this is an advantage for _PyObject_GC_TRACK
which before compiled to something like this:
        cmpq    $-2, -16(%rdi)
        jne     .LBB0_2
        movq    $-3, -16(%rdi)
        movq    _PyGC_generation0(%rip), %rax
        movq    %rax, -32(%rdi)
        movq    _PyGC_generation0(%rip), %rax
        movq    8(%rax), %rax
        movq    %rax, -24(%rdi)
        leaq    -32(%rdi), %rcx
        movq    %rcx, (%rax)
        movq    _PyGC_generation0(%rip), %rax
        movq    %rcx, 8(%rax)

and now compiles to
        cmpq    $-2, -16(%rdi)
        jne     .LBB0_2
        movq    $-3, -16(%rdi)
        movq    _PyGC_generation0(%rip), %rax
        movq    %rax, -32(%rdi)
        movq    8(%rax), %rcx
        movq    %rcx, -24(%rdi)
        leaq    -32(%rdi), %rdx
        movq    %rdx, (%rcx)
        movq    %rdx, 8(%rax)

notice that it had to load _PyGC_generation0 three times because the compiler had to assume that because of aliasing it got motified.
(and this loads actually showed up in profiling as somewhat expensive)