<div dir="ltr">It's not clear that these would need to be totally new instructions as opposed to a mask operand to the existing store instruction? I'm curious what Owen is actually imagining here...</div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Oct 27, 2014 at 12:02 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 class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">we just follow a common recommendation to start with intrinsics:<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><a href="http://llvm.org/docs/ExtendingLLVM.html" target="_blank">http://llvm.org/docs/ExtendingLLVM.html</a><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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<u></u><span style="font-family:"Calibri","sans-serif";color:#31849b"><span>-<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span dir="LTR"></span><b><i><span style="color:#31849b"> Elena<u></u><u></u></span></i></b></p>
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<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""> Owen Anderson [mailto:<a href="mailto:resistor@mac.com" target="_blank">resistor@mac.com</a>]
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<b>Sent:</b> Sunday, October 26, 2014 23:57<br>
<b>To:</b> Demikhovsky, Elena<br>
<b>Cc:</b> <a href="mailto:llvmdev@cs.uiuc.edu" target="_blank">llvmdev@cs.uiuc.edu</a>; <a href="mailto:dag@cray.com" target="_blank">dag@cray.com</a><span class=""><br>
<b>Subject:</b> Re: [LLVMdev] Adding masked vector load and store intrinsics<u></u><u></u></span></span></p>
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<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">What is the motivation for using intrinsics versus adding new instructions?<u></u><u></u></p><div><div class="h5">
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">—Owen<u></u><u></u></p>
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<p class="MsoNormal">On Oct 24, 2014, at 4:24 AM, Demikhovsky, Elena <<a href="mailto:elena.demikhovsky@intel.com" target="_blank">elena.demikhovsky@intel.com</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal"><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">Hi,</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">We would like to add support for masked vector loads and stores by introducing new target-independent intrinsics. The loop vectorizer will then be enhanced
to optimize loops containing conditional memory accesses by generating these intrinsics for existing targets such as AVX2 and AVX-512. The vectorizer will first ask the target about availability of masked vector loads and stores. The SLP vectorizer can potentially
be enhanced to use these intrinsics as well.</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">The intrinsics would be legal for all targets; targets that do not support masked vector loads or stores will scalarize them.</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">The addressed memory will not be touched for masked-off lanes. In particular, if all lanes are masked off no address will be accessed.</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> call void @llvm.masked.store (i32* %addr, <16 x i32> %data, i32 4, <16 x i1> %mask)</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> %data = call <8 x i32> @llvm.masked.load (i32* %addr, <8 x i32> %passthru, i32 4, <8 x i1> %mask)</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">where %passthru is used to fill the elements of %data that are masked-off (if any; can be zeroinitializer or undef).</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Comments so far, before we dive into more details?</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Thank you.</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">- Elena and Ayal</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <u></u><u></u></span></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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