<div dir="ltr">I don't need scatter but only gather on AVX-2, and performance is not the biggest concern. Could you please kindly suggest me how to switch masked gather on?<div><br></div><div>Best,</div><div>Zhi</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sat, Jan 23, 2016 at 12:01 AM, Demikhovsky, Elena <span dir="ltr"><<a href="mailto:elena.demikhovsky@intel.com" target="_blank">elena.demikhovsky@intel.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><a name="-1828824380__MailEndCompose"><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 dir="LTR"></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">I did not switch-on masked_load/store to AVX1, I can do this.<u></u><u></u></span></a></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 dir="LTR"></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">I did not switch-on masked gather on AVX2 because the instruction is slow. There is no scatter on AVX2.<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 dir="LTR"></span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Currently, gather/scatter does not work on SKX because the patch is still under review
</span><a href="http://reviews.llvm.org/D15690" target="_blank"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">http://reviews.llvm.org/D15690</span></a><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">. I’d be happy if you agree
to review it.<u></u><u></u></span></p>
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<u></u><span style="font-family:"Calibri",sans-serif;color:#2f5496"><span>-<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span dir="LTR"></span><b><i><span style="color:#2f5496"> Elena<u></u><u></u></span></i></b></p>
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<p class="MsoNormal"><a name="-1828824380______replyseparator"></a><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"> zhi chen [mailto:<a href="mailto:zchenhn@gmail.com" target="_blank">zchenhn@gmail.com</a>]
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<b>Sent:</b> Saturday, January 23, 2016 02:58<br>
<b>To:</b> Sanjay Patel <<a href="mailto:spatel@rotateright.com" target="_blank">spatel@rotateright.com</a>><br>
<b>Cc:</b> Demikhovsky, Elena <<a href="mailto:elena.demikhovsky@intel.com" target="_blank">elena.demikhovsky@intel.com</a>>; LLVM Developers Mailing List <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>><br>
<b>Subject:</b> Re: [llvm-dev] how to force llvm generate gather intrinsic<u></u><u></u></span></p><div><div class="h5">
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<p class="MsoNormal">Thanks for your response, Sanjay. I know there are intrinsics available in C/C++. But the problem is that I want to instrument my code at the IR level and generate those instructions. I don't want to touch the source code. <u></u><u></u></p>
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<p class="MsoNormal">Best,<u></u><u></u></p>
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<p class="MsoNormal">Zhi<u></u><u></u></p>
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<p class="MsoNormal">On Fri, Jan 22, 2016 at 4:54 PM, Sanjay Patel <<a href="mailto:spatel@rotateright.com" target="_blank">spatel@rotateright.com</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">I was just looking at the related masked load/store operations, and I think there are at least 2 bugs:<br>
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1. X86TTIImpl::isLegalMaskedLoad/Store() should be legal for FP types with AVX1 (not just AVX2).<br>
2. X86TTIImpl::isLegalMaskedGather/Scatter() should be legal for 128/256 bit vectors with AVX2 (not just AVX512).<u></u><u></u></p>
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<p class="MsoNormal">I looked at this for the first time today, so I may be missing something...<u></u><u></u></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">So for the moment, the answer to your question is 'no'; there's no generic way to produce these instructions. You should be able to use the _mm_* intrinsics in C though.<u></u><u></u></p>
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<p class="MsoNormal">On Fri, Jan 22, 2016 at 5:00 PM, zhi chen via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal">Hi,<u></u><u></u></p>
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<p class="MsoNormal">I used clang -O3 -c -emit-llvm on the follow code to generate a bitcode, say a.bc. I read the .ll file and didn't see any gather intrinsic. Also, I used opt -O3 -mcpu=core-avx2/-mcpu=skx, but there is still no gather intrinsic generated.<u></u><u></u></p>
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<p class="MsoNormal"> A[B[i]] = i + 5;<u></u><u></u></p>
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<p class="MsoNormal"> }<u></u><u></u></p>
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<p class="MsoNormal"> A[B[i]]++;<u></u><u></u></p>
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<p class="MsoNormal"> A[i] = B[C[i]];<u></u><u></u></p>
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<p class="MsoNormal">Could some give me an example that will generate gather intrinsic for AVX2? I tried to used the masked_gather intrinsic provided in the language ref. But it seemed that it only generates gather intrinsic for AVX-512 but for AVX-2. I found
that there are 16 gather intrinsic versions depending on the data types provided for AVX-2. Do I have to check the data type before calling them specifically? or is there a generic way to use AVX-2 gather intrinsic? <u></u><u></u></p>
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<p class="MsoNormal">Best,<u></u><u></u></p>
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<p class="MsoNormal">Zhi <u></u><u></u></p>
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