gh-118335: Configure Tier 2 interpreter at build time (#118339)

The code for Tier 2 is now only compiled when configured
with `--enable-experimental-jit[=yes|interpreter]`.

We drop support for `PYTHON_UOPS` and -`Xuops`,
but you can disable the interpreter or JIT
at runtime by setting `PYTHON_JIT=0`.
You can also build it without enabling it by default
using `--enable-experimental-jit=yes-off`;
enable with `PYTHON_JIT=1`.

On Windows, the `build.bat` script supports
`--experimental-jit`, `--experimental-jit-off`,
`--experimental-interpreter`.

In the C code, `_Py_JIT` is defined as before
when the JIT is enabled; the new variable
`_Py_TIER2` is defined when the JIT *or* the
interpreter is enabled. It is actually a bitmask:
1: JIT; 2: default-off; 4: interpreter.

Lib/test/support/__init__.py

@@ -2539,17 +2539,17 @@ Py_TRACE_REFS = hasattr(sys, 'getobjects')
 # Decorator to disable optimizer while a function run
 def without_optimizer(func):
     try:
-        import _testinternalcapi
+        from _testinternalcapi import get_optimizer, set_optimizer
     except ImportError:
         return func
     @functools.wraps(func)
     def wrapper(*args, **kwargs):
-        save_opt = _testinternalcapi.get_optimizer()
+        save_opt = get_optimizer()
         try:
-            _testinternalcapi.set_optimizer(None)
+            set_optimizer(None)
             return func(*args, **kwargs)
         finally:
-            _testinternalcapi.set_optimizer(save_opt)
+            set_optimizer(save_opt)
     return wrapper
 
 

Lib/test/test_capi/test_opt.py

@@ -34,6 +34,8 @@ def clear_executors(func):
 
 
 @requires_specialization
+@unittest.skipUnless(hasattr(_testinternalcapi, "get_optimizer"),
+                     "Requires optimizer infrastructure")
 class TestOptimizerAPI(unittest.TestCase):
 
     def test_new_counter_optimizer_dealloc(self):
@@ -136,6 +138,8 @@ def get_opnames(ex):
 
 
 @requires_specialization
+@unittest.skipUnless(hasattr(_testinternalcapi, "get_optimizer"),
+                     "Requires optimizer infrastructure")
 class TestExecutorInvalidation(unittest.TestCase):
 
     def setUp(self):
@@ -215,6 +219,8 @@ class TestExecutorInvalidation(unittest.TestCase):
 
 
 @requires_specialization
+@unittest.skipUnless(hasattr(_testinternalcapi, "get_optimizer"),
+                     "Requires optimizer infrastructure")
 @unittest.skipIf(os.getenv("PYTHON_UOPS_OPTIMIZE") == "0", "Needs uop optimizer to run.")
 class TestUops(unittest.TestCase):
 
@@ -579,6 +585,8 @@ class TestUops(unittest.TestCase):
 
 
 @requires_specialization
+@unittest.skipUnless(hasattr(_testinternalcapi, "get_optimizer"),
+                     "Requires optimizer infrastructure")
 @unittest.skipIf(os.getenv("PYTHON_UOPS_OPTIMIZE") == "0", "Needs uop optimizer to run.")
 class TestUopsOptimization(unittest.TestCase):
 

Lib/test/test_monitoring.py

@@ -1831,15 +1831,17 @@ class TestOptimizer(MonitoringTestBase, unittest.TestCase):
 
     def setUp(self):
         _testinternalcapi = import_module("_testinternalcapi")
-        self.old_opt = _testinternalcapi.get_optimizer()
-        opt = _testinternalcapi.new_counter_optimizer()
-        _testinternalcapi.set_optimizer(opt)
+        if hasattr(_testinternalcapi, "get_optimizer"):
+            self.old_opt = _testinternalcapi.get_optimizer()
+            opt = _testinternalcapi.new_counter_optimizer()
+            _testinternalcapi.set_optimizer(opt)
         super(TestOptimizer, self).setUp()
 
     def tearDown(self):
         super(TestOptimizer, self).tearDown()
         import _testinternalcapi
-        _testinternalcapi.set_optimizer(self.old_opt)
+        if hasattr(_testinternalcapi, "get_optimizer"):
+            _testinternalcapi.set_optimizer(self.old_opt)
 
     def test_for_loop(self):
         def test_func(x):

Lib/test/test_opcache.py

@@ -16,6 +16,8 @@ _testinternalcapi = import_module("_testinternalcapi")
 
 def disabling_optimizer(func):
     def wrapper(*args, **kwargs):
+        if not hasattr(_testinternalcapi, "get_optimizer"):
+            return func(*args, **kwargs)
         old_opt = _testinternalcapi.get_optimizer()
         _testinternalcapi.set_optimizer(None)
         try:

Lib/test/test_optimizer.py

@@ -80,6 +80,8 @@ class TestRareEventCounters(unittest.TestCase):
 
 class TestOptimizerSymbols(unittest.TestCase):
 
+    @unittest.skipUnless(hasattr(_testinternalcapi, "uop_symbols_test"),
+                "requires _testinternalcapi.uop_symbols_test")
     def test_optimizer_symbols(self):
         _testinternalcapi.uop_symbols_test()
 

Lib/test/test_weakref.py

@@ -17,6 +17,7 @@ from test.support import script_helper, ALWAYS_EQ, suppress_immortalization
 from test.support import gc_collect
 from test.support import import_helper
 from test.support import threading_helper
+from test.support import is_wasi, Py_DEBUG
 
 # Used in ReferencesTestCase.test_ref_created_during_del() .
 ref_from_del = None
@@ -960,6 +961,7 @@ class ReferencesTestCase(TestBase):
         self.assertEqual(hash(a), hash(42))
         self.assertRaises(TypeError, hash, b)
 
+    @unittest.skipIf(is_wasi and Py_DEBUG, "requires deep stack")
     def test_trashcan_16602(self):
         # Issue #16602: when a weakref's target was part of a long
         # deallocation chain, the trashcan mechanism could delay clearing