SIMPLE: A language-independent tree IR

[law@redhat.com]

> On Jan  6, 2002, Alexandre Oliva <aoliva at redhat dot com> wrote:
  > But rtl does not have a simple representation for switch,for,do {}while,
  > AFAIK.  SIMPLE has high-level control structures compared to RTL.  
Functions
  > for expanding these to rtl can be shared by front ends.
True, but the whole point behind a higher level RTL was to standardize
how everything is represented earlier in the compiler in order to make
writing optimizers which are easier to understand and hopefully work better
than the stuff we've currently got.

jeff