GH-131798: Remove type checks for _TO_BOOL_STR (GH-131816)

Include/internal/pycore_opcode_metadata.h

@@ -1465,7 +1465,7 @@ _PyOpcode_macro_expansion[256] = {
     [TO_BOOL_INT] = { .nuops = 1, .uops = { { _TO_BOOL_INT, OPARG_SIMPLE, 3 } } },
     [TO_BOOL_LIST] = { .nuops = 1, .uops = { { _TO_BOOL_LIST, OPARG_SIMPLE, 3 } } },
     [TO_BOOL_NONE] = { .nuops = 1, .uops = { { _TO_BOOL_NONE, OPARG_SIMPLE, 3 } } },
-    [TO_BOOL_STR] = { .nuops = 1, .uops = { { _TO_BOOL_STR, OPARG_SIMPLE, 3 } } },
+    [TO_BOOL_STR] = { .nuops = 2, .uops = { { _GUARD_TOS_UNICODE, OPARG_SIMPLE, 0 }, { _TO_BOOL_STR, OPARG_SIMPLE, 3 } } },
     [UNARY_INVERT] = { .nuops = 1, .uops = { { _UNARY_INVERT, OPARG_SIMPLE, 0 } } },
     [UNARY_NEGATIVE] = { .nuops = 1, .uops = { { _UNARY_NEGATIVE, OPARG_SIMPLE, 0 } } },
     [UNARY_NOT] = { .nuops = 1, .uops = { { _UNARY_NOT, OPARG_SIMPLE, 0 } } },

