GH-131798: Optimize cached class attributes and methods in the JIT (GH-134403)

Include/internal/pycore_backoff.h

@@ -95,8 +95,10 @@ backoff_counter_triggers(_Py_BackoffCounter counter)
     return counter.value_and_backoff < UNREACHABLE_BACKOFF;
 }
 
-/* Initial JUMP_BACKWARD counter.
+// Initial JUMP_BACKWARD counter.
- * This determines when we create a trace for a loop. */
+// Must be larger than ADAPTIVE_COOLDOWN_VALUE, otherwise when JIT code is
+// invalidated we may construct a new trace before the bytecode has properly
+// re-specialized:
 #define JUMP_BACKWARD_INITIAL_VALUE 4095
 #define JUMP_BACKWARD_INITIAL_BACKOFF 12
 static inline _Py_BackoffCounter

Include/internal/pycore_code.h

@@ -451,6 +451,9 @@ write_location_entry_start(uint8_t *ptr, int code, int length)
 #define ADAPTIVE_COOLDOWN_BACKOFF 0
 
 // Can't assert this in pycore_backoff.h because of header order dependencies
+#if JUMP_BACKWARD_INITIAL_VALUE <= ADAPTIVE_COOLDOWN_VALUE
+#  error  "JIT threshold value should be larger than adaptive cooldown value"
+#endif
 #if SIDE_EXIT_INITIAL_VALUE <= ADAPTIVE_COOLDOWN_VALUE
 #  error  "Cold exit value should be larger than adaptive cooldown value"
 #endif

