GHC API: Access to nativeCodeGen?

[Simon Marlow]

On 04 July 2005 12:44, Peter A Jonsson wrote:

> dons at cse.unsw.edu.au (Donald Bruce Stewart) writes:
>> pj:
>>> I would like to use nativeCodeGen outside of GHC to generate code
>>> from an IR. The IR would be produced by a third party program, not
>>> the GHC frontend. 
>>> 
>>> Looking at CVS HEAD I can see that GHC.hs exports plenty of things
>>> (for the GHC API I presume), but I can't find anything that lets me
>>> input some sort of IR and have ASM in return. Am I missing it
>>> somewhere or is there no way to input IR and get ASM in return? If
>>> there isn't, is such a feature planned/wanted?
>>> 
>>> If such a feature isn't planned, I would appreciate any ideas on how
>>> to to accomplish the same thing. I have no problems with having a
>>> build tree of GHC laying around if that makes things easier. It
>>> would be a nice bonus if it made my maintenance burden low.
>> 
>> You could use External Core with GHC, couldn't you?
> 
> Thanks for the quick answer!
> 
> Maybe it's my lack of understanding of the inner workings of GHC but
> reading "An External Representation for the GHC Core Language" I get
> the impression that the dumping of Core Language is basically targeted
> at researchers writing their own optimization passes or backends for
> Haskell/GHC so they can use the existing infrastructure of GHC. My
> request is the other way around - I want to throw out the frontend but
> use* ("low-level") parts of the backend of GHC.
> 
> The Core Language seems to be translated into STG-machine code, which
> according to my understanding is an abstract machine desinged to
> support non-strict higher-order functional languages. I was hoping
> that the laziness was in the STG-syntax, not in Cmm. Looking at output
> of -ddump-cmm it resembles C-- quite closely (also implied by comments
> in PprCmm.hs), which makes me believe that is the "correct" level of
> abstraction for me.
> 
> *) The reasons are two-fold, one is that it is written in Haskell, the
>    other is that it generates code for more than one architecture
>    today.

If the language you want to generate code for is at the level of C--,
then you could indeed use GHC's native code generator.  There isn't an
interface to it exposed by the GHC API, but you can use the interfaces
directly: the AsmCodeGen module is the top-level of the native code
generator, and basically takes Cmm (defined in module Cmm) and produces
assembly code.

However, if you want to do this, I wonder whether you would be better
off just using the real C-- compiler.

Cheers,
	Simon