Re: -mcx16 vs. not using CAS for atomic loads

[Richard Henderson <rth at redhat dot com>]

On 01/24/2017 01:08 AM, Torvald Riegel wrote:
> Unless HW transactions are guaranteed to succeed for scenarios that are
> sufficient for the atomics, HTM won't help because we'd have to consider
> the worst-case, which would mean some non-HTM fallback.

We're talking about a 16 byte aligned load here -- one cacheline, probably 3-4
instructions.  If an HTM cannot succeed with that, I'm happy to call it useless.

The only possible concern I see might be with simulators that force HTM
failure, for the purpose of forcibly testing fallback paths.  I guess we'd have
to continue to fall back to the lock path for that case.


r~