Re: tree decl stored during LGEN does not map to a symtab_node during WPA

[Erick Ochoa <eochoa@gcc.gnu.org>]

> > > 1. pid of lgen process that generated the encoding
> > > 2. index returned by lto_symtab_encoder_encode
> > > 3. varpool_node->name ()
> > > 4. the pointer address being pointed by varpool node
>
> Well, yes, during LGEN no WPA has run.  Do you mean LTRANS after WPA?
> Sure, the encoder numbers do not have to match up between different
> LTRANS units but then they don't speak to each other so that shouldn't
> matter, no?

No. I mean during WPA. On a different e-mail I clarified the following:

```
>
> fopen $PID1 8 $ADDR1
> fopen $PID2 7 $ADDR2
>

Just to clarify a bit further. $PID is generated and stored during
LGEN. The encoding is obviously generated during LGEN.
These are read during WPA. And the encoding is decoded and dyn_casted
into a cgraph_node at WPA time.
All these are printed during WPA.
```

>
> I _think_ that it should work if you stream at LGEN constraint variables
> as their varpool node (using the varpool encoder), get the nodes merged
> at WPA time, and thus your constraints from different LGEN runs "merged"
> properly, then stream them the same way to the LTRANS units?
>

The only reference to a varpool encoder is on the Changelog. The only
encoder I know of is the symtab_encoder (which I believe should be the
same as varpool_nodes and cgraph_nodes are both symtab_nodes). But
again, I do not know what you mean by "merged" here, since they have
different addresses.

>
> And the same solution should exist.  For "merged" function definitions
> (like multiple same inline definitions) you'd simply drop all but one set of
> constraints.
>

Yes, this is what I would like, but I don't see how to detect "merged"
function definitions. I can get their cgraphs but as I mentioned for
every encoding I decode and dyn_cast all I get is a cgraph holding a
different address. What does "merged" concretely mean?