<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><meta http-equiv="Content-Type" content="text/html; charset=us-ascii" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><meta http-equiv="Content-Type" content="text/html; charset=us-ascii" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi<br class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On May 16, 2022, at 17:56, Sanjay Patel via llvm-commits <<a href="mailto:llvm-commits@lists.llvm.org" class="">llvm-commits@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class=""><br class="">Author: Sanjay Patel<br class="">Date: 2022-05-16T12:55:52-04:00<br class="">New Revision: 3794cc0e996481e10307b67c8436aa44e0d65d22<br class=""><br class="">URL: <a href="https://github.com/llvm/llvm-project/commit/3794cc0e996481e10307b67c8436aa44e0d65d22" class="">https://github.com/llvm/llvm-project/commit/3794cc0e996481e10307b67c8436aa44e0d65d22</a><br class="">DIFF: <a href="https://github.com/llvm/llvm-project/commit/3794cc0e996481e10307b67c8436aa44e0d65d22.diff" class="">https://github.com/llvm/llvm-project/commit/3794cc0e996481e10307b67c8436aa44e0d65d22.diff</a><br class=""><br class="">LOG: [InstCombine] invert canonicalization for cast of signbit test<br class=""><br class="">The existing transform was wrong in 3 ways:<br class="">1. It created an extra instruction when the source and dest types don't match.<br class="">2. It did not account for an extra use of the icmp, so could create 2 extra insts.<br class="">3. It favored bit hacks over icmp (icmp generally has better analysis).<br class=""><br class="">This fixes #54692 (modeled by the PhaseOrdering tests).<br class=""><br class="">This is a minimal step to fix the bug, but we should likely invert<br class="">the sibling transform for the "is negative" pattern too.<br class=""><br class="">The backend should be able to invert this back to a shift if that<br class="">leads to better codegen.<br class=""></div></div></blockquote></div><br class=""><div class=""><br class=""></div><div class="">I believe this change may be causing a hang in bootstrap builds when building llvm-project/clang/unittests/Frontend/CompilerInvocationTest.cpp during stage2. With this patch reverted, building that file completes within 5 seconds. With the patch, Clang spins in instcombine.</div><div class=""><br class=""></div><div class="">It looks like the following bots are timing out because of this:</div><div class=""><br class=""></div><div class=""><a href="https://lab.llvm.org/buildbot#builders/179/builds/3688" class=""><font color="#1155cc" face="Arial, Helvetica, sans-serif" class="">https://lab.llvm.org/buildbot#</font><font color="#1155cc" face="Arial, Helvetica, sans-serif" class=""><wbr class="">builders/179/builds/3688</font></a></div><div class=""><a href="https://lab.llvm.org/buildbot#builders/85/builds/8641" class=""><font color="#1155cc" face="Arial, Helvetica, sans-serif" class="">https://lab.llvm.org/buildbot#</font><font color="#1155cc" face="Arial, Helvetica, sans-serif" class=""><wbr class="">builders/85/builds/8641</font></a></div><div class=""><a href="https://lab.llvm.org/buildbot#builders/168/builds/6486" class=""><font color="#1155cc" face="Arial, Helvetica, sans-serif" class="">https://lab.llvm.org/buildbot#</font><font color="#1155cc" face="Arial, Helvetica, sans-serif" class=""><wbr class="">builders/168/builds/6486</font></a></div><div class=""><a href="https://lab.llvm.org/buildbot#builders/74/builds/11107" class=""><font color="#1155cc" face="Arial, Helvetica, sans-serif" class="">https://lab.llvm.org/buildbot#</font><font color="#1155cc" face="Arial, Helvetica, sans-serif" class=""><wbr class="">builders/74/builds/11107</font></a></div><div class=""><br class=""></div><div class="">It might be good to revert the change if it cannot be fixed quickly, to get the bots back to green.</div><div class=""><br class=""></div><div class="">Cheers,</div><div class="">Florian</div></div></div></body></html>