[tree-ssa] GENERIC and GIMPLE documentation

[Geert Bosch]

I'm studying the GCC Internals manual from the tree-ssa branch.
Although Chapter 7 describes the high-level process of going
from language-specific trees to GENERIC, then lowering to GIMPLE
and finally going through the various SSA and non-SSA passes
is described in sufficient detail, there seems to be no
information on the GENERIC and GIMPLE representations themselves.

Chapter 8 describes C and C++ front end specific trees, but
there seems to be a complete disconnect with tree-ssa.

Chapter 9, which deals with analysis and optimization of
GIMPLE trees starts with a small introduction that
refers to "the chapter describing GENERIC and GIMPLE" for
more details.

I wonder where this chapter is... can anyone give some pointers?
This seems a major piece of documentation that definitely should
be in the GCC Internals manual before the merge.

   -Geert