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gh-160147: Inline PyObject_IS_GC() in _PyObject_GC_MAY_BE_TRACKED() - #161189

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vstinner:gc_inline
Nov 3, 2026
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gh-160147: Inline PyObject_IS_GC() in _PyObject_GC_MAY_BE_TRACKED()#161189
vstinner merged 1 commit into
python:mainfrom
vstinner:gc_inline

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@vstinner vstinner commented Nov 2, 2026 •
edited by bedevere-app Bot
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Move _PyType_IS_GC() and _PyObject_IS_GC() from pycore_object.h to pycore_gc.h. Replace PyObject_IS_GC() call with _PyObject_IS_GC() in _PyObject_GC_MAY_BE_TRACKED().

Help the compiler to inline _PyObject_IS_GC() code in _PyObject_GC_MAY_BE_TRACKED(), especially when LTO is not used.

@vstinner
pythongh-160147: Inline PyObject_IS_GC() in _PyObject_GC_MAY_BE_TRACK…
d367d4c 
…ED()

Move _PyType_IS_GC() and _PyObject_IS_GC() from pycore_object.h to
pycore_gc.h. Replace PyObject_IS_GC() call with _PyObject_IS_GC() in
_PyObject_GC_MAY_BE_TRACKED().

Help the compiler to inline _PyObject_IS_GC() code in
_PyObject_GC_MAY_BE_TRACKED(), especially when LTO is not used.
@vstinner vstinner added performance Performance or resource usage skip news labels Nov 2, 2026
@bedevere-app bedevere-app Bot added awaiting core review type-feature A feature request or enhancement labels Nov 2, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Nov 2, 2026
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vstinner commented Nov 2, 2026

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I built Python with gcc -O3 on Fedora 44 (gcc 16.2.1).

x86-64 assembly code, before: call 0x64b300 <PyObject_IS_GC>.

Details 
(gdb) disassemble _PyTuple_MaybeUntrack
Dump of assembler code for function _PyTuple_MaybeUntrack:
   0x000000000052f860 <+0>:	cmp    QWORD PTR [rdi+0x8],0x9a4a80
   0x000000000052f868 <+8>:	je     0x52f870 <_PyTuple_MaybeUntrack+16>
   0x000000000052f86a <+10>:	ret
   0x000000000052f86b <+11>:	nop    DWORD PTR [rax+rax*1+0x0]
   0x000000000052f870 <+16>:	mov    rax,QWORD PTR [rdi-0x10]
   0x000000000052f874 <+20>:	test   rax,rax
   0x000000000052f877 <+23>:	je     0x52f86a <_PyTuple_MaybeUntrack+10>
   0x000000000052f879 <+25>:	push   rbp
   0x000000000052f87a <+26>:	mov    rdx,rdi
   0x000000000052f87d <+29>:	mov    rbp,rsp
   0x000000000052f880 <+32>:	push   rbx
   0x000000000052f881 <+33>:	sub    rsp,0x28
   0x000000000052f885 <+37>:	mov    rsi,QWORD PTR [rdi+0x10]
   0x000000000052f889 <+41>:	mov    rbx,rsi
   0x000000000052f88c <+44>:	test   rsi,rsi
   0x000000000052f88f <+47>:	jle    0x52f8ec <_PyTuple_MaybeUntrack+140>
   0x000000000052f891 <+49>:	xor    esi,esi
   0x000000000052f893 <+51>:	mov    rcx,QWORD PTR [rdx+rsi*8+0x20]
   0x000000000052f898 <+56>:	test   rcx,rcx
   0x000000000052f89b <+59>:	je     0x52f8cb <_PyTuple_MaybeUntrack+107>

   # _PyObject_GC_MAY_BE_TRACKED: PyObject_IS_GC()
   0x000000000052f89d <+61>:	mov    rdi,rcx
   0x000000000052f8a0 <+64>:	mov    QWORD PTR [rbp-0x18],rsi
   0x000000000052f8a4 <+68>:	mov    QWORD PTR [rbp-0x20],rdx
   0x000000000052f8a8 <+72>:	mov    QWORD PTR [rbp-0x28],rcx
   0x000000000052f8ac <+76>:	call   0x64b300 <PyObject_IS_GC>

