https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103069
--- Comment #10 from Thiago Macieira <thiago at kde dot org> ---
(In reply to H.J. Lu from comment #9)
> nptl/nptl_setxid.c in glibc has
>
> do
> {
> flags = THREAD_GETMEM (self, cancelhandling);
> newval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling,
> flags & ~SETXID_BITMASK, flags);
> }
> while (flags != newval);
>
> GCC 12 generates:
>
> 899f0: 64 8b 14 25 08 03 00 mov %fs:0x308,%edx
> 899f8: 89 d6 mov %edx,%esi
> 899fa: 89 d0 mov %edx,%eax
> 899fc: 83 e6 bf and $0xffffffbf,%esi
> 899ff: f0 0f b1 31 lock cmpxchg %esi,(%rcx)
> 89a03: 75 eb jne 899f0 <__GI___nptl_setxid_sighand
> ler+0x90>
This one is a single bit. This one should be replaced with a LOCK BTC and no
loop.
