[Aarch64] Vector Function Application Binary Interface Specification for OpenMP

Sekhar, Ashwin Ashwin.Sekhar@cavium.com
Mon Mar 20 04:30:00 GMT 2017

On Friday 17 March 2017 07:31 PM, James Greenhalgh wrote:
> On Wed, Mar 15, 2017 at 09:50:18AM +0000, Sekhar, Ashwin wrote:
>> Hi GCC Team, Aarch64 Maintainers,
>> The rules in Vector Function Application Binary Interface Specification  for
>> OpenMP
>> (https://sourceware.org/glibc/wiki/libmvec?action=AttachFile&do=view&target=VectorABI.txt)
>> is used in x86 for generating the simd clones of a function.
>> Is there a similar one defined for Aarch64?
>> If not, would like to start a discussion on the same for Aarch64. To  kick
>> start the same, a draft proposal for Aarch64 (on the same lines as  x86 ABI)
>> is included below. The only change from x86 ABI is in the  function name
>> mangling. Here the letter 'b' is used for indicating the  ASIMD isa.
> Hi Ashwin,
> Thanks for the question. ARM has defined a vector function ABI, based
> on the Vector Function ABI Specification you linked below, which
> is designed to be suitable for both the Advanced SIMD and Scalable
> Vector Extensions. There has not yet been a release of this document
> which I can point you at, nor can I give you an estimate of when the
> document will be published.
> However, Francesco Petrogalli has recently made a proposal to the
> LLVM mailing list ( https://reviews.llvm.org/D30739 ) which I would
> note conflicts with your proposal in one way. You choose 'b' for name
> mangling for a vector function using Advanced SIMD, while Francesco
> uses 'n', which is the agreed character in the Vector Function ABI
> Specification we have been working on.
> I'd encourage you to wait for formal publication of the ARM Vector
> Function ABI to prevent any unexpected divergence between
> implementations.
Thanks for the information. We at Cavium are also working on libraries 
which requires this ABI specification. So we would like to see this 
published as early as possible.

> Thanks,
> James

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