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From Tim Armstrong <tarmstr...@cloudera.com>
Subject Re: Fw: LLVM codegen functionality
Date Tue, 14 Jun 2016 18:44:34 GMT
Yeah, codegen typically gives very large speedups. Another option may be to
avoid using the altivec extensions. We get a lot more benefit from codegen
than SIMD instructions. On Intel we don't require any extensions beyond the
base x86-64 instruction set (SSE4.2 is only used on systems that support
it), so many of those code paths may work ok on powerpc.

- Tim

On Tue, Jun 14, 2016 at 6:58 AM, Nishidha Panpaliya <nishidha@us.ibm.com>
wrote:

>
>
> Hi Jim,
>
> Thank you for your reply. Links that you sent us helped to understand the
> impact. But I believe, if it is only performance related and not blocking
> any Impala's feature, we can still live with that issue if it is just not
> possible to fix either for LLVM community or for us. Please correct me if I
> misunderstood.
>
> On another note, I could fix gcc 4.9.3 issue with ALTIVEC and could build
> Impala with it on power. And llvm-codegen test passed on it. So, if
> everything else works with this setup, we would rather go with gcc 4.9.3 on
> power for Impala.
>
> Thanks again for helping us always.
>
> Regards,
> Nishidha
>
> ----- Forwarded by Nishidha Panpaliya/Austin/Contr/IBM on 06/14/2016 07:17
> PM -----
>
> From:   Sudarshan Jagadale/Austin/Contr/IBM
> To:     Nishidha Panpaliya/Austin/Contr/IBM@IBMUS
> Date:   06/14/2016 10:35 AM
> Subject:        Fw: LLVM codegen functionality
>
>
> FYI
> Thanks and Regards
> Sudarshan Jagadale
> Power Open Source Solutions
> ----- Forwarded by Sudarshan Jagadale/Austin/Contr/IBM on 06/14/2016 10:34
> AM -----
>
> From:   Jim Apple <jbapple@cloudera.com>
> To:     dev@impala.incubator.apache.org
> Cc:     Silvius Rus <srus@cloudera.com>, Manish
>             Patil/Austin/Contr/IBM@IBMUS, Sudarshan
>             Jagadale/Austin/Contr/IBM@IBMUS, Valencia
>             Serrao/Austin/Contr/IBM@IBMUS, Anup
>             Halarnkar/Austin/Contr/IBM@IBMUS
> Date:   06/13/2016 08:33 PM
> Subject:        Re: LLVM codegen functionality
>
>
>
> LLVM codegen has a significant (and good) effect on performance.
>
>
> https://blog.cloudera.com/blog/2013/02/inside-cloudera-impala-runtime-code-generation/
>
>
> http://llvm.org/devmtg/2013-11/slides/Wanderman-Milne-Cloudera.pdf
>
> As for GCC/altivec problems, you might want to file a bug suggesting
> that the toolchain use a newer GCC.
>
> On Mon, Jun 13, 2016 at 7:58 AM, Nishidha Panpaliya <nishidha@us.ibm.com>
> wrote:
> >
> >
> > Hi All,
> >
> > We wanted to know about the significance of llvm codegen feature in
> Impala.
> > For us, it is failing on power. And so far, it seems to be due to
> > incompatibility of LLVM 3.8 with gcc 5.
> > And building Impala on ppc64le with gcc 4.9 is giving lot of other errors
> > related to Altivec library. Even LLVM community have no plans to provide
> > this as a hotfix before 3.9 release. So, we wanted to know how
> significant
> > is this functionality. Can we move ahead with this one issue left? What
> > features are impacted or how users will be affected due to this feature.
> >
> > Thanks,
> > Nishidha
>
>
>

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