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Subject: [Bug target/103069] cmpxchg isn't optimized
Date: Tue, 22 Feb 2022 08:21:00 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103069

--- Comment #15 from Hongyu Wang <wwwhhhyyy333 at gmail dot com> ---
(In reply to Thiago Macieira from comment #14)
> I'd restrict relaxations to loops emitted by the compiler. All other atom=
ic
> operations shouldn't be modified at all, unless the user asks for it. That
> includes non-looping atomic operations (like LOCK BTC, LOCK XADD) as well=
 as
> a pure LOCK CMPXCHG that came from a single __atomic_compare_exchange by =
the
> user.
>=20
> I'd welcome the ability to relax the latter, especially if with one codeb=
ase
> I could be efficient in CAS architectures as well as LL/SC ones.

The latest patch relaxed the pure LOCK CMPXCHG with -mrelax-cmpxchg-loop as=
 the
commit message shows. So if you want, I can split this part to another swit=
ch
like -mrelax-cmpxchg-insn.=