Cgraph Modification Plan

[Jan Hubicka]

> On 9/5/12, Xinliang David Li <davidxl@google.com> wrote:
> > On Sep 5, 2012 Jan Hubicka <hubicka@ucw.cz> wrote:
> > > OK, the basic idea is that symtab_node is basetype of
> > > cgraph_node and varpool_node.  We may want to drop the historica
> > > cgraph/varpool names here, since function_node/variable_node
> > > would sound better. Cgraph still exists, but varpool is more
> > > or less historical relic.
> >
> > The cgraph redesign probably deserves more discussion.
> 
> Hence, the post!
> 
> > 1) It may be worthwhile to abstract the graph manipulation code
> > into a utility class which is templatized.
> >
> > graph<T>, node<T> with node inheriting from T.
> 
> While I won't dispute the statement, getting from here to there
> will likely involve some intermediate steps.

Commonizing some of cfg/cgraph/ssa graph handling would not hurt, but
there is not _that_ much code in common - we do some strongly connected
components discovery on all three kinds of graphs and basic traversals.
> 
> > 2) Introduce a global symbol table containing a function table
> > and a global variable table. The function table should replace
> > the current cgraph node link list, and the variable table replaces
> > the varpool.  The symbol table should provide basic interfaces to
> > do named based lookup, traversal, alias handling etc.  I noticed
> > trunk already has some of that -- but it seems more abstraction
> > is needed.
> 
> Do you mean moving away from a pointer-based approach?

I would say that trunk now have what is described here.  I still plan to unify
some of code (like alias handling) that is split for historical reasons, but
those are mostly cleanups still intended for 4.8.

Honza