8000 gh-127022: Simplify `PyStackRef_FromPyObjectSteal` (#127024) · python/cpython@4759ba6 · GitHub
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gh-127022: Simplify PyStackRef_FromPyObjectSteal (#127024)
This gets rid of the immortal check in `PyStackRef_FromPyObjectSteal()`. Overall, this improves performance about 2% in the free threading build. This also renames `PyStackRef_Is()` to `PyStackRef_IsExactly()` because the macro requires that the tag bits of the arguments match, which is only true in certain special cases.
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‎Include/internal/pycore_stackref.h

Lines changed: 10 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -99,8 +99,7 @@ _PyStackRef_FromPyObjectSteal(PyObject *obj)
9999
assert(obj != NULL);
100100
// Make sure we don't take an already tagged value.
101101
assert(((uintptr_t)obj & Py_TAG_BITS) == 0);
102-
unsigned int tag = _Py_IsImmortal(obj) ? (Py_TAG_DEFERRED) : Py_TAG_PTR;
103-
return ((_PyStackRef){.bits = ((uintptr_t)(obj)) | tag});
102+
return (_PyStackRef){ .bits = (uintptr_t)obj };
104103
}
105104
# define PyStackRef_FromPyObjectSteal(obj) _PyStackRef_FromPyObjectSteal(_PyObject_CAST(obj))
106105

@@ -190,9 +189,16 @@ static const _PyStackRef PyStackRef_NULL = { .bits = 0 };
190189

191190
#endif // Py_GIL_DISABLED
192191

193-
// Note: this is a macro because MSVC (Windows) has trouble inlining it.
192+
// Check if a stackref is exactly the same as another stackref, including the
193+
// the deferred bit. This can only be used safely if you know that the deferred
194+
// bits of `a` and `b` match.
195+
#define PyStackRef_IsExactly(a, b) \
196+
(assert(((a).bits & Py_TAG_BITS) == ((b).bits & Py_TAG_BITS)), (a).bits == (b).bits)
194197

195-
#define PyStackRef_Is(a, b) ((a).bits == (b).bits)
198+
// Checks that mask out the deferred bit in the free threading build.
199+
#define PyStackRef_IsNone(ref) (PyStackRef_AsPyObjectBorrow(ref) == Py_None)
200+
#define PyStackRef_IsTrue(ref) (PyStackRef_AsPyObjectBorrow(ref) == Py_True)
201+
#define PyStackRef_IsFalse(ref) (PyStackRef_AsPyObjectBorrow(ref) == Py_False)
196202

197203
// Converts a PyStackRef back to a PyObject *, converting the
198204
// stackref to a new reference.

‎Python/bytecodes.c

Lines changed: 17 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -376,7 +376,7 @@ dummy_func(
376376

377377
pure inst(UNARY_NOT, (value -- res)) {
378378
assert(PyStackRef_BoolCheck(value));
379-
res = PyStackRef_Is(value, PyStackRef_False)
379+
res = PyStackRef_IsFalse(value)
380380
? PyStackRef_True : PyStackRef_False;
381381
DEAD(value);
382382
}
@@ -441,7 +441,7 @@ dummy_func(
441441

442442
inst(TO_BOOL_NONE, (unused/1, unused/2, value -- res)) {
443443
// This one is a bit weird, because we expect *some* failures:
444-
EXIT_IF(!PyStackRef_Is(value, PyStackRef_None));
444+
EXIT_IF(!PyStackRef_IsNone(value));
445445
DEAD(value);
446446
STAT_INC(TO_BOOL, hit);
447447
res = PyStackRef_False;
@@ -651,9 +651,7 @@ dummy_func(
651651
// specializations, but there is no output.
652652
// At the end we just skip over the STORE_FAST.
653653
op(_BINARY_OP_INPLACE_ADD_UNICODE, (left, right --)) {
654-
#ifndef NDEBUG 8000
655654
PyObject *left_o = PyStackRef_AsPyObjectBorrow(left);
656-
#endif
657655
PyObject *right_o = PyStackRef_AsPyObjectBorrow(right);
658656

