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Re: [RFC] How to add vector math functions to Glibc


On 09/25/2014 04:03 PM, H.J. Lu wrote:
>> Sorry, I don't understand this part, and perhaps that's why I didn't
>> understand question 7 in the previous post.
>>
>> What does it mean for the vector library to target GCC?
>>
> 
> From
> 
> https://sourceware.org/glibc/wiki/libm#Addition_of_x86_64_vector_math_functions_to_Glibc

Thanks for the pointer. I understand now.
 
> 3.1. Goal
> 
> Main goal is to improve vectorization of GCC with OpenMP4.0 SIMD
> constructs (#2.8 in http://www.openmp.org/mp-documents/OpenMP4.0.0.pdf
> and Cilk Plus constructs (#6-8 in
> http://www.cilkplus.org/sites/default/files/open_specifications/Intel_Cilk_plus_lang_spec_1.2.htm)
> on x86_64 by adding SSE4, AVX and AVX2 vector implementations of
> several vector math functions (float and double versions). AVX-512
> versions are planned to be added later. These functions can be also
> used manually (with intrinsics) by developers to obtain speedup.
> 
> So it is mainly for GCC.

The only counter-argument to that is that a single implementation
in glibc can be shared by gcc and llvm or any other compiler. As
noted in "3.5 Open questions, a."

Intel needs to decide where they want this piece of technology
to reside. I don't know that the community can make this choice
for Intel.

The community is ready to work with Intel to implement this in
glibc.

I've tried to clarify a few of these:
https://sourceware.org/glibc/wiki/libm#Open_questions

Cheers,
Carlos.


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