject **items = _PyTuple_ITEMS(seq);
+            while (len--) {
+                PUSH(Py_NewRef(items[len]));
+            }
+            Py_DECREF(seq);
+            NOTRACE_DISPATCH();
+        }
+
+        TARGET(UNPACK_SEQUENCE_LIST) {
+            PyObject *seq = TOP();
+            int len = GET_CACHE()->adaptive.original_oparg;
+            DEOPT_IF(!PyList_CheckExact(seq), UNPACK_SEQUENCE);
+            DEOPT_IF(PyList_GET_SIZE(seq) != len, UNPACK_SEQUENCE);
+            STAT_INC(UNPACK_SEQUENCE, hit);
+            STACK_SHRINK(1);
+            PyObject **items = _PyList_ITEMS(seq);
+            while (len--) {
+                PUSH(Py_NewRef(items[len]));
+            }
+            Py_DECREF(seq);
+            NOTRACE_DISPATCH();
+        }
+
         TARGET(UNPACK_EX) {
             int totalargs = 1 + (oparg & 0xFF) + (oparg >> 8);
             PyObject *seq = POP();
-
-            if (unpack_iterable(tstate, seq, oparg & 0xFF, oparg >> 8,
-                                stack_pointer + totalargs)) {
-                stack_pointer += totalargs;
-            } else {
+            PyObject **top = stack_pointer + totalargs;
+            if (!unpack_iterable(tstate, seq, oparg & 0xFF, oparg >> 8, top)) {
                 Py_DECREF(seq);
                 goto error;
             }
+            STACK_GROW(totalargs);
             Py_DECREF(seq);
             DISPATCH();
         }
@@ -5396,6 +5428,7 @@ MISS_WITH_CACHE(CALL)
 MISS_WITH_CACHE(BINARY_OP)
 MISS_WITH_CACHE(COMPARE_OP)
 MISS_WITH_CACHE(BINARY_SUBSCR)
+MISS_WITH_CACHE(UNPACK_SEQUENCE)
 MISS_WITH_OPARG_COUNTER(STORE_SUBSCR)
 
 binary_subscr_dict_error:

Python/specialize.c

@@ -51,6 +51,7 @@ static uint8_t adaptive_opcodes[256] = {
     [STORE_ATTR] = STORE_ATTR_ADAPTIVE,
     [BINARY_OP] = BINARY_OP_ADAPTIVE,
     [COMPARE_OP] = COMPARE_OP_ADAPTIVE,
+    [UNPACK_SEQUENCE] = UNPACK_SEQUENCE_ADAPTIVE,
 };
 
 /* The number of cache entries required for a "family" of instructions. */
@@ -64,6 +65,7 @@ static uint8_t cache_requirements[256] = {
     [STORE_ATTR] = 2, /* _PyAdaptiveEntry and _PyAttrCache */
     [BINARY_OP] = 1,  // _PyAdaptiveEntry
     [COMPARE_OP] = 1, /* _PyAdaptiveEntry */
+    [UNPACK_SEQUENCE] = 1,  // _PyAdaptiveEntry
 };
 
 Py_ssize_t _Py_QuickenedCount = 0;
@@ -155,6 +157,7 @@ _Py_GetSpecializationStats(void) {
     err += add_stat_dict(stats, CALL, "call");
     err += add_stat_dict(stats, BINARY_OP, "binary_op");
     err += add_stat_dict(stats, COMPARE_OP, "compare_op");
+    err += add_stat_dict(stats, UNPACK_SEQUENCE, "unpack_sequence");
     if (err < 0) {
         Py_DECREF(stats);
         return NULL;
@@ -607,27 +610,10 @@ initial_counter_value(void) {
 #define SPEC_FAIL_FOR_ITER_DICT_VALUES 22
 #define SPEC_FAIL_FOR_ITER_ENUMERATE 23
 
