Optimize handling of inline summaries

[Jan Hubicka]

> On 11/4/19 3:12 PM, Jan Hubicka wrote:
> > Martin, do you know why this flag was introduced?
> 
> Hi.
> 
> The flag is used in IPA CP:
> 
> call_summary <edge_clone_summary *>
> 
> class edge_clone_summary
> {
> ...
>   cgraph_edge *prev_clone;
>   cgraph_edge *next_clone;
> }

I see, so it is there to collect chains of duplications. I suppose it
makes sense even though it is bit unexpected use of summaries (I suppose
I approved it :)

In this case we want to more know that something was duplicated and
trigger creation. There are other cases where we do not want to
duplicate in all siutations (like when inline clone is created).
I was wondering about adding duplicate_p function which will by default
return true if source summary exists and which one can overwrite with
different behaviour.  What do you think?

Honza