LLVM IR influence on compiler debugging

[Sönke Ludwig]

I implemented a compiler back end with LLVM some time ago. The IM helped 
a lot in both, spotting errors in IM codegen and issues with target 
codegen (e.g. because of some misconfiguration). You always have the 
high level IM available as text and the unoptimized target assembler 
usually is pretty similar to the IM code and thus provides a great guide 
deciphering the assembler.

Also the fact that you can output and modify a module as IM code to try 
certain things is really useful sometimes.