Re: [PATCH] Fix type correctness of fold_indirect_ref

[Steven Bosscher <stevenb at suse dot de>]

On Tuesday 17 May 2005 01:09, Mark Mitchell wrote:
> Andrew Pinski wrote:
> > This is where I am going to say, lets define a type system then because
> > right
> > now the middle-end does this which is wrong.
>
> I agree, better typing rules would be nice.
>
> >> Furthermore, the C++ front end probably shouldn't be doing this kind
> >> of optimization anyhow; we really want it to be faithful to the source
> >> representation to the extent reasonable.  (See extensive previous
> >> discussions on this point.)  It may be that the C++ gimplifier should
> >> be doing this, but not the front end proper.
> >
> > I am going to say the C++ front-end should not using trees
>
> That's orthogonal.  There's no reason you can't write a great front end
> using trees.

But it is hard to write a great back end using trees when at least one
front end has its own set of rules about using trees.

> The biggest negative -- and one of the reasons that both 
> Fortran and Ada do not do it that way -- is that using trees does tie
> you to the rest of GCC.

...and the other way around.  Right now, _only_ g++ is in the way of
some of the major cleanups we could do to the tree data structures,
because the rest of GCC is tied to G++ via trees.

G++ abuses trees in horrible ways by linking together trees of different
kinds (e.g. TREE_LISTs, *_DECLs, and OVERLOADs) and also by overloading
many tree fields (e.g. TREE_TYPE).  This makes cleaning up some fields
in the existing tree structures a tough job.

G++ also needs to define a lot of language-specific tree nodes because
it wants a representation that is close to the source code.  This means
we risk running out of tree codes.  Right now Obj-C++ defines 221 tree
codes and we have room for 255.  With OpenMP codes and further tree
optimizer codes still coming up.

(The current situation is still better than a few months back, when
Obj-C++ defined 246 tree codes...)

Not that I can blame you, trees were there before the tree optimizers...

Gr.
Steven