<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Jun 10, 2016 at 9:58 PM, Mehdi Amini via llvm-dev <span dir="ltr"><<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</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"><div style="word-wrap:break-word">Hi,<div><br><div><span class=""><blockquote type="cite"><div>On Jun 10, 2016, at 7:00 PM, Lawrence, Peter via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:</div><br><div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Daniel,<u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"> My point is this,<u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">If (cond) ---- optimizer takes advantage of knowing cond == true within the “then” part<u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Assert(cond) ---- optimizer takes advantage of knowing cond == true for the rest of the scope<u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Assume(cond) ---- optimizer takes advantage of knowing cond == true for the rest of the scope<u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">If we aren’t implementing these in a consistent manner (like using an intrinsic for one but not the others)<u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Then we aren’t doing a good job of engineering,</span></div></div></div></blockquote><div><br></div></span><div>It is not clear cut for me.</div><div>First the Assert(cond) is not an llvm construct AFAIK. At the source level it is usually a macro that turns into `if (!Cond) abort()` and thus can be reduced to your first case.</div><div>(Also I believe it disappears in optimized build and the optimizer/LLVM will never see the test).</div><div><br></div><div>And second, it seems to me that there is a fundamental difference between the first and last case: in the first case the optimizer deduces some properties from the control flow (i.e. cond==true within the "then" part), while in the assume case it is an information that the optimizer can't deduce itself, and that is *not related to the control flow* but is present thanks to a hint from the programmer (or the front-end).</div><div><br></div><div>It is not clear that these two sources of information can be reconcile easily with a common representation.</div></div></div></div></blockquote><div><br></div><div>Perhaps a naive question then is: why don't we represent assume as `if (!cond) unreachable; else <the rest of the code>`?</div><div><br></div><div>-- Sean Silva</div><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"><div style="word-wrap:break-word"><div><div><span class=""><br><blockquote type="cite"><div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">IE we should be able to get “assume” to work for free if we are doing it right.</span></div></div></div></blockquote><div><br></div></span><div>I'm not sure what you mean by "work for free"?</div><span class=""><font color="#888888"><div><br></div><div>-- </div><div>Mehdi</div><br></font></span><blockquote type="cite"><div><span class=""><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Asking “how do I get this intrinsic to work” is perhaps the wrong question,<u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Perhaps the right question is, how do we represent assume so that we get it for free.<u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">---Peter Lawrence.<u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><b><span style="font-size:11pt;font-family:Calibri,sans-serif">From:</span></b><span style="font-size:11pt;font-family:Calibri,sans-serif"><span> </span>Daniel Berlin [<a href="mailto:dberlin@dberlin.org" target="_blank">mailto:dberlin@dberlin.org</a>]<span> </span><br><b>Sent:</b><span> </span>Friday, June 10, 2016 6:32 PM<br><b>To:</b><span> </span>Lawrence, Peter <<a href="mailto:c_plawre@qca.qualcomm.com" target="_blank">c_plawre@qca.qualcomm.com</a>><br><b>Cc:</b><span> </span><a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a><br><b>Subject:</b><span> </span>Re: [llvm-dev] Early CSE clobbering llvm.assume<u></u><u></u></span></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><u></u> <u></u></div><p class="MsoNormal" style="margin:0in 0in 12pt;font-size:12pt;font-family:'Times New Roman',serif">We do, implicitly, because assert generates if conditions. Or at least, gvn knows how to propagate that implicit info. We can do better by exposing it more, most likely<u></u><u></u></p><div><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif">On Fri, Jun 10, 2016, 5:59 PM Lawrence, Peter <<a href="mailto:c_plawre@qca.qualcomm.com" style="color:purple;text-decoration:underline" target="_blank">c_plawre@qca.qualcomm.com</a>> wrote:<u></u><u></u></div></div><blockquote style="border-style:none none none solid;border-left-color:rgb(204,204,204);border-left-width:1pt;padding:0in 0in 0in 6pt;margin:5pt 0in 5pt 4.8pt"><div><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Daniel,</span><u></u><u></u></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"> Well then my next (dumb?) question is why aren’t we using source level assert information</span><u></u><u></u></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">For optimization ?</span><u></u><u></u></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"> </span><u></u><u></u></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">--Peter Lawrence.</span><u></u><u></u></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"> </span><u></u><u></u></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"> </span><u></u><u></u></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"><b><span style="font-size:11pt;font-family:Calibri,sans-serif">From:</span></b><span style="font-size:11pt;font-family:Calibri,sans-serif"><span> </span>Daniel Berlin [mailto:</span><a href="mailto:dberlin@dberlin.org" style="color:purple;text-decoration:underline" target="_blank"><span style="font-size:11pt;font-family:Calibri,sans-serif">dberlin@dberlin.org</span></a><span style="font-size:11pt;font-family:Calibri,sans-serif">]<span> </span><br><b>Sent:</b><span> </span>Friday, June 10, 2016 5:39 PM<br><b>To:</b><span> </span>Lawrence, Peter <</span><a href="mailto:c_plawre@qca.qualcomm.com" style="color:purple;text-decoration:underline" target="_blank"><span style="font-size:11pt;font-family:Calibri,sans-serif">c_plawre@qca.qualcomm.com</span></a><span style="font-size:11pt;font-family:Calibri,sans-serif">><br><b>Cc:</b><span> </span></span><a href="mailto:llvm-dev@lists.llvm.org" style="color:purple;text-decoration:underline" target="_blank"><span style="font-size:11pt;font-family:Calibri,sans-serif">llvm-dev@lists.llvm.org</span></a><span style="font-size:11pt;font-family:Calibri,sans-serif"><br><b>Subject:</b><span> </span>Re: [llvm-dev] Early CSE clobbering llvm.assume</span><u></u><u></u></div></div></div><div><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"> <u></u><u></u></div><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"> <u></u><u></u></div><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"> <u></u><u></u></div><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif">On Fri, Jun 10, 2016 at 5:34 PM, Lawrence, Peter via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" style="color:purple;text-decoration:underline" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<u></u><u></u></div><blockquote style="border-style:none none none solid;border-left-color:rgb(204,204,204);border-left-width:1pt;padding:0in 0in 0in 6pt;margin:5pt 0in 5pt 4.8pt"><div><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif">My (dumb?) question would be: why is llvm.assume being handled any differently than llvm.assert ?<u></u><u></u></div></div></div></blockquote><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"> <u></u><u></u></div></div><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif">There is no llvm.assert intrinsic, so i'm not sure what you mean here. Care to give an example?<u></u><u></u></div></div><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"> <u></u><u></u></div></div><blockquote style="border-style:none none none solid;border-left-color:rgb(204,204,204);border-left-width:1pt;padding:0in 0in 0in 6pt;margin:5pt 0in 5pt 4.8pt"><div><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif">Other than one trapping and one not-trapping, they should be identical, in both cases they are giving<u></u><u></u></div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif">The optimizers information, and that shouldn’t be any different from being inside an “if” statement with the same condition ?<u></u><u></u></div></div></div></blockquote><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"> <u></u><u></u></div></div><div><div style="margin:0in 0in 0.0001pt;font-size:12pt;font-family:'Times New Roman',serif"> <u></u><u></u></div></div></div></div></div></div></div></blockquote></div></div></span><span style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">_______________________________________________</span><span class=""><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><span style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">LLVM Developers mailing list</span><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><span style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important"><a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a></span><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><span style="font-family:Helvetica;font-size:12px;font-style:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important"><a href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev" target="_blank">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a></span></span></div></blockquote></div><br></div></div><br>_______________________________________________<br>
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