659657
int next_oparg;
@@ -664,7 +662,7 @@ dummy_func(
664662
next_oparg = CURRENT_OPERAND0();
665663
#endif
666664
_PyStackRef *target_local = &GETLOCAL(next_oparg);
667-
DEOPT_IF(!PyStackRef_Is(*target_local, left));
665+
DEOPT_IF(PyStackRef_AsPyObjectBorrow(*target_local) != left_o);
668666
STAT_INC(BINARY_OP, hit);
669667
/* Handle `left = left + right` or `left += right` for str.
670668
*
@@ -1141,7 +1139,7 @@ dummy_func(
11411139
gen_frame->previous = frame;
11421140
DISPATCH_INLINED(gen_frame);
11431141
}
1144-
if (PyStackRef_Is(v, PyStackRef_None) && PyIter_Check(receiver_o)) {
1142+
if (PyStackRef_IsNone(v) && PyIter_Check(receiver_o)) {
11451143
retval_o = Py_TYPE(receiver_o)->tp_iternext(receiver_o);
11461144
}
11471145
else {
@@ -1249,7 +1247,7 @@ dummy_func(
12491247
inst(POP_EXCEPT, (exc_value -- )) {
12501248
_PyErr_StackItem *exc_info = tstate->exc_info;
12511249
Py_XSETREF(exc_info->exc_value,
1252-
PyStackRef_Is(exc_value, PyStackRef_None)
1250+
PyStackRef_IsNone(exc_value)
12531251
? NULL : PyStackRef_AsPyObjectSteal(exc_value));
12541252
}
12551253

@@ -2502,13 +2500,7 @@ dummy_func(
25022500
}
25032501

25042502
inst(IS_OP, (left, right -- b)) {
2505-
#ifdef Py_GIL_DISABLED
2506-
// On free-threaded builds, objects are conditionally immortalized.
2507-
// So their bits don't always compare equally.
25082503
int res = Py_Is(PyStackRef_AsPyObjectBorrow(left), PyStackRef_AsPyObjectBorrow(right)) ^ oparg;
2509-
#else
2510-
int res = PyStackRef_Is(left, right) ^ oparg;
2511-
#endif
25122504
DECREF_INPUTS();
25132505
b = res ? PyStackRef_True : PyStackRef_False;
25142506
}
@@ -2715,22 +2707,22 @@ dummy_func(
27152707

27162708
replaced op(_POP_JUMP_IF_FALSE, (cond -- )) {
27172709
assert(PyStackRef_BoolCheck(cond));
2718-
int flag = PyStackRef_Is(cond, PyStackRef_False);
2710+
int flag = PyStackRef_IsFalse(cond);
27192711
DEAD(cond);
27202712
RECORD_BRANCH_TAKEN(this_instr[1].cache, flag);
27212713
JUMPBY(oparg * flag);
27222714
}
27232715

27242716
replaced op(_POP_JUMP_IF_TRUE, (cond -- )) {
27252717
assert(PyStackRef_BoolCheck(cond));
2726-
int flag = PyStackRef_Is(cond, PyStackRef_True);
2718+
int flag = PyStackRef_IsTrue(cond);
27272719
DEAD(cond);
27282720
RECORD_BRANCH_TAKEN(this_instr[1].cache, flag);
27292721
JUMPBY(oparg * flag);
27302722
}
27312723

27322724
op(_IS_NONE, (value -- b)) {
2733-
if (PyStackRef_Is(value, PyStackRef_None)) {
2725+
if (PyStackRef_IsNone(value)) {
27342726
b = PyStackRef_True;
27352727
DEAD(value);
27362728
}
@@ -3774,7 +3766,7 @@ dummy_func(
37743766