-/* UNPACK_SEQUENCE */
-#define SPEC_FAIL_UNPACK_SEQUENCE_TUPLE_0 9
-#define SPEC_FAIL_UNPACK_SEQUENCE_TUPLE_1 10
-#define SPEC_FAIL_UNPACK_SEQUENCE_TUPLE_2 11
-#define SPEC_FAIL_UNPACK_SEQUENCE_TUPLE_3 12
-#define SPEC_FAIL_UNPACK_SEQUENCE_TUPLE_4 13
-#define SPEC_FAIL_UNPACK_SEQUENCE_TUPLE_N 14
-
-#define SPEC_FAIL_UNPACK_SEQUENCE_LIST_0 15
-#define SPEC_FAIL_UNPACK_SEQUENCE_LIST_1 16
-#define SPEC_FAIL_UNPACK_SEQUENCE_LIST_2 17
-#define SPEC_FAIL_UNPACK_SEQUENCE_LIST_3 18
-#define SPEC_FAIL_UNPACK_SEQUENCE_LIST_4 19
-#define SPEC_FAIL_UNPACK_SEQUENCE_LIST_N 20
-
-#define SPEC_FAIL_UNPACK_SEQUENCE_OTHER_0 21
-#define SPEC_FAIL_UNPACK_SEQUENCE_OTHER_1 22
-#define SPEC_FAIL_UNPACK_SEQUENCE_OTHER_2 23
-#define SPEC_FAIL_UNPACK_SEQUENCE_OTHER_3 24
-#define SPEC_FAIL_UNPACK_SEQUENCE_OTHER_4 25
-#define SPEC_FAIL_UNPACK_SEQUENCE_OTHER_N 26
+// UNPACK_SEQUENCE
+
+#define SPEC_FAIL_UNPACK_SEQUENCE_ITERATOR 8
+#define SPEC_FAIL_UNPACK_SEQUENCE_SEQUENCE 9
 
 
 static int
@@ -1949,6 +1935,56 @@ _Py_Specialize_CompareOp(PyObject *lhs, PyObject *rhs,
     adaptive->counter = initial_counter_value();
 }
 
+#ifdef Py_STATS
+static int
+unpack_sequence_fail_kind(PyObject *seq)
+{
+    if (PySequence_Check(seq)) {
+        return SPEC_FAIL_UNPACK_SEQUENCE_SEQUENCE;
+    }
+    if (PyIter_Check(seq)) {
+        return SPEC_FAIL_UNPACK_SEQUENCE_ITERATOR;
+    }
+    return SPEC_FAIL_OTHER;
+}
+#endif
+
+void
+_Py_Specialize_UnpackSequence(PyObject *seq, _Py_CODEUNIT *instr,
+                              SpecializedCacheEntry *cache)
+{
+    _PyAdaptiveEntry *adaptive = &cache->adaptive;
+    if (PyTuple_CheckExact(seq)) {
+        if (PyTuple_GET_SIZE(seq) != adaptive->original_oparg) {
+            SPECIALIZATION_FAIL(UNPACK_SEQUENCE, SPEC_FAIL_EXPECTED_ERROR);
+            goto failure;
+        }
+        if (PyTuple_GET_SIZE(seq) == 2) {
+            *instr = _Py_MAKECODEUNIT(UNPACK_SEQUENCE_TWO_TUPLE,
+                                      _Py_OPARG(*instr));
+            goto success;
+        }
+        *instr = _Py_MAKECODEUNIT(UNPACK_SEQUENCE_TUPLE, _Py_OPARG(*instr));
+        goto success;
+    }
+    if (PyList_CheckExact(seq)) {
+        if (PyList_GET_SIZE(seq) != adaptive->original_oparg) {
+            SPECIALIZATION_FAIL(UNPACK_SEQUENCE, SPEC_FAIL_EXPECTED_ERROR);
+            goto failure;
+        }
+        *instr = _Py_MAKECODEUNIT(UNPACK_SEQUENCE_LIST, _Py_OPARG(*instr));
+        goto success;
+    }
+    SPECIALIZATION_FAIL(UNPACK_SEQUENCE, unpack_sequence_fail_kind(seq));
+failure:
+    STAT_INC(UNPACK_SEQUENCE, failure);
+    cache_backoff(adaptive);
+    return;
+success:
+    STAT_INC(UNPACK_SEQUENCE, success);
+    adaptive->counter = initial_counter_value();
+}
+
 #ifdef Py_STATS
 
 int
@@ -2001,22 +2037,6 @@ int
     return SPEC_FAIL_OTHER;
 }
 
-int
-_PySpecialization_ClassifySequence(PyObject *seq, int n)
-{
-    assert(n >= 0);
-    if (n > 4) {
-        n = 5;
-    }
-    if (PyTuple_CheckExact(seq)) {
-        return SPEC_FAIL_UNPACK_SEQUENCE_TUPLE_0 + n;
-    }
-    if (PyList_CheckExact(seq)) {
-        return SPEC_FAIL_UNPACK_SEQUENCE_LIST_0 + n;
-    }
-    return SPEC_FAIL_UNPACK_SEQUENCE_OTHER_0 + n;
-}
-
 int
 _PySpecialization_ClassifyCallable(PyObject *callable)
 {