[cfe-dev] A proposal for adding OpenCL C++ support (Spec v2.2)

[John McCall via cfe-dev]

> On Apr 4, 2018, at 10:09 AM, Anastasia Stulova <Anastasia.Stulova at arm.com> wrote:
> Hi John,
> 
> The OpenCL C++ patch contains integration with the SPIR-V translation tool. We have restared the discussion about that tool on llvm dev recently:
> http://lists.llvm.org/pipermail/llvm-dev/2018-March/121794.html <http://lists.llvm.org/pipermail/llvm-dev/2018-March/121794.html>
> 
> If you look for example in the README file it explain such things as new option -emit-spirv.
> https://github.com/KhronosGroup/SPIR/commit/0cfb6f7533d42ae3398a8574efd8abbdac88ac44 <https://github.com/KhronosGroup/SPIR/commit/0cfb6f7533d42ae3398a8574efd8abbdac88ac44>
> 
> Also there is support for the SPIR-V friendly format:
> https://github.com/KhronosGroup/SPIRV-LLVM/blob/khronos/spirv-3.6.1/docs/SPIRVRepresentationInLLVM.rst <https://github.com/KhronosGroup/SPIRV-LLVM/blob/khronos/spirv-3.6.1/docs/SPIRVRepresentationInLLVM.rst>
> This is mainly located in lib/CodeGen/OclCxxRewrite directory.
> 
> Because, we have a separate activity to redesign the integration with SPIRV, we won't be contributing those bits currently. But the plan is to restart the discussion around this at some point hopefully soon.
> 
> Supporting SPIR-V is essential to us because it gives to many tool vendor a path to use Clang directly from upstream. So we will be working on its integration as well. But for now we would like to start with the generic OpenCL C++ support - Parsing, Sema, basic CodeGen, etc.

I see.  So this is support for the full language, just not SPIR output.  That seems totally reasonable to me.

John.

> 
> I hope it clarifies your question.
> Thanks!
> Anastasia
> 
> 
> From: rjmccall at apple.com <mailto:rjmccall at apple.com> <rjmccall at apple.com <mailto:rjmccall at apple.com>> on behalf of John McCall <rjmccall at apple.com <mailto:rjmccall at apple.com>>
> Sent: 28 March 2018 22:25
> To: Anastasia Stulova
> Cc: clang-dev developer list; nd
> Subject: Re: [cfe-dev] A proposal for adding OpenCL C++ support (Spec v2.2)
>  
> 
>> On Mar 23, 2018, at 2:30 PM, Anastasia Stulova via cfe-dev <cfe-dev at lists.llvm.org <mailto:cfe-dev at lists.llvm.org>> wrote:
>> There were no objections to this so far. I assume it means nobody is opposing this new feature.
> 
> I have no objections.
> 
>> Just to give a bit more info and a chance for the last feedback. We don't plan to contribute the whole patch but only around 3K lines + tests. The overall changes will be smaller than OpenCL 2.0. And they will mainly affect C++ code paths in Sema and CodeGen, but some parsing bits too.
>> 
>> The time frame to start this work will hopefully be the beginning of April.
> 
> Okay.  Can you explain what it means that you won't be contributing the whole patch?
> 
> John.
> 
>> 
>> Cheers,
>> Anastasia
>> 
>> From: cfe-dev <cfe-dev-bounces at lists.llvm.org <mailto:cfe-dev-bounces at lists.llvm.org>> on behalf of Anastasia Stulova via cfe-dev <cfe-dev at lists.llvm.org <mailto:cfe-dev at lists.llvm.org>>
>> Sent: 23 February 2018 16:29
>> To: clang-dev developer list
>> Cc: nd
>> Subject: [cfe-dev] A proposal for adding OpenCL C++ support (Spec v2.2)
>>  
>> Hello,
>> 
>> A number of developers from the member companies within the Khronos Group are interested to contribute the prototype implementation of OpenCL C++ that is currently located on github and based on version 3.6:
>> https://github.com/KhronosGroup/SPIR/commit/0cfb6f7533d42ae3398a8574efd8abbdac88ac44 <https://github.com/KhronosGroup/SPIR/commit/0cfb6f7533d42ae3398a8574efd8abbdac88ac44>
>> 
>> This implementation is compliant to OpenCL v2.2 standard:
>> https://www.khronos.org/registry/OpenCL/specs/opencl-2.2-cplusplus.pdf <https://www.khronos.org/registry/OpenCL/specs/opencl-2.2-cplusplus.pdf>
>> Similarly to OpenCL C being based on C99, OpenCL C++ support is entirely based on C++14 with a number of extensions (some of which will be shared with OpenCL C) and a few minor restrictions.
>> 
>> The plan would be to take small patches from the github repository and perform any necessary rework and clean up before putting up for review. From the OpenCL side, I don't see any issue with this plan as it doesn't interfere with any current development I am aware of, and also it would be great to progress to the next OpenCL standard. I just want to check if there are any objections from anyone or things we should be aware of before the start. I'm particularly looking for feedback from C++ implementers as there might be some overlap.
>> 
>> Additionally, there are two more related threads, which I plan to discuss separately. There is:
>> (i) standard library support libclcxx: https://github.com/KhronosGroup/libclcxx. <https://github.com/KhronosGroup/libclcxx.>
>> (ii) and IR generation to SPIRV: http://lists.llvm.org/pipermail/llvm-dev/2018-February/121317.html <http://lists.llvm.org/pipermail/llvm-dev/2018-February/121317.html>
>> that we would like to provide as well, in order to allow Clang to produce an end binary targeting a wider range of architectures directly (not just AMD GPU). We expect that the complete open source solution for OpenCL C++ will increase significantly Clang users and unify our development forces i.e. refactoring, bug hunting, etc. The plan would be to do similar for OpenCL C too at a later point of time. 
>> 
>> Please, contact me if you have any thoughts or comments.
>> 
>> Cheers,
>> Anastasia
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