[cfe-dev] [RFC][OpenCL] Allow users to add supported OpenCL extensions by pragma

[Bader, Alexey via cfe-dev]

Hi,

Sorry for being late to the discussion, but I didn't get the use case of the proposed feature.
Why vendor/library developer would need compiler to support for some pragma that doesn't change to behavior of the compiler?

Thanks,
Alexey

From: Anastasia Stulova [mailto:Anastasia.Stulova at arm.com]
Sent: Tuesday, June 14, 2016 6:56 PM
To: Sumner, Brian <Brian.Sumner at amd.com>; Liu, Yaxun (Sam) <Yaxun.Liu at amd.com>; cfe-dev (cfe-dev at lists.llvm.org) <cfe-dev at lists.llvm.org>; Bader, Alexey <alexey.bader at intel.com>; Pan, Xiuli <xiuli.pan at intel.com>
Cc: Jeroen Ketema <j.ketema at imperial.ac.uk>; nd <nd at arm.com>
Subject: RE: [RFC][OpenCL] Allow users to add supported OpenCL extensions by pragma

Thanks, Brian!

Yes, perhaps we could try to make the extension list fully dynamic. Although I would imagine it's still useful to have standard extensions from the Spec directly in Clang to be available for the cases without standard header include.

Cheers,
Anastasia

From: Sumner, Brian [mailto:Brian.Sumner at amd.com]
Sent: 14 June 2016 16:18
To: Anastasia Stulova; Liu, Yaxun (Sam); cfe-dev (cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>); Bader, Alexey (alexey.bader at intel.com<mailto:alexey.bader at intel.com>); Pan, Xiuli
Cc: Jeroen Ketema; nd
Subject: RE: [RFC][OpenCL] Allow users to add supported OpenCL extensions by pragma

Hi Anastasia,

To answer your last question, this would be specific to clang.  It will allow those of us using clang for OpenCL languages to implement many of our vendor specific extensions without any other changes to clang.  I expect a few of the current KHR extensions that do not involve new or special types could be moved into opencl-c.h using this mechanism if desired as well.

Thanks,
Brian

From: Anastasia Stulova [mailto:Anastasia.Stulova at arm.com]
Sent: Monday, June 13, 2016 11:25 AM
To: Liu, Yaxun (Sam); cfe-dev (cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>); Bader, Alexey (alexey.bader at intel.com<mailto:alexey.bader at intel.com>); Pan, Xiuli
Cc: Sumner, Brian; Jeroen Ketema; nd
Subject: RE: [RFC][OpenCL] Allow users to add supported OpenCL extensions by pragma

Interesting idea! Just to be clear, you are suggesting to add parsing of the following into Clang:

#pragma OPENCL EXTENSION the_new_extension_name : register

Which would add custom the_new_extension_name to the list of known and supported OpenCL extensions dynamically?

Normally, target triple that combines RT and specific hardware type would be used for those purposes.
But I believe it shouldn't be too complicated to add this pragma considering that OpenCL already has similar ones.

This approach could offer some degree of flexibility to the library implementations,
which would otherwise have to add separate triple representing their library ABIs.

Would this be allowed in any OpenCL code as some sort of Clang extension or is there a plan to add this into Spec?

Thanks,
Anastasia

From: Liu, Yaxun (Sam) [mailto:Yaxun.Liu at amd.com]
Sent: 10 June 2016 19:40
To: cfe-dev (cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>); Anastasia Stulova; Bader, Alexey (alexey.bader at intel.com<mailto:alexey.bader at intel.com>); Pan, Xiuli
Cc: Sumner, Brian; Jeroen Ketema
Subject: [RFC][OpenCL] Allow users to add supported OpenCL extensions by pragma

Currently Clang defines supported OpenCL extensions for each target based on triple and CPU. As a default configuration this seems sufficient.

However if vendors and library developers want to add support of their own extensions, they have to modify Clang, which is very inconvenient.

We need a flexible and expressive way to add supported extensions for vendors and library developers.

Brian has a proposal which introduces a pragma to add supported extensions:

#pragma OPENCL EXTENSION the_new_extension_name : register

This pragma tells clang the name of a new OpenCL extension and request that it process it just like any other OpenCL extension, e.g. recognize

#pragma OPENCL EXTENSION the_new_extension_name : enable/disable

in subsequent code.

Since this pragma can be used in the header file of vendors or library developers' OpenCL implementations, it can provide flexible and expressive way to represent supported extensions when combined with other preprocessor constructs.

Any feedbacks? Thanks.

Sam




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