   0x000000000052f8b1 <+81>:	mov    rsi,QWORD PTR [rbp-0x18]
   0x000000000052f8b5 <+85>:	mov    rdx,QWORD PTR [rbp-0x20]
   0x000000000052f8b9 <+89>:	test   eax,eax
   0x000000000052f8bb <+91>:	je     0x52f8df <_PyTuple_MaybeUntrack+127>
   0x000000000052f8bd <+93>:	mov    rcx,QWORD PTR [rbp-0x28]
   0x000000000052f8c1 <+97>:	cmp    QWORD PTR [rcx+0x8],0x9a4a80
   0x000000000052f8c9 <+105>:	je     0x52f8d8 <_PyTuple_MaybeUntrack+120>
   0x000000000052f8cb <+107>:	mov    rbx,QWORD PTR [rbp-0x8]
   0x000000000052f8cf <+111>:	leave
   0x000000000052f8d0 <+112>:	ret
   0x000000000052f8d1 <+113>:	nop    DWORD PTR [rax+0x0]
   0x000000000052f8d8 <+120>:	cmp    QWORD PTR [rcx-0x10],0x0
   0x000000000052f8dd <+125>:	jne    0x52f8cb <_PyTuple_MaybeUntrack+107>
   0x000000000052f8df <+127>:	add    rsi,0x1
   0x000000000052f8e3 <+131>:	cmp    rsi,rbx
   0x000000000052f8e6 <+134>:	jne    0x52f893 <_PyTuple_MaybeUntrack+51>
   0x000000000052f8e8 <+136>:	mov    rax,QWORD PTR [rdx-0x10]
   0x000000000052f8ec <+140>:	mov    rsi,QWORD PTR [rdx-0x8]
   0x000000000052f8f0 <+144>:	mov    rcx,QWORD PTR [rax+0x8]
   0x000000000052f8f4 <+148>:	and    rsi,0xfffffffffffffffc
   0x000000000052f8f8 <+152>:	and    ecx,0x3
   0x000000000052f8fb <+155>:	or     rcx,rsi
   0x000000000052f8fe <+158>:	mov    QWORD PTR [rsi],rax
   0x000000000052f901 <+161>:	mov    QWORD PTR [rax+0x8],rcx
   0x000000000052f905 <+165>:	mov    rax,0xfffffffffffffff0
   0x000000000052f90c <+172>:	and    QWORD PTR [rdx-0x8],0x1
   0x000000000052f911 <+177>:	mov    QWORD PTR [rdx-0x10],0x0
   0x000000000052f919 <+185>:	mov    rax,QWORD PTR fs:[rax]
   0x000000000052f91d <+189>:	sub    QWORD PTR [rax+0x1d78],0x1
   0x000000000052f925 <+197>:	jmp    0x52f8cb <_PyTuple_MaybeUntrack+107>
End of assembler dump.

x86-64 assembly code, after: _PyObject_IS_GC() is inlined.

Details 
(gdb) disassemble _PyTuple_MaybeUntrack
Dump of assembler code for function _PyTuple_MaybeUntrack:
   0x000000000052f860 <+0>:	cmp    QWORD PTR [rdi+0x8],0x9a4a80
   0x000000000052f868 <+8>:	je     0x52f870 <_PyTuple_MaybeUntrack+16>
   0x000000000052f86a <+10>:	ret
   0x000000000052f86b <+11>:	nop    DWORD PTR [rax+rax*1+0x0]
   0x000000000052f870 <+16>:	mov    rax,QWORD PTR [rdi-0x10]
   0x000000000052f874 <+20>:	test   rax,rax
   0x000000000052f877 <+23>:	je     0x52f86a <_PyTuple_MaybeUntrack+10>
   0x000000000052f879 <+25>:	push   rbp
   0x000000000052f87a <+26>:	mov    rbp,rsp
   0x000000000052f87d <+29>:	sub    rsp,0x20
   0x000000000052f881 <+33>:	mov    QWORD PTR [rbp-0x8],r14
   0x000000000052f885 <+37>:	mov    r14,QWORD PTR [rdi+0x10]
   0x000000000052f889 <+41>:	mov    QWORD PTR [rbp-0x10],r13
   0x000000000052f88d <+45>:	mov    r13,rdi
   0x000000000052f890 <+48>:	test   r14,r14
   0x000000000052f893 <+51>:	jle    0x52f925 <_PyTuple_MaybeUntrack+197>
   0x000000000052f899 <+57>:	mov    QWORD PTR [rbp-0x18],r12
   0x000000000052f89d <+61>:	mov    QWORD PTR [rbp-0x20],rbx
   0x000000000052f8a1 <+65>:	xor    ebx,ebx
   0x000000000052f8a3 <+67>:	xchg   ax,ax
   0x000000000052f8a5 <+69>:	data16 cs nop WORD PTR [rax+rax*1+0x0]
   0x000000000052f8b0 <+80>:	mov    r12,QWORD PTR [r13+rbx*8+0x20]
   0x000000000052f8b5 <+85>:	test   r12,r12
   0x000000000052f8b8 <+88>:	je     0x52f8ea <_PyTuple_MaybeUntrack+138>

