Returning large structs == bad

[Tim Burrell]

downs wrote:
> Another interesting observation.
> 
> If I change all my opFoo's to opFooAssign's, and use those instead, speed goes up from 16s to 13s; indicating that returning large structs (12 bytes/vector) causes a significant speed hit. Still not close to the C++ version though. The weird thing is that all those ops have been inlined (or so says the assembler dump). Weird.
> 
>  --downs

Yeah, I was about to say the same.  See here:

http://paste.dprogramming.com/dpolmzhw

It's ugly, but no struct returning.

On my machine it's about a second slower than g++ (8.9s vs. 7.8s)
compiled via:

gdc -fversion=Posix -fversion=Tango -O3 -fomit-frame-pointer -fweb
-frelease -finline-functions

and

g++ -O3 -fomit-frame-pointer -fweb -finline-functions

There's probably some other optimizations that could be made.  But
really I think this comes down to the compiler not being as mature.  The
stuff that I did should all be done by an optimizing compiler.  You're
basically tricking the compiler into moving less bits around.

Tim.