[cfe-dev] [Openmp-dev] RFC: Proposing an LLVM subproject for parallelism runtime and support libraries

Cownie, James H via cfe-dev cfe-dev at lists.llvm.org
Tue Mar 15 04:13:25 PDT 2016


Chandler,

That raises a more meta-question for me, which is “Why should StreamExecutor be in LLVM at all?”

AFAICS, with you approach

·         It is not a runtime library whose interface the compiler needs to understand.

·         It does not depend on any LLVM runtime libraries.

·         It is expected to be used with out-of-tree plugins.

If I got all of that right, what connection does it have with LLVM that makes having it in the LLVM tree necessary, or an improvement over simply having it on github (or whatever your favourite open-source hosting location is)?

Did I misunderstand something?

-- Jim

James Cownie <james.h.cownie at intel.com>
SSG/DPD/TCAR (Technical Computing, Analyzers and Runtimes)
Tel: +44 117 9071438

From: Chandler Carruth [mailto:chandlerc at google.com]
Sent: Tuesday, March 15, 2016 10:44 AM
To: Jason Henline <jhen at google.com>; C Bergström <cbergstrom at pathscale.com>; Cownie, James H <james.h.cownie at intel.com>
Cc: llvm-dev <llvm-dev at lists.llvm.org>; cfe-dev <cfe-dev at lists.llvm.org>; openmp-dev at lists.llvm.org
Subject: Re: [cfe-dev] [Openmp-dev] RFC: Proposing an LLVM subproject for parallelism runtime and support libraries

On Mon, Mar 14, 2016 at 6:51 PM Jason Henline via cfe-dev <cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>> wrote:
I think it would be great if StreamExecutor could use liboffload to perform its offloading under the hood. Right now offloading is handled in StreamExecutor using platform plugins, so I think it could be very natural for us to write a plugin which basically forwards to liboffload.

I think that having a liboffload plugin would be nice, but I don't think we should really base everything on top of this for a few reasons:

1) I think we already have a nice plugin interface specifically designed to support out-of-tree platforms with StreamExecutor, and it wouldn't make a lot of sense to force them to re-implement there stuff.

2) Some platforms may not want or be able to use the liboffload style plugin.

It seems like if the OpenMP folks want to add a liboffload plugin to StreamExecutor, that would be an awesome additional platform, but I don't see why we need to force the coupling here.

My 2 cents.
-Chandler
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