From: Sacul <183588943+Sacul0457@users.noreply.github.com>
Date: Tue, 17 Mar 2026 14:07:17 +0000 (+0800)
Subject: gh-131798: Optimize `_ITER_CHECK_RANGE` and `_ITER_CHECK_LIST` in the JIT (GH-144583)
X-Git-Tag: v3.15.0a8~276
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1efd9939c8742a251f232f09ccd0c1def7fda66e;p=thirdparty%2FPython%2Fcpython.git

gh-131798: Optimize `_ITER_CHECK_RANGE` and `_ITER_CHECK_LIST` in the JIT (GH-144583)
---

diff --git a/Lib/test/test_capi/test_opt.py b/Lib/test/test_capi/test_opt.py
index 1385a7f840d7..2a126a7b29cc 100644
--- a/Lib/test/test_capi/test_opt.py
+++ b/Lib/test/test_capi/test_opt.py
@@ -3981,6 +3981,22 @@ class TestUopsOptimization(unittest.TestCase):
         self.assertIn("_POP_TOP_NOP", uops)
         self.assertLessEqual(count_ops(ex, "_POP_TOP"), 2)
 
+    def test_iter_check_list(self):
+        def testfunc(n):
+            x = 0
+            for _ in range(n):
+                l = [1]
+                for num in l: # unguarded
+                    x += num
+            return x
+
+        res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
+        self.assertEqual(res, TIER2_THRESHOLD)
+        uops = get_opnames(ex)
+
+        self.assertIn("_BUILD_LIST", uops)
+        self.assertNotIn("_ITER_CHECK_LIST", uops)
+
     def test_match_class(self):
         def testfunc(n):
             class A:
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-02-08-01-19-50.gh-issue-131798.PaWDNH.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-02-08-01-19-50.gh-issue-131798.PaWDNH.rst
new file mode 100644
index 000000000000..fe80c2d911b6
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-02-08-01-19-50.gh-issue-131798.PaWDNH.rst
@@ -0,0 +1 @@
+Optimize ``_ITER_CHECK_RANGE`` and ``_ITER_CHECK_LIST`` in the JIT
diff --git a/Python/optimizer_bytecodes.c b/Python/optimizer_bytecodes.c
index f3a391b2e37e..9b77fd0c32d9 100644
--- a/Python/optimizer_bytecodes.c
+++ b/Python/optimizer_bytecodes.c
@@ -1091,6 +1091,24 @@ dummy_func(void) {
         sym_set_type(iter, &PyTuple_Type);
     }
 
+    op(_ITER_CHECK_LIST, (iter, null_or_index -- iter, null_or_index)) {
+        if (sym_matches_type(iter, &PyList_Type)) {
+            ADD_OP(_NOP, 0, 0);
+        }
+        else {
+            sym_set_type(iter, &PyList_Type);
+        }
+    }
+
+    op(_ITER_CHECK_RANGE, (iter, null_or_index -- iter, null_or_index)) {
+        if (sym_matches_type(iter, &PyRange_Type)) {
+            ADD_OP(_NOP, 0, 0);
+        }
+        else {
+            sym_set_type(iter, &PyRange_Type);
+        }
+    }
+
     op(_ITER_NEXT_RANGE, (iter, null_or_index -- iter, null_or_index, next)) {
        next = sym_new_type(ctx, &PyLong_Type);
     }
diff --git a/Python/optimizer_cases.c.h b/Python/optimizer_cases.c.h
index 52a0c08ac677..eef07cedaf38 100644
--- a/Python/optimizer_cases.c.h
+++ b/Python/optimizer_cases.c.h
@@ -2752,6 +2752,14 @@
         /* _INSTRUMENTED_FOR_ITER is not a viable micro-op for tier 2 */
 
         case _ITER_CHECK_LIST: {
+            JitOptRef iter;
+            iter = stack_pointer[-2];
+            if (sym_matches_type(iter, &PyList_Type)) {
+                ADD_OP(_NOP, 0, 0);
+            }
+            else {
+                sym_set_type(iter, &PyList_Type);
+            }
             break;
         }
 
@@ -2800,6 +2808,14 @@
         }
 
         case _ITER_CHECK_RANGE: {
+            JitOptRef iter;
+            iter = stack_pointer[-2];
+            if (sym_matches_type(iter, &PyRange_Type)) {
+                ADD_OP(_NOP, 0, 0);
+            }
+            else {
+                sym_set_type(iter, &PyRange_Type);
+            }
             break;
         }