Include/internal/pycore_uop_ids.h

@@ -209,129 +209,131 @@ extern "C" {
 #define _LOAD_CONST LOAD_CONST
 #define _LOAD_CONST_INLINE 446
 #define _LOAD_CONST_INLINE_BORROW 447
+#define _LOAD_CONST_UNDER_INLINE 448
+#define _LOAD_CONST_UNDER_INLINE_BORROW 449
 #define _LOAD_DEREF LOAD_DEREF
-#define _LOAD_FAST 448
+#define _LOAD_FAST 450
-#define _LOAD_FAST_0 449
+#define _LOAD_FAST_0 451
-#define _LOAD_FAST_1 450
+#define _LOAD_FAST_1 452
-#define _LOAD_FAST_2 451
+#define _LOAD_FAST_2 453
-#define _LOAD_FAST_3 452
+#define _LOAD_FAST_3 454
-#define _LOAD_FAST_4 453
+#define _LOAD_FAST_4 455
-#define _LOAD_FAST_5 454
+#define _LOAD_FAST_5 456
-#define _LOAD_FAST_6 455
+#define _LOAD_FAST_6 457
-#define _LOAD_FAST_7 456
+#define _LOAD_FAST_7 458
 #define _LOAD_FAST_AND_CLEAR LOAD_FAST_AND_CLEAR
-#define _LOAD_FAST_BORROW 457
+#define _LOAD_FAST_BORROW 459
-#define _LOAD_FAST_BORROW_0 458
+#define _LOAD_FAST_BORROW_0 460
-#define _LOAD_FAST_BORROW_1 459
+#define _LOAD_FAST_BORROW_1 461
-#define _LOAD_FAST_BORROW_2 460
+#define _LOAD_FAST_BORROW_2 462
-#define _LOAD_FAST_BORROW_3 461
+#define _LOAD_FAST_BORROW_3 463
-#define _LOAD_FAST_BORROW_4 462
+#define _LOAD_FAST_BORROW_4 464
-#define _LOAD_FAST_BORROW_5 463
+#define _LOAD_FAST_BORROW_5 465
-#define _LOAD_FAST_BORROW_6 464
+#define _LOAD_FAST_BORROW_6 466
-#define _LOAD_FAST_BORROW_7 465
+#define _LOAD_FAST_BORROW_7 467
 #define _LOAD_FAST_BORROW_LOAD_FAST_BORROW LOAD_FAST_BORROW_LOAD_FAST_BORROW
 #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 466
+#define _LOAD_GLOBAL 468
-#define _LOAD_GLOBAL_BUILTINS 467
+#define _LOAD_GLOBAL_BUILTINS 469
-#define _LOAD_GLOBAL_MODULE 468
+#define _LOAD_GLOBAL_MODULE 470
 #define _LOAD_LOCALS LOAD_LOCALS
 #define _LOAD_NAME LOAD_NAME
-#define _LOAD_SMALL_INT 469
+#define _LOAD_SMALL_INT 471
-#define _LOAD_SMALL_INT_0 470
+#define _LOAD_SMALL_INT_0 472
-#define _LOAD_SMALL_INT_1 471
+#define _LOAD_SMALL_INT_1 473
-#define _LOAD_SMALL_INT_2 472
+#define _LOAD_SMALL_INT_2 474
-#define _LOAD_SMALL_INT_3 473
+#define _LOAD_SMALL_INT_3 475
-#define _LOAD_SPECIAL 474
+#define _LOAD_SPECIAL 476
 #define _LOAD_SUPER_ATTR_ATTR LOAD_SUPER_ATTR_ATTR
 #define _LOAD_SUPER_ATTR_METHOD LOAD_SUPER_ATTR_METHOD
-#define _MAKE_CALLARGS_A_TUPLE 475
+#define _MAKE_CALLARGS_A_TUPLE 477
 #define _MAKE_CELL MAKE_CELL
 #define _MAKE_FUNCTION MAKE_FUNCTION
-#define _MAKE_WARM 476
+#define _MAKE_WARM 478
 #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 477
+#define _MAYBE_EXPAND_METHOD 479
-#define _MAYBE_EXPAND_METHOD_KW 478
+#define _MAYBE_EXPAND_METHOD_KW 480
-#define _MONITOR_CALL 479
+#define _MONITOR_CALL 481
-#define _MONITOR_CALL_KW 480
+#define _MONITOR_CALL_KW 482
-#define _MONITOR_JUMP_BACKWARD 481
+#define _MONITOR_JUMP_BACKWARD 483
-#define _MONITOR_RESUME 482
+#define _MONITOR_RESUME 484
 #define _NOP NOP
-#define _POP_CALL_TWO_LOAD_CONST_INLINE_BORROW 483
+#define _POP_CALL_TWO_LOAD_CONST_INLINE_BORROW 485
 #define _POP_EXCEPT POP_EXCEPT
-#define _POP_JUMP_IF_FALSE 484
+#define _POP_JUMP_IF_FALSE 486
-#define _POP_JUMP_IF_TRUE 485
+#define _POP_JUMP_IF_TRUE 487
 #define _POP_TOP POP_TOP
-#define _POP_TOP_LOAD_CONST_INLINE 486
+#define _POP_TOP_LOAD_CONST_INLINE 488
-#define _POP_TOP_LOAD_CONST_INLINE_BORROW 487
+#define _POP_TOP_LOAD_CONST_INLINE_BORROW 489
-#define _POP_TWO 488
+#define _POP_TWO 490
-#define _POP_TWO_LOAD_CONST_INLINE_BORROW 489
+#define _POP_TWO_LOAD_CONST_INLINE_BORROW 491
 #define _PUSH_EXC_INFO PUSH_EXC_INFO
-#define _PUSH_FRAME 490
+#define _PUSH_FRAME 492
 #define _PUSH_NULL PUSH_NULL
-#define _PUSH_NULL_CONDITIONAL 491
+#define _PUSH_NULL_CONDITIONAL 493
-#define _PY_FRAME_GENERAL 492
+#define _PY_FRAME_GENERAL 494
-#define _PY_FRAME_KW 493
+#define _PY_FRAME_KW 495
-#define _QUICKEN_RESUME 494
+#define _QUICKEN_RESUME 496
-#define _REPLACE_WITH_TRUE 495
+#define _REPLACE_WITH_TRUE 497
 #define _RESUME_CHECK RESUME_CHECK
 #define _RETURN_GENERATOR RETURN_GENERATOR
 #define _RETURN_VALUE RETURN_VALUE
-#define _SAVE_RETURN_OFFSET 496
+#define _SAVE_RETURN_OFFSET 498
-#define _SEND 497
+#define _SEND 499
-#define _SEND_GEN_FRAME 498
+#define _SEND_GEN_FRAME 500
 #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 499
+#define _START_EXECUTOR 501
-#define _STORE_ATTR 500
+#define _STORE_ATTR 502
-#define _STORE_ATTR_INSTANCE_VALUE 501
+#define _STORE_ATTR_INSTANCE_VALUE 503
-#define _STORE_ATTR_SLOT 502
+#define _STORE_ATTR_SLOT 504
-#define _STORE_ATTR_WITH_HINT 503
+#define _STORE_ATTR_WITH_HINT 505
 #define _STORE_DEREF STORE_DEREF
-#define _STORE_FAST 504
+#define _STORE_FAST 506
-#define _STORE_FAST_0 505
+#define _STORE_FAST_0 507
-#define _STORE_FAST_1 506
+#define _STORE_FAST_1 508
-#define _STORE_FAST_2 507
+#define _STORE_FAST_2 509
-#define _STORE_FAST_3 508
+#define _STORE_FAST_3 510
-#define _STORE_FAST_4 509
+#define _STORE_FAST_4 511
-#define _STORE_FAST_5 510
+#define _STORE_FAST_5 512
-#define _STORE_FAST_6 511
+#define _STORE_FAST_6 513
-#define _STORE_FAST_7 512
+#define _STORE_FAST_7 514
 #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 513
+#define _STORE_SLICE 515
-#define _STORE_SUBSCR 514
+#define _STORE_SUBSCR 516
-#define _STORE_SUBSCR_DICT 515
+#define _STORE_SUBSCR_DICT 517
-#define _STORE_SUBSCR_LIST_INT 516
+#define _STORE_SUBSCR_LIST_INT 518
 #define _SWAP SWAP
-#define _TIER2_RESUME_CHECK 517
+#define _TIER2_RESUME_CHECK 519
-#define _TO_BOOL 518
+#define _TO_BOOL 520
 #define _TO_BOOL_BOOL TO_BOOL_BOOL
 #define _TO_BOOL_INT TO_BOOL_INT
-#define _TO_BOOL_LIST 519
+#define _TO_BOOL_LIST 521
 #define _TO_BOOL_NONE TO_BOOL_NONE
-#define _TO_BOOL_STR 520
+#define _TO_BOOL_STR 522
 #define _UNARY_INVERT UNARY_INVERT
 #define _UNARY_NEGATIVE UNARY_NEGATIVE
 #define _UNARY_NOT UNARY_NOT
 #define _UNPACK_EX UNPACK_EX
-#define _UNPACK_SEQUENCE 521
+#define _UNPACK_SEQUENCE 523
-#define _UNPACK_SEQUENCE_LIST 522
+#define _UNPACK_SEQUENCE_LIST 524
-#define _UNPACK_SEQUENCE_TUPLE 523
+#define _UNPACK_SEQUENCE_TUPLE 525
-#define _UNPACK_SEQUENCE_TWO_TUPLE 524
+#define _UNPACK_SEQUENCE_TWO_TUPLE 526
 #define _WITH_EXCEPT_START WITH_EXCEPT_START
 #define _YIELD_VALUE YIELD_VALUE
-#define MAX_UOP_ID 524
+#define MAX_UOP_ID 526
 
