python
@@ -31,7 +31,7 @@ extern "C" {
 #include "pycore_list.h"          // struct _Py_list_state
 #include "pycore_mimalloc.h"      // struct _mimalloc_interp_state
 #include "pycore_object_state.h"  // struct _py_object_state
-#include "pycore_optimizer.h"     // _PyOptimizerObject
+#include "pycore_optimizer.h"     // _PyExecutorObject
 #include "pycore_obmalloc.h"      // struct _obmalloc_state
 #include "pycore_qsbr.h"          // struct _qsbr_state
 #include "pycore_stackref.h"      // Py_STACKREF_DEBUG
@@ -262,7 +262,7 @@ struct _is {
     struct ast_state ast;
     struct types_state types;
     struct callable_cache callable_cache;
-    _PyOptimizerObject *optimizer;
+    bool jit;
     _PyExecutorObject *executor_list_head;
     size_t trace_run_counter;
     _rare_events rare_events;

diff --git a/Include/internal/pycore_opcode_metadata.h b/Include/internal/pycore_opcode_metadata.h
diff --git a/Include/internal/pycore_optimizer.h b/Include/internal/pycore_optimizer.h
@@ -83,23 +83,6 @@ typedef struct _PyExecutorObject {
     _PyExitData exits[1];
 } _PyExecutorObject;
 
-typedef struct _PyOptimizerObject _PyOptimizerObject;
-
-/* Should return > 0 if a new executor is created. O if no executor is produced and < 0 if an error occurred. */
-typedef int (*_Py_optimize_func)(
-    _PyOptimizerObject* self, struct _PyInterpreterFrame *frame,
-    _Py_CODEUNIT *instr, _PyExecutorObject **exec_ptr,
-    int curr_stackentries, bool progress_needed);
-
-struct _PyOptimizerObject {
-    PyObject_HEAD
-    _Py_optimize_func optimize;
-    /* Data needed by the optimizer goes here, but is opaque to the VM */
-};
-
-/** Test support **/
-_PyOptimizerObject *_Py_SetOptimizer(PyInterpreterState *interp, _PyOptimizerObject* optimizer);
-
 
 // Export for '_opcode' shared extension (JIT compiler).
 PyAPI_FUNC(_PyExecutorObject*) _Py_GetExecutor(PyCodeObject *code, int offset);
@@ -110,12 +93,6 @@ void _Py_BloomFilter_Init(_PyBloomFilter *);
 void _Py_BloomFilter_Add(_PyBloomFilter *bloom, void *obj);
 PyAPI_FUNC(void) _Py_Executor_DependsOn(_PyExecutorObject *executor, void *obj);
 
-// For testing
-// Export for '_testinternalcapi' shared extension.
-PyAPI_FUNC(_PyOptimizerObject *) _Py_GetOptimizer(void);
-PyAPI_FUNC(int) _Py_SetTier2Optimizer(_PyOptimizerObject* optimizer);
-PyAPI_FUNC(PyObject *) _PyOptimizer_NewUOpOptimizer(void);
-
 #define _Py_MAX_ALLOWED_BUILTINS_MODIFICATIONS 3
 #define _Py_MAX_ALLOWED_GLOBALS_MODIFICATIONS 6
 
@@ -144,9 +121,7 @@ int _Py_uop_analyze_and_optimize(struct _PyInterpreterFrame *frame,
     _PyUOpInstruction *trace, int trace_len, int curr_stackentries,
     _PyBloomFilter *dependencies);
 
-extern PyTypeObject _PyDefaultOptimizer_Type;
 extern PyTypeObject _PyUOpExecutor_Type;
-extern PyTypeObject _PyUOpOptimizer_Type;
 
 
 #define UOP_FORMAT_TARGET 0

diff --git a/Include/opcode_ids.h b/Include/opcode_ids.h
@@ -38,12 +38,8 @@ executor in `co_executors`.
 
 ## The micro-op optimizer
 
-The optimizer that `_PyOptimizer_Optimize()` runs is configurable via the
-`_Py_SetTier2Optimizer()` function (this is used in test via
-`_testinternalcapi.set_optimizer()`.)
-
 The micro-op (abbreviated `uop` to approximate `μop`) optimizer is defined in
-[`Python/optimizer.c`](../Python/optimizer.c) as the type `_PyUOpOptimizer_Type`.
+[`Python/optimizer.c`](../Python/optimizer.c) as `_PyOptimizer_Optimize`.
 It translates an instruction trace into a sequence of micro-ops by replacing
 each bytecode by an equivalent sequence of micro-ops (see
 `_PyOpcode_macro_expansion` in

diff --git a/Lib/_opcode_metadata.py b/Lib/_opcode_metadata.py
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
@@ -58,7 +58,8 @@
     "LOOPBACK_TIMEOUT", "INTERNET_TIMEOUT", "SHORT_TIMEOUT", "LONG_TIMEOUT",
     "Py_DEBUG", "exceeds_recursion_limit", "get_c_recursion_limit",
     "skip_on_s390x",
-    "without_optimizer",
+    "requires_jit_enabled",
+    "requires_jit_disabled",
     "force_not_colorized",
     "force_not_colorized_test_class",
     "make_clean_env",
@@ -2620,21 +2621,13 @@ def exceeds_recursion_limit():
 
 Py_TRACE_REFS = hasattr(sys, 'getobjects')
 
-# Decorator to disable optimizer while a function run
-def without_optimizer(func):
-    try:
-        from _testinternalcapi import get_optimizer, set_optimizer
-    except ImportError:
-        return func
-    @functools.wraps(func)
-    def wrapper(*args, **kwargs):
-        save_opt = get_optimizer()
-        try:
-            set_optimizer(None)
-            return func(*args, **kwargs)
-        finally:
-            set_optimizer(save_opt)
-    return wrapper
+try:
+    from _testinternalcapi import jit_enabled
+except ImportError:
+    requires_jit_enabled = requires_jit_disabled = unittest.skip("requires _testinternalcapi")
+else:
+    requires_jit_enabled = unittest.skipUnless(jit_enabled(), "requires JIT enabled")
+    requires_jit_disabled = unittest.skipIf(jit_enabled(), "requires JIT disabled")
 
 
 _BASE_COPY_SRC_DIR_IGNORED_NAMES = frozenset({

@@ -306,7 +306,7 @@ def test_getitem_with_error(self):
                     CURRENT_THREAD_REGEX +
                     r'  File .*, line 6 in <module>\n'
                     r'\n'
-                    r'Extension modules: _testcapi \(total: 1\)\n')
+                    r'Extension modules: _testcapi, _testinternalcapi \(total: 2\)\n')
         else:
             # Python built with NDEBUG macro defined:
             # test _Py_CheckFunctionResult() instead.