what about a compiler probe?

[Ben Elliston]

> I am considering implementing the following feature into GCC using
> the patch on http://gcc.gnu.org/ml/gcc-patches/2006-11/msg01769.html
> : a compiler probe which permits to probe the run of a compilation,
> e.g. by displaying in emacs or a graphical GTK application the
> current pass, Gimple representations, etc..

What you're describing sounds a bit like the VISTA interactive
compilation environment which allows users to dynamically adjust the
optimisation regime of individual functions and examine the effect:

  http://citeseer.ist.psu.edu/433065.html

Ben