GCC middle-end

[Thomas Lavergne]

Dear all,

I would like to have a brief chat in order to understand (roughly) the 
way gcc deals with optimization and language-independent function's 
representation. I read already some documents (not the gcc internal doc) 
and am aware of GENERIC, GIMPLE, tree SSA but I am  not confident on 
several points:

*) is GIMPLE truely front-end independent (no nore specific hacks)?
*) are all tree SSA optimizations run on individual function's GIMPLE 
trees or do some start at GENERIC level?
*) are all front-end designed to pass GENERIC to the middle-end (which 
then gimplify) or do some directly provide GIMPLE trees?
*) are the various function's GIMPLE tree the only structure that the 
middle-end needs to write back-end code or are there other data that 
should be created/obtained from the front-end?
*) is there a tool to browse the gimpled tree of your functions (before 
and after some optimizations)?

I rapidly saw an option to dump the generic/gimpled tree to a C form. 
(-fdump-generic-tree). Do you think it is theoretically possible to 
design "inverse front-end" which would translate the gimple tree to a 
selected language (transforming C++ code to C, C99 to C89, fortran95 to 
C,...)? An other way of putting this, is: did we loose information or 
can a smart tool recover from gimplifying? Are some open source projects 
already looking at these aspects?

I am sorry, these are a lot of questions. You can point me to any 
forum/mailing list archive or document: I can learn by myself. Are gcc's 
internal documentation available somewhere (without installing the gcc 
grom source)?

Thank you,
Thomas