[fpc-devel] Patch to speed up Uppercase/Lowercase functions

[Christian Iversen]

On Saturday 11 June 2005 00:02, Joost van der Sluis wrote:
> > > I don't know if rtl-optimilisation patches have a large priority, but
> > > nevertheless this patch improves the speed of the sysutils.uppercase
> > > and lowercase functions.
> >
> > I fail to see how changing a while loop to a for loop improves speed ?
> > I could understand if you'd use a PChar and use pointer math, but not
> > this ?
>
> I wasn't completely sure, so i made a test-prog which called the function
> 50.000 times, and measured the time it took to run a few times.
>
> And then again with the other version. (approx 2.5 sec against 1.4)
>
> And I think it's because the removal of the begin/end. And Peter always
> says that you can't change the running variable in a for-loop because of
> the optimilisations... So i suppose that a for-loop has several
> optimilisations which a while doesn't...

While this is _potentially_ true of a for-loop, don't expect it to hold in 
every situation. (and trust me, it's _certainly_ not because of the begin-end 
removal)

-- 
Regards,
Christian Iversen