 #ifdef __cplusplus
 }

Include/internal/pycore_uop_metadata.h

@@ -306,6 +306,8 @@ const uint16_t _PyUop_Flags[MAX_UOP_ID+1] = {
     [_POP_TOP_LOAD_CONST_INLINE_BORROW] = HAS_ESCAPES_FLAG | HAS_PURE_FLAG,
     [_POP_TWO_LOAD_CONST_INLINE_BORROW] = HAS_ESCAPES_FLAG | HAS_PURE_FLAG,
     [_POP_CALL_TWO_LOAD_CONST_INLINE_BORROW] = HAS_ESCAPES_FLAG | HAS_PURE_FLAG,
+    [_LOAD_CONST_UNDER_INLINE] = 0,
+    [_LOAD_CONST_UNDER_INLINE_BORROW] = 0,
     [_CHECK_FUNCTION] = HAS_DEOPT_FLAG,
     [_START_EXECUTOR] = 0,
     [_MAKE_WARM] = 0,
@@ -504,6 +506,8 @@ const char *const _PyOpcode_uop_name[MAX_UOP_ID+1] = {
     [_LOAD_CONST] = "_LOAD_CONST",
     [_LOAD_CONST_INLINE] = "_LOAD_CONST_INLINE",
     [_LOAD_CONST_INLINE_BORROW] = "_LOAD_CONST_INLINE_BORROW",
+    [_LOAD_CONST_UNDER_INLINE] = "_LOAD_CONST_UNDER_INLINE",
+    [_LOAD_CONST_UNDER_INLINE_BORROW] = "_LOAD_CONST_UNDER_INLINE_BORROW",
     [_LOAD_DEREF] = "_LOAD_DEREF",
     [_LOAD_FAST] = "_LOAD_FAST",
     [_LOAD_FAST_0] = "_LOAD_FAST_0",
@@ -1196,6 +1200,10 @@ int _PyUop_num_popped(int opcode, int oparg)
             return 2;
         case _POP_CALL_TWO_LOAD_CONST_INLINE_BORROW:
             return 4;
+        case _LOAD_CONST_UNDER_INLINE:
+            return 1;
+        case _LOAD_CONST_UNDER_INLINE_BORROW:
+            return 1;
         case _CHECK_FUNCTION:
             return 0;
         case _START_EXECUTOR:

Lib/test/test_capi/test_opt.py

@@ -1280,8 +1280,8 @@ class TestUopsOptimization(unittest.TestCase):
         self.assertIsNotNone(ex)
         self.assertEqual(res, TIER2_THRESHOLD * 6 + 1)
         call = opnames.index("_CALL_BUILTIN_FAST")
-        load_attr_top = opnames.index("_LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES", 0, call)
+        load_attr_top = opnames.index("_POP_TOP_LOAD_CONST_INLINE_BORROW", 0, call)
-        load_attr_bottom = opnames.index("_LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES", call)
+        load_attr_bottom = opnames.index("_POP_TOP_LOAD_CONST_INLINE_BORROW", call)
         self.assertEqual(opnames[:load_attr_top].count("_GUARD_TYPE_VERSION"), 1)
         self.assertEqual(opnames[call:load_attr_bottom].count("_CHECK_VALIDITY"), 2)
 
