Re: ticket for adding ARM backend to NCG?

On 03/01/14 12:37, Simon Peyton-Jones wrote:

| I've been tinkering with ARM NCG idea for quite some time now, but | honestly I've been always in doubts if it's the best way for GHC at all. | I've thought that the plan was to kind of move out of NCG to LLVM based | backends and I've though that although this plan may be kind of stuck | now, it's still on the table.

I have not been following the ARM and LLVM threads very closely, but here's my take:

* LLVM is (I hope) very much on the table. LLVM itself is a well-resourced project, and we can expect it to continue to exist. We should piggy-back on all the hard work that is going into it.

* But using LLVM has some disadvantages. a) it imposes a dependency on LLVM b) it makes compilation slower

Correct

c) we play some efficiency tricks (notably "tables next to code") that LLVM can't play (yet). I think.

Actually we have to generate tables-next-to-code from LLVM too, because the LLVM and NCG backends must be compatible (you can choose to use LLVM on a module-by-module basis using -fllvm). So tables-next-to-code is currently done using a post-processing step on the asm generated by LLVM. Cheers, Simon

So GHC currently aims to have a built-in NCG for popular platforms, and to rely on LLVM for more esoteric platforms and also for superior optimisation.

Is this still a sensible policy?

Maybe you can articulate your doubts on the ARM NCG?

Simon

| -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Karel | Gardas | Sent: 03 January 2014 11:24 | To: Jens Petersen | Cc: ghc-devs@haskell.org | Subject: Re: ticket for adding ARM backend to NCG? | | | Guys, | | I've been tinkering with ARM NCG idea for quite some time now, but | honestly I've been always in doubts if it's the best way for GHC at all. | I've thought that the plan was to kind of move out of NCG to LLVM based | backends and I've though that although this plan may be kind of stuck | now, it's still on the table. | | Yes, I know that GHC is volunteering effort so if someone comes and asks | for an ARM NCG implementation merge it'll be probably done in some time, | but I'm not sure if it's what's the most welcome at the end. | | Just some of my doubts about it... | | I would really appreciate some authoritative word about the topic from | more involved GHC developers... I mean especially about NCG future... | | Thanks! | Karel | | On 01/ 3/14 09:35 AM, Jens Petersen wrote: | > On 3 January 2014 03:10, Corey O'Connor mailto:coreyoconnor@gmail.com> wrote: | > | > My interest is just to get involved somehow in the NCG. Starting a | > new backend seemed reasonable only because I couldn't break | > something that didn't exist. ;-) | > | > | > Well a big +1 from me for armv7 NCG. | > | > | > _______________________________________________ | > ghc-devs mailing list | > ghc-devs@haskell.org | > http://www.haskell.org/mailman/listinfo/ghc-devs | | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-devs _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://www.haskell.org/mailman/listinfo/ghc-devs