On Thursday, 15 December 2016 at 15:29:13 UTC, Adam D. Ruppe
wrote:
General rule of thumb: if you are refing for performance,
actually check it before and after first, ref isn't always
faster.
But D doesn't make this easy, as it disallows rvalues to be
passed by ref. It's a very common pitfall for C++ guys. `auto
ref` for templates is an insufficient workaround/hack for that.
On a side note, wrt. `ref isn't always faster` (due to the
indirection): it's almost always faster on Windows 64, as all
value types > 64 bit (excluding vectors for the vectorcall
convention, but let's keep things simple) need to be passed by
reference (ABI requirement). What this means and what keeps on
being ignored is that passing a D value type > 64 bits by value
(to allow rvalue args, although the parameter is a read-only one)
yields the worst of both worlds - a bitcopy of the original
argument passed by reference.
