https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98110
--- Comment #12 from Florian Weimer <fw at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #11)
> Ah, RTL loop_invariant. Perhaps because the inline asm is buggy?
> asm ("mov %%fs:%c1,%0" : "=r" (__self) : "i" (__builtin_offsetof (struct
> pthread, header.self)));
> The only input of the asm is the constant, so really nothing tells the
> optimizers it can't move it arbitrarily. I think it needs to have some
> memory input or clobber to properly model that it reads from unknown memory.
Ahh, do you mean the THREAD_SELF macro?
# define THREAD_SELF \
({ struct pthread *__self; \
asm ("mov %%fs:%c1,%0" : "=r" (__self) \
: "i" (offsetof (struct pthread, header.self))); \
__self;})
I had only looked at the other macros.
glibc relies on GCC optimizing away THREAD_SELF reads on x86-64 because most of
the TCB access does not need it.
