<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:Helvetica;
panose-1:2 11 6 4 2 2 2 2 2 4;}
@font-face
{font-family:SimSun;
panose-1:2 1 6 0 3 1 1 1 1 1;}
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:"\@SimSun";
panose-1:2 1 6 0 3 1 1 1 1 1;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p
{mso-style-priority:99;
mso-margin-top-alt:auto;
margin-right:0in;
mso-margin-bottom-alt:auto;
margin-left:0in;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
span.EmailStyle18
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-US" link="blue" vlink="purple">
<div class="WordSection1">
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Adam, yes, there are more stuff we need to consider, e.g. masked gather / scatter, masked arithmetic ops, …etc. This proposal serves the first step which
is an important, as a direction check w/ community. <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">Xinmin Tian
<o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></a></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<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""> llvmdev-bounces@cs.uiuc.edu [mailto:llvmdev-bounces@cs.uiuc.edu]
<b>On Behalf Of </b>Adam Nemet<br>
<b>Sent:</b> Friday, October 24, 2014 10:58 AM<br>
<b>To:</b> Demikhovsky, Elena<br>
<b>Cc:</b> dag@cray.com; llvmdev@cs.uiuc.edu<br>
<b>Subject:</b> Re: [LLVMdev] Adding masked vector load and store intrinsics<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">On Oct 24, 2014, at 4:24 AM, Demikhovsky, Elena <<a href="mailto:elena.demikhovsky@intel.com">elena.demikhovsky@intel.com</a>> wrote:<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><br>
<br>
<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
</div>
</blockquote>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">I do agree that we would like to have one IR node to capture these so that they survive until ISel and that their specific semantics can be expressed. However, can you discuss the other options (new IR instructions, target-specific intrinsics)
and why you went with target-independent intrinsics.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">My intuition would have been to go with target-specific intrinsics until we have something solid implemented and then potentially turn this into native IR instructions as the next step (for other targets, etc.). I am particularly worried
whether we really want to generate these for targets that don’t have vector predication support.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<div>
<p class="MsoNormal">There is also the related question of vector predicating any other instruction beyond just loads and stores which AVX512 supports. This is probably a smaller gain but should probably be part of the plan as well.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
</div>
<div>
<p class="MsoNormal">Adam<o:p></o:p></p>
</div>
<p class="MsoNormal"><br>
<br>
<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<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""><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
</div>
<p><span style="font-size:10.5pt;font-family:"Helvetica","sans-serif"">---------------------------------------------------------------------<br>
Intel Israel (74) Limited<o:p></o:p></span></p>
<p><span style="font-size:10.5pt;font-family:"Helvetica","sans-serif"">This e-mail and any attachments may contain confidential material for<br>
the sole use of the intended recipient(s). Any review or distribution<br>
by others is strictly prohibited. If you are not the intended<br>
recipient, please contact the sender and delete all copies.<o:p></o:p></span></p>
</div>
</blockquote>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
</body>
</html>