Include/internal/pycore_uop_ids.h

@@ -135,17 +135,18 @@ extern "C" {
 #define _GUARD_NOT_EXHAUSTED_TUPLE 381
 #define _GUARD_TOS_FLOAT 382
 #define _GUARD_TOS_INT 383
-#define _GUARD_TYPE_VERSION 384
+#define _GUARD_TOS_UNICODE 384
-#define _GUARD_TYPE_VERSION_AND_LOCK 385
+#define _GUARD_TYPE_VERSION 385
+#define _GUARD_TYPE_VERSION_AND_LOCK 386
 #define _IMPORT_FROM IMPORT_FROM
 #define _IMPORT_NAME IMPORT_NAME
-#define _INIT_CALL_BOUND_METHOD_EXACT_ARGS 386
+#define _INIT_CALL_BOUND_METHOD_EXACT_ARGS 387
-#define _INIT_CALL_PY_EXACT_ARGS 387
+#define _INIT_CALL_PY_EXACT_ARGS 388
-#define _INIT_CALL_PY_EXACT_ARGS_0 388
+#define _INIT_CALL_PY_EXACT_ARGS_0 389
-#define _INIT_CALL_PY_EXACT_ARGS_1 389
+#define _INIT_CALL_PY_EXACT_ARGS_1 390
-#define _INIT_CALL_PY_EXACT_ARGS_2 390
+#define _INIT_CALL_PY_EXACT_ARGS_2 391
-#define _INIT_CALL_PY_EXACT_ARGS_3 391
+#define _INIT_CALL_PY_EXACT_ARGS_3 392
-#define _INIT_CALL_PY_EXACT_ARGS_4 392
+#define _INIT_CALL_PY_EXACT_ARGS_4 393
 #define _INSTRUMENTED_FOR_ITER INSTRUMENTED_FOR_ITER
 #define _INSTRUMENTED_INSTRUCTION INSTRUMENTED_INSTRUCTION
 #define _INSTRUMENTED_JUMP_FORWARD INSTRUMENTED_JUMP_FORWARD
@@ -155,153 +156,153 @@ extern "C" {
 #define _INSTRUMENTED_POP_JUMP_IF_NONE INSTRUMENTED_POP_JUMP_IF_NONE
 #define _INSTRUMENTED_POP_JUMP_IF_NOT_NONE INSTRUMENTED_POP_JUMP_IF_NOT_NONE
 #define _INSTRUMENTED_POP_JUMP_IF_TRUE INSTRUMENTED_POP_JUMP_IF_TRUE
-#define _IS_NONE 393
+#define _IS_NONE 394
 #define _IS_OP IS_OP
-#define _ITER_CHECK_LIST 394
+#define _ITER_CHECK_LIST 395
-#define _ITER_CHECK_RANGE 395
+#define _ITER_CHECK_RANGE 396
-#define _ITER_CHECK_TUPLE 396
+#define _ITER_CHECK_TUPLE 397
-#define _ITER_JUMP_LIST 397
+#define _ITER_JUMP_LIST 398
-#define _ITER_JUMP_RANGE 398
+#define _ITER_JUMP_RANGE 399
-#define _ITER_JUMP_TUPLE 399
+#define _ITER_JUMP_TUPLE 400
-#define _ITER_NEXT_LIST 400
+#define _ITER_NEXT_LIST 401
-#define _ITER_NEXT_LIST_TIER_TWO 401
+#define _ITER_NEXT_LIST_TIER_TWO 402
-#define _ITER_NEXT_RANGE 402
+#define _ITER_NEXT_RANGE 403
-#define _ITER_NEXT_TUPLE 403
+#define _ITER_NEXT_TUPLE 404
-#define _JUMP_TO_TOP 404
+#define _JUMP_TO_TOP 405
 #define _LIST_APPEND LIST_APPEND
 #define _LIST_EXTEND LIST_EXTEND
-#define _LOAD_ATTR 405
+#define _LOAD_ATTR 406
-#define _LOAD_ATTR_CLASS 406
+#define _LOAD_ATTR_CLASS 407
 #define _LOAD_ATTR_GETATTRIBUTE_OVERRIDDEN LOAD_ATTR_GETATTRIBUTE_OVERRIDDEN
-#define _LOAD_ATTR_INSTANCE_VALUE 407
+#define _LOAD_ATTR_INSTANCE_VALUE 408
-#define _LOAD_ATTR_METHOD_LAZY_DICT 408
+#define _LOAD_ATTR_METHOD_LAZY_DICT 409
-#define _LOAD_ATTR_METHOD_NO_DICT 409
+#define _LOAD_ATTR_METHOD_NO_DICT 410
-#define _LOAD_ATTR_METHOD_WITH_VALUES 410
+#define _LOAD_ATTR_METHOD_WITH_VALUES 411
-#define _LOAD_ATTR_MODULE 411
+#define _LOAD_ATTR_MODULE 412
-#define _LOAD_ATTR_NONDESCRIPTOR_NO_DICT 412
+#define _LOAD_ATTR_NONDESCRIPTOR_NO_DICT 413
-#define _LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES 413
+#define _LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES 414
-#define _LOAD_ATTR_PROPERTY_FRAME 414
