[Haskell-cafe] Improving GHC's LLVM Backend

[Erik de Castro Lopo]

Alex,

I really suggest you take this to the ghc-devs mailing list.

Cheers,
Erik


Alex Ford wrote:

> Hello,
> 
> I'm interested in improving the LLVM backend of GHC by using the existing
> Haskell LLVM bindings to the C API, as suggested by option 1 in the LLVM
> FAQ:
> http://llvm.org/docs/FAQ.html#i-d-like-to-write-a-self-hosting-llvm-compiler-how-should-i-interface-with-the-llvm-middle-end-optimizers-and-back-end-code-generators
> 
> At the moment, the backend uses the option 2: emitting LLVM assembly code
> which is then assembled to LLVM bitcode, optimised, and compiled to machine
> code by standard LLVM tools. Changing this to use the Haskell FFI bindings
> to the LLVM C API would allow better tracking of any changes to the LLVM
> IR, and hopefully a reasonable speed increase by avoiding the overhead of
> first emitting LLVM Assembly to be assembled.
> 
> 
> In his bachelor's thesis, David Terei considered this approach when
> initially writing the LLVM backend, but dismissed it due to the existing
> Haskell bindings being too large and high level to use with GHC. I have not
> personally looked at the high level Haskell bindings in much depth, but the
> low level (llvm-base) bindings appear to be somewhat incomplete with
> respect to LLVM 3.3. Therefore, I plan to extend the FFI bindings to cover
> more or all of the C API, and then to modify the GHC LLVM backend to use
> these bindings to call into the LLVM libraries directly.
> 
> http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/Backends/LLVMcontains
> a link to David's thesis, as well as documentation of the LLVM
> backend.
> 
> I'd really appreciate it if anyone who knows about the Haskell LLVM
> bindings or about the GHC LLVM backend could give any advice regarding what
> sort of work needs to be done with the LLVM bindings to make them more
> appropriate for use within GHC, or how to approach modifying the existing
> LLVM backend.
> 
> Many thanks,
> Alex


-- 
----------------------------------------------------------------------
Erik de Castro Lopo
http://www.mega-nerd.com/