-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 05/03/2010 02:26 PM, Jeffrey Lee Hellrung, Jr. wrote:
RVO works independently of (emulated) move semantics. [...]
If that's the case, and GCC is doing that as it should, why would adding move semantics to the library provide any speed increase at all?
Hmmm...good question. For something like "w = x * y + z", if you can't reuse any resources, I don't think move semantics will give you anything other than optimizing the final assignment... [...]
Sorry, I meant why does adding Boost.Move make any difference to the timings I posted yesterday at all, if the compiler is already eliding the copy operations on return values even without it? If I understand what you're trying to explain (which is far from certain), there's no need to wrap the return values in a boost::move call, but in that case Boost.Move should be completely superfluous -- the code should run at the same speed with or without it. I just realized that, since I have the boost::move calls wrapped in a #define already, it would be easy to check on that, so I did. The timings all indicate that without the boost::move() call for the return values, XInt runs as if Boost.Move weren't even there. So the boost::move call *is* required to get the benefits of emulated move semantics, as I originally thought. - -- Chad Nelson Oak Circle Software, Inc. * * * -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkvfRj0ACgkQp9x9jeZ9/wQwvwCgtCUiDrDRdHZvjg8EBqdzXDxY raEAoOY4N5VFF1qlHSNBFehbW8QpgpHD =z0hb -----END PGP SIGNATURE-----