@@ -1303,8 +1303,8 @@ class TestUopsOptimization(unittest.TestCase):
         self.assertIsNotNone(ex)
         self.assertEqual(res, TIER2_THRESHOLD * 2)
         call = opnames.index("_CALL_BUILTIN_FAST_WITH_KEYWORDS")
-        load_attr_top = opnames.index("_LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES", 0, call)
+        load_attr_top = opnames.index("_POP_TOP_LOAD_CONST_INLINE_BORROW", 0, call)
-        load_attr_bottom = opnames.index("_LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES", call)
+        load_attr_bottom = opnames.index("_POP_TOP_LOAD_CONST_INLINE_BORROW", call)
         self.assertEqual(opnames[:load_attr_top].count("_GUARD_TYPE_VERSION"), 1)
         self.assertEqual(opnames[call:load_attr_bottom].count("_CHECK_VALIDITY"), 2)
 
@@ -2169,6 +2169,45 @@ class TestUopsOptimization(unittest.TestCase):
         self.assertNotIn("_LOAD_SMALL_INT", uops)
         self.assertIn("_LOAD_CONST_INLINE_BORROW", uops)
 
+    def test_cached_attributes(self):
+        class C:
+            A = 1
+            def m(self):
+                return 1
+        class D:
+            __slots__ = ()
+            A = 1
+            def m(self):
+                return 1
+        class E(Exception):
+            def m(self):
+                return 1
+        def f(n):
+            x = 0
+            c = C()
+            d = D()
+            e = E()
+            for _ in range(n):
+                x += C.A  # _LOAD_ATTR_CLASS
+                x += c.A  # _LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES
+                x += d.A  # _LOAD_ATTR_NONDESCRIPTOR_NO_DICT
+                x += c.m()  # _LOAD_ATTR_METHOD_WITH_VALUES
+                x += d.m()  # _LOAD_ATTR_METHOD_NO_DICT
+                x += e.m()  # _LOAD_ATTR_METHOD_LAZY_DICT
+            return x
+
+        res, ex = self._run_with_optimizer(f, TIER2_THRESHOLD)
+        self.assertEqual(res, 6 * TIER2_THRESHOLD)
+        self.assertIsNotNone(ex)
+        uops = get_opnames(ex)
+        self.assertNotIn("_LOAD_ATTR_CLASS", uops)
+        self.assertNotIn("_LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES", uops)
+        self.assertNotIn("_LOAD_ATTR_NONDESCRIPTOR_NO_DICT", uops)
+        self.assertNotIn("_LOAD_ATTR_METHOD_WITH_VALUES", uops)
+        self.assertNotIn("_LOAD_ATTR_METHOD_NO_DICT", uops)
+        self.assertNotIn("_LOAD_ATTR_METHOD_LAZY_DICT", uops)
+
+
 def global_identity(x):
     return x
 

Misc/NEWS.d/next/Core_and_Builtins/2025-05-20-23-32-11.gh-issue-131798.G9ZQZw.rst

@@ -0,0 +1,2 @@
+Improve the JIT's ability to optimize away cached class attribute and method
+loads.

Python/bytecodes.c

@@ -5307,6 +5307,18 @@ dummy_func(
             value = PyStackRef_FromPyObjectBorrow(ptr);
         }
 
+        tier2 op(_LOAD_CONST_UNDER_INLINE, (ptr/4, old -- value, new)) {
+            new = old;
+            DEAD(old);
+            value = PyStackRef_FromPyObjectNew(ptr);
+        }
+
+        tier2 op(_LOAD_CONST_UNDER_INLINE_BORROW, (ptr/4, old -- value, new)) {
+            new = old;
+            DEAD(old);
+            value = PyStackRef_FromPyObjectBorrow(ptr);
+        }
+
         tier2 op(_CHECK_FUNCTION, (func_version/2 -- )) {
             assert(PyStackRef_FunctionCheck(frame->f_funcobj));
             PyFunctionObject *func = (PyFunctionObject *)PyStackRef_AsPyObjectBorrow(frame->f_funcobj);

Python/executor_cases.c.h

@@ -7105,6 +7105,36 @@
             break;
         }
 
+        case _LOAD_CONST_UNDER_INLINE: {
+            _PyStackRef old;
+            _PyStackRef value;
+            _PyStackRef new;
+            old = stack_pointer[-1];
+            PyObject *ptr = (PyObject *)CURRENT_OPERAND0();
+            new = old;
+            value = PyStackRef_FromPyObjectNew(ptr);
+            stack_pointer[-1] = value;
+            stack_pointer[0] = new;
+            stack_pointer += 1;
+            assert(WITHIN_STACK_BOUNDS());
+            break;
+        }
+
+        case _LOAD_CONST_UNDER_INLINE_BORROW: {
+            _PyStackRef old;
+            _PyStackRef value;
+            _PyStackRef new;
+            old = stack_pointer[-1];
+            PyObject *ptr = (PyObject *)CURRENT_OPERAND0();
+            new = old;
+            value = PyStackRef_FromPyObjectBorrow(ptr);
+            stack_pointer[-1] = value;
+            stack_pointer[0] = new;
+            stack_pointer += 1;
+            assert(WITHIN_STACK_BOUNDS());
+            break;
+        }
+
         case _CHECK_FUNCTION: {
             uint32_t func_version = (uint32_t)CURRENT_OPERAND0();
             assert(PyStackRef_FunctionCheck(frame->f_funcobj));

