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pythongh-127022: Simplify PyStackRef_FromPyObjectSteal (python#127024)
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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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@colesbury
colesbury authored Nov 22, 2024
1 parent 8214e0f commit 4759ba6
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Showing 5 changed files with 57 additions and 72 deletions.
14 changes: 10 additions & 4 deletions Include/internal/pycore_stackref.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -99,8 +99,7 @@ _PyStackRef_FromPyObjectSteal(PyObject *obj)
assert(obj != NULL);
// Make sure we don't take an already tagged value.
assert(((uintptr_t)obj & Py_TAG_BITS) == 0);
unsigned int tag = _Py_IsImmortal(obj) ? (Py_TAG_DEFERRED) : Py_TAG_PTR;
return ((_PyStackRef){.bits = ((uintptr_t)(obj)) | tag});
return (_PyStackRef){ .bits = (uintptr_t)obj };
}
# define PyStackRef_FromPyObjectSteal(obj) _PyStackRef_FromPyObjectSteal(_PyObject_CAST(obj))

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

#endif // Py_GIL_DISABLED

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

#define PyStackRef_Is(a, b) ((a).bits == (b).bits)
// Checks that mask out the deferred bit in the free threading build.
#define PyStackRef_IsNone(ref) (PyStackRef_AsPyObjectBorrow(ref) == Py_None)
#define PyStackRef_IsTrue(ref) (PyStackRef_AsPyObjectBorrow(ref) == Py_True)
#define PyStackRef_IsFalse(ref) (PyStackRef_AsPyObjectBorrow(ref) == Py_False)

// Converts a PyStackRef back to a PyObject *, converting the
// stackref to a new reference.
Expand Down
42 changes: 17 additions & 25 deletions Python/bytecodes.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -376,7 +376,7 @@ dummy_func(

pure inst(UNARY_NOT, (value -- res)) {
assert(PyStackRef_BoolCheck(value));
res = PyStackRef_Is(value, PyStackRef_False)
res = PyStackRef_IsFalse(value)
? PyStackRef_True : PyStackRef_False;
DEAD(value);
}
Expand Down Expand Up @@ -441,7 +441,7 @@ dummy_func(

inst(TO_BOOL_NONE, (unused/1, unused/2, value -- res)) {
// This one is a bit weird, because we expect *some* failures:
EXIT_IF(!PyStackRef_Is(value, PyStackRef_None));
EXIT_IF(!PyStackRef_IsNone(value));
DEAD(value);
STAT_INC(TO_BOOL, hit);
res = PyStackRef_False;
Expand Down Expand Up @@ -651,9 +651,7 @@ dummy_func(
// specializations, but there is no output.
// At the end we just skip over the STORE_FAST.
op(_BINARY_OP_INPLACE_ADD_UNICODE, (left, right --)) {
#ifndef NDEBUG
PyObject *left_o = PyStackRef_AsPyObjectBorrow(left);
#endif
PyObject *right_o = PyStackRef_AsPyObjectBorrow(right);

int next_oparg;
Expand All @@ -664,7 +662,7 @@ dummy_func(
next_oparg = CURRENT_OPERAND0();
#endif
_PyStackRef *target_local = &GETLOCAL(next_oparg);
DEOPT_IF(!PyStackRef_Is(*target_local, left));
DEOPT_IF(PyStackRef_AsPyObjectBorrow(*target_local) != left_o);
STAT_INC(BINARY_OP, hit);
/* Handle `left = left + right` or `left += right` for str.
*
Expand Down Expand Up @@ -1141,7 +1139,7 @@ dummy_func(
gen_frame->previous = frame;
DISPATCH_INLINED(gen_frame);
}
if (PyStackRef_Is(v, PyStackRef_None) && PyIter_Check(receiver_o)) {
if (PyStackRef_IsNone(v) && PyIter_Check(receiver_o)) {
retval_o = Py_TYPE(receiver_o)->tp_iternext(receiver_o);
}
else {
Expand Down Expand Up @@ -1249,7 +1247,7 @@ dummy_func(
inst(POP_EXCEPT, (exc_value -- )) {
_PyErr_StackItem *exc_info = tstate->exc_info;
Py_XSETREF(exc_info->exc_value,
PyStackRef_Is(exc_value, PyStackRef_None)
PyStackRef_IsNone(exc_value)
? NULL : PyStackRef_AsPyObjectSteal(exc_value));
}

