System programming in D (Was: The God Language)

[Vladimir Panteleev]

On Thursday, 29 December 2011 at 14:44:45 UTC, Don wrote:
>> http://www.danielvik.com/2010/02/fast-memcpy-in-c.html . It 
>> doesn't even
>> use inline assembler or compiler intrinsics.
>
> Note that the memcpy described there is _far_ from optimal. 
> Memcpy is all about cache effciency. DMD translates memcpy to 
> the single instruction "rep movsd" which you'd think would be 
> optimal, but you can actually beat it by a factor of four or 
> more for long lengths.

I've never seen DMD emit rep movsd. Does rep movsd even make 
sense when the memory areas do not have the same alignment? 
memcpy in snn.lib has a rep movsd instruction, but there's lots 
of other code (including what looks like Duff's device).