[LLVMdev] [PATCH] parallel loop metadata
hfinkel at anl.gov
Tue Jan 29 13:34:55 PST 2013
----- Original Message -----
> From: "Paul Redmond" <paul.redmond at intel.com>
> To: "Pekka Jääskeläinen" <pekka.jaaskelainen at tut.fi>
> Cc: "CVS Commit Messages for LLVM repository" <llvm-commits at cs.uiuc.edu>, "LLVM Developers Mailing List"
> <llvmdev at cs.uiuc.edu>
> Sent: Tuesday, January 29, 2013 3:27:03 PM
> Subject: Re: [PATCH] parallel loop metadata
> Hi Pekka,
> On 2013-01-29, at 2:42 PM, Pekka Jääskeläinen wrote:
> > Maybe the safe thing here is to rename it back to the honest
> > "llvm.loop.parallel" or similar and we can add a separate one for
> > the assumed_dep later on. This one would support the truly parallel
> > loops (at least OpenMP for and OpenCL WIloops) where no compiler
> > checking at all can be assumed by the programmer.
> > Any objections? Paul Redmond?
> I don't have any objections. I think the only requirement is that the
> semantics are clearly defined.
> Personally I think this metadata should be used to guide the
> vectorizer only. I'm not sure how it will be used in the context of
> OpenMP or OpenCL. For OpenMP I assume you'd add this metadata to
> parallel_for loops. At what point do you insert the runtime calls?
> Does LLVM need to know how to target each runtime?
I think that the general direction being pursued for OpenMP is to do frontend lowering (outlining). However, we'd still want iteration-independence metadata to attach to the outlined loop bodies.
> > --
> > --Pekka
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