[llvm-dev] LLVM: mapping unoptimized IR back to clang AST

[Tomas Kalibera via llvm-dev]

Hi,

I would like to rewrite a C program based on analyzing the LLVM IR of 
that C program, produced by CLANG. Did anyone have any hints on how to 
map the IR back to CLANG AST?

Can I do better than invoking clang with "-g -O0" to produce an IR for 
this task? (can I get more debug info, disable more optimizations?)

The debug info in LLVM IR does not seem to have information on C macros 
(while CLANG AST does) - is there a way to get that information from the IR?

Is it possible to add some custom meta-data to CLANG AST nodes that 
would somehow propagate through CLANG to the LLVM IR?
I could think of wrapping some AST nodes into dummy function calls, but 
that seems rather crude.

Indeed, some analysis can also be done at AST level, but it seems to me 
that it is easier to do at the IR level. Also the IR level has linking 
information, one can do inter-procedural analyses.

Thanks
Tomas