[cfe-dev] OpenCL & SPIR specific types - proposal and patch

[Tanya Lattner]

On Oct 4, 2012, at 1:14 PM, "Villmow, Micah" <Micah.Villmow at amd.com> wrote:

> There needs to be a way to differentiate between an integer and a sampler by only looking at the type. The sampler itself is an opaque type in OpenCL. The only requirement is that it is initialized with a 32bit unsigned integer, not that the type itself is an integer.
>  

I understand that the spec doesn't require it to be a 32 bit integer, but if you are only ever assigning it a 32 bit integer, it doesn't make any sense to have the extra inttoptr instruction. 

Secondly, your idea of differentiating an integer and sampler by type alone is then based upon the name of the type that you are pointing to and not actually the type itself. Anything based upon names can be risky. There was a point in time where the linker was not properly merging structures that were identical and therefore renaming them. It makes much more sense to attach metadata to samplers and images to denote what is what.

The image types being pointers I am fine with as there isn't any other way to do those.

-Tanya


> Micah
>  
> From: Tanya Lattner [mailto:lattner at apple.com] 
> Sent: Thursday, October 04, 2012 11:49 AM
> To: Benyei, Guy
> Cc: cfe-dev at cs.uiuc.edu; Villmow, Micah; Anton.Lokhmotov at arm.com
> Subject: Re: [cfe-dev] OpenCL & SPIR specific types - proposal and patch
>  
> I'm hoping to have comments on this patch tomorrow, but since I have proposed several patches to Clang for the sampler type (and have another in revision).. can you explain why you want to change the type from an integer to a pointer? 
>  
> -Tanya
>  
> On Oct 3, 2012, at 8:06 AM, "Benyei, Guy" <guy.benyei at intel.com> wrote:
> 
> 
> I’d like to renew the discussion about making the OpenCL specific types first class citizens in Clang.
>  
> I think this change is required by the OpenCL specifications, since these type names are keywords of the OpenCL C language.
> This change is also needed in order to enable efficient checking of OpenCL restrictions on these types (OpenCL 1.2 spec, section 6.9).
> Furthermore, the proposed change will turn these types to pointers to opaque types, which means that it will hide the actual (vendor specific) implementation, so the OpenCL vendors using Clang will be able to implement these types in their own way.
>  
> This change would also be a basis for the implementation of SPIR generation by Clang. The SPIR discussion and spec can be found here:
> http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-September/024132.html
> http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-September/024178.html
>  
> Earlier discussion about the OpenCL types was started by Anton Lokhmotov:
> http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-May/015297.html
> http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-April/014741.html
> http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-March/014118.html
> http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-March/014121.html
>  
>  
> <image001.png>
>  
> <opencl_types.patch>
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