Python/optimizer_analysis.c

@@ -375,6 +375,23 @@ eliminate_pop_guard(_PyUOpInstruction *this_instr, bool exit)
     }
 }
 
+static JitOptSymbol *
+lookup_attr(JitOptContext *ctx, _PyUOpInstruction *this_instr,
+            PyTypeObject *type, PyObject *name, uint16_t immortal,
+            uint16_t mortal)
+{
+    // The cached value may be dead, so we need to do the lookup again... :(
+    if (type && PyType_Check(type)) {
+        PyObject *lookup = _PyType_Lookup(type, name);
+        if (lookup) {
+            int opcode = _Py_IsImmortal(lookup) ? immortal : mortal;
+            REPLACE_OP(this_instr, opcode, 0, (uintptr_t)lookup);
+            return sym_new_const(ctx, lookup);
+        }
+    }
+    return sym_new_not_null(ctx);
+}
+
 /* _PUSH_FRAME/_RETURN_VALUE's operand can be 0, a PyFunctionObject *, or a
  * PyCodeObject *. Retrieve the code object if possible.
  */
@@ -527,6 +544,8 @@ const uint16_t op_without_push[MAX_UOP_ID + 1] = {
     [_COPY] = _NOP,
     [_LOAD_CONST_INLINE] = _NOP,
     [_LOAD_CONST_INLINE_BORROW] = _NOP,
+    [_LOAD_CONST_UNDER_INLINE] = _POP_TOP_LOAD_CONST_INLINE,
+    [_LOAD_CONST_UNDER_INLINE_BORROW] = _POP_TOP_LOAD_CONST_INLINE_BORROW,
     [_LOAD_FAST] = _NOP,
     [_LOAD_FAST_BORROW] = _NOP,
     [_LOAD_SMALL_INT] = _NOP,
@@ -535,10 +554,16 @@ const uint16_t op_without_push[MAX_UOP_ID + 1] = {
     [_POP_TWO_LOAD_CONST_INLINE_BORROW] = _POP_TWO,
 };
 
+const bool op_skip[MAX_UOP_ID + 1] = {
+    [_NOP] = true,
+    [_CHECK_VALIDITY] = true,
+};
+
 const uint16_t op_without_pop[MAX_UOP_ID + 1] = {
     [_POP_TOP] = _NOP,
     [_POP_TOP_LOAD_CONST_INLINE] = _LOAD_CONST_INLINE,
     [_POP_TOP_LOAD_CONST_INLINE_BORROW] = _LOAD_CONST_INLINE_BORROW,
+    [_POP_TWO] = _POP_TOP,
     [_POP_TWO_LOAD_CONST_INLINE_BORROW] = _POP_TOP_LOAD_CONST_INLINE_BORROW,
 };
 
@@ -578,7 +603,7 @@ remove_unneeded_uops(_PyUOpInstruction *buffer, int buffer_size)
                 //     _NOP + _POP_TOP + _NOP
                 while (op_without_pop[opcode]) {
                     _PyUOpInstruction *last = &buffer[pc - 1];
-                    while (last->opcode == _NOP) {
+                    while (op_skip[last->opcode]) {
                         last--;
                     }
                     if (!op_without_push[last->opcode]) {
@@ -586,6 +611,10 @@ remove_unneeded_uops(_PyUOpInstruction *buffer, int buffer_size)
                     }
                     last->opcode = op_without_push[last->opcode];
                     opcode = buffer[pc].opcode = op_without_pop[opcode];
+                    if (op_without_pop[last->opcode]) {
+                        opcode = last->opcode;
+                        pc = last - buffer;
+                    }
                 }
                 /* _PUSH_FRAME doesn't escape or error, but it
                  * does need the IP for the return address */

