GH-128682: Account for escapes in DECREF_INPUTS (GH-129953)

* Handle escapes in DECREF_INPUTS

* Mark a few more functions as escaping

* Replace DECREF_INPUTS with PyStackRef_CLOSE where possible

Author: markshannon

Include/internal/pycore_ceval.h

@@ -274,7 +274,7 @@ PyAPI_FUNC(PyObject *) _PyEval_ImportName(PyThreadState *, _PyInterpreterFrame *
 PyAPI_FUNC(PyObject *)_PyEval_MatchClass(PyThreadState *tstate, PyObject *subject, PyObject *type, Py_ssize_t nargs, PyObject *kwargs);
 PyAPI_FUNC(PyObject *)_PyEval_MatchKeys(PyThreadState *tstate, PyObject *map, PyObject *keys);
 PyAPI_FUNC(void) _PyEval_MonitorRaise(PyThreadState *tstate, _PyInterpreterFrame *frame, _Py_CODEUNIT *instr);
-PyAPI_FUNC(int) _PyEval_UnpackIterableStackRef(PyThreadState *tstate, _PyStackRef v, int argcnt, int argcntafter, _PyStackRef *sp);
+PyAPI_FUNC(int) _PyEval_UnpackIterableStackRef(PyThreadState *tstate, PyObject *v, int argcnt, int argcntafter, _PyStackRef *sp);
 PyAPI_FUNC(void) _PyEval_FrameClearAndPop(PyThreadState *tstate, _PyInterpreterFrame *frame);
 PyAPI_FUNC(PyObject **) _PyObjectArray_FromStackRefArray(_PyStackRef *input, Py_ssize_t nargs, PyObject **scratch);
 

Include/internal/pycore_opcode_metadata.h

@@ -1723,6 +1723,7 @@ def test_stack_save_reload(self):
         input = """
         inst(BALANCED, ( -- )) {
             SAVE_STACK();
+            code();
             RELOAD_STACK();
         }
         """
@@ -1737,12 +1738,36 @@ def test_stack_save_reload(self):
             next_instr += 1;
             INSTRUCTION_STATS(BALANCED);
             _PyFrame_SetStackPointer(frame, stack_pointer);
+            code();
             stack_pointer = _PyFrame_GetStackPointer(frame);
             DISPATCH();
         }
         """
         self.run_cases_test(input, output)
 
+    def test_stack_save_reload_paired(self):
+
+        input = """
+        inst(BALANCED, ( -- )) {
+            SAVE_STACK();
+            RELOAD_STACK();
+        }
+        """
+
+        output = """
+        TARGET(BALANCED) {
+            #if defined(Py_TAIL_CALL_INTERP)
+            int opcode = BALANCED;
+            (void)(opcode);
+            #endif
+            frame->instr_ptr = next_instr;
+            next_instr += 1;
+            INSTRUCTION_STATS(BALANCED);
+            DISPATCH();
+        }
+        """
+        self.run_cases_test(input, output)
+
     def test_stack_reload_only(self):
 
         input = """

Include/internal/pycore_uop_metadata.h

@@ -0,0 +1,4 @@
+The internal (evaluation) stack is now spilled to memory whenever execution
+esacpes from the interpreter or JIT compiled code. This should have no
+observable effect in either Python or builtin extensions, but will allow
+various important optimizations in the future.

Lib/test/test_generated_cases.py

@@ -2994,6 +2994,11 @@ _Py_Dealloc(PyObject *op)
     destructor dealloc = type->tp_dealloc;
 #ifdef Py_DEBUG
     PyThreadState *tstate = _PyThreadState_GET();
+#ifndef Py_GIL_DISABLED
+    /* This assertion doesn't hold for the free-threading build, as
+     * PyStackRef_CLOSE_SPECIALIZED is not implemented */
+    assert(tstate->current_frame == NULL || tstate->current_frame->stackpointer != NULL);
+#endif
     PyObject *old_exc = tstate != NULL ? tstate->current_exception : NULL;
     // Keep the old exception type alive to prevent undefined behavior
     // on (tstate->curexc_type != old_exc_type) below