[RFC] Design issues with multiple IRs

[Joseph S. Myers]

On Thu, 6 Dec 2001, Diego Novillo wrote:

> Should files dealing with tree transformations go into a
> different directory?  Right now, the trees are closely tied to
> the front-end.  In the future I'd like to start introducing trees
> that are more language independent.
> 
> For the current analyses and transformation I was thinking that
> we could keep the current setup.  The tree-* files in the main
> directory deal with the C front-end, each language directory
> would need its own set of files.

I don't see any need to use extra subdirectories for each internal
representation.  Subdirectories directly under gcc/ for front ends (with C
moved to such a directory) should suffice.

It is a bug when any tree-* files depend on any c-* files.  Enough
infrastructure for functions as trees should be language-independent that
such dependencies do not occur.

> But that doesn't fix the problem of what to do with common code.
> We will likely have a lot of tree code that can be shared among
> the different front-ends.  Maybe we should start putting common
> code in tree-* and have C-specific files in c-tree-*?

C tree handling (in c/*.c, say) ought in principle to be lowering
C-specific trees to language-independent ones (with explicit ordering and
aliasing constraints represented in the latter).

-- 
Joseph S. Myers
jsm28@cam.ac.uk