Python/optimizer_bytecodes.c

@@ -522,7 +522,7 @@ dummy_func(void) {
     }
 
     op(_LOAD_CONST, (-- value)) {
-        PyObject *val = PyTuple_GET_ITEM(co->co_consts, this_instr->oparg);
+        PyObject *val = PyTuple_GET_ITEM(co->co_consts, oparg);
         REPLACE_OP(this_instr, _LOAD_CONST_INLINE_BORROW, 0, (uintptr_t)val);
         value = sym_new_const(ctx, val);
     }
@@ -608,7 +608,7 @@ dummy_func(void) {
     op(_LOAD_ATTR, (owner -- attr, self_or_null[oparg&1])) {
         (void)owner;
         attr = sym_new_not_null(ctx);
-        if (oparg &1) {
+        if (oparg & 1) {
             self_or_null[0] = sym_new_unknown(ctx);
         }
     }
@@ -624,25 +624,59 @@ dummy_func(void) {
     }
 
     op(_LOAD_ATTR_CLASS, (descr/4, owner -- attr)) {
-        attr = sym_new_not_null(ctx);
         (void)descr;
+        PyTypeObject *type = (PyTypeObject *)sym_get_const(ctx, owner);
+        PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+        attr = lookup_attr(ctx, this_instr, type, name,
+                           _POP_TOP_LOAD_CONST_INLINE_BORROW,
+                           _POP_TOP_LOAD_CONST_INLINE);
+    }
+
+    op(_LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES, (descr/4, owner -- attr)) {
+        (void)descr;
+        PyTypeObject *type = sym_get_type(owner);
+        PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+        attr = lookup_attr(ctx, this_instr, type, name,
+                           _POP_TOP_LOAD_CONST_INLINE_BORROW,
+                           _POP_TOP_LOAD_CONST_INLINE);
+    }
+
+    op(_LOAD_ATTR_NONDESCRIPTOR_NO_DICT, (descr/4, owner -- attr)) {
+        (void)descr;
+        PyTypeObject *type = sym_get_type(owner);
+        PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+        attr = lookup_attr(ctx, this_instr, type, name,
+                           _POP_TOP_LOAD_CONST_INLINE_BORROW,
+                           _POP_TOP_LOAD_CONST_INLINE);
     }
 
     op(_LOAD_ATTR_METHOD_WITH_VALUES, (descr/4, owner -- attr, self)) {
         (void)descr;
-        attr = sym_new_not_null(ctx);
+        PyTypeObject *type = sym_get_type(owner);
+        PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+        attr = lookup_attr(ctx, this_instr, type, name,
+                           _LOAD_CONST_UNDER_INLINE_BORROW,
+                           _LOAD_CONST_UNDER_INLINE);
         self = owner;
     }
 
     op(_LOAD_ATTR_METHOD_NO_DICT, (descr/4, owner -- attr, self)) {
         (void)descr;
-        attr = sym_new_not_null(ctx);
+        PyTypeObject *type = sym_get_type(owner);
+        PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+        attr = lookup_attr(ctx, this_instr, type, name,
+                           _LOAD_CONST_UNDER_INLINE_BORROW,
+                           _LOAD_CONST_UNDER_INLINE);
         self = owner;
     }
 
     op(_LOAD_ATTR_METHOD_LAZY_DICT, (descr/4, owner -- attr, self)) {
         (void)descr;
-        attr = sym_new_not_null(ctx);
+        PyTypeObject *type = sym_get_type(owner);
+        PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+        attr = lookup_attr(ctx, this_instr, type, name,
+                           _LOAD_CONST_UNDER_INLINE_BORROW,
+                           _LOAD_CONST_UNDER_INLINE);
         self = owner;
     }
 

Python/optimizer_cases.c.h

@@ -68,7 +68,7 @@
 
         case _LOAD_CONST: {
             JitOptSymbol *value;
-            PyObject *val = PyTuple_GET_ITEM(co->co_consts, this_instr->oparg);
+            PyObject *val = PyTuple_GET_ITEM(co->co_consts, oparg);
             REPLACE_OP(this_instr, _LOAD_CONST_INLINE_BORROW, 0, (uintptr_t)val);
             value = sym_new_const(ctx, val);
             stack_pointer[0] = value;
@@ -1174,7 +1174,7 @@
             self_or_null = &stack_pointer[0];
             (void)owner;
             attr = sym_new_not_null(ctx);
-            if (oparg &1) {
+            if (oparg & 1) {
                 self_or_null[0] = sym_new_unknown(ctx);
             }
             stack_pointer[-1] = attr;
@@ -1284,10 +1284,16 @@
         }
 
