<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Apr 11, 2016 at 10:28 AM, Daniel Berlin <span dir="ltr"><<a href="mailto:dberlin@dberlin.org" target="_blank">dberlin@dberlin.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote"><span class="">On Mon, Apr 11, 2016 at 10:18 AM, Teresa Johnson <span dir="ltr"><<a href="mailto:tejohnson@google.com" target="_blank">tejohnson@google.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">tejohnson added a comment.<br>
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In <a href="http://reviews.llvm.org/D15537#397257" rel="noreferrer" target="_blank">http://reviews.llvm.org/D15537#397257</a>, @davidxl wrote:<br>
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> yes -- MemSSA will get there. Short term workaround might also be needed :)<br>
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</span>I think we need a stopgap fix for this non-linear compile time issue. </blockquote><div><br></div></span><div>Again, my main concern is that literally every other "stopgap" fix around memory optimization issues has not been a stopgap.</div><div>There is no other way to put it.</div><div>These things have compounded *very* badly over time. </div><div>I'm not approving yet another compile time knob for another N^2/N^3 pass that we know how to fix the right way.<br></div><div><div>(In part because i am the one who ends up having to fix it later :P) </div><div><br></div><div>We have to hold the line somewhere. This is where i am holding it. If you want to get someone else to approve it, i won't stand in the way.</div><div> <br></div></div><span class=""><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">I don't think waiting until it is reimplemented to use MemorySSA is a good strategy given the extreme compile time issues,</blockquote><div><br></div></span><div>Which, for the most part, only occur in new build modes or very artificial code.</div></div></div></div></blockquote><div><br></div><div>Machine generated code (not specifically related to ThinLTO although that was where I found it - I can reproduce with all ThinLTO importing disabled). Regardless of how artificial, it is still blocking my -O2 compilation.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class=""><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"> and I can't even find a switch to disable this pass.<br></blockquote><div><br></div></span><div>This is definitely a problem. Honestly, at this point, i would rather see us disable the pass entirely with a large number of stores than add yet another knob to control other things (like how many instructions it visits).</div></div></div></div></blockquote><div><br></div><div>I'm fine with that approach, just arguing that we need something to address this as soon as possible.</div><div> <br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class=""><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><br>
BTW, the author had provided a test case on the mailing list (there are two threads for this patch):<br>
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<a href="http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160201/330335.html" rel="noreferrer" target="_blank">http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160201/330335.html</a></blockquote><div><br></div></span><div>If you look at the testcase, it is *very* artificial :)</div></div></div></div></blockquote><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><div><br></div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><br>
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<a href="http://reviews.llvm.org/D15537" rel="noreferrer" target="_blank">http://reviews.llvm.org/D15537</a><br>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><span style="font-family:Times;font-size:medium"><table cellspacing="0" cellpadding="0"><tbody><tr style="color:rgb(85,85,85);font-family:sans-serif;font-size:small"><td nowrap style="border-top-style:solid;border-top-color:rgb(213,15,37);border-top-width:2px">Teresa Johnson |</td><td nowrap style="border-top-style:solid;border-top-color:rgb(51,105,232);border-top-width:2px"> Software Engineer |</td><td nowrap style="border-top-style:solid;border-top-color:rgb(0,153,57);border-top-width:2px"> <a href="mailto:tejohnson@google.com" target="_blank">tejohnson@google.com</a> |</td><td nowrap style="border-top-style:solid;border-top-color:rgb(238,178,17);border-top-width:2px"> 408-460-2413</td></tr></tbody></table></span></div>
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