+#define _LOAD_ATTR_PROPERTY_FRAME 415
-#define _LOAD_ATTR_SLOT 415
+#define _LOAD_ATTR_SLOT 416
-#define _LOAD_ATTR_WITH_HINT 416
+#define _LOAD_ATTR_WITH_HINT 417
 #define _LOAD_BUILD_CLASS LOAD_BUILD_CLASS
-#define _LOAD_BYTECODE 417
+#define _LOAD_BYTECODE 418
 #define _LOAD_COMMON_CONSTANT LOAD_COMMON_CONSTANT
 #define _LOAD_CONST LOAD_CONST
 #define _LOAD_CONST_IMMORTAL LOAD_CONST_IMMORTAL
-#define _LOAD_CONST_INLINE 418
+#define _LOAD_CONST_INLINE 419
-#define _LOAD_CONST_INLINE_BORROW 419
+#define _LOAD_CONST_INLINE_BORROW 420
 #define _LOAD_CONST_MORTAL LOAD_CONST_MORTAL
 #define _LOAD_DEREF LOAD_DEREF
-#define _LOAD_FAST 420
+#define _LOAD_FAST 421
-#define _LOAD_FAST_0 421
+#define _LOAD_FAST_0 422
-#define _LOAD_FAST_1 422
+#define _LOAD_FAST_1 423
-#define _LOAD_FAST_2 423
+#define _LOAD_FAST_2 424
-#define _LOAD_FAST_3 424
+#define _LOAD_FAST_3 425
-#define _LOAD_FAST_4 425
+#define _LOAD_FAST_4 426
-#define _LOAD_FAST_5 426
+#define _LOAD_FAST_5 427
-#define _LOAD_FAST_6 427
+#define _LOAD_FAST_6 428
-#define _LOAD_FAST_7 428
+#define _LOAD_FAST_7 429
 #define _LOAD_FAST_AND_CLEAR LOAD_FAST_AND_CLEAR
 #define _LOAD_FAST_CHECK LOAD_FAST_CHECK
 #define _LOAD_FAST_LOAD_FAST LOAD_FAST_LOAD_FAST
 #define _LOAD_FROM_DICT_OR_DEREF LOAD_FROM_DICT_OR_DEREF
 #define _LOAD_FROM_DICT_OR_GLOBALS LOAD_FROM_DICT_OR_GLOBALS
-#define _LOAD_GLOBAL 429
+#define _LOAD_GLOBAL 430
-#define _LOAD_GLOBAL_BUILTINS 430
+#define _LOAD_GLOBAL_BUILTINS 431
-#define _LOAD_GLOBAL_MODULE 431
+#define _LOAD_GLOBAL_MODULE 432
 #define _LOAD_LOCALS LOAD_LOCALS
 #define _LOAD_NAME LOAD_NAME
-#define _LOAD_SMALL_INT 432
+#define _LOAD_SMALL_INT 433
-#define _LOAD_SMALL_INT_0 433
+#define _LOAD_SMALL_INT_0 434
-#define _LOAD_SMALL_INT_1 434
+#define _LOAD_SMALL_INT_1 435
-#define _LOAD_SMALL_INT_2 435
+#define _LOAD_SMALL_INT_2 436
-#define _LOAD_SMALL_INT_3 436
+#define _LOAD_SMALL_INT_3 437
 #define _LOAD_SPECIAL LOAD_SPECIAL
 #define _LOAD_SUPER_ATTR_ATTR LOAD_SUPER_ATTR_ATTR
 #define _LOAD_SUPER_ATTR_METHOD LOAD_SUPER_ATTR_METHOD
-#define _MAKE_CALLARGS_A_TUPLE 437
+#define _MAKE_CALLARGS_A_TUPLE 438
 #define _MAKE_CELL MAKE_CELL
 #define _MAKE_FUNCTION MAKE_FUNCTION
-#define _MAKE_WARM 438
+#define _MAKE_WARM 439
 #define _MAP_ADD MAP_ADD
 #define _MATCH_CLASS MATCH_CLASS
 #define _MATCH_KEYS MATCH_KEYS
 #define _MATCH_MAPPING MATCH_MAPPING
 #define _MATCH_SEQUENCE MATCH_SEQUENCE
-#define _MAYBE_EXPAND_METHOD 439
+#define _MAYBE_EXPAND_METHOD 440
-#define _MAYBE_EXPAND_METHOD_KW 440
+#define _MAYBE_EXPAND_METHOD_KW 441
-#define _MONITOR_CALL 441
+#define _MONITOR_CALL 442
-#define _MONITOR_CALL_KW 442
+#define _MONITOR_CALL_KW 443
-#define _MONITOR_JUMP_BACKWARD 443
+#define _MONITOR_JUMP_BACKWARD 444
-#define _MONITOR_RESUME 444
+#define _MONITOR_RESUME 445
 #define _NOP NOP
 #define _POP_EXCEPT POP_EXCEPT
-#define _POP_JUMP_IF_FALSE 445
+#define _POP_JUMP_IF_FALSE 446
-#define _POP_JUMP_IF_TRUE 446
+#define _POP_JUMP_IF_TRUE 447
 #define _POP_TOP POP_TOP
-#define _POP_TOP_LOAD_CONST_INLINE 447
+#define _POP_TOP_LOAD_CONST_INLINE 448