         case _LOAD_ATTR_CLASS: {
+            JitOptSymbol *owner;
             JitOptSymbol *attr;
+            owner = stack_pointer[-1];
             PyObject *descr = (PyObject *)this_instr->operand0;
-            attr = sym_new_not_null(ctx);
             (void)descr;
+            PyTypeObject *type = (PyTypeObject *)sym_get_const(ctx, owner);
+            PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+            attr = lookup_attr(ctx, this_instr, type, name,
+                           _POP_TOP_LOAD_CONST_INLINE_BORROW,
+                           _POP_TOP_LOAD_CONST_INLINE);
             stack_pointer[-1] = attr;
             break;
         }
@@ -1701,7 +1707,11 @@
             owner = stack_pointer[-1];
             PyObject *descr = (PyObject *)this_instr->operand0;
             (void)descr;
-            attr = sym_new_not_null(ctx);
+            PyTypeObject *type = sym_get_type(owner);
+            PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+            attr = lookup_attr(ctx, this_instr, type, name,
+                           _LOAD_CONST_UNDER_INLINE_BORROW,
+                           _LOAD_CONST_UNDER_INLINE);
             self = owner;
             stack_pointer[-1] = attr;
             stack_pointer[0] = self;
@@ -1717,7 +1727,11 @@
             owner = stack_pointer[-1];
             PyObject *descr = (PyObject *)this_instr->operand0;
             (void)descr;
-            attr = sym_new_not_null(ctx);
+            PyTypeObject *type = sym_get_type(owner);
+            PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+            attr = lookup_attr(ctx, this_instr, type, name,
+                           _LOAD_CONST_UNDER_INLINE_BORROW,
+                           _LOAD_CONST_UNDER_INLINE);
             self = owner;
             stack_pointer[-1] = attr;
             stack_pointer[0] = self;
@@ -1727,15 +1741,31 @@
         }
 
         case _LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES: {
+            JitOptSymbol *owner;
             JitOptSymbol *attr;
-            attr = sym_new_not_null(ctx);
+            owner = stack_pointer[-1];
+            PyObject *descr = (PyObject *)this_instr->operand0;
+            (void)descr;
+            PyTypeObject *type = sym_get_type(owner);
+            PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+            attr = lookup_attr(ctx, this_instr, type, name,
+                           _POP_TOP_LOAD_CONST_INLINE_BORROW,
+                           _POP_TOP_LOAD_CONST_INLINE);
             stack_pointer[-1] = attr;
             break;
         }
 
         case _LOAD_ATTR_NONDESCRIPTOR_NO_DICT: {
+            JitOptSymbol *owner;
             JitOptSymbol *attr;
-            attr = sym_new_not_null(ctx);
+            owner = stack_pointer[-1];
+            PyObject *descr = (PyObject *)this_instr->operand0;
+            (void)descr;
+            PyTypeObject *type = sym_get_type(owner);
+            PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+            attr = lookup_attr(ctx, this_instr, type, name,
+                           _POP_TOP_LOAD_CONST_INLINE_BORROW,
+                           _POP_TOP_LOAD_CONST_INLINE);
             stack_pointer[-1] = attr;
             break;
         }
@@ -1751,7 +1781,11 @@
             owner = stack_pointer[-1];
             PyObject *descr = (PyObject *)this_instr->operand0;
             (void)descr;
-            attr = sym_new_not_null(ctx);
+            PyTypeObject *type = sym_get_type(owner);
+            PyObject *name = PyTuple_GET_ITEM(co->co_names, oparg >> 1);
+            attr = lookup_attr(ctx, this_instr, type, name,
+                           _LOAD_CONST_UNDER_INLINE_BORROW,
+                           _LOAD_CONST_UNDER_INLINE);
             self = owner;
             stack_pointer[-1] = attr;
             stack_pointer[0] = self;
@@ -2594,6 +2628,30 @@
             break;
         }
 
+        case _LOAD_CONST_UNDER_INLINE: {
+            JitOptSymbol *value;
+            JitOptSymbol *new;
+            value = sym_new_not_null(ctx);
+            new = sym_new_not_null(ctx);
+            stack_pointer[-1] = value;
+            stack_pointer[0] = new;
+            stack_pointer += 1;
+            assert(WITHIN_STACK_BOUNDS());
+            break;
+        }
+
+        case _LOAD_CONST_UNDER_INLINE_BORROW: {
+            JitOptSymbol *value;
+            JitOptSymbol *new;
+            value = sym_new_not_null(ctx);
+            new = sym_new_not_null(ctx);
+            stack_pointer[-1] = value;
+            stack_pointer[0] = new;
+            stack_pointer += 1;
+            assert(WITHIN_STACK_BOUNDS());
+            break;
+        }
+
         case _CHECK_FUNCTION: {
             break;
         }

Python/optimizer_symbols.c

@@ -13,22 +13,46 @@
 #include <stdint.h>
 #include <stddef.h>
 
-/* Symbols
+/*
-   =======
 
-   See the diagram at
+Symbols
-   https://github.com/faster-cpython/ideas/blob/main/3.13/redundancy_eliminator.md
+=======
 
