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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Tanya Lattner [mailto:lattner@apple.com]
<br>
<b>Sent:</b> Tuesday, October 09, 2012 11:30 AM<br>
<b>To:</b> Villmow, Micah<br>
<b>Cc:</b> Benyei, Guy; cfe-dev@cs.uiuc.edu; Anton.Lokhmotov@arm.com<br>
<b>Subject:</b> Re: [cfe-dev] OpenCL & SPIR specific types - proposal and patch<o:p></o:p></span></p>
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<p class="MsoNormal">On Oct 4, 2012, at 1:14 PM, "Villmow, Micah" <<a href="mailto:Micah.Villmow@amd.com">Micah.Villmow@amd.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">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.</span><o:p></o:p></p>
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<p class="MsoNormal">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. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">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.<o:p></o:p></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">[Villmow, Micah] Metadata isn’t possible because you can’t attach metadata to arguments.<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Take these functions:<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Kernel void foo(sampler_t a, int b)<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">{<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">}<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Kernel void foo(int a, int b)<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">{<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">}<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">In LLVMIR with sampler as i32, they are both the same function, but they are fundamentally different and have to be handled differently(not only at the
compiler level, but also at the runtime level). On a 32bit system, on the runtime side, the size of a sampler_t object is 4 bytes, on a 64bit system it is 8 bytes, but as an i32, its always 4 bytes.<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Another problem is this case:<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Module 1:<o:p></o:p></span></i></b></p>
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<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">{<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Return 0;<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">}<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Module 2:<o:p></o:p></span></i></b></p>
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<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Return 0;<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">}<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Module 3:<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Kernel void bar(global int* a, sampler_t b)<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">{<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">*a = foo(b, *a);<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">}<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Linking Module 1 and 3 together is fine, linking module 2 and 3 together should produce a linker error. If a sampler is an i32, they both are accepted
since they have the same signature.<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I agree that the opaque pointer with a specific name isn’t the best solution, but unless we add these as fundamental LLVM types, I don’t know of a better
way to handle this. I however think relying on metadata for information that is required for correctness is wrong(metadata should not affect correctness) and differentiating if an i32 is a sampler or not based on its use is not the right approach either.<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal">The image types being pointers I am fine with as there isn't any other way to do those.<o:p></o:p></p>
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<p class="MsoNormal">-Tanya<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Micah</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> </span><o:p></o:p></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span class="apple-converted-space"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> </span></span><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">Tanya
Lattner [mailto:lattner@<a href="http://apple.com"><span style="color:purple">apple.com</span></a>]<span class="apple-converted-space"> </span><br>
<b>Sent:</b><span class="apple-converted-space"> </span>Thursday, October 04, 2012 11:49 AM<br>
<b>To:</b><span class="apple-converted-space"> </span>Benyei, Guy<br>
<b>Cc:</b><span class="apple-converted-space"> </span><a href="mailto:cfe-dev@cs.uiuc.edu"><span style="color:purple">cfe-dev@cs.uiuc.edu</span></a>; Villmow, Micah;<span class="apple-converted-space"> </span><a href="mailto:Anton.Lokhmotov@arm.com"><span style="color:purple">Anton.Lokhmotov@arm.com</span></a><br>
<b>Subject:</b><span class="apple-converted-space"> </span>Re: [cfe-dev] OpenCL & SPIR specific types - proposal and patch</span><o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">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? <o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">-Tanya<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">On Oct 3, 2012, at 8:06 AM, "Benyei, Guy" <<a href="mailto:guy.benyei@intel.com"><span style="color:purple">guy.benyei@intel.com</span></a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">I’d like to renew the discussion about making the OpenCL specific types first class citizens in Clang.</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">I think this change is required by the OpenCL specifications, since these type names are keywords of the OpenCL C language.</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">This change is also needed in order to enable efficient checking of OpenCL restrictions on these types (OpenCL 1.2 spec, section 6.9).</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">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.</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">This change would also be a basis for the implementation of SPIR generation by Clang. The SPIR discussion and spec can be found here:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><a href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-September/024132.html"><span style="color:purple">http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-September/024132.html</span></a></span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><a href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-September/024178.html"><span style="color:purple">http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-September/024178.html</span></a></span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Earlier discussion about the OpenCL types was started by Anton Lokhmotov:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><a href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-May/015297.html"><span style="color:purple">http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-May/015297.html</span></a></span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><a href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-April/014741.html"><span style="color:purple">http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-April/014741.html</span></a></span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><a href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-March/014118.html"><span style="color:purple">http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-March/014118.html</span></a></span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><a href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-March/014121.html"><span style="color:purple">http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-March/014121.html</span></a></span><o:p></o:p></p>
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