[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 #3 from mw <mingwu at gmail.com> ---
Yes, verified, not on MacOS.

Thank you (at least there is a system I can use now).


$ objdump -disassemble-all c.o > c.o.asm
$ grep -i cmpxchg  c.o.asm
     80a:       49 0f c7 08     cmpxchg16b      (%r8)

$ uname -a
Darwin 19.4.0 Darwin Kernel Version 19.4.0: Wed Mar  4 22:28:40 PST 2020;
root:xnu-6153.101.6~15/RELEASE_X86_64 x86_64

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