GH-126892: Reset warmup counters when JIT compiling code (GH-126893)

Author: brandtbucher

Lib/test/support/strace_helper.py

@@ -91,7 +91,10 @@ def _make_error(reason, details):
         res, cmd_line = run_python_until_end(
             "-c",
             textwrap.dedent(code),
-            __run_using_command=[_strace_binary] + strace_flags)
+            __run_using_command=[_strace_binary] + strace_flags,
+            # Don't want to trace our JIT's own mmap and mprotect calls:
+            PYTHON_JIT="0",
+        )
     except OSError as err:
         return _make_error("Caught OSError", err)
 

Lib/test/test_capi/test_opt.py

@@ -1385,20 +1385,17 @@ class Foo:
         guard_type_version_count = opnames.count("_GUARD_TYPE_VERSION")
         self.assertEqual(guard_type_version_count, 1)
 
-    def test_guard_type_version_not_removed(self):
-        """
-        Verify that the guard type version is not removed if we modify the class
-        """
+    def test_guard_type_version_removed_invalidation(self):
 
         def thing(a):
             x = 0
-            for i in range(TIER2_THRESHOLD + 100):
+            for i in range(TIER2_THRESHOLD * 2 + 1):
                 x += a.attr
-                # for the first (TIER2_THRESHOLD + 90) iterations we set the attribute on this dummy function which shouldn't
-                # trigger the type watcher
-                # then after for the next 10 it should trigger it and stop optimizing
-                # Note that the code needs to be in this weird form so it's optimized inline without any control flow
-                setattr((Foo, Bar)[i < TIER2_THRESHOLD + 90], "attr", 2)
+                # The first TIER2_THRESHOLD iterations we set the attribute on
+                # this dummy class, which shouldn't trigger the type watcher.
+                # Note that the code needs to be in this weird form so it's
+                # optimized inline without any control flow:
+                setattr((Bar, Foo)[i == TIER2_THRESHOLD + 1], "attr", 2)
                 x += a.attr
             return x
 
@@ -1410,24 +1407,21 @@ class Bar:
 
         res, ex = self._run_with_optimizer(thing, Foo())
         opnames = list(iter_opnames(ex))
-
         self.assertIsNotNone(ex)
-        self.assertEqual(res, (TIER2_THRESHOLD * 2) + 219)
-        guard_type_version_count = opnames.count("_GUARD_TYPE_VERSION")
-        self.assertEqual(guard_type_version_count, 2)
+        self.assertEqual(res, TIER2_THRESHOLD * 6 + 1)
+        call = opnames.index("_CALL_BUILTIN_FAST")
+        load_attr_top = opnames.index("_LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES", 0, call)
+        load_attr_bottom = opnames.index("_LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES", call)
+        self.assertEqual(opnames[:load_attr_top].count("_GUARD_TYPE_VERSION"), 1)
+        self.assertEqual(opnames[call:load_attr_bottom].count("_CHECK_VALIDITY"), 1)
 
-
-    @unittest.expectedFailure
-    def test_guard_type_version_not_removed_escaping(self):
-        """
-        Verify that the guard type version is not removed if have an escaping function
-        """
+    def test_guard_type_version_removed_escaping(self):
 
         def thing(a):
             x = 0
-            for i in range(100):
+            for i in range(TIER2_THRESHOLD):
                 x += a.attr
-                # eval should be escaping and so should cause optimization to stop and preserve both type versions
+                # eval should be escaping
                 eval("None")
                 x += a.attr
             return x
@@ -1437,12 +1431,12 @@ class Foo:
         res, ex = self._run_with_optimizer(thing, Foo())
         opnames = list(iter_opnames(ex))
         self.assertIsNotNone(ex)
-        self.assertEqual(res, 200)
-        guard_type_version_count = opnames.count("_GUARD_TYPE_VERSION")
-        # Note: This will actually be 1 for noe
-        # https://github.com/python/cpython/pull/119365#discussion_r1626220129
-        self.assertEqual(guard_type_version_count, 2)
-
+        self.assertEqual(res, TIER2_THRESHOLD * 2)
+        call = opnames.index("_CALL_BUILTIN_FAST_WITH_KEYWORDS")
+        load_attr_top = opnames.index("_LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES", 0, call)
+        load_attr_bottom = opnames.index("_LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES", call)
+        self.assertEqual(opnames[:load_attr_top].count("_GUARD_TYPE_VERSION"), 1)
+        self.assertEqual(opnames[call:load_attr_bottom].count("_CHECK_VALIDITY"), 1)
 
     def test_guard_type_version_executor_invalidated(self):
         """

Misc/NEWS.d/next/Core_and_Builtins/2024-11-15-16-39-37.gh-issue-126892.QR6Yo3.rst

@@ -0,0 +1,2 @@
+Require cold or invalidated code to "warm up" before being JIT compiled
+again.

Python/bytecodes.c

@@ -2624,15 +2624,16 @@ dummy_func(
                 }
                 _PyExecutorObject *executor;
                 int optimized = _PyOptimizer_Optimize(frame, start, stack_pointer, &executor, 0);
-                ERROR_IF(optimized < 0, error);
-                if (optimized) {
+                if (optimized <= 0) {
+                    this_instr[1].counter = restart_backoff_counter(counter);
+                    ERROR_IF(optimized < 0, error);
+                }
+                else {
+                    this_instr[1].counter = initial_jump_backoff_counter();
                     assert(tstate->previous_executor == NULL);
                     tstate->previous_executor = Py_None;
                     GOTO_TIER_TWO(executor);
                 }
-                else {
-                    this_instr[1].counter = restart_backoff_counter(counter);
-                }
             }
             else {
                 ADVANCE_ADAPTIVE_COUNTER(this_instr[1].counter);
@@ -4875,6 +4876,9 @@ dummy_func(
                         tstate->previous_executor = (PyObject *)current_executor;
                         GOTO_TIER_ONE(target);
                     }
+                    else {
+                        exit->temperature = initial_temperature_backoff_counter();
+                    }
                 }
                 exit->executor = executor;
             }