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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi James,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks for your response and explanation. It sounds as if this may be LLVM, instead of Clang.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I have a very simple OpenCL Kernel:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">__kernel void vecAdd(__global float* a) {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> int gid = get_global_id(0);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> a[gid] += a[gid];<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I am using the Clang/LLVM tools to reproduce the GPU specific binary being generated by Mesa Clover with the following commands:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">clang –O0 –emit-llvm –include /usr/local/include/clc.clc.h –I /usr/local/include –Dcl_clang_storage_class_specifies –target r600 –mcpu=turks –c kernel.cl –o
kernel.bc<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">llvm-link kernel.bc /usr/local/lib/clc/turks-r600--.bc –o kernel-linked.bc<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">opt –O2 –internalize-public-api-list=vecAdd –internalize –inline –inline-threshold=1000000000 kernel-linked.bc –o kernel-linked-opt.bc<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">llc –march=r600 –mcpu=turks kernel-linked-opt.bc –filetype=obj –o kernel.o<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Currently the clCreateProgramWithBinary() accepts the LLVM IR, not the ELF binary objects. I am looking to change that, for an embedded environment where the
kernels would be pre-compiled using the LLVM/Clang tools.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The problem that I see is that the kernel.o ELF file does not appear to list the function names in the symbol table. So, I’m not seeing how I could implement
the clCreateKernel() call to lookup the function within the ELF object. Or for that matter, if the ELF contained more than one kernel function, how I would retrieve the names within a clCreateKernelsInProgram() call.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">It seems that, using the build steps I described above, that the information I am looking for is lost with the llc command.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">-Al<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></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"><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""> mankeyrabbit@gmail.com [mailto:mankeyrabbit@gmail.com]
<b>On Behalf Of </b>James Molloy<br>
<b>Sent:</b> Tuesday, January 21, 2014 4:16 AM<br>
<b>To:</b> Dorrington, Albert<br>
<b>Cc:</b> cfe-dev@cs.uiuc.edu<br>
<b>Subject:</b> EXTERNAL: Re: [cfe-dev] OpenCL compile object file symbol tables<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi Albert,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Clang is not in and of itself an OpenCL compiler. It has a frontend for OpenCL-C, and can produce LLVM-IR from that (which can then be pushed through LLVM to produce some machine code). But those generated functions would be useless.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Clang is often used as *part of* a CL compiler - for example in POCL (<a href="http://pocl.sourceforge.net/">http://pocl.sourceforge.net/</a>). The IR generated from Clang for CL-C code doesn't contain any details of how it is going to
be executed. For example, is it going on a GPU or a CPU? In the latter case, loops will need to be inserted and calls to get_local_id() will need to reference the loop induction variables. There'll need to be some way inserted of being able to pass the group
ID and other payload-global data too.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Have you looked at POCL as an example of using Clang in a CL stack?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Cheers,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">James<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
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<p class="MsoNormal">On 20 January 2014 20:15, Dorrington, Albert <<a href="mailto:albert.dorrington@lmco.com" target="_blank">albert.dorrington@lmco.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">When I compile an OpenCL kernel to a binary file, using llvm/clang, I don’t see the kernel functions defined within the symbol table.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Is this by design?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Without the function names in the symbol table, I’m not sure how I would look up a function within a pre-compiled object file.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">For instance, after loading a pre-compiled binary with clCreateProgramWithBinary() and then validating that the kernel function contained therein is the expected kernel.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span style="font-size:14.0pt">Al Dorrington</span></b><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><i><span style="font-size:10.0pt">Software Engineer Sr</span></i><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><i><span style="font-size:10.0pt">Lockheed Martin, Mission Systems and Training</span></i><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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