
<html>

  <head>

    <meta content="text/html; charset=utf-8" http-equiv="Content-Type">

  </head>

  <body bgcolor="#FFFFFF" text="#000000">

    <p><br>

    </p>

    <div class="moz-cite-prefix">On 12/05/2017 01:47 PM, Lei Huang via

      cfe-dev wrote:<br>

    </div>

    <blockquote

cite="mid:OFB022F28E.4057B6DB-ON002581ED.006C5D8F-002581ED.006CC1F5@notes.na.collabserv.com"

      type="cite">

      <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

      <div class="socmaildefaultfont" dir="ltr"

        style="font-family:Arial, Helvetica,

        sans-serif;font-size:10.5pt">

        <div class="socmaildefaultfont" dir="ltr"

          style="font-family:Arial, Helvetica,

          sans-serif;font-size:10.5pt">

          <div dir="ltr">Â </div>

          <div dir="ltr"><font style="outline: none;" size="3"

              face="Arial">Hello,</font><br style="outline: none;

              font-family: "Helvetica Neue", Helvetica, Arial,

              "Lucida Grande", sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Arial">Â </font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Arial">In the

              discussion on bugzilla 30729, it is mentioned that theÂ <span

                style="outline: none; font-family: "Courier

                New", Courier, monospace;">'</span></font><span

              style="outline: none; font-family: "Courier

              New", Courier, monospace;"><font style="outline:

                none;" size="3">this'</font></span><font style="outline:

              none;" size="3" face="Arial">Â pointer needs to be valid

              upon entry to a non-static method. Â Does the standard

              guaranteeÂ </font><font style="outline: none;" size="3"

              face="Courier">this</font><font style="outline: none;"

              size="3" face="Arial">Â is non-null on entry?</font></div>

        </div>

      </div>

    </blockquote>

    <br>

    Yes. You have to call a non-static member function on a valid

    object.<br>

    <br>

    <blockquote

cite="mid:OFB022F28E.4057B6DB-ON002581ED.006C5D8F-002581ED.006CC1F5@notes.na.collabserv.com"

      type="cite">

      <div class="socmaildefaultfont" dir="ltr"

        style="font-family:Arial, Helvetica,

        sans-serif;font-size:10.5pt">

        <div class="socmaildefaultfont" dir="ltr"

          style="font-family:Arial, Helvetica,

          sans-serif;font-size:10.5pt">

          <div dir="ltr"><font style="outline: none;" size="3"

              face="Arial"> Â If so, is there a reason we can't use that

              fact to mark '</font><font style="outline: none;" size="3"

              face="Courier New">this'</font><font style="outline:

              none;" size="3" face="Arial">Â as '</font><font

              style="outline: none;" size="3" face="Courier New">dereferenceable(sizeof(*this))'</font><font

              style="outline: none;" size="3" face="Arial">?</font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

          </div>

        </div>

      </div>

    </blockquote>

    <br>

    Yes, this seems like a good idea.<br>

    <br>

    Â -Hal<br>

    <br>

    <blockquote

cite="mid:OFB022F28E.4057B6DB-ON002581ED.006C5D8F-002581ED.006CC1F5@notes.na.collabserv.com"

      type="cite">

      <div class="socmaildefaultfont" dir="ltr"

        style="font-family:Arial, Helvetica,

        sans-serif;font-size:10.5pt">

        <div class="socmaildefaultfont" dir="ltr"

          style="font-family:Arial, Helvetica,

          sans-serif;font-size:10.5pt">

          <div dir="ltr"><font style="outline: none;" size="3"

              face="Arial">Â </font><br style="outline: none;

              font-family: "Helvetica Neue", Helvetica, Arial,

              "Lucida Grande", sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Arial">There are

              LICM optimizations we can do based on the knowledge that '</font><font

              style="outline: none;" size="3" face="Courier New">this'Â </font><font

              style="outline: none;" size="3" face="Arial">is non-null

              on entry to a non-static member function.Â </font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Arial">Â </font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Arial">eg. Â For

              the following IR, Â the two highlighted loads are not being

              hoisted out of the for loop because we are not able to

              guarantee that the pointer is non-null. Â If the '</font><font

              style="outline: none;" size="3" face="Courier New">this</font><font

              style="outline: none;" size="3" face="Arial">'Â pointer is

              guaranteed to be non-null on entry and we mark it thus,

              Â then the 2 loads within the for-loop body can then be

              hoisted out into the loop preheader.</font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Arial">Â </font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Arial">This is

              of course just one example of an optimization we could

              perform based on this knowledge, but there are probably a

              number of others (i.e. anything that relies on a pointer

              being '</font><font style="outline: none;" size="3"

              face="Courier New">dereferenceable(N)'</font><font

              style="outline: none;" size="3" face="Arial">).</font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Arial">Â </font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <b style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;"><font style="outline: none;"

                size="3" face="Courier New">$ cat a.ll</font></b><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Courier New">target

              datalayout = "e-m:e-i64:64-n32:64"<br style="outline:

                none;">

              target triple = "powerpc64le-unknown-linux-gnu"</font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Courier New">%struct.S

              = type { <4 x i32>, <4 x i32> }</font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Courier New">;

              Function Attrs: norecurse nounwind readonly<br

                style="outline: none;">

              define <4 x i32>

              @_ZNK1S20constShouldBeHoistedEmDv4_i(%struct.S* nocapture

              readonly %this, i64 %n, <4 x<br style="outline: none;">

              i32> %x) align 2 {<br style="outline: none;">

              entry:<br style="outline: none;">

              Â %tobool9 = icmp eq i64 %n, 0<br style="outline: none;">

              Â br i1 %tobool9, label %for.end, label %for.body.lr.ph</font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Courier New">for.body.lr.ph:

              Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  ; preds = %entry<br

                style="outline: none;">

              Â %k1 = getelementptr inbounds %struct.S, %struct.S* %this,

              i64 0, i32 0<br style="outline: none;">

              Â %k2 = getelementptr inbounds %struct.S, %struct.S* %this,

              i64 0, i32 1<br style="outline: none;">

              Â br label %for.body</font><br style="outline: none;

              font-family: "Helvetica Neue", Helvetica, Arial,

              "Lucida Grande", sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Courier New">for.body:

              Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  ; preds =

              %for.body.lr.ph, %if.end<br style="outline: none;">

              Â %n.addr.011 = phi i64 [ %n, %for.body.lr.ph ], [ %div,

              %if.end ]<br style="outline: none;">

              Â %x.addr.010 = phi <4 x i32> [ %x, %for.body.lr.ph

              ], [ %x.addr.1, %if.end ]<br style="outline: none;">

              Â %rem = and i64 %n.addr.011, 15<br style="outline: none;">

              Â %cmp = icmp eq i64 %rem, 0<br style="outline: none;">

              Â br i1 %cmp, label %if.end, label %if.then</font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Courier New">if.then:

              Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â ; preds =

              %for.body<br style="outline: none;">

              Â </font><b style="outline: none; font-family:

              "Helvetica Neue", Helvetica, Arial, "Lucida

              Grande", sans-serif; font-size: 12px;"><font

                style="outline: none;" size="3" face="Courier New">%0 =

                load <4 x i32>, <4 x i32>* %k1, align 16</font></b><br

              style="outline: none;">

            <font style="outline: none;" size="3" face="Courier New">Â %add

              = add <4 x i32> %0, %x.addr.010<br style="outline:

                none;">

              Â </font><b style="outline: none; font-family:

              "Helvetica Neue", Helvetica, Arial, "Lucida

              Grande", sans-serif; font-size: 12px;"><font

                style="outline: none;" size="3" face="Courier New">%1 =

                load <4 x i32>, <4 x i32>* %k2, align 16</font></b><br

              style="outline: none;">

            <font style="outline: none;" size="3" face="Courier New">Â %xor

              = xor <4 x i32> %add, %1<br style="outline: none;">

              Â br label %if.end</font><br style="outline: none;

              font-family: "Helvetica Neue", Helvetica, Arial,

              "Lucida Grande", sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Courier New">if.end:

              Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  ; preds =

              %for.body, %if.then<br style="outline: none;">

              Â %x.addr.1 = phi <4 x i32> [ %xor, %if.then ], [

              %x.addr.010, %for.body ]<br style="outline: none;">

              Â %div = lshr i64 %n.addr.011, 4<br style="outline: none;">

              Â %tobool = icmp eq i64 %div, 0<br style="outline: none;">

              Â br i1 %tobool, label %for.end, label %for.body</font><br

              style="outline: none; font-family: "Helvetica

              Neue", Helvetica, Arial, "Lucida Grande",

              sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Courier New">for.end:

              Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â ; preds =

              %if.end, %entry<br style="outline: none;">

              Â %x.addr.0.lcssa = phi <4 x i32> [ %x, %entry ], [

              %x.addr.1, %if.end ]<br style="outline: none;">

              Â ret <4 x i32> %x.addr.0.lcssa<br style="outline:

                none;">

              }</font><br style="outline: none; font-family:

              "Helvetica Neue", Helvetica, Arial, "Lucida

              Grande", sans-serif; font-size: 12px;">

            <font style="outline: none;" size="3" face="Arial">Â </font></div>

          <div dir="ltr">Â </div>

          <div dir="ltr">

            <div class="socmaildefaultfont" dir="ltr"

              style="font-family:Arial, Helvetica,

              sans-serif;font-size:10.5pt">

              <div class="socmaildefaultfont" dir="ltr"

                style="font-family:Arial, Helvetica,

                sans-serif;font-size:10.5pt">

                <div class="socmaildefaultfont" dir="ltr"

                  style="font-family:Arial, Helvetica,

                  sans-serif;font-size:10.5pt">

                  <div dir="ltr"><br>

                    Regards,<br>

                    Lei Huang</div>

                  <div dir="ltr">Â </div>

                  <div dir="ltr">Â </div>

                  <div dir="ltr">LLVM Development on POWER</div>

                  <div dir="ltr">Internal mail: C2/YGK/8200/MKM<br>

                    Phone: (905) 413-4419<br>

                    TieLine: 969-4419<br>

                    E-mail: <a class="moz-txt-link-abbreviated" href="mailto:lei@ca.ibm.com">lei@ca.ibm.com</a></div>

                </div>

              </div>

            </div>

          </div>

        </div>

      </div>

      <br>

      <br>

      <fieldset class="mimeAttachmentHeader"></fieldset>

      <br>

      <pre wrap="">_______________________________________________

cfe-dev mailing list

<a class="moz-txt-link-abbreviated" href="mailto:cfe-dev@lists.llvm.org">cfe-dev@lists.llvm.org</a>

<a class="moz-txt-link-freetext" href="http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev">http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev</a>

</pre>

    </blockquote>

    <br>

    <pre class="moz-signature" cols="72">-- 

Hal Finkel

Lead, Compiler Technology and Programming Languages

Leadership Computing Facility

Argonne National Laboratory</pre>

  </body>

</html>