On Sat, Jul 04, 2020 at 09:07:35AM -0400, Brian Brombacher wrote:
>
> >> On Jul 1, 2020, at 1:14 PM, gwes <g...@oat.com> wrote:
> >>
> >> On 7/1/20 8:05 AM, Luke Small wrote:
> >> I spoke to my favorite university computer science professor who said
> >> ++n is faster than n++ because the function needs to store the initial
> >> value, increment, then return the stored value in the former case,
> >> while the later merely increments, and returns the value. Apparently,
> >> he is still correct on modern hardware.
> > For decades the ++ and *p could be out of order, in different
> > execution units, writes speculatively queued, assigned to aliased registers,
> > etc, etc, etc.
> >
> > Geoff Steckel
>
> Hey Luke,
>
> I love the passion but try to focus your attention on the fact that their are
> multiple architectures supported and compiler optimizations are key here. Go
> with Marc’s approach using arch/ asm. Implementations can be made over time
> for the various arch’s, if such an approach is desirable by the project. You
> can pull a well-optimized version based on your code, for your arch, and then
> slim it down a bunch.
>
> Cheers,
> Brian
>
> [Not a project developer. Just an observer.]
>
>
Another data point for consideration: the pdp11 instruction set had
post-increment and pre-decrement indirect memory reference
instructions. If I'm not mistaken, using pre-increment or post
decrement on this architecture would impose a penalty. So your
university computer science professor making such sweeping statements
maybe doesn't deserve to be your favorite.
-Otto
