gh-115999: Add free-threaded specialization for FOR_ITER (#128798)

Add free-threaded versions of existing specialization for FOR_ITER (list, tuples, fast range iterators and generators), without significantly affecting their thread-safety. (Iterating over shared lists/tuples/ranges should be fine like before. Reusing iterators between threads is not fine, like before. Sharing generators between threads is a recipe for significant crashes, like before.)

1 files changed, 39 insertions, 0 deletions

diff --git a/Lib/test/test_opcache.py b/Lib/test/test_opcache.py
index e4224b843b2..946a4827fe7 100644
--- a/Lib/test/test_opcache.py
+++ b/Lib/test/test_opcache.py
@@ -1802,5 +1802,44 @@ class TestSpecializer(TestBase):
         self.assert_specialized(load_const, "LOAD_CONST_MORTAL")
         self.assert_no_opcode(load_const, "LOAD_CONST")
 
+    @cpython_only
+    @requires_specialization_ft
+    def test_for_iter(self):
+        L = list(range(10))
+        def for_iter_list():
+            for i in L:
+                self.assertIn(i, L)
+
+        for_iter_list()
+        self.assert_specialized(for_iter_list, "FOR_ITER_LIST")
+        self.assert_no_opcode(for_iter_list, "FOR_ITER")
+
+        t = tuple(range(10))
+        def for_iter_tuple():
+            for i in t:
+                self.assertIn(i, t)
+
+        for_iter_tuple()
+        self.assert_specialized(for_iter_tuple, "FOR_ITER_TUPLE")
+        self.assert_no_opcode(for_iter_tuple, "FOR_ITER")
+
+        r = range(10)
+        def for_iter_range():
+            for i in r:
+                self.assertIn(i, r)
+
+        for_iter_range()
+        self.assert_specialized(for_iter_range, "FOR_ITER_RANGE")
+        self.assert_no_opcode(for_iter_range, "FOR_ITER")
+
+        def for_iter_generator():
+            for i in (i for i in range(10)):
+                i + 1
+
+        for_iter_generator()
+        self.assert_specialized(for_iter_generator, "FOR_ITER_GEN")
+        self.assert_no_opcode(for_iter_generator, "FOR_ITER")
+
+
 if __name__ == "__main__":
     unittest.main()