<div dir="ltr">Further updating this: Taking the compiler from rL318299 with the new llvm/Transforms/Scalar/SimplifyCFG.h and setting needCanonicalLoops to false fixes the issue; taking the old llvm/Transforms/Scalar/SimplifyCFG.h and setting needCanonicalLoops to true reintroduces the issue.  The values of other flags seem to be unrelated to this regression.<div><br></div><div>With profiling we're particularly seeing slowdowns in the DecompressAllTags<SnappyArrayWriter> function.</div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Dec 15, 2017 at 2:09 PM, Chandler Carruth via llvm-commits <span dir="ltr"><<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.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">FYI, this benchmark actually exists in some form open source: <a href="https://github.com/google/snappy" target="_blank">https://github.com/<wbr>google/snappy</a><div><br></div><div>Still, we'll need to investigate to know why this is slowing things down (so much).</div></div><div class="HOEnZb"><div class="h5"><br><div class="gmail_quote"><div dir="ltr">On Fri, Dec 15, 2017 at 2:02 PM Brooks Moses via Phabricator via llvm-commits <<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">brooksmoses added a comment.<br>
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We're seeing about 10% regressions in an internal benchmark as a result of this change.  Still digging further, but wanted to send a heads-up.<br>
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<a href="https://reviews.llvm.org/D39407" rel="noreferrer" target="_blank">https://reviews.llvm.org/<wbr>D39407</a><br>
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