Is NRVO part of the spec?

[Peter Alexander via Digitalmars-d]

I'm writing a blog post about why we don't need rvalue references 
in D. It seems that we rely on NRVO being performed, not just as 
an optimization, but for correct semantics (e.g. for objects 
without destructors or postblits). This doesn't appear to be 
documented anywhere.

Is it meant to be part of the spec?
Relevant issues:
See: https://issues.dlang.org/show_bug.cgi?id=10372
https://issues.dlang.org/show_bug.cgi?id=12180