llvm dev - Mar 2014 - [LLVMdev] Contributing the Apple ARM64 compiler backend

Hi Renato,
>> 2. Test it. Benchmark it. Explore it. Get data for the community to
work with about the state of the back end. ARM has some excellent data that will
help guide us here.
>
> Count me in. Would that be a different triple? arm64-linux-gnu?
Yep. "--target arm64-linux-gnu" should behave basically the same as
aarch64-linux-gnu, except ending up in the ARM64 backend. Complete
with the usual issues of finding your toolchain's includes & libs;
we've not solved that.

Cheers.

Tim.

----- Original Message -----
> From: "Tim Northover" <t.p.northover at gmail.com>
> To: "Renato Golin" <renato.golin at linaro.org>
> Cc: "LLVM Developers Mailing List" <LLVMdev at cs.uiuc.edu>
> Sent: Friday, March 28, 2014 3:47:49 PM
> Subject: Re: [LLVMdev] Contributing the Apple ARM64 compiler backend
> 
> Hi Renato,
> >> 2. Test it. Benchmark it. Explore it. Get data for the community
> >> to work with about the state of the back end. ARM has some
> >> excellent data that will help guide us here.
> >
> > Count me in. Would that be a different triple? arm64-linux-gnu?
> 
> Yep. "--target arm64-linux-gnu" should behave basically the same
as
> aarch64-linux-gnu, except ending up in the ARM64 backend. Complete
> with the usual issues of finding your toolchain's includes & libs;
> we've not solved that.
Is a different target triple the right thing to do here? I think that would
introduce a ton of user confusion. How about we keep the target triples as they
are, and add some other way to choose the desired backend?

 -Hal
> 
> Cheers.
> 
> Tim.
> _______________________________________________
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> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory

On Fri, Mar 28, 2014 at 2:31 PM, Hal Finkel <hfinkel at anl.gov> wrote:
> ----- Original Message -----
> > From: "Tim Northover" <t.p.northover at gmail.com>
> > To: "Renato Golin" <renato.golin at linaro.org>
> > Cc: "LLVM Developers Mailing List" <LLVMdev at
cs.uiuc.edu>
> > Sent: Friday, March 28, 2014 3:47:49 PM
> > Subject: Re: [LLVMdev] Contributing the Apple ARM64 compiler backend
> >
> > Hi Renato,
> > >> 2. Test it. Benchmark it. Explore it. Get data for the
community
> > >> to work with about the state of the back end. ARM has some
> > >> excellent data that will help guide us here.
> > >
> > > Count me in. Would that be a different triple? arm64-linux-gnu?
> >
> > Yep. "--target arm64-linux-gnu" should behave basically the
same as
> > aarch64-linux-gnu, except ending up in the ARM64 backend. Complete
> > with the usual issues of finding your toolchain's includes &
libs;
> > we've not solved that.
>
> Is a different target triple the right thing to do here? I think that
> would introduce a ton of user confusion. How about we keep the target
> triples as they are, and add some other way to choose the desired backend?
>
I share your concern. However, I suspect that a) we will always have at
least an alias as both triples are probably in use at this point, and b) it
won't be the end of the world to have two triples for the same arch long
term. amd64 and x86_64 wasn't the end of the world either. ::shrug::
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Hi Hal,
> Is a different target triple the right thing to do here? I think that would
introduce a ton of user confusion. How about we keep the target triples as they
are, and add some other way to choose the desired backend?
In the short term, it's almost essential. Both of these targets are
going to be existing simultaneously for a while and all the LLVM tools
(for testing if nothing else) are setup to select the target based on
the triple.

Longer term we want a single backend (probably in the AArch64
directory since that's the official name). Theoretically, we could
drop "arm64" as a triple then (provided Clang still supported
"-arch
arm64" for compatibility), but in reality it would be a little odd if
"-arch arm64" worked but "--target arm64" didn't. I
suspect arm64 and
aarch64 will just become synonyms at that point.

Cheers.

Tim.