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    <div class="moz-cite-prefix">On 5/14/2018 2:21 AM,
      Gopalasubramanian, Ganesh wrote:<br>
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cite="mid:DM5PR1201MB015514E314773B28EB9CA5C8829C0@DM5PR1201MB0155.namprd12.prod.outlook.com">
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          <li class="MsoNormal" style="color:windowtext;mso-list:l0
            level1 lfo1"><span style="color:black">Looks like some sort
              of pass ordering issue; it will vectorize if indvars runs
              sometime between loop unswitch and the vectorizer.</span><o:p></o:p></li>
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        <p class="MsoNormal"><o:p> </o:p></p>
        <p class="MsoNormal" style="margin-left:.25in">That insight is
          helpful. I scheduled Canonicalization of induction variable
          before loop vectorization and could get the loop vectorized.<o:p></o:p></p>
        <p class="MsoNormal" style="margin-left:.25in">The indvars are
          heavily dependent on SCEV. If there a scalar like tmp which is
          of real type, we may not be able to get the indvars sorted out
          because of the integer type limitation in SCEV!<o:p></o:p></p>
        <p class="MsoNormal"
style="mso-margin-top-alt:0in;margin-right:0in;margin-bottom:12.0pt;margin-left:.25in">Is
          there a way out when we have a scalar float computation that
          is dependent on induction variable?</p>
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    <br>
    In general, a loop can't be vectorized if there's a PHI node; a
    scalar dependency means the iterations have to run in order.  But
    there are some special cases for reductions and induction
    variables.  For the LLVM loop vectorizer, see
    LoopVectorizationLegality::canVectorizeInstrs.<br>
    <br>
    -Eli<br>
    <br>
    <pre class="moz-signature" cols="72">-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project</pre>
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