Re: [RFC/patch] Callgraph based inlining heuristics

[Jan Hubicka <jh at suse dot cz>]

> On Mon, 23 Jun 2003, Jan Hubicka wrote:
> 
> > > >very much from cse/gcse if you remove all calls inside a loop by
> > > >leafifying it for my scientific C++ application (POOMA based). Also
> > > >the loop optimizer could probably do better in this case (it doesnt, but
> > > >thats another problem). And I never want the compiler to do so much
> > > >inlining without telling it explicitly (of course some profile feedback
> > > >on the resulting asm code speed/size would really cut it).
> > > >
> > > That is what we should be aiming for instead: Find a way to include some
> > > kind of profile information to guide inlining.  What I would really like
> >
> > I am aiming towards this with the current cfg code cleanups.  I hope to
> > be able to preserve CFG over post-treeSSA branch RTL expander and be
> > able to read profile in much easier than we do right now.  Then we can
> > propagate the frequencies into the callgraph.
> >
> > How much of inlining do you actually need in your application?   Perhaps
> > improving the heuristics further will help it to get it without
> > additional hints?
> 
> The code I have is about
> 
> void kernel(Array1, Array2, ...) {
>  ..setup..
>  for (int k=...)
>   for (int j=...)
>     for (int i=...)
>       very_large_function(Array1, Array2, Array3,... , i, j, k);
> }
> 
> and very_large_function does a _lot_ of function calls that need to be
> inlined due to C++ abstraction (these are small functions where we should
> be able to get these inlined with sane heuristics -- I currently hit the
> artificial total inlining limit here (see PR10679)!!). For the loop
> optimizer (and cse/gcse!) to do its work, we need to inline very_large_function. As you
> may expect there is a lot of index arithmetic to be optimized (and even
> with inlining it doesnt look as good as it could).

Hmm, can you please send me preprocessed file of this thing?  I would be
interested how my curent code behaves on this.
I've killed the current total limit (and introduced different :) so
perhaps it can work now.

Honza
> 
> So here, specializing the inliner for inlining a call in a loop consisting
> only of a call would cut it. But this is another speciality, just as
> __attribute__((leafify)).
> 
> Richard.
>