37753767
inst(EXIT_INIT_CHECK, (should_be_none -- )) {
37763768
assert(STACK_LEVEL() == 2);
3777-
if (!PyStackRef_Is(should_be_none, PyStackRef_None)) {
3769+
if (!PyStackRef_IsNone(should_be_none)) {
37783770
PyErr_Format(PyExc_TypeError,
37793771
"__init__() should return None, not '%.200s'",
37803772
Py_TYPE(PyStackRef_AsPyObjectBorrow(should_be_none))->tp_name);
@@ -4734,7 +4726,7 @@ dummy_func(
47344726
inst(INSTRUMENTED_POP_JUMP_IF_TRUE, (unused/1 -- )) {
47354727
_PyStackRef cond = POP();
47364728
assert(PyStackRef_BoolCheck(cond));
4737-
int flag = PyStackRef_Is(cond, PyStackRef_True);
4729+
int flag = PyStackRef_IsTrue(cond);
47384730
int offset = flag * oparg;
47394731
RECORD_BRANCH_TAKEN(this_instr[1].cache, flag);
47404732
INSTRUMENTED_JUMP(this_instr, next_instr + offset, PY_MONITORING_EVENT_BRANCH);
@@ -4743,15 +4735,15 @@ dummy_func(
47434735
inst(INSTRUMENTED_POP_JUMP_IF_FALSE, (unused/1 -- )) {
47444736
_PyStackRef cond = POP();
47454737
assert(PyStackRef_BoolCheck(cond));
4746-
int flag = PyStackRef_Is(cond, PyStackRef_False);
4738+
int flag = PyStackRef_IsFalse(cond);
47474739
int offset = flag * oparg;
47484740
RECORD_BRANCH_TAKEN(this_instr[1].cache, flag);
47494741
INSTRUMENTED_JUMP(this_instr, next_instr + offset, PY_MONITORING_EVENT_BRANCH);
47504742
}
47514743

47524744
inst(INSTRUMENTED_POP_JUMP_IF_NONE, (unused/1 -- )) {
47534745
_PyStackRef value_stackref = POP();
4754-
int flag = PyStackRef_Is(value_stackref, PyStackRef_None);
4746+
int flag = PyStackRef_IsNone(value_stackref);
47554747
int offset;
47564748
if (flag) {
47574749
offset = oparg;
@@ -4767,7 +4759,7 @@ dummy_func(
47674759
inst(INSTRUMENTED_POP_JUMP_IF_NOT_NONE, (unused/1 -- )) {
47684760
_PyStackRef value_stackref = POP();
47694761
int offset;
4770-
int nflag = PyStackRef_Is(value_stackref, PyStackRef_None);
4762+
int nflag = PyStackRef_IsNone(value_stackref);
47714763
if (nflag) {
47724764
offset = 0;
47734765
}
@@ -4802,21 +4794,21 @@ dummy_func(
48024794
///////// Tier-2 only opcodes /////////
48034795

48044796
op (_GUARD_IS_TRUE_POP, (flag -- )) {
4805-
int is_true = PyStackRef_Is(flag, PyStackRef_True);
4797+
int is_true = PyStackRef_IsTrue(flag);
48064798
DEAD(flag);
48074799
SYNC_SP();
48084800
EXIT_IF(!is_true);
48094801
}
48104802

48114803
op (_GUARD_IS_FALSE_POP, (flag -- )) {
4812-
int is_false = PyStackRef_Is(flag, PyStackRef_False);
4804+
int is_false = PyStackRef_IsFalse(flag);
48134805
DEAD(flag);
48144806
SYNC_SP();
48154807
EXIT_IF(!is_false);
48164808
}
48174809

48184810
op (_GUARD_IS_NONE_POP, (val -- )) {
4819-
int is_none = PyStackRef_Is(val, PyStackRef_None);
4811+
int is_none = PyStackRef_IsNone(val);
48204812
if (!is_none) {
48214813
PyStackRef_CLOSE(val);
48224814
SYNC_SP();
@@ -4826,7 +4818,7 @@ dummy_func(
48264818
}
48274819

48284820
op (_GUARD_IS_NOT_NONE_POP, (val -- )) {
4829-
int is_none = PyStackRef_Is(val, PyStackRef_None);
4821+
int is_none = PyStackRef_IsNone(val);
48304822
PyStackRef_CLOSE(val);
48314823
SYNC_SP();
48324824
EXIT_IF(is_none);

‎Python/executor_cases.c.h

Lines changed: 10 additions & 18 deletions
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