Add CONSTANT_EMPTY_TUPLE to LOAD_COMMON_CONSTANT

eendebakpt · claude · eendebakpt · commit 84e6f855a1f3 · 2026-05-11T17:12:19.000+02:00
Co-Authored-By: Claude Opus 4.7 (1M context) &lt;noreply@anthropic.com&gt;
diff --git a/Include/internal/pycore_magic_number.h b/Include/internal/pycore_magic_number.h
@@ -298,6 +298,7 @@ Known values:
     Python 3.15a8 3665 (Add FOR_ITER_VIRTUAL and GET_ITER specializations)
     Python 3.15b1 3666 (Add SEND_VIRTUAL and SEND_ASYNC_GEN specializations)
     Python 3.16a0 3700 (Initial version)
+    Python 3.16a0 3701 (Add CONSTANT_EMPTY_TUPLE to LOAD_COMMON_CONSTANT)
 
 
     Python 3.17 will start with 3750
@@ -311,7 +312,7 @@ PC/launcher.c must also be updated.
 
 */
 
-#define PYC_MAGIC_NUMBER 3700
+#define PYC_MAGIC_NUMBER 3701
 /* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
    (little-endian) and then appending b'\r\n'. */
 #define PYC_MAGIC_NUMBER_TOKEN \
diff --git a/Include/internal/pycore_opcode_utils.h b/Include/internal/pycore_opcode_utils.h
@@ -80,7 +80,8 @@ extern "C" {
 #define CONSTANT_TRUE 9
 #define CONSTANT_FALSE 10
 #define CONSTANT_MINUS_ONE 11
-#define NUM_COMMON_CONSTANTS 12
+#define CONSTANT_EMPTY_TUPLE 12
+#define NUM_COMMON_CONSTANTS 13
 
 /* Values used in the oparg for RESUME */
 #define RESUME_AT_FUNC_START 0
diff --git a/Lib/dis.py b/Lib/dis.py
@@ -698,8 +698,8 @@ def _get_const_value(op, arg, co_consts):
     if op == LOAD_SMALL_INT:
         return arg
     if op == LOAD_COMMON_CONSTANT:
-        # Opargs 0-6 are callables; 7-11 are literal values.
-        if 7 <= arg <= 11:
+        # Opargs 0-6 are callables; 7-12 are literal values.
+        if 7 <= arg <= 12:
             return _common_constants[arg]
         return UNKNOWN
     argval = UNKNOWN
diff --git a/Lib/opcode.py b/Lib/opcode.py
@@ -44,7 +44,7 @@
                      builtins.set,
                      # Append-only — must match CONSTANT_* in
                      # Include/internal/pycore_opcode_utils.h.
-                     None, "", True, False, -1]
+                     None, "", True, False, -1, ()]
 _nb_ops = _opcode.get_nb_ops()
 
 hascompare = [opmap["COMPARE_OP"]]
diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
@@ -1307,10 +1307,10 @@ def test_build_empty_tuple(self):
             ('RETURN_VALUE', None, 0),
         ]
         after = [
-            ('LOAD_CONST', 0, 0),
+            ('LOAD_COMMON_CONSTANT', opcode._common_constants.index(()), 0),
             ('RETURN_VALUE', None, 0),
         ]
-        self.cfg_optimization_test(before, after, consts=[], expected_consts=[()])
+        self.cfg_optimization_test(before, after, consts=[], expected_consts=[])
 
     def test_fold_tuple_of_constants(self):
         before = [
@@ -1365,10 +1365,10 @@ def test_fold_constant_intrinsic_list_to_tuple(self):
             ('RETURN_VALUE', None, 0)
         ]
         after = [
-            ('LOAD_CONST', 0, 0),
+            ('LOAD_COMMON_CONSTANT', opcode._common_constants.index(()), 0),
             ('RETURN_VALUE', None, 0)
         ]
-        self.cfg_optimization_test(before, after, consts=[], expected_consts=[()])
+        self.cfg_optimization_test(before, after, consts=[], expected_consts=[])
 