-#define _POP_TOP_LOAD_CONST_INLINE_BORROW 448
+#define _POP_TOP_LOAD_CONST_INLINE_BORROW 449
-#define _POP_TWO_LOAD_CONST_INLINE_BORROW 449
+#define _POP_TWO_LOAD_CONST_INLINE_BORROW 450
 #define _PUSH_EXC_INFO PUSH_EXC_INFO
-#define _PUSH_FRAME 450
+#define _PUSH_FRAME 451
 #define _PUSH_NULL PUSH_NULL
-#define _PUSH_NULL_CONDITIONAL 451
+#define _PUSH_NULL_CONDITIONAL 452
-#define _PY_FRAME_GENERAL 452
+#define _PY_FRAME_GENERAL 453
-#define _PY_FRAME_KW 453
+#define _PY_FRAME_KW 454
-#define _QUICKEN_RESUME 454
+#define _QUICKEN_RESUME 455
-#define _REPLACE_WITH_TRUE 455
+#define _REPLACE_WITH_TRUE 456
 #define _RESUME_CHECK RESUME_CHECK
 #define _RETURN_GENERATOR RETURN_GENERATOR
 #define _RETURN_VALUE RETURN_VALUE
-#define _SAVE_RETURN_OFFSET 456
+#define _SAVE_RETURN_OFFSET 457
-#define _SEND 457
+#define _SEND 458
-#define _SEND_GEN_FRAME 458
+#define _SEND_GEN_FRAME 459
 #define _SETUP_ANNOTATIONS SETUP_ANNOTATIONS
 #define _SET_ADD SET_ADD
 #define _SET_FUNCTION_ATTRIBUTE SET_FUNCTION_ATTRIBUTE
 #define _SET_UPDATE SET_UPDATE
-#define _START_EXECUTOR 459
+#define _START_EXECUTOR 460
-#define _STORE_ATTR 460
+#define _STORE_ATTR 461
-#define _STORE_ATTR_INSTANCE_VALUE 461
+#define _STORE_ATTR_INSTANCE_VALUE 462
-#define _STORE_ATTR_SLOT 462
+#define _STORE_ATTR_SLOT 463
-#define _STORE_ATTR_WITH_HINT 463
+#define _STORE_ATTR_WITH_HINT 464
 #define _STORE_DEREF STORE_DEREF
-#define _STORE_FAST 464
+#define _STORE_FAST 465
-#define _STORE_FAST_0 465
+#define _STORE_FAST_0 466
-#define _STORE_FAST_1 466
+#define _STORE_FAST_1 467
-#define _STORE_FAST_2 467
+#define _STORE_FAST_2 468
-#define _STORE_FAST_3 468
+#define _STORE_FAST_3 469
-#define _STORE_FAST_4 469
+#define _STORE_FAST_4 470
-#define _STORE_FAST_5 470
+#define _STORE_FAST_5 471
-#define _STORE_FAST_6 471
+#define _STORE_FAST_6 472
-#define _STORE_FAST_7 472
+#define _STORE_FAST_7 473
 #define _STORE_FAST_LOAD_FAST STORE_FAST_LOAD_FAST
 #define _STORE_FAST_STORE_FAST STORE_FAST_STORE_FAST
 #define _STORE_GLOBAL STORE_GLOBAL
 #define _STORE_NAME STORE_NAME
-#define _STORE_SLICE 473
+#define _STORE_SLICE 474
-#define _STORE_SUBSCR 474
+#define _STORE_SUBSCR 475
 #define _STORE_SUBSCR_DICT STORE_SUBSCR_DICT
 #define _STORE_SUBSCR_LIST_INT STORE_SUBSCR_LIST_INT
 #define _SWAP SWAP
-#define _TIER2_RESUME_CHECK 475
+#define _TIER2_RESUME_CHECK 476
-#define _TO_BOOL 476
+#define _TO_BOOL 477
 #define _TO_BOOL_BOOL TO_BOOL_BOOL
 #define _TO_BOOL_INT TO_BOOL_INT
 #define _TO_BOOL_LIST TO_BOOL_LIST
 #define _TO_BOOL_NONE TO_BOOL_NONE
-#define _TO_BOOL_STR TO_BOOL_STR
+#define _TO_BOOL_STR 478
 #define _UNARY_INVERT UNARY_INVERT
 #define _UNARY_NEGATIVE UNARY_NEGATIVE
 #define _UNARY_NOT UNARY_NOT
 #define _UNPACK_EX UNPACK_EX
-#define _UNPACK_SEQUENCE 477
+#define _UNPACK_SEQUENCE 479
 #define _UNPACK_SEQUENCE_LIST UNPACK_SEQUENCE_LIST
 #define _UNPACK_SEQUENCE_TUPLE UNPACK_SEQUENCE_TUPLE
 #define _UNPACK_SEQUENCE_TWO_TUPLE UNPACK_SEQUENCE_TWO_TUPLE
 #define _WITH_EXCEPT_START WITH_EXCEPT_START
 #define _YIELD_VALUE YIELD_VALUE
-#define MAX_UOP_ID 477
+#define MAX_UOP_ID 479
 
