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<div class="moz-cite-prefix">On 09/13/2017 07:30 AM, C Bergström
wrote:<br>
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cite="mid:CAOnawYoekA6eA--njqPrc4knXDihGkAfS0u1bWr=dhHGnaooDw@mail.gmail.com"
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<div class="gmail_quote">On Wed, Sep 13, 2017 at 8:05 PM, Hal
Finkel <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:hfinkel@anl.gov" target="_blank">hfinkel@anl.gov</a>></span>
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<div
class="m_-459361835952577216m_-2802422639224529799moz-cite-prefix">On
09/13/2017 06:53 AM, C Bergström wrote:<br>
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<div class="gmail_quote">On Wed, Sep 13, 2017 at
7:43 PM, Hal Finkel <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:hfinkel@anl.gov"
target="_blank">hfinkel@anl.gov</a>></span>
wrote:<br>
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<div
class="m_-459361835952577216m_-2802422639224529799m_-268822120178151296moz-cite-prefix">On
09/13/2017 02:16 AM, C Bergström
wrote:<br>
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<div>A completely
non-technical point, but
what's the current "polly"
license? Does integrating
that code conflict in any
way with the work being
done to relicense llvm?<br>
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</span> Good question. I discussed this
explicitly with Tobias, and his general
feeling is that relicensing isl again
would be doable if necessary (we already
did this once, to an MIT license, in order
to enable better LLVM integration).<span><br>
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Does adding polly expose any
additional legal risks? Some
people from Reservoir labs
have explicitly stated to me
that some of their patents
target polyhedral
optimizations. You should
almost certainly review
their portfolio or contact
them.<br>
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If at some point someone wants
to add real loop optimizations
- will there be a conflict?<br>
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</span> Can you define "real loop
optimizations"?<span><br>
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<div>I think most readers here will understand
what I mean. I can go find specific chapters
of textbooks if it's unclear. Maybe the word
"real" could be replaced with traditional,
well tested, industry standard or something
else. (ok I'll stop being snarky)<br>
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</span> That's what I thought you meant. No, I believe
there's not a conflict. In fact, this will provide
infrastructure to make this easier. While you can handle
a bunch of these as one problem using this kind of
framework, you don't need to do so.<span><br>
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<div>By this I think you either mean A) the polly stuff will
provide a better analysis pass or B) the llvm side will
have a better analysis pass, correct?<br>
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<div>If you mean A, then that's cool. I was unaware that
poly had an interface and could be used like this.</div>
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It does now (I believe that it was developed as part of a GSoC
project last year:
<a class="moz-txt-link-freetext" href="http://llvm.org/svn/llvm-project/polly/trunk/include/polly/DependenceInfo.h">http://llvm.org/svn/llvm-project/polly/trunk/include/polly/DependenceInfo.h</a>).
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<div> The cost model aspect is very important. I'm mildly
curious how it builds this.<br>
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<div>(correct me if I'm wrong please) It's my lay
understanding that poly optimizations are an either or and
do not generally play well with tradtional methods. More
specifically, after poly things are "messed up" and it
would be difficult to do another (traditional type)
transformation that it missed.</div>
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Polly doesn't really use this currently, but isl has an incremental
scheduling interface, and other ways to guide the transformation
process, so it should be possible to build passes that use the
infrastructure to do a restricted subset of transformations. In
short, it can do a bunch of stuff at the same time, but doesn't have
to be used that way. As such, you can actually use Polly's
infrastructure to build many of these individual classical
transformations (in what I believe is a relatively-simply way -
although take this with a grain of salt because I don't know how
much this has been tried in practice).<br>
<br>
-Hal<br>
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<div> Since llvm doesn't have or doesn't do the traditional
side very well, this is less a concern though.<br>
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<pre class="moz-signature" cols="72">--
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory</pre>
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