<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<p>Chandler/All,</p>
<p>We've just started testing the new pass manager this week and we
ran into a 548x slowdown (i.e., 6.28s to 3443.83s) for one of the
files from SPEC2017/blender. The issue arises only in debug
builds due to the numerous calls to RefSCC::verify() and
SCC::verify() in the LazyCallGraph implementation. Would it make
sense to start predicating these calls with the EXPENSIVE_CHECKS
macro, rather than NDEBUG?</p>
<p> Chad<br>
</p>
<br>
<div class="moz-cite-prefix">On 10/18/2017 2:50 AM, Chandler Carruth
via llvm-dev wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAGCO0Kh2FXY4D9WSLTmdHvOi8i-=fb-+i=6V6iv8LzzMV3NL6g@mail.gmail.com">
<div dir="ltr">Greetings everyone!
<div><br>
</div>
<div>The new pass manager is getting extremely close to the
point where I'm not aware of any significant outstanding work
needed, and I'd like to see what else would be needed to
enable it by default. Here are the current functionality I'm
aware of outstanding:</div>
<div><br>
</div>
<div>1) Does not do non-trivial loop unswitching. Majority of
this is in <a href="https://reviews.llvm.org/D34200"
moz-do-not-send="true">https://reviews.llvm.org/D34200</a> but
will need one or two small follow-ups.</div>
<div><br>
</div>
<div>2) Currently, sanitizers don't work correctly with it.
Thanks to the work of others, the missing infrastructure has
been added and I'll send a patch to wire this up this week.</div>
<div><br>
</div>
<div>3) Missing support for 'optnone'. I've been working on
this, but the existing testing wasn't as thorough as I wanted,
so it is going slowly. I've got about 1/4 of this implemented
and should have patches this week or next.</div>
<div><br>
</div>
<div>4) Missing opt-bisect (or similar) facility. This looks
pretty trivial to add, but I've not even started. If anyone is
interested in it, go for it. We might even be able to do
something simpler using the generic debug counters and get
equivalent functionality.</div>
<div><br>
</div>
<div>... that's it?</div>
<div><br>
</div>
<div>Optimization quality / run-time performance:</div>
<div>- We've been using it at Google extensively and are very
happy with the optimization quality. Benchmarks look *very*
good here.</div>
<div>- More data from other users would be important.</div>
<div>- You can try it out with `-fexperimental-new-pass-manager`
to Clang</div>
<div><br>
</div>
<div>Compile-time performance:</div>
<div>- Sometimes *much* better due to cached analyses.</div>
<div>- Sometimes worse, typically due to more / different
inlining in turn running main pipeline (GVN + InstCombine)
more times or over more code.</div>
<div>- Overall somewhat a wash, but the increased compile times
typically due to the optimizer "trying" harder, so not too
concerning on our end.</div>
<div>- Again, more feedback from other users good:
`-fexperimental-new-pass-manager` to Clang</div>
<div><br>
</div>
<div>Once the four missing things land, I'll also happily work
on collecting some of the basics on the test-suite and CTMark.
But I suspect more "in the wild" data would really be useful
here given the significance of the change.</div>
<div><br>
</div>
<div>Thoughts? What else (beyond the four items above and
feedback on run-time and compile-time) would folks like to
see?</div>
<div><br>
</div>
<div>Once this happens, I'll also be preparing some batch,
mechanical updates to the test suite to primarily use the new
pass manager. Also there is lots of documentation updates that
will be needed here.</div>
<div><br>
</div>
<div>-Chandler</div>
<div><br>
</div>
<div>PS: I'll be sending a note to cfe-dev as a "heads up" about
this discussion as in some ways, the