[RFC] How to add vector math functions to Glibc

[Carlos O'Donell]

On 09/26/2014 12:08 PM, H.J. Lu wrote:
>> I think this chioce may actually be larger than just Intel.
>>
>> For example IBM, and particularly their Power vector math
>> functions were explained to me as being callable directly
>> by developers. Thus Power might want libmvec.so in glibc?
> 
> Does Power have the same API as x86?  If not, how will they
> be used by programmers?

Power does not have the same API.

I expect that David Edhelson was talking about these:
http://pic.dhe.ibm.com/infocenter/compbg/v121v141/index.jsp?topic=%2Fcom.ibm.xlcpp121.bg.doc%2Fproguide%2Fvector.html

Though I haven't verified.

> Again, we need to decide
> 
> 1. Who is the main user.

Normal developers.

> 2. How it is used by the main user.

They call those functions.

> 3. What is the impact on the programmers.

If the functions are in glibc, we can deploy them independent
of compiler.

> If we put it in GLIBC, we should have a API with a generic
> implementation and each target can have optimized implementation.

I disagree.

Each target will likely have two APIs:

(a) The legacy API supported for compatibility with existing
    applications following the existing published APIs.
    e.g. IBM and Intel vector functions.

(b) A generic GNU implemetnation that all targets can have.

We aren't even talking about (b) yet.

Cheers,
Carlos.