gh-134584: Eliminate redundant refcounting from TO_BOOL_STR

Signed-off-by: Manjusaka <[email protected]>
python · Fidget-Spinner · Jan 6, 2026 · Jan 4, 2026 · Jan 6, 2026 · Jan 6, 2026
commit a0895de282b7edbaf733941ea2f3d459e73e2aba
diff --git a/Include/internal/pycore_opcode_metadata.h b/Include/internal/pycore_opcode_metadata.h
diff --git a/Include/internal/pycore_uop_ids.h b/Include/internal/pycore_uop_ids.h
diff --git a/Include/internal/pycore_uop_metadata.h b/Include/internal/pycore_uop_metadata.h
diff --git a/Lib/test/test_capi/test_opt.py b/Lib/test/test_capi/test_opt.py
@@ -2935,6 +2935,22 @@ def testfunc(n):
         self.assertLessEqual(count_ops(ex, "_POP_TOP"), 1)
         self.assertIn("_POP_TOP_NOP", uops)
 
+    def test_to_bool_str(self):
+        def f(n):
+            for i in range(n):
+                false = i == TIER2_THRESHOLD
+                empty = "X"[:false]
+                if empty:
+                    return 1
+            return 0
+
+        res, ex = self._run_with_optimizer(f, TIER2_THRESHOLD)
+        self.assertEqual(res, 0)
+        self.assertIsNotNone(ex)
+        uops = get_opnames(ex)
+        self.assertIn("_TO_BOOL_STR", uops)
+        self.assertIn("_POP_TOP_NOP", uops)
+
     def test_attr_promotion_failure(self):
         # We're not testing for any specific uops here, just
         # testing it doesn't crash.

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-01-04-23-53-42.gh-issue-134584.CNrxI_.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-01-04-23-53-42.gh-issue-134584.CNrxI_.rst
@@ -0,0 +1 @@
+Eliminate redundant refcounting from ``TO_BOOL_STR``.
@@ -547,23 +547,25 @@ dummy_func(
             EXIT_IF(!PyUnicode_CheckExact(value_o));
         }
 
-        op(_TO_BOOL_STR, (value -- res)) {
+        op(_TO_BOOL_STR, (value -- res, v)) {
             STAT_INC(TO_BOOL, hit);
             PyObject *value_o = PyStackRef_AsPyObjectBorrow(value);
             if (value_o == &_Py_STR(empty)) {
                 assert(_Py_IsImmortal(value_o));
+                v = value;
                 DEAD(value);
                 res = PyStackRef_False;
             }
             else {
                 assert(Py_SIZE(value_o));
-                PyStackRef_CLOSE(value);
+                v = value;
+                DEAD(value);
                 res = PyStackRef_True;
             }
         }
 
         macro(TO_BOOL_STR) =
-            _GUARD_TOS_UNICODE + unused/1 + unused/2 + _TO_BOOL_STR;
+            _GUARD_TOS_UNICODE + unused/1 + unused/2 + _TO_BOOL_STR + _POP_TOP_UNICODE;
 
         op(_REPLACE_WITH_TRUE, (value -- res)) {
             PyStackRef_CLOSE(value);

diff --git a/Python/executor_cases.c.h b/Python/executor_cases.c.h
diff --git a/Python/generated_cases.c.h b/Python/generated_cases.c.h
@@ -431,8 +431,9 @@ dummy_func(void) {
         sym_set_type(value, &PyUnicode_Type);
     }
 
-    op(_TO_BOOL_STR, (value -- res)) {
+    op(_TO_BOOL_STR, (value -- res, v)) {
         int already_bool = optimize_to_bool(this_instr, ctx, value, &res);
+        v = value;
         if (!already_bool) {
             res = sym_new_truthiness(ctx, value, true);
         }

diff --git a/Python/optimizer_cases.c.h b/Python/optimizer_cases.c.h
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Eliminate redundant refcounting from ``TO_BOOL_STR``.