Re: [patch, fortran] Make frontend walker more general

[Jakub Jelinek <jakub at redhat dot com>]

On Sat, Sep 11, 2010 at 11:00:30PM +0200, Thomas Koenig wrote:
> > Furthermore, I think having process_pointer_assign etc. special hooks
> > is not the right thing for a walker.  IMNSHO you should look e.g. at
> > walk_tree or perhaps better walk_gimple_stmt.
> > The walker should call one hook (which takes gfc_code *) at each gfc_code
> > node, and another hook at each gfc_expr node.  The API should have a way
> > to stop processing and return some value to the caller, have some void *
> > pointer passed to the callbacks in which the caller can keep some state,
> > and have a way how to say that subtrees shouldn't be traversed.
> 
> Why would this be better?
> 
> Given the complexity of Fortran, wouldn't this lead to lots of code
> duplication, with a big switch statement both in the statement walker
> and the handler for the individual statements?

Because otherwise it isn't a general Fortran FE walker, but quite
specialized one, and each time you need to handle some code that doesn't
have a hook or where the hook doesn't have generic enough argument,
you will need to modify the walker.

I believe in most cases you'll be looking only at a handful of different
codes, so even if you use a switch stmt in the hook, it will be small enough
that it will be implemented using a series of ifs.

	Jakub