Re: LLVM--Low Level Virtual Machine--and Ada

[Duncan Sands <baldrick@free.fr>]

> > That's not quite true, as the use of displays rather than static links would
> > allow up-level access without any fat pointers.
> 
> I don't get it (how displays help, here).  If you have displays instead
> of static links, you need to pass display, or pointers to them.

I was wondering the same thing.

> >> Trampolines are not efficient!  Because after writing the code, the
> >> instruction cache needs to be flushed before calling the thing -- that
> >> is expensive on modern machines.
> >
> > True. Thunks have similar issues in that the address of the thing isn't
> > known before the call (so there is a pipeline stall), but at least we don't
> > have to flush the cache. And there sometimes is the possibility of in-lining
> > the call (something we don't currently do, but it is on the radar).
> 
> Trampolines are worse than thunks, efficiency-wise.
> 
> But it's only in Ada 2005 that it started to matter much.

In programs that use Ada.Containers heavily, my profiling tools regularly
show "code on the stack" (i.e. trampolines) as where the program is spending
most of its time.

Ciao,

Duncan.