Expand Down Expand Up @@ -2502,13 +2500,7 @@ dummy_func(
}

inst(IS_OP, (left, right -- b)) {
#ifdef Py_GIL_DISABLED
// On free-threaded builds, objects are conditionally immortalized.
// So their bits don't always compare equally.
int res = Py_Is(PyStackRef_AsPyObjectBorrow(left), PyStackRef_AsPyObjectBorrow(right)) ^ oparg;
#else
int res = PyStackRef_Is(left, right) ^ oparg;
#endif
DECREF_INPUTS();
b = res ? PyStackRef_True : PyStackRef_False;
}
Expand Down Expand Up @@ -2715,22 +2707,22 @@ dummy_func(

replaced op(_POP_JUMP_IF_FALSE, (cond -- )) {
assert(PyStackRef_BoolCheck(cond));
int flag = PyStackRef_Is(cond, PyStackRef_False);
int flag = PyStackRef_IsFalse(cond);
DEAD(cond);
RECORD_BRANCH_TAKEN(this_instr[1].cache, flag);
JUMPBY(oparg * flag);
}

replaced op(_POP_JUMP_IF_TRUE, (cond -- )) {
assert(PyStackRef_BoolCheck(cond));
int flag = PyStackRef_Is(cond, PyStackRef_True);
int flag = PyStackRef_IsTrue(cond);
DEAD(cond);
RECORD_BRANCH_TAKEN(this_instr[1].cache, flag);
JUMPBY(oparg * flag);
}

op(_IS_NONE, (value -- b)) {
if (PyStackRef_Is(value, PyStackRef_None)) {
if (PyStackRef_IsNone(value)) {
b = PyStackRef_True;
DEAD(value);
}
Expand Down Expand Up @@ -3774,7 +3766,7 @@ dummy_func(

inst(EXIT_INIT_CHECK, (should_be_none -- )) {
assert(STACK_LEVEL() == 2);
if (!PyStackRef_Is(should_be_none, PyStackRef_None)) {
if (!PyStackRef_IsNone(should_be_none)) {
PyErr_Format(PyExc_TypeError,
"__init__() should return None, not '%.200s'",
Py_TYPE(PyStackRef_AsPyObjectBorrow(should_be_none))->tp_name);
Expand Down Expand Up @@ -4734,7 +4726,7 @@ dummy_func(
inst(INSTRUMENTED_POP_JUMP_IF_TRUE, (unused/1 -- )) {
_PyStackRef cond = POP();
assert(PyStackRef_BoolCheck(cond));
int flag = PyStackRef_Is(cond, PyStackRef_True);
int flag = PyStackRef_IsTrue(cond);
int offset = flag * oparg;
RECORD_BRANCH_TAKEN(this_instr[1].cache, flag);
INSTRUMENTED_JUMP(this_instr, next_instr + offset, PY_MONITORING_EVENT_BRANCH);
Expand All @@ -4743,15 +4735,15 @@ dummy_func(
inst(INSTRUMENTED_POP_JUMP_IF_FALSE, (unused/1 -- )) {
_PyStackRef cond = POP();
assert(PyStackRef_BoolCheck(cond));
int flag = PyStackRef_Is(cond, PyStackRef_False);
int flag = PyStackRef_IsFalse(cond);
int offset = flag * oparg;
RECORD_BRANCH_TAKEN(this_instr[1].cache, flag);
INSTRUMENTED_JUMP(this_instr, next_instr + offset, PY_MONITORING_EVENT_BRANCH);
}

inst(INSTRUMENTED_POP_JUMP_IF_NONE, (unused/1 -- )) {
_PyStackRef value_stackref = POP();
int flag = PyStackRef_Is(value_stackref, PyStackRef_None);
int flag = PyStackRef_IsNone(value_stackref);
int offset;
if (flag) {
offset = oparg;
Expand All @@ -4767,7 +4759,7 @@ dummy_func(
inst(INSTRUMENTED_POP_JUMP_IF_NOT_NONE, (unused/1 -- )) {
_PyStackRef value_stackref = POP();
int offset;
int nflag = PyStackRef_Is(value_stackref, PyStackRef_None);
int nflag = PyStackRef_IsNone(value_stackref);
if (nflag) {
offset = 0;
}
Expand Down Expand Up @@ -4802,21 +4794,21 @@ dummy_func(
///////// Tier-2 only opcodes /////////

op (_GUARD_IS_TRUE_POP, (flag -- )) {
int is_true = PyStackRef_Is(flag, PyStackRef_True);
int is_true = PyStackRef_IsTrue(flag);
DEAD(flag);
SYNC_SP();
EXIT_IF(!is_true);
}

op (_GUARD_IS_FALSE_POP, (flag -- )) {
int is_false = PyStackRef_Is(flag, PyStackRef_False);
int is_false = PyStackRef_IsFalse(flag);
DEAD(flag);
SYNC_SP();
EXIT_IF(!is_false);
}

op (_GUARD_IS_NONE_POP, (val -- )) {
int is_none = PyStackRef_Is(val, PyStackRef_None);
int is_none = PyStackRef_IsNone(val);
if (!is_none) {
PyStackRef_CLOSE(val);
SYNC_SP();
Expand All @@ -4826,7 +4818,7 @@ dummy_func(
}

op (_GUARD_IS_NOT_NONE_POP, (val -- )) {
int is_none = PyStackRef_Is(val, PyStackRef_None);
int is_none = PyStackRef_IsNone(val);
PyStackRef_CLOSE(val);
SYNC_SP();
EXIT_IF(is_none);
Expand Down
28 changes: 10 additions & 18 deletions Python/executor_cases.c.h
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