[LLVMdev] Support of arbitrary bit-width types in LLVM backend

[Adam Husar]

Hello everyone!

   We are currently trying to add support e.g. for 24-bitm or 40-bit  
integers to the LLVM backend.
Such datatypes are very useful for diverse areas such as DSP applications,
where the programmers and processor designers can optimize the area and  
power by using
narrower data types.

   We already added attribute bitwidth support to the clang. This attribute  
specifies
a bitwidth of an integer. We can share the implementation it if someone  
would be interested.

   Regarding the backend, it will be more complex, so I would like to ask  
for some guidelines
and ideas, how can be this done. E.g. if there are some "tricks" how to  
add a variable-bitwidth
integer type to the backend system, or it is better to add separate types  
for i24, i40, etc.
Also, what should we be careful about.


Thank you very much
   Adam