<div dir="ltr"><div>Forwarding to llvm mailing list, because I again forgot to include it.</div><br><div class="gmail_quote">---------- Forwarded message ----------<br>From: <b class="gmail_sendername">Rail Shafigulin</b> <span dir="ltr"><<a href="mailto:rail@esenciatech.com">rail@esenciatech.com</a>></span><br>Date: Fri, May 6, 2016 at 1:51 PM<br>Subject: Re: [llvm-dev] sum elements in the vector<br>To: "Shahid, Asghar-ahmad" <<a href="mailto:Asghar-ahmad.Shahid@amd.com">Asghar-ahmad.Shahid@amd.com</a>><br>Cc: "Das, Dibyendu" <<a href="mailto:Dibyendu.Das@amd.com">Dibyendu.Das@amd.com</a>><br><br><br><div dir="ltr">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"><font color="#888888"><div><br></div><div>Rail</div></font></span></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Apr 4, 2016 at 9:02 PM, Shahid, Asghar-ahmad <span dir="ltr"><<a href="mailto:Asghar-ahmad.Shahid@amd.com" target="_blank">Asghar-ahmad.Shahid@amd.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Hi Rail,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><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<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Llvm intrinsic. Doing this requires following<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><span>1.<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Define an intrinsic, xyz(), for the required instruction and corresponding SDNode<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><span>2.<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Generate the “call xyz() “ IR based the matched pattern<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><span>3.<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Map “call xyz()” IR to corresponding SDNode in SelectionDagBuilder.cpp<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><span>4.<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Provide default expansion of the xyz() intrinsic<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><span>5.<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Legalize type and/or operation<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><span>6.<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Provide Lowering of intrinsic/SDNode to generate your target instruction<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><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.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Regards,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Shahid
<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></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""> 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<u></u><u></u></span></p>
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<p class="MsoNormal">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.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">1. How do I identify that pattern that should be used?<u></u><u></u></p>
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<p class="MsoNormal">2. How do I specify a given pattern? <u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Do you (or someone else) mind helping me out? <u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Any help is appreciated.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">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:<u></u><u></u></p>
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<p class="MsoNormal"><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><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><u></u><u></u></p>
<p class="MsoNormal"><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><u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal">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.<u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal">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 ). <u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal">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? <u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal">Any help is appreciated.<br clear="all">
<u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal">--
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<p class="MsoNormal">Rail Shafigulin<u></u><u></u></p>
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<p class="MsoNormal">Software Engineer
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Esencia Technologies<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">-- <u></u><u></u></p>
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<p class="MsoNormal">Rail Shafigulin<u></u><u></u></p>
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<p class="MsoNormal">Software Engineer <br>
Esencia Technologies<u></u><u></u></p>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div><div dir="ltr"><div><div dir="ltr"><div>Rail Shafigulin<br></div>Software Engineer <br>Esencia Technologies<br></div></div></div></div>
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</div></div></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div>Rail Shafigulin<br></div>Software Engineer <br>Esencia Technologies<br></div></div></div></div>
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