[LLVMdev] Is there any llvm neon intrinsic that maps to vmla.f32 instruction ?

[Renato Golin]

On 8 February 2013 12:28, Sebastien DELDON-GNB <sebastien.deldon at st.com>wrote:

> Why for cortex-a9 vmlx-forwarding is enabled by default ? Is it to
> guarantee correctness or for performance purpose ? I’ve made some
> experiments and DISABLING vmlx-forwarding for cortex-a9 leads to generation
> of more vmla/vmls .f32 and  significantly improve some benchmarks. I’ve not
> enter into a case where it significantly  degrades performance or give
> incorrect answers.
>
I believe this is what you're looking for:

http://article.gmane.org/gmane.comp.compilers.llvm.cvs/90709

Performance only, but if you're seeing regressions, I'm interested to know
what benchmarks and how much are they regressing/improving.



> ****
>
> Thus my goal is to use my front-end to generate llvm neon intrinsics that
> maps to LLVM vmla/vmls f32 when I think it is appropriate and not to rely
> on disabling/enabling vmlx-forwarding.
>
In that case, you must disable the pass when you call the back-end.

cheers,
--renato
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