On Sunday, 14 February 2016 at 12:53:08 UTC, Lars T. Kyllingstad
wrote:
I know you said afterwards you didn't need a reference, but
I'll give you one anyway. :) That is the formal requirement
for C++ standard library types; see sec. 17.6.5.15
[lib.types.movedfrom] of the C++ specification.
k thx. ;-) (I'll look at it later)
For your lowest-level resource owners, I guess that is the
case. But if a and b are largeish compound types that don't
fit in a register, that's not the case, right? Or can the
optimiser deal with this in a good way too?
This is where measuring different compiler switch setups starts
to matter, inlining and also cache effects... :-)
I don't think the size matters, for swap, except for potential
cache misses. As long as there are no barriers you can just swap
field after field. If the loop is tight, then the loop is
unrolled inside the CPU before the micro-ops are scheduled into
the pipeline IIRC.
That is of course very unfortunate, but I guess it can be
worked around?
You can work around it by having extra pointers/containers in or
held by the struct (pointers to the source that is pointing to
you). But that takes more space.
