Someone inquired on IRC about the atomic increment/decrement functions on
i386/amd64.
The atomic_{inc,dec}_*_nv functions are implemented as a leaq + cmpxchg
loop. For example:
http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/common/atomic/amd64/atomic.s#76
The question was why these don't use an xadd instead. I'm pretty sure it
would take fewer cycles in any case, so this is weird.
Any thoughts?
-Albert
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