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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">></span> why in order to add this particular instruction (sum elements in a vector) I need to add an insrinsic?<o:p></o:p></p>
<p class="MsoNormal">Adding intrinsic is not the only way, it is one of the way and user WILL-NOT be required to invoke<o:p></o:p></p>
<p class="MsoNormal">It specifically.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Currently LLVM does not have any instruction to directly represent “sum of elements in a vector” and<o:p></o:p></p>
<p class="MsoNormal">generate your particular instruction.However, you can do it without intrinsic by pattern matching the<o:p></o:p></p>
<p class="MsoNormal">LLVM-IRs representing “sum of elements in vector” to your particular instruction in DAGCombiner.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal">Shahid<o:p></o:p></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""> Rail Shafigulin [mailto:rail@esenciatech.com]
<br>
<b>Sent:</b> Monday, May 09, 2016 11:59 PM<br>
<b>To:</b> Shahid, Asghar-ahmad; llvm-dev<br>
<b>Cc:</b> Das, Dibyendu<br>
<b>Subject:</b> Re: [llvm-dev] sum elements in the vector<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">I'm a little confused. Here is why.<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 was able to add a vector add instruction to my target without using any intrinsics and without adding any new instructions to LLVM. So here is my question: how come I managed to add a new vector instruction without adding an intrinsic
and why in order to add this particular instruction (sum elements in a vector) I need to add an insrinsic?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Another question that I have is whether compiler will be able to target this new instruction (sum elements in a vector) if it is implemented as an intrinsic or the user will have to specifically invoke an instrinsic.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Pardon if questions seem dumb, I'm still learning things.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Any help is appreciated. <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 Fri, May 6, 2016 at 1:51 PM, Rail Shafigulin <<a href="mailto:rail@esenciatech.com" target="_blank">rail@esenciatech.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Thanks for the reply. These steps will add an instruction as an intrinsic. Is it possible to add an actual new instruction so that a compiler could target it during an optimization? How hard is it to do it? Is that a realistic objective.<span class="hoenzb"><span style="color:#888888"><o:p></o:p></span></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="color:#888888">Rail<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">On Mon, Apr 4, 2016 at 9:02 PM, Shahid, Asghar-ahmad <<a href="mailto:Asghar-ahmad.Shahid@amd.com" target="_blank">Asghar-ahmad.Shahid@amd.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"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi Rail,</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">We had done this for generation of X86 PSAD (sum of absolute difference) instruction through</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Llvm intrinsic. Doing this requires following</span><o:p></o:p></p>
<p><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">1.</span><span style="font-size:7.0pt;color:#1F497D">
</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Define an intrinsic, xyz(), for the required instruction and corresponding SDNode</span><o:p></o:p></p>
<p><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">2.</span><span style="font-size:7.0pt;color:#1F497D">
</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Generate the “call xyz() “ IR based the matched pattern</span><o:p></o:p></p>
<p><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">3.</span><span style="font-size:7.0pt;color:#1F497D">
</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Map “call xyz()” IR to corresponding SDNode in SelectionDagBuilder.cpp</span><o:p></o:p></p>
<p><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">4.</span><span style="font-size:7.0pt;color:#1F497D">
</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Provide default expansion of the xyz() intrinsic</span><o:p></o:p></p>
<p><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">5.</span><span style="font-size:7.0pt;color:#1F497D">
</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Legalize type and/or operation</span><o:p></o:p></p>
<p><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">6.</span><span style="font-size:7.0pt;color:#1F497D">
</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Provide Lowering of intrinsic/SDNode to generate your target instruction</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">You can visit
<a href="http://llvm.org/docs/ExtendingLLVM.html" target="_blank">http://llvm.org/docs/ExtendingLLVM.html</a> for details.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Regards,</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Shahid
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><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""> llvm-dev [mailto:<a href="mailto:llvm-dev-bounces@lists.llvm.org" target="_blank">llvm-dev-bounces@lists.llvm.org</a>]
<b>On Behalf Of </b>Rail Shafigulin via llvm-dev<br>
<b>Sent:</b> Monday, April 04, 2016 11:00 PM<br>
<b>To:</b> Das, Dibyendu<br>
<b>Cc:</b> <a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a><br>
<b>Subject:</b> Re: [llvm-dev] sum elements in the vector</span><o:p></o:p></p>
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<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" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Thanks for the pointers. I looked at hadd instructions. They seem to do very similar to what I need. Unfortunately as I said before my LLVM experience is limited. My understanding
is that when I create a new type of SDNode I need to specify a pattern for it, so that when LLVM is analyzing the code and is seeing a given pattern it would create this particular node. I'm really struggling to understand how it is done. So here are the problems
that I'm having.<o:p></o:p></p>
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<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" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">1. How do I identify that pattern that should be used?<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">2. How do I specify a given pattern? <o:p></o:p></p>
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<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" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Do you (or someone else) mind helping me out? <o:p></o:p></p>
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<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" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Any help is appreciated.<o:p></o:p></p>
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<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" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">On Mon, Apr 4, 2016 at 9:59 AM, Das, Dibyendu <<a href="mailto:Dibyendu.Das@amd.com" target="_blank">Dibyendu.Das@amd.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"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">This is roughly along the lines of x86 hadd* instructions though the semantics of hadd* may not exactly
match what you are looking for. This is probably more in line with x86/ARM SAD-like instructions but I don’t think llvm generates SAD without intrinsics.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> llvm-dev [mailto:<a href="mailto:llvm-dev-bounces@lists.llvm.org" target="_blank">llvm-dev-bounces@lists.llvm.org</a>]
<b>On Behalf Of </b>Rail Shafigulin via llvm-dev<br>
<b>Sent:</b> Monday, April 04, 2016 9:34 AM<br>
<b>To:</b> llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>><br>
<b>Subject:</b> [llvm-dev] sum elements in the vector</span><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" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">My target has an instruction that adds up all elements in the vector and stores the result in a register. I'm trying to implement it in my compiler but I'm not sure even where to
start.<o:p></o:p></p>
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<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" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I did look at other targets, but they don't seem to have anything like it ( I could be wrong. My experience with LLVM is limited, so if I missed it, I'd appreciate if someone could
point it out ). <o:p></o:p></p>
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<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" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">My understanding is that if SDNode for such an instruction doesn't exist I have to define one. Unfortunately, I don't know how to do it. I don't even know where to start looking.
Would someone care to point me in the right direction? <o:p></o:p></p>
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<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" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Any help is appreciated.<br clear="all">
<o:p></o:p></p>
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<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" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Rail Shafigulin<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Software Engineer
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Esencia Technologies<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Rail Shafigulin<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Software Engineer
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Esencia Technologies<o:p></o:p></p>
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<p class="MsoNormal">Rail Shafigulin<o:p></o:p></p>
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<p class="MsoNormal">Software Engineer <br>
Esencia Technologies<o:p></o:p></p>
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<p class="MsoNormal">Rail Shafigulin<o:p></o:p></p>
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<p class="MsoNormal">Software Engineer <br>
Esencia Technologies<o:p></o:p></p>
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