Where did my function go?

[Jan Hubicka]

> On Tue, Oct 20, 2020 at 1:02 PM Martin Jambor <mjambor@suse.cz> wrote:
> >
> > Hi,
> >
> > On Tue, Oct 20 2020, Richard Biener wrote:
> > > On Mon, Oct 19, 2020 at 7:52 PM Gary Oblock <gary@amperecomputing.com> wrote:
> > >>
> > >> Richard,
> > >>
> > >> I guess that will work for me. However, since it
> > >> was decided to remove an identical function,
> > >> why weren't the calls to it adjusted to reflect it?
> > >> If the call wasn't transformed that means it will
> > >> be mapped at some later time. Is that mapping
> > >> available to look at? Because using that would
> > >> also be a potential solution (assuming call
> > >> graph information exists for the deleted function.)
> > >
> > > I'm not sure how the transitional cgraph looks like
> > > during WPA analysis (which is what we're talking about?),
> > > but definitely the IL is unmodified in that state.
> > >
> > > Maybe Martin has an idea.
> > >
> >
> > Exactly, the cgraph_edges is where the correct call information is
> > stored until the inlining transformation phase calls
> > cgraph_edge::redirect_call_stmt_to_callee is called on it - inlining is
> > a special pass in this regard that performs this IPA-infrastructure
> > function in addition to actual inlining.
> >
> > In cgraph means the callee itself but also information in
> > e->callee->clone.param_adjustments which might be interesting for any
> > struct-reorg-like optimizations (...and in future possibly in other
> > transformation summaries).
> >
> > The late IPA passes are in very unfortunate spot here since they run
> > before the real-IPA transformation phases but after unreachable node
> > removals and after clone materializations and so can see some but not
> > all of the changes performed by real IPA passes.  The reason for that is
> > good cache locality when late IPA passes are either not run at all or
> > only look at small portion of the compilation unit.  In such case IPA
> > transformations of a function are followed by all the late passes
> > working on the same function.
> >
> > Late IPA passes are unfortunately second class citizens and I would
> > strongly recommend not to use them since they do not fit into our
> > otherwise robust IPA framework very well.  We could probably provide a
> > mechanism that would allow late IPA passes to run all normal IPA
> > transformations on a function so they could clearly see what they are
> > looking at, but extensive use would slow compilation down so its use
> > would be frowned upon at the very least.
> 
> So IPA PTA does get_body () on the nodes it wants to analyze and I
> thought that triggers any pending IPA transforms?

Yes, it does (and get_untransormed_body does not)

Honza
> 
> Richard.
> 
> > Martin
> >