<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Feb 4, 2015, at 10:15 PM, Hal Finkel <<a href="mailto:hfinkel@anl.gov" class="">hfinkel@anl.gov</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><br class="Apple-interchange-newline"><hr id="zwchr" style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><blockquote style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; border-left-width: 2px; border-left-style: solid; border-left-color: rgb(16, 16, 255); margin-left: 5px; padding-left: 5px; text-decoration: none; font-family: Helvetica, Arial, sans-serif; font-size: 12pt;" class=""><b class="">From:<span class="Apple-converted-space"> </span></b>"Adam Nemet" <<a href="mailto:anemet@apple.com" class="">anemet@apple.com</a>><br class=""><b class="">To:<span class="Apple-converted-space"> </span></b>"Hal Finkel" <<a href="mailto:hfinkel@anl.gov" class="">hfinkel@anl.gov</a>><br class=""><b class="">Cc:<span class="Apple-converted-space"> </span></b><a href="mailto:reviews+D7421+public+86df0334cf13545b@reviews.llvm.org" class="">reviews+D7421+public+86df0334cf13545b@reviews.llvm.org</a>, "llvm-commits" <<a href="mailto:llvm-commits@cs.uiuc.edu" class="">llvm-commits@cs.uiuc.edu</a>>, "Nadav Rotem <<a href="mailto:nrotem@apple.com" class="">nrotem@apple.com</a>> (<a href="mailto:nrotem@apple.com" class="">nrotem@apple.com</a>)" <<a href="mailto:nrotem@apple.com" class="">nrotem@apple.com</a>>, "Arnold Schwaighofer" <<a href="mailto:aschwaighofer@apple.com" class="">aschwaighofer@apple.com</a>>,<span class="Apple-converted-space"> </span><a href="mailto:chandlerc@gmail.com" class="">chandlerc@gmail.com</a><br class=""><b class="">Sent:<span class="Apple-converted-space"> </span></b>Wednesday, February 4, 2015 10:04:54 PM<br class=""><b class="">Subject:<span class="Apple-converted-space"> </span></b>Re: [PATCH] IRBuilder: Allow retrieval of the inserted instructions<br class=""><br class=""><br class=""><div class=""><blockquote class=""><div class="">On Feb 4, 2015, at 6:14 PM, Hal Finkel <<a href="mailto:hfinkel@anl.gov" class="" target="_blank">hfinkel@anl.gov</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span class="" style="font-family: Helvetica; font-size: 10px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; float: none; display: inline !important;"><hr id="zwchr" class=""></span><br class="" style="font-family: Helvetica; font-size: 10px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;"><blockquote class="" style="font-family: Helvetica; font-size: 10px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;">From: "Adam Nemet" <<a href="mailto:anemet@apple.com" class="" target="_blank">anemet@apple.com</a>><br class="">To:<span class="Apple-converted-space"> </span><a href="mailto:anemet@apple.com" class="" target="_blank">anemet@apple.com</a>,<span class="Apple-converted-space"> </span><a href="mailto:hfinkel@anl.gov" class="" target="_blank">hfinkel@anl.gov</a>,<span class="Apple-converted-space"> </span><a href="mailto:nrotem@apple.com" class="" target="_blank">nrotem@apple.com</a>,<span class="Apple-converted-space"> </span><a href="mailto:aschwaighofer@apple.com" class="" target="_blank">aschwaighofer@apple.com</a>,<span class="Apple-converted-space"> </span><a href="mailto:chandlerc@gmail.com" class="" target="_blank">chandlerc@gmail.com</a><br class="">Cc:<span class="Apple-converted-space"> </span><a href="mailto:llvm-commits@cs.uiuc.edu" class="" target="_blank">llvm-commits@cs.uiuc.edu</a><br class="">Sent: Wednesday, February 4, 2015 5:58:45 PM<br class="">Subject: [PATCH] IRBuilder: Allow retrieval of the inserted instructions<br class=""><br class="">Hi hfinkel, nadav, aschwaighofer, chandlerc,<br class=""><br class="">This is an RFC.<br class=""><br class="">When the Loop Vectorizer builds the instruction sequence for checks<br class="">it tries<br class="">to determine the first instruction that was emitted in the current<br class="">block.<br class="">This is then used to split the block.<br class=""></blockquote><br class="" style="font-family: Helvetica; font-size: 10px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;"><span class="" style="font-family: Helvetica; font-size: 10px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; float: none; display: inline !important;">Silly question: Why don't we split the block first?</span><br class="" style="font-family: Helvetica; font-size: 10px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;"></div></blockquote><div class=""><br class=""></div><div id="DWT22676" class="">Because we may end up not needing any checks in which case we don’t split. The decision of whether checks are necessary is local to both addRuntimeCheck and addStrideCheck.</div></div></blockquote><br style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Okay, but an alternative design would be to always split early, and then let SimplifyCFG put them back together again should we not actually end up with any checks, right? I'm not necessarily advocating for this approach, and think that the marker code will be cleaner than the existing getFirstInst code, but splitting the block eagerly will also create a trivial way of marking that point, and I want to understand if there are any downsides to that approach before we invent something new.</span><br style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""></div></blockquote><div><br class=""></div><div>I am not aware of any other downsides but I haven’t written this code of course. Hopefully Nadav/Arnold will chime in if there is something to add here.</div><div><br class=""></div><div>Perhaps as another argument you could consider that there seems to be some existing practice to fix up simple things like this in the pass itself rather than relying on other passes. Especially in this case where we could avoid producing the potential inefficiency.</div><div><br class=""></div><div>I guess I am also interested if you see some gotchas with the marker feature or you just think that it’s not a generally useful new addition.</div><div><br class=""></div><div>Thanks,</div><div>Adam</div><div><br class=""></div><blockquote type="cite" class=""><div class=""><span style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Thanks again,</span><br style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Hal</span><br style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><blockquote style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; border-left-width: 2px; border-left-style: solid; border-left-color: rgb(16, 16, 255); margin-left: 5px; padding-left: 5px; text-decoration: none; font-family: Helvetica, Arial, sans-serif; font-size: 12pt;" class=""><div class=""><div class=""></div><div class=""><br class=""></div><div class="">Adam </div><br class=""><blockquote class=""><div class=""><span class="" style="font-family: Helvetica; font-size: 10px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; float: none; display: inline !important;">-Hal</span><br class="" style="font-family: Helvetica; font-size: 10px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;"><br class="" style="font-family: Helvetica; font-size: 10px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;"><blockquote class="" style="font-family: Helvetica; font-size: 10px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;"><br class="">It uses a custom solution for this implemented in the static function<br class="">getFirstInst. The pattern is something like:<br class=""><br class="">Value *V = IRBuilder.CreateBlah(...);<br class="">FirstInst = getFirstInst(FirstInst, V, Loc)<br class="">Value *V2 = IRBuilder.CreateBlah(...);<br class="">FirstInst = getFirstInst(FirstInst, V2, Loc);<br class=""><br class="">(Since CreateBlah may return a constant we may not generate the first<br class="">instruction for V.)<br class=""><br class=""><span class="" style="font-family: Helvetica; font-size: 10px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; float: none; display: inline !important;"></span></blockquote></div></blockquote></div><br class=""></blockquote><br style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">--<span class="Apple-converted-space"> </span></span><br style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><div style="font-family: arial, helvetica, sans-serif; font-size: 13px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span name="x" class=""></span>Hal Finkel<br class="">Assistant Computational Scientist<br class="">Leadership Computing Facility<br class="">Argonne National Laboratory<span name="x" class=""></span><br class=""></div></div></blockquote></div><br class=""></body></html>