From 85bc489b649fe261f9625163c684a69a470b3dc1 Mon Sep 17 00:00:00 2001
From: "Tomas R." <tomas.roun8@gmail.com>
Date: Sun, 6 Apr 2025 00:56:01 +0200
Subject: GH-131798: Narrow the result of _CONTAINS_OP_SET to bool in the JIT
 (GH-132057)

---
 Lib/test/test_capi/test_opt.py                     | 26 ++++++++++++++++++++++
 .../2025-04-03-20-11-02.gh-issue-131798.yhdUKW.rst |  2 ++
 Python/optimizer_bytecodes.c                       |  4 ++++
 Python/optimizer_cases.c.h                         |  6 ++---
 4 files changed, 35 insertions(+), 3 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2025-04-03-20-11-02.gh-issue-131798.yhdUKW.rst

diff --git a/Lib/test/test_capi/test_opt.py b/Lib/test/test_capi/test_opt.py
index 9ac5d1e..0e13799 100644
--- a/Lib/test/test_capi/test_opt.py
+++ b/Lib/test/test_capi/test_opt.py
@@ -1603,6 +1603,32 @@ class TestUopsOptimization(unittest.TestCase):
         self.assertNotIn("_COMPARE_OP_INT", uops)
         self.assertIn("_POP_TWO_LOAD_CONST_INLINE_BORROW", uops)
 
+    def test_to_bool_bool_contains_op_set(self):
+        """
+        Test that _TO_BOOL_BOOL is removed from code like:
+
+        res = foo in some_set
+        if res:
+            ....
+
+        """
+        def testfunc(n):
+            x = 0
+            s = {1, 2, 3}
+            for _ in range(n):
+                a = 2
+                in_set = a in s
+                if in_set:
+                    x += 1
+            return x
+
+        res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
+        self.assertEqual(res, TIER2_THRESHOLD)
+        self.assertIsNotNone(ex)
+        uops = get_opnames(ex)
+        self.assertIn("_CONTAINS_OP_SET", uops)
+        self.assertNotIn("_TO_BOOL_BOOL", uops)
+
     def test_remove_guard_for_known_type_str(self):
         def f(n):
             for i in range(n):
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-04-03-20-11-02.gh-issue-131798.yhdUKW.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-04-03-20-11-02.gh-issue-131798.yhdUKW.rst
new file mode 100644
index 0000000..8a448ee
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-04-03-20-11-02.gh-issue-131798.yhdUKW.rst
@@ -0,0 +1,2 @@
+Allow the JIT to remove an extra ``_TO_BOOL_BOOL`` instruction after
+``_CONTAINS_OP_SET`` by setting the return type to bool.
diff --git a/Python/optimizer_bytecodes.c b/Python/optimizer_bytecodes.c
index da36704..d7b3564 100644
--- a/Python/optimizer_bytecodes.c
+++ b/Python/optimizer_bytecodes.c
@@ -477,6 +477,10 @@ dummy_func(void) {
         res = sym_new_type(ctx, &PyBool_Type);
     }
 
+    op(_CONTAINS_OP_SET, (left, right -- res)) {
+        res = sym_new_type(ctx, &PyBool_Type);
+    }
+
     op(_LOAD_CONST, (-- value)) {
         PyObject *val = PyTuple_GET_ITEM(co->co_consts, this_instr->oparg);
         int opcode = _Py_IsImmortal(val) ? _LOAD_CONST_INLINE_BORROW : _LOAD_CONST_INLINE;
diff --git a/Python/optimizer_cases.c.h b/Python/optimizer_cases.c.h
index f5cd169..870c32d 100644
--- a/Python/optimizer_cases.c.h
+++ b/Python/optimizer_cases.c.h
@@ -1283,9 +1283,9 @@
         }
 
         case _CONTAINS_OP_SET: {
-            JitOptSymbol *b;
-            b = sym_new_not_null(ctx);
-            stack_pointer[-2] = b;
+            JitOptSymbol *res;
+            res = sym_new_type(ctx, &PyBool_Type);
+            stack_pointer[-2] = res;
             stack_pointer += -1;
             assert(WITHIN_STACK_BOUNDS());
             break;
-- 
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