-   We represent the nodes in the diagram as follows
+https://github.com/faster-cpython/ideas/blob/main/3.13/redundancy_eliminator.md
-   (the flag bits are only defined in optimizer_symbols.c):
+
-   - Top: no flag bits, typ and const_val are NULL.
+Logically, all symbols begin as UNKNOWN, and can transition downwards along the
-   - NULL: IS_NULL flag set, type and const_val NULL.
+edges of the lattice, but *never* upwards (see the diagram below). The UNKNOWN
-   - Not NULL: NOT_NULL flag set, type and const_val NULL.
+state represents no information, and the BOTTOM state represents contradictory
-   - None/not None: not used. (None could be represented as any other constant.)
+information. Though symbols logically progress through all intermediate nodes,
-   - Known type: NOT_NULL flag set and typ set; const_val is NULL.
+we often skip in-between states for convenience:
-   - Known constant: NOT_NULL flag set, type set, const_val set.
+
-   - Bottom: IS_NULL and NOT_NULL flags set, type and const_val NULL.
+   UNKNOWN
- */
+   |     |
+NULL     |
+|        |                <- Anything below this level is an object.
+|        NON_NULL
+|        |      |         <- Anything below this level has a known type version.
+| TYPE_VERSION  |
+| |             |         <- Anything below this level has a known type.
+| KNOWN_CLASS   |
+| |         |   |         <- Anything below this level has a known truthiness.
+| |         |  TRUTHINESS
+| |         |  |
+| TUPLE     |  |
+|     |     |  |          <- Anything below this level is a known constant.
+|    KNOWN_VALUE
+|    |                    <- Anything below this level is unreachable.
+BOTTOM
+
+For example, after guarding that the type of an UNKNOWN local is int, we can
+narrow the symbol to KNOWN_CLASS (logically progressing though NON_NULL and
+TYPE_VERSION to get there). Later, we may learn that it is falsey based on the
+result of a truth test, which would allow us to narrow the symbol to KNOWN_VALUE
+(with a value of integer zero). If at any point we encounter a float guard on
+the same symbol, that would be a contradiction, and the symbol would be set to
+BOTTOM (indicating that the code is unreachable).
+
+*/
 
 #ifdef Py_DEBUG
 static inline int get_lltrace(void) {
@@ -420,7 +444,6 @@ _Py_uop_sym_get_type(JitOptSymbol *sym)
     JitSymType tag = sym->tag;
     switch(tag) {
         case JIT_SYM_NULL_TAG:
-        case JIT_SYM_TYPE_VERSION_TAG:
         case JIT_SYM_BOTTOM_TAG:
         case JIT_SYM_NON_NULL_TAG:
         case JIT_SYM_UNKNOWN_TAG:
@@ -429,6 +452,8 @@ _Py_uop_sym_get_type(JitOptSymbol *sym)
             return sym->cls.type;
         case JIT_SYM_KNOWN_VALUE_TAG:
             return Py_TYPE(sym->value.value);
+        case JIT_SYM_TYPE_VERSION_TAG:
+            return _PyType_LookupByVersion(sym->version.version);
         case JIT_SYM_TUPLE_TAG:
             return &PyTuple_Type;
         case JIT_SYM_TRUTHINESS_TAG:
@@ -464,21 +489,7 @@ _Py_uop_sym_get_type_version(JitOptSymbol *sym)
 bool
 _Py_uop_sym_has_type(JitOptSymbol *sym)
 {
-    JitSymType tag = sym->tag;
+    return _Py_uop_sym_get_type(sym) != NULL;
-    switch(tag) {
-        case JIT_SYM_NULL_TAG:
-        case JIT_SYM_TYPE_VERSION_TAG:
-        case JIT_SYM_BOTTOM_TAG:
-        case JIT_SYM_NON_NULL_TAG:
-        case JIT_SYM_UNKNOWN_TAG:
-            return false;
-        case JIT_SYM_KNOWN_CLASS_TAG:
-        case JIT_SYM_KNOWN_VALUE_TAG:
-        case JIT_SYM_TUPLE_TAG:
-        case JIT_SYM_TRUTHINESS_TAG:
-            return true;
-    }
-    Py_UNREACHABLE();
 }
 
 bool
@@ -576,7 +587,7 @@ _Py_uop_sym_tuple_getitem(JitOptContext *ctx, JitOptSymbol *sym, int item)
     else if (sym->tag == JIT_SYM_TUPLE_TAG && item < sym->tuple.length) {
         return allocation_base(ctx) + sym->tuple.items[item];
     }
-    return _Py_uop_sym_new_unknown(ctx);
+    return _Py_uop_sym_new_not_null(ctx);
 }
 
 int
@@ -863,6 +874,11 @@ _Py_uop_symbols_test(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(ignored))
         _Py_uop_sym_get_const(ctx, _Py_uop_sym_tuple_getitem(ctx, sym, 1)) == val_43,
         "tuple item does not match value used to create tuple"
     );
+    sym = _Py_uop_sym_new_type(ctx, &PyTuple_Type);
+    TEST_PREDICATE(
+        _Py_uop_sym_is_not_null(_Py_uop_sym_tuple_getitem(ctx, sym, 42)),
+        "Unknown tuple item is not narrowed to non-NULL"
+    );
     JitOptSymbol *value = _Py_uop_sym_new_type(ctx, &PyBool_Type);
     sym = _Py_uop_sym_new_truthiness(ctx, value, false);
     TEST_PREDICATE(_Py_uop_sym_matches_type(sym, &PyBool_Type), "truthiness is not boolean");