         # multiple BUILD_LIST 0: ([], 1, [], 2)
         same = [
diff --git a/Python/flowgraph.c b/Python/flowgraph.c
@@ -1468,6 +1468,10 @@ maybe_instr_make_load_common_const(cfg_instr *instr, PyObject *newconst)
              && PyUnicode_GET_LENGTH(newconst) == 0) {
         oparg = CONSTANT_EMPTY_STR;
     }
+    else if (PyTuple_CheckExact(newconst)
+             && PyTuple_GET_SIZE(newconst) == 0) {
+        oparg = CONSTANT_EMPTY_TUPLE;
+    }
     else if (PyLong_CheckExact(newconst)) {
         int overflow;
         long val = PyLong_AsLongAndOverflow(newconst, &overflow);
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
@@ -892,6 +892,8 @@ pycore_init_builtins(PyThreadState *tstate)
     interp->common_consts[CONSTANT_FALSE] = Py_False;
     interp->common_consts[CONSTANT_MINUS_ONE] =
         (PyObject *)&_PyLong_SMALL_INTS[_PY_NSMALLNEGINTS - 1];
+    interp->common_consts[CONSTANT_EMPTY_TUPLE] =
+        Py_GetConstantBorrowed(Py_CONSTANT_EMPTY_TUPLE);
     for (int i = 0; i < NUM_COMMON_CONSTANTS; i++) {
         assert(interp->common_consts[i] != NULL);
     }

Original file line number	Diff line number	Diff line change
`@@ -1307,10 +1307,10 @@ def test_build_empty_tuple(self):`
`1307`	`1307`	`('RETURN_VALUE', None, 0),`
`1308`	`1308`	`]`
`1309`	`1309`	`after = [`
`1310`		`- ('LOAD_CONST', 0, 0),`
	`1310`	`+ ('LOAD_COMMON_CONSTANT', opcode._common_constants.index(()), 0),`
`1311`	`1311`	`('RETURN_VALUE', None, 0),`
`1312`	`1312`	`]`
`1313`		`- self.cfg_optimization_test(before, after, consts=[], expected_consts=[()])`
	`1313`	`+ self.cfg_optimization_test(before, after, consts=[], expected_consts=[])`
`1314`	`1314`
`1315`	`1315`	`def test_fold_tuple_of_constants(self):`
`1316`	`1316`	`before = [`
`@@ -1365,10 +1365,10 @@ def test_fold_constant_intrinsic_list_to_tuple(self):`
`1365`	`1365`	`('RETURN_VALUE', None, 0)`
`1366`	`1366`	`]`
`1367`	`1367`	`after = [`
`1368`		`- ('LOAD_CONST', 0, 0),`
	`1368`	`+ ('LOAD_COMMON_CONSTANT', opcode._common_constants.index(()), 0),`
`1369`	`1369`	`('RETURN_VALUE', None, 0)`
`1370`	`1370`	`]`
`1371`		`- self.cfg_optimization_test(before, after, consts=[], expected_consts=[()])`
	`1371`	`+ self.cfg_optimization_test(before, after, consts=[], expected_consts=[])`
`1372`	`1372`
`1373`	`1373`	`# multiple BUILD_LIST 0: ([], 1, [], 2)`
`1374`	`1374`	`same = [`
Original file line number	Diff line number	Diff line change
`@@ -892,6 +892,8 @@ pycore_init_builtins(PyThreadState *tstate)`
`892`	`892`	`interp->common_consts[CONSTANT_FALSE] = Py_False;`
`893`	`893`	`interp->common_consts[CONSTANT_MINUS_ONE] =`
`894`	`894`	`(PyObject *)&_PyLong_SMALL_INTS[_PY_NSMALLNEGINTS - 1];`
	`895`	`+ interp->common_consts[CONSTANT_EMPTY_TUPLE] =`
	`896`	`+ Py_GetConstantBorrowed(Py_CONSTANT_EMPTY_TUPLE);`
`895`	`897`	`for (int i = 0; i < NUM_COMMON_CONSTANTS; i++) {`
`896`	`898`	`assert(interp->common_consts[i] != NULL);`
`897`	`899`	`}`