[LLVMdev] SLP vectorizer on AVX feature

[Hal Finkel]

----- Original Message -----
> From: "Frank Winter" <fwinter at jlab.org>
> To: "Renato Golin" <renato.golin at linaro.org>
> Cc: "LLVM Dev" <llvmdev at cs.uiuc.edu>
> Sent: Wednesday, July 1, 2015 3:33:18 PM
> Subject: Re: [LLVMdev] SLP vectorizer on AVX feature
> 
> On 07/01/2015 04:29 PM, Renato Golin wrote:
> > On 1 July 2015 at 21:22, Frank Winter <fwinter at jlab.org> wrote:
> >> there were two follow-up emails.
> > I only got one... weird...
> >
> >
> >> The issue is solved. The SLP vectorizer has
> >> a magic number built into the code which determines the max.
> >> vector length
> >> to search for. That was set to 128 bits. Increasing it to 256 bits
> >> solved
> >> the issue.
> > That looks like a simple fix. Is it upstream yet? :)
> 
> That's not up to me. There were concerns raised about an increased
> compile time.
> https://llvm.org/bugs/show_bug.cgi?id=17170#c8

The first step, likely, is to transform this bound into a command-line option for ease of benchmarking. I think that a patch that does that (along with a test case) would be nice.

 -Hal

> 
> Frank
> 
> >
> >
> >> For inconsistency reasons it must be '--debug-only=SLP' and the
> >> output can
> >> be found in one of the follow-up emails.
> > Of course. Maybe we should mean "vectorize" as all of them? Anyway,
> > that's unrelated.
> >
> > cheers,
> > --renato
> 
> 
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory