[LLVMdev] Please review my patch to make GHC calling convention work on ARM

[David Terei]

Hi Steve,

I'm not an LLVM developer but am the author/maintainer of the LLVM
backend in GHC.

The patch looks mostly good to me (although I am not that familiar
with ARM so could easily have missed something). My main concern is
why are you avoiding using the R0 - R3 registers?

Also, could you please update me on the status of this work. I assume
you are getting GHC running in registerised mode on ARM. There is also
a guy called Karel Gardas (karel.gardas at centrum.cz) who is working on
this as well and making good progress. Would be good (off this mailing
list though) to all get in contact.

Cheers,
David

On 30 June 2011 17:16, Stephen Blackheath [to LLVM-dev]
<effusively.proffer.stephen at blacksapphire.com> wrote:
> All,
>
> I would like to submit the attached patch, which allows the GHC (Glasgow
> Haskell Compiler) calling convention to work on ARM targets.
>
> Could some nice person please review this code, so I can move towards
> getting it committed?
>
> I have thoroughly tested this patch again GHC on a Debian-ARM (armel)
> system.  Unfortunately my understanding of LLVM is limited, so it's likely
> I'm not doing things the best way.
>
> Some explanation:
> In the GHC calling convention, all calls are "tail calls" (really just
> jumps) and there is no returning. The meanings of the registers are
> determined by the GHC compiler. GHC calling convention code must not touch
> the stack pointer, because that's used to preserve the state for our return
> to C-land. Jumps between C and GHC are implemented directly in assembly
> language so LLVM doesn't have to deal with them.
>
> So, I disabled the generation of prologues and epilogues, and I found that I
> also needed to tell it that there are no callee-saves registers in the GHC
> calling convention.
>
> Thanks very much and keep up the excellent work, everyone!
>
>
> Steve
>
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