   # _PyObject_IS_GC: PyTypeObject *type = Py_TYPE(obj);
   0x000000000052f8ba <+90>:	mov    rax,QWORD PTR [r12+0x8]

   # _PyObject_IS_GC: _PyType_IS_GC(type)
   # _PyType_HasFeature(type, Py_TPFLAGS_HAVE_GC)
   0x000000000052f8bf <+95>:	test   BYTE PTR [rax+0xa9],0x40
   0x000000000052f8c6 <+102>:	je     0x52f910 <_PyTuple_MaybeUntrack+176>

   # _PyObject_IS_GC: type->tp_is_gc == NULL
   0x000000000052f8c8 <+104>:	mov    rdx,QWORD PTR [rax+0x148]
   0x000000000052f8cf <+111>:	test   rdx,rdx
   0x000000000052f8d2 <+114>:	je     0x52f8e2 <_PyTuple_MaybeUntrack+130>

   # _PyObject_IS_GC: type->tp_is_gc(obj)
   0x000000000052f8d4 <+116>:	mov    rdi,r12
   0x000000000052f8d7 <+119>:	call   rdx
   0x000000000052f8d9 <+121>:	test   eax,eax
   0x000000000052f8db <+123>:	je     0x52f910 <_PyTuple_MaybeUntrack+176>

   0x000000000052f8dd <+125>:	mov    rax,QWORD PTR [r12+0x8]
   0x000000000052f8e2 <+130>:	cmp    rax,0x9a4a80
   0x000000000052f8e8 <+136>:	je     0x52f900 <_PyTuple_MaybeUntrack+160>
   0x000000000052f8ea <+138>:	mov    rbx,QWORD PTR [rbp-0x20]
   0x000000000052f8ee <+142>:	mov    r12,QWORD PTR [rbp-0x18]
   0x000000000052f8f2 <+146>:	mov    r13,QWORD PTR [rbp-0x10]
   0x000000000052f8f6 <+150>:	mov    r14,QWORD PTR [rbp-0x8]
   0x000000000052f8fa <+154>:	leave
   0x000000000052f8fb <+155>:	ret
   0x000000000052f8fc <+156>:	nop    DWORD PTR [rax+0x0]
   0x000000000052f900 <+160>:	cmp    QWORD PTR [r12-0x10],0x0
   0x000000000052f906 <+166>:	jne    0x52f8ea <_PyTuple_MaybeUntrack+138>
   0x000000000052f908 <+168>:	nop    DWORD PTR [rax+rax*1+0x0]
   0x000000000052f910 <+176>:	add    rbx,0x1
   0x000000000052f914 <+180>:	cmp    rbx,r14
   0x000000000052f917 <+183>:	jne    0x52f8b0 <_PyTuple_MaybeUntrack+80>
   0x000000000052f919 <+185>:	mov    rax,QWORD PTR [r13-0x10]
   0x000000000052f91d <+189>:	mov    rbx,QWORD PTR [rbp-0x20]
   0x000000000052f921 <+193>:	mov    r12,QWORD PTR [rbp-0x18]
   0x000000000052f925 <+197>:	mov    rcx,QWORD PTR [r13-0x8]
   0x000000000052f929 <+201>:	mov    rdx,QWORD PTR [rax+0x8]
   0x000000000052f92d <+205>:	mov    r14,QWORD PTR [rbp-0x8]
   0x000000000052f931 <+209>:	and    rcx,0xfffffffffffffffc
   0x000000000052f935 <+213>:	and    edx,0x3
   0x000000000052f938 <+216>:	or     rdx,rcx
   0x000000000052f93b <+219>:	mov    QWORD PTR [rcx],rax
   0x000000000052f93e <+222>:	mov    QWORD PTR [rax+0x8],rdx
   0x000000000052f942 <+226>:	mov    rax,0xfffffffffffffff0
   0x000000000052f949 <+233>:	and    QWORD PTR [r13-0x8],0x1
   0x000000000052f94e <+238>:	mov    QWORD PTR [r13-0x10],0x0
   0x000000000052f956 <+246>:	mov    rax,QWORD PTR fs:[rax]
   0x000000000052f95a <+250>:	mov    r13,QWORD PTR [rbp-0x10]
   0x000000000052f95e <+254>:	sub    QWORD PTR [rax+0x1d78],0x1
   0x000000000052f966 <+262>:	leave
   0x000000000052f967 <+263>:	ret
End of assembler dump.

@vstinner

vstinner commented Nov 2, 2026

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This PR is interesting for #160154 which adds a _PyObject_GC_MAY_BE_TRACKED() call to Objects/setobject.c. But it's also interesting even if the frozenset change is not merged.

@vstinner vstinner removed the type-feature A feature request or enhancement label Nov 2, 2026
@vstinner
vstinner merged commit ce841a9 into python:main Nov 3, 2026
58 of 63 checks passed
@vstinner
vstinner deleted the gc_inline branch November 3, 2026 17:30
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