[Haskell-cafe] haskell on llvm?

[Thomas Schilling]

On Thu, 2007-09-13 at 15:55 -0700, brad clawsie wrote:
> has anyone ever considered using llvm as a infrastructure for haskell
> compilation? it wold seem people are looking at building frontends for
> scheme, ocaml, etc. i don't know if an alternate backend is
> appropriate, but it would seem to be an interesting way to aggregate
> the best thinking for various optimizations over a more diverse group
> of developers.

I applied for Google Summer of Code with the suggestion to write a
library to generate (and compile) LLVM code (not my idea in the first
place, but I liked it), but it didn't get into the top 9 (i.e., funded)
projects.  It's certainly not a bad idea, but the immediate use to the
community would admittedly not be too great.  Targeting an existing
Haskell compiler would probably be doable, but I am unsure what the big
advantages would be.  Many optimizations implemented for llvm are more
high-level in nature and wouldn't make much sense for Haskell compilers,
since translating to llvm would lose some information, and Haskell,
being a lazy language, requires/enables non-standard transformations.
Haskell-compilers currently require better low-level optimizations
(instruction scheduling, register allocation, maybe memory locality
optimazitions).  I'm not up to date with how well llvm scores in these
areas, but last time I checked it was slower than ghc, and ghc already
isn't too great at this kind of stuff (compared to icc).

I could however see some applications of an llvm-generation library for
DSLs that require high performance, and currently have to invoke gcc at
runtime.

/ Thomas