gh-115999: Add free-threaded specialization for UNPACK_SEQUENCE

Lib/test/test_opcache.py

@@ -1256,6 +1256,37 @@ def g():
         self.assert_no_opcode(g, "CONTAINS_OP")
 
 
+    @cpython_only
+    @requires_specialization_ft
+    def test_unpack_sequence(self):
+        def f():
+            for _ in range(100):
+                a, b = 1, 2
+                self.assertEqual(a, 1)
+                self.assertEqual(b, 2)
+
+        f()
+        self.assert_specialized(f, "UNPACK_SEQUENCE_TWO_TUPLE")
+        self.assert_no_opcode(f, "UNPACK_SEQUENCE")
+
+        def g():
+            for _ in range(100):
+                a, = 1,
+                self.assertEqual(a, 1)
+
+        g()
+        self.assert_specialized(g, "UNPACK_SEQUENCE_TUPLE")
+        self.assert_no_opcode(g, "UNPACK_SEQUENCE")
+
+        def x():
+            for _ in range(100):
+                a, b = [1, 2]
+                self.assertEqual(a, 1)
+                self.assertEqual(b, 2)
+
+        x()
+        self.assert_specialized(x, "UNPACK_SEQUENCE_LIST")
+        self.assert_no_opcode(x, "UNPACK_SEQUENCE")
 
 if __name__ == "__main__":
     unittest.main()

Python/bytecodes.c

@@ -1381,15 +1381,15 @@ dummy_func(
         };
 
         specializing op(_SPECIALIZE_UNPACK_SEQUENCE, (counter/1, seq -- seq)) {
-            #if ENABLE_SPECIALIZATION
+            #if ENABLE_SPECIALIZATION_FT
             if (ADAPTIVE_COUNTER_TRIGGERS(counter)) {
                 next_instr = this_instr;
                 _Py_Specialize_UnpackSequence(seq, next_instr, oparg);
                 DISPATCH_SAME_OPARG();
             }
             OPCODE_DEFERRED_INC(UNPACK_SEQUENCE);
             ADVANCE_ADAPTIVE_COUNTER(this_instr[1].counter);
-            #endif  /* ENABLE_SPECIALIZATION */
+            #endif  /* ENABLE_SPECIALIZATION_FT */
             (void)seq;
             (void)counter;
         }
@@ -1429,12 +1429,24 @@ dummy_func(
         inst(UNPACK_SEQUENCE_LIST, (unused/1, seq -- values[oparg])) {
             PyObject *seq_o = PyStackRef_AsPyObjectBorrow(seq);
             DEOPT_IF(!PyList_CheckExact(seq_o));
-            DEOPT_IF(PyList_GET_SIZE(seq_o) != oparg);
+            #ifdef Py_GIL_DISABLED
+            PyCriticalSection cs;
+            PyCriticalSection_Begin(&cs, seq_o);
+            #endif
+            if (PyList_GET_SIZE(seq_o) != oparg) {
+                #ifdef Py_GIL_DISABLED
+                PyCriticalSection_End(&cs);
+                #endif
+                DEOPT_IF(true);
+            }
             STAT_INC(UNPACK_SEQUENCE, hit);
             PyObject **items = _PyList_ITEMS(seq_o);
             for (int i = oparg; --i >= 0; ) {
                 *values++ = PyStackRef_FromPyObjectNew(items[i]);
             }
+            #ifdef Py_GIL_DISABLED
+            PyCriticalSection_End(&cs);
+            #endif
             DECREF_INPUTS();
         }
 
@@ -2512,7 +2524,7 @@ dummy_func(
             }
             OPCODE_DEFERRED_INC(CONTAINS_OP);
             ADVANCE_ADAPTIVE_COUNTER(this_instr[1].counter);
-            #endif  /* ENABLE_SPECIALIZATION */
+            #endif  /* ENABLE_SPECIALIZATION_FT */
         }
 
         macro(CONTAINS_OP) = _SPECIALIZE_CONTAINS_OP + _CONTAINS_OP;

Python/specialize.c

@@ -2478,46 +2478,40 @@ unpack_sequence_fail_kind(PyObject *seq)
     }
     return SPEC_FAIL_OTHER;
 }
-#endif   // Py_STATS
+#endif
 
 void
 _Py_Specialize_UnpackSequence(_PyStackRef seq_st, _Py_CODEUNIT *instr, int oparg)
 {
     PyObject *seq = PyStackRef_AsPyObjectBorrow(seq_st);
 
-    assert(ENABLE_SPECIALIZATION);
+    assert(ENABLE_SPECIALIZATION_FT);
     assert(_PyOpcode_Caches[UNPACK_SEQUENCE] ==
            INLINE_CACHE_ENTRIES_UNPACK_SEQUENCE);
-    _PyUnpackSequenceCache *cache = (_PyUnpackSequenceCache *)(instr + 1);
     if (PyTuple_CheckExact(seq)) {
         if (PyTuple_GET_SIZE(seq) != oparg) {
             SPECIALIZATION_FAIL(UNPACK_SEQUENCE, SPEC_FAIL_EXPECTED_ERROR);
-            goto failure;
+            unspecialize(instr);
+            return;
         }
         if (PyTuple_GET_SIZE(seq) == 2) {
-            instr->op.code = UNPACK_SEQUENCE_TWO_TUPLE;
-            goto success;
+            specialize(instr, UNPACK_SEQUENCE_TWO_TUPLE);
+            return;
         }
-        instr->op.code = UNPACK_SEQUENCE_TUPLE;
-        goto success;
+        specialize(instr, UNPACK_SEQUENCE_TUPLE);
+        return;
     }
     if (PyList_CheckExact(seq)) {
         if (PyList_GET_SIZE(seq) != oparg) {
             SPECIALIZATION_FAIL(UNPACK_SEQUENCE, SPEC_FAIL_EXPECTED_ERROR);
-            goto failure;
+            unspecialize(instr);
+            return;
         }
-        instr->op.code = UNPACK_SEQUENCE_LIST;
-        goto success;
+        specialize(instr, UNPACK_SEQUENCE_LIST);
+        return;
     }
     SPECIALIZATION_FAIL(UNPACK_SEQUENCE, unpack_sequence_fail_kind(seq));
-failure:
-    STAT_INC(UNPACK_SEQUENCE, failure);
-    instr->op.code = UNPACK_SEQUENCE;
-    cache->counter = adaptive_counter_backoff(cache->counter);
-    return;
-success:
-    STAT_INC(UNPACK_SEQUENCE, success);
-    cache->counter = adaptive_counter_cooldown();
+    unspecialize(instr);
 }
 
 #ifdef Py_STATS