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<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>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">I’m checking aliasing of two pointers:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> %GEP1 = getelementptr inbounds %struct.s, %struct.s* %0, i64 0, i32 1, i64 %indvars.iv41, i64 %indvars.iv39<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> %GEP2 = getelementptr inbounds %struct.s, %struct.s* %0, i64 0, i32 16<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> <o:p></o:p></span></p>
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<div id="DWT16163">
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">The result I got is “PartialAlias” because the indices of the GEP1 are variable.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">That seems like a bug. PartialAlias should only be returned when we can prove a partial overlap. Otherwise, MayAlias should be returned.<o:p></o:p></span></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">[Demikhovsky, Elena] There are some comments inside:<o:p></o:p></span></i></b></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white">
</span><span style="font-size:11.0pt;font-family:Consolas;color:green;background:white;mso-highlight:white">// Statically, we can see that the base objects are the same, but the</span><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white">
</span><span style="font-size:11.0pt;font-family:Consolas;color:green;background:white;mso-highlight:white">// pointers have dynamic offsets which we can't resolve. And none of our</span><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white">
</span><span style="font-size:11.0pt;font-family:Consolas;color:green;background:white;mso-highlight:white">// little tricks above worked.</span><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white">
</span><span style="font-size:11.0pt;font-family:Consolas;color:green;background:white;mso-highlight:white">//</span><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white">
</span><span style="font-size:11.0pt;font-family:Consolas;color:green;background:white;mso-highlight:white">// TODO: Returning PartialAlias instead of MayAlias is a mild hack; the</span><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white">
</span><span style="font-size:11.0pt;font-family:Consolas;color:green;background:white;mso-highlight:white">// practical effect of this is protecting TBAA in the case of dynamic</span><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white"> </span><span style="font-size:11.0pt;font-family:Consolas;color:green;background:white;mso-highlight:white">//
indices into arrays of unions or malloc'd memory.</span><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white"><o:p></o:p></span></p>
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</span><span style="font-size:11.0pt;font-family:Consolas;color:blue;background:white;mso-highlight:white">return</span><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white">
</span><span style="font-size:11.0pt;font-family:Consolas;color:darkslategray;background:white;mso-highlight:white">PartialAlias</span><span style="font-size:11.0pt;font-family:Consolas;color:black;background:white;mso-highlight:white">;<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>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Shouldn’t the “inbounds” keyword mean that the access to sub-array is also in-bounds?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">No. inbounds applies only to the whole object.<o:p></o:p></span></p>
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<div id="DWT16165">
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">I’m trying to reach “NoAlias” consensus between GEP1 and GEP2.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Did the original code come from C or C++? What are we modeling here?</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">[Demikhovsky, Elena] C-code:<o:p></o:p></span></i></b></p>
<p class="MsoNormal" style="margin-left:5.25pt"><b><i><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> for (m=0; m < params->num; m++) {<o:p></o:p></span></i></b></p>
<p class="MsoNormal" style="margin-left:5.25pt"><b><i><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> params->a[i][m] = expr;<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> }<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">%GEP1 is the store for params->a[i][m]<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">%GEP2 is the load for params->num.<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">The loop is not vectorized due to a possible collision between params->num and params->a[i][m]. If I take loading of params->num outside the loop, it is
vectorized.<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Bounds of array “a” are known at compile time. Limit of “i” and “m” are runtime variables.<o:p></o:p></span></i></b></p>
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<br>
-Hal<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">Thanks.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> <o:p></o:p></span></p>
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<![if !supportLists]><span style="font-size:10.0pt;font-family:Symbol;color:#2F5496"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span dir="LTR"></span><b><i><span style="color:#2F5496">Elena</span></i></b><span style="color:#2F5496"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> <o:p></o:p></span></p>
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<p><span style="font-family:"Helvetica",sans-serif;color:black">---------------------------------------------------------------------<br>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Hal Finkel<br>
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