[LLVMdev] [PATCH] parallel loop metadata
paul.redmond at intel.com
Tue Jan 29 13:53:01 PST 2013
I'm all for finally getting something into LLVM.. just need to make sure the name and the semantics are sorted out before the next release :) This is a fine start.
On 2013-01-29, at 4:34 PM, Hal Finkel wrote:
> ----- 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.
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