[Issue 20838] on modern (x86_64) CPUs, dmd emit cmpxchg8b instead of CMPXCHG16B

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20838

--- Comment #16 from mhh <maxhaton at gmail.com> ---
Actually I should've read the thread. Turns out it is indeed a problem with
Walters disassembler. Even more fun.

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