 #ifdef __cplusplus
 }

Include/internal/pycore_uop_metadata.h

@@ -64,7 +64,8 @@ const uint16_t _PyUop_Flags[MAX_UOP_ID+1] = {
     [_TO_BOOL_INT] = HAS_EXIT_FLAG | HAS_ESCAPES_FLAG,
     [_TO_BOOL_LIST] = HAS_EXIT_FLAG,
     [_TO_BOOL_NONE] = HAS_EXIT_FLAG,
-    [_TO_BOOL_STR] = HAS_EXIT_FLAG | HAS_ESCAPES_FLAG,
+    [_GUARD_TOS_UNICODE] = HAS_EXIT_FLAG,
+    [_TO_BOOL_STR] = HAS_ESCAPES_FLAG,
     [_REPLACE_WITH_TRUE] = HAS_ESCAPES_FLAG,
     [_UNARY_INVERT] = HAS_ERROR_FLAG | HAS_ESCAPES_FLAG,
     [_GUARD_BOTH_INT] = HAS_EXIT_FLAG,
@@ -413,6 +414,7 @@ const char *const _PyOpcode_uop_name[MAX_UOP_ID+1] = {
     [_GUARD_NOT_EXHAUSTED_TUPLE] = "_GUARD_NOT_EXHAUSTED_TUPLE",
     [_GUARD_TOS_FLOAT] = "_GUARD_TOS_FLOAT",
     [_GUARD_TOS_INT] = "_GUARD_TOS_INT",
+    [_GUARD_TOS_UNICODE] = "_GUARD_TOS_UNICODE",
     [_GUARD_TYPE_VERSION] = "_GUARD_TYPE_VERSION",
     [_GUARD_TYPE_VERSION_AND_LOCK] = "_GUARD_TYPE_VERSION_AND_LOCK",
     [_IMPORT_FROM] = "_IMPORT_FROM",
@@ -649,6 +651,8 @@ int _PyUop_num_popped(int opcode, int oparg)
             return 1;
         case _TO_BOOL_NONE:
             return 1;
+        case _GUARD_TOS_UNICODE:
+            return 0;
         case _TO_BOOL_STR:
             return 1;
         case _REPLACE_WITH_TRUE:

Lib/test/test_capi/test_opt.py

@@ -1581,6 +1581,24 @@ class TestUopsOptimization(unittest.TestCase):
         self.assertNotIn("_COMPARE_OP_INT", uops)
         self.assertIn("_POP_TWO_LOAD_CONST_INLINE_BORROW", uops)
 
+    def test_remove_guard_for_known_type_str(self):
+        def f(n):
+            for i in range(n):
+                false = i == TIER2_THRESHOLD
+                empty = "X"[:false]
+                empty += ""  # Make JIT realize this is a string.
+                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.assertNotIn("_GUARD_TOS_UNICODE", uops)
+
+
 def global_identity(x):
     return x
 

Misc/NEWS.d/next/Core_and_Builtins/2025-03-28-19-02-55.gh-issue-131798.fNZ5-2.rst

@@ -0,0 +1 @@
+Allow JIT to omit str guard in truthiness test when str type is known.

Python/bytecodes.c

@@ -512,10 +512,14 @@ dummy_func(
             res = PyStackRef_False;
         }
 
-        inst(TO_BOOL_STR, (unused/1, unused/2, value -- res)) {
+        op(_GUARD_TOS_UNICODE, (value -- value)) {
             PyObject *value_o = PyStackRef_AsPyObjectBorrow(value);
             EXIT_IF(!PyUnicode_CheckExact(value_o));
+        }
+
+        op(_TO_BOOL_STR, (value -- res)) {
             STAT_INC(TO_BOOL, hit);
+            PyObject *value_o = PyStackRef_AsPyObjectBorrow(value);
             if (value_o == &_Py_STR(empty)) {
                 assert(_Py_IsImmortal(value_o));
                 DEAD(value);
@@ -528,6 +532,9 @@ dummy_func(
             }
         }
 
+        macro(TO_BOOL_STR) =
+            _GUARD_TOS_UNICODE + unused/1 + unused/2 + _TO_BOOL_STR;
+
         op(_REPLACE_WITH_TRUE, (value -- res)) {
             PyStackRef_CLOSE(value);
             res = PyStackRef_True;

Python/executor_cases.c.h

@@ -653,16 +653,23 @@
             break;
         }
 
-        case _TO_BOOL_STR: {
+        case _GUARD_TOS_UNICODE: {
             _PyStackRef value;
-            _PyStackRef res;
             value = stack_pointer[-1];
             PyObject *value_o = PyStackRef_AsPyObjectBorrow(value);
             if (!PyUnicode_CheckExact(value_o)) {
                 UOP_STAT_INC(uopcode, miss);
                 JUMP_TO_JUMP_TARGET();
             }
+            break;
+        }
+
+        case _TO_BOOL_STR: {
+            _PyStackRef value;
+            _PyStackRef res;
+            value = stack_pointer[-1];
             STAT_INC(TO_BOOL, hit);
+            PyObject *value_o = PyStackRef_AsPyObjectBorrow(value);
             if (value_o == &_Py_STR(empty)) {
                 assert(_Py_IsImmortal(value_o));
                 res = PyStackRef_False;

