<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: arial,helvetica,sans-serif; font-size: 10pt; color: #000000'><br><hr id="zwchr"><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px; color: rgb(0, 0, 0); font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;"><b>From: </b>"Mehdi Amini" <mehdi.amini@apple.com><br><b>To: </b>"Hal Finkel" <hfinkel@anl.gov><br><b>Cc: </b>"Elena Demikhovsky" <elena.demikhovsky@intel.com>, "llvm-dev" <llvm-dev@lists.llvm.org><br><b>Sent: </b>Tuesday, July 26, 2016 1:37:28 PM<br><b>Subject: </b>Re: [llvm-dev] Alias Analysis with inbound GEPs<br><br>
<br class=""><div><blockquote class=""><div class="">On Jul 25, 2016, at 10:16 AM, Hal Finkel via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" class="" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div style="font-style: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; font-family: arial,helvetica,sans-serif; font-size: 10pt;" class=""><br class="Apple-interchange-newline"><hr id="zwchr" class=""><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;" class=""><b class="">From:<span class="Apple-converted-space"> </span></b>"Elena via llvm-dev Demikhovsky" <<a href="mailto:llvm-dev@lists.llvm.org" class="" target="_blank">llvm-dev@lists.llvm.org</a>><br class=""><b class="">To:<span class="Apple-converted-space"> </span></b>"llvm-dev" <<a href="mailto:llvm-dev@lists.llvm.org" class="" target="_blank">llvm-dev@lists.llvm.org</a>><br class=""><b class="">Sent:<span class="Apple-converted-space"> </span></b>Monday, July 25, 2016 9:45:55 AM<br class=""><b class="">Subject:<span class="Apple-converted-space"> </span></b>[llvm-dev] Alias Analysis with inbound GEPs<br class=""><br class=""><font class="" face="Calibri" size="2"><span style="font-size: 11pt;" class=""><div class="">Hi,</div><div class=""> </div><div class="">I’m checking aliasing of two pointers:</div><div class=""> </div><div class=""> %GEP1 = getelementptr inbounds %struct.s, %struct.s* %0, i64 0, i32 1, i64 %indvars.iv41, i64 %indvars.iv39</div><div class=""> %GEP2 = getelementptr inbounds %struct.s, %struct.s* %0, i64 0, i32 16</div><div class=""> </div><div id="DWT16163" class="">The result I got is “PartialAlias” because the indices of the GEP1 are variable.</div></span></font></blockquote>That seems like a bug. PartialAlias should only be returned when we can prove a partial overlap. Otherwise, MayAlias should be returned.<br class=""><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;" class=""><font class="" face="Calibri" size="2"><span style="font-size: 11pt;" class=""><div id="DWT16164" class="">Shouldn’t the “inbounds” keyword mean that the access to sub-array is also in-bounds?</div></span></font></blockquote>No. inbounds applies only to the whole object.<br class=""></div></div></blockquote><div><br class=""></div><div id="DWT8065">Would this proposal help: <a href="https://reviews.llvm.org/D22793" class="" target="_blank">https://reviews.llvm.org/D22793</a> ?</div></div></blockquote>Yes, it looks like that would help.<br><br> -Hal<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px; color: rgb(0, 0, 0); font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;"><div><div></div><div><br class=""></div><div>— </div><div>Mehdi</div><div><br class=""></div><br class=""><blockquote class=""><div class=""><div style="font-style: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; font-family: arial,helvetica,sans-serif; font-size: 10pt;" class=""><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;" class=""><font class="" face="Calibri" size="2"><span style="font-size: 11pt;" class=""><div class=""></div><div id="DWT16165" class="">I’m trying to reach “NoAlias” consensus between GEP1 and GEP2.</div></span></font></blockquote>Did the original code come from C or C++? What are we modeling here?<br class=""><br class=""> -Hal<br class=""><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;" class=""><font class="" face="Calibri" size="2"><span style="font-size: 11pt;" class=""><div class=""></div><div class=""> </div><div class="">Thanks.</div><div class=""> </div><ul style="margin: 0pt; padding-left: 36pt;" class=""><font class="" color="#2f5496" face="Times New Roman" size="3"><span style="font-size: 12pt;" class=""><li class=""><b class=""><i class="">Elena</i></b></li></span></font></ul><div class=""> </div><div class=""> </div><div class=""> </div></span></font><div style="margin: 0px;" class="">---------------------------------------------------------------------<br class="">Intel Israel (74) Limited</div><div style="margin: 0px;" class="">This e-mail and any attachments may contain confidential material for<br class="">the sole use of the intended recipient(s). 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