RFC: Update Intel386, x86-64 and IA MCU psABIs for passing/returning empty struct

[Michael Matz via cfe-commits]

Hi,

On Thu, 11 Feb 2016, Jonathan Wakely wrote:

> On 11 February 2016 at 12:40, Matthijs van Duin wrote:
> > You never define "POD for the purposes of layout", and I can only
> > interpret it as being equivalent to "standard-layout".
> 
> As Richard pointed out, it's defined in the C++ ABI.

Which is C++y as well (and hence doesn't in itself solve the C/C++ 
compatibility we should strive for in the ABI).  I'll concur with Matthijs 
and think that trivially copyable is the correct distinction for passing 
without registers (in addition of it being clearer than a strangly defined 
concept of "POD-but-not-quite-POD").  Do you think different?  Are there 
non-trivially copyable examples that we'd wish to pass without registers 
as well?


Ciao,
Michael.