Python/generated_cases.c.h

@@ -11616,30 +11616,37 @@
             static_assert(INLINE_CACHE_ENTRIES_TO_BOOL == 3, "incorrect cache size");
             _PyStackRef value;
             _PyStackRef res;
+            // _GUARD_TOS_UNICODE
+            {
+                value = stack_pointer[-1];
+                PyObject *value_o = PyStackRef_AsPyObjectBorrow(value);
+                if (!PyUnicode_CheckExact(value_o)) {
+                    UPDATE_MISS_STATS(TO_BOOL);
+                    assert(_PyOpcode_Deopt[opcode] == (TO_BOOL));
+                    JUMP_TO_PREDICTED(TO_BOOL);
+                }
+            }
             /* Skip 1 cache entry */
             /* Skip 2 cache entries */
-            value = stack_pointer[-1];
+            // _TO_BOOL_STR
-            PyObject *value_o = PyStackRef_AsPyObjectBorrow(value);
+            {
-            if (!PyUnicode_CheckExact(value_o)) {
+                STAT_INC(TO_BOOL, hit);
-                UPDATE_MISS_STATS(TO_BOOL);
+                PyObject *value_o = PyStackRef_AsPyObjectBorrow(value);
-                assert(_PyOpcode_Deopt[opcode] == (TO_BOOL));
+                if (value_o == &_Py_STR(empty)) {
-                JUMP_TO_PREDICTED(TO_BOOL);
+                    assert(_Py_IsImmortal(value_o));
-            }
+                    res = PyStackRef_False;
-            STAT_INC(TO_BOOL, hit);
+                }
-            if (value_o == &_Py_STR(empty)) {
+                else {
-                assert(_Py_IsImmortal(value_o));
+                    assert(Py_SIZE(value_o));
-                res = PyStackRef_False;
+                    stack_pointer += -1;
-            }
+                    assert(WITHIN_STACK_BOUNDS());
-            else {
+                    _PyFrame_SetStackPointer(frame, stack_pointer);
-                assert(Py_SIZE(value_o));
+                    PyStackRef_CLOSE(value);
-                stack_pointer += -1;
+                    stack_pointer = _PyFrame_GetStackPointer(frame);
-                assert(WITHIN_STACK_BOUNDS());
+                    res = PyStackRef_True;
-                _PyFrame_SetStackPointer(frame, stack_pointer);
+                    stack_pointer += 1;
-                PyStackRef_CLOSE(value);
+                    assert(WITHIN_STACK_BOUNDS());
-                stack_pointer = _PyFrame_GetStackPointer(frame);
+                }
-                res = PyStackRef_True;
-                stack_pointer += 1;
-                assert(WITHIN_STACK_BOUNDS());
             }
             stack_pointer[-1] = res;
             DISPATCH();

Python/optimizer_bytecodes.c

@@ -414,10 +414,16 @@ dummy_func(void) {
         }
     }
 
+    op(_GUARD_TOS_UNICODE, (value -- value)) {
+        if (sym_matches_type(value, &PyUnicode_Type)) {
+            REPLACE_OP(this_instr, _NOP, 0, 0);
+        }
+        sym_set_type(value, &PyUnicode_Type);
+    }
+
     op(_TO_BOOL_STR, (value -- res)) {
         if (!optimize_to_bool(this_instr, ctx, value, &res)) {
             res = sym_new_truthiness(ctx, value, true);
-            sym_set_type(value, &PyUnicode_Type);
         }
     }
 

Python/optimizer_cases.c.h

@@ -208,13 +208,22 @@
             break;
         }
 
+        case _GUARD_TOS_UNICODE: {
+            JitOptSymbol *value;
+            value = stack_pointer[-1];
+            if (sym_matches_type(value, &PyUnicode_Type)) {
+                REPLACE_OP(this_instr, _NOP, 0, 0);
+            }
+            sym_set_type(value, &PyUnicode_Type);
+            break;
+        }
+
         case _TO_BOOL_STR: {
             JitOptSymbol *value;
             JitOptSymbol *res;
             value = stack_pointer[-1];
             if (!optimize_to_bool(this_instr, ctx, value, &res)) {
                 res = sym_new_truthiness(ctx, value, true);
-                sym_set_type(value, &PyUnicode_Type);
             }
             stack_pointer[-1] = res;
             break;