[mypyc] feat: __mypyc_empty_tuple__ constant

Author: BobTheBuidler

mypyc/irbuild/ll_builder.py

@@ -183,7 +183,7 @@
     str_ssize_t_size_op,
     unicode_compare,
 )
-from mypyc.primitives.tuple_ops import list_tuple_op, new_tuple_op, new_tuple_with_length_op
+from mypyc.primitives.tuple_ops import list_tuple_op, load_empty_tuple_constant_op, new_tuple_op, new_tuple_with_length_op
 from mypyc.rt_subtype import is_runtime_subtype
 from mypyc.sametype import is_same_type
 from mypyc.subtype import is_subtype
@@ -2305,8 +2305,11 @@ def builtin_len(self, val: Value, line: int, use_pyssize_t: bool = False) -> Val
             return self.call_c(generic_len_op, [val], line)
 
     def new_tuple(self, items: list[Value], line: int) -> Value:
-        size: Value = Integer(len(items), c_pyssize_t_rprimitive)
-        return self.call_c(new_tuple_op, [size] + items, line)
+        if items:
+            size: Value = Integer(len(items), c_pyssize_t_rprimitive)
+            return self.call_c(new_tuple_op, [size] + items, line)
+        else:
+            return self.call_c(load_empty_tuple_constant_op, [], line)
 
     def new_tuple_with_length(self, length: Value, line: int) -> Value:
         """This function returns an uninitialized tuple.

mypyc/lib-rt/CPy.h

@@ -64,6 +64,13 @@ typedef struct tuple_T4CIOO {
 } tuple_T4CIOO;
 #endif
 
+// System-wide empty tuple constant
+extern PyObject * __mypyc_empty_tuple__;
+
+static inline PyObject *_CPyTuple_LoadEmptyTupleConstant() {
+    Py_INCREF(__mypyc_empty_tuple__);
+    return __mypyc_empty_tuple__;
+}
 
 // Native object operations
 

mypyc/lib-rt/init.c

@@ -10,4 +10,14 @@ PyObject *_CPy_ExcDummy = (PyObject *)&_CPy_ExcDummyStruct;
 // things at load time.
 void CPy_Init(void) {
     _CPy_ExcDummyStruct.ob_base.ob_type = &PyBaseObject_Type;
+
+    // Initialize system-wide empty tuple constant
+    if (__mypyc_empty_tuple__ == NULL) {
+        __mypyc_empty_tuple__ = PyTuple_New(0);
+        if (!__mypyc_empty_tuple__) {
+            PyErr_SetString(PyExc_RuntimeError, "Failed to initialize __mypyc_empty_tuple__");
+            return;
+        }
+        Py_INCREF(__mypyc_empty_tuple__);
+    }
 }

mypyc/lib-rt/tuple_ops.c

@@ -5,6 +5,9 @@
 #include <Python.h>
 #include "CPy.h"
 
+// System-wide empty tuple constant
+PyObject * __mypyc_empty_tuple__ = NULL;
+
 PyObject *CPySequenceTuple_GetItem(PyObject *tuple, CPyTagged index) {
     if (CPyTagged_CheckShort(index)) {
         Py_ssize_t n = CPyTagged_ShortAsSsize_t(index);

mypyc/primitives/tuple_ops.py

@@ -55,6 +55,13 @@
     error_kind=ERR_MAGIC,
 )
 
+load_empty_tuple_constant_op = custom_op(
+    arg_types=[],
+    return_type=tuple_rprimitive,
+    c_function_name="_CPyTuple_LoadEmptyTupleConstant",
+    error_kind=ERR_NEVER,
+)
+
 # PyTuple_SET_ITEM does no error checking,
 # and should only be used to fill in brand new tuples.
 new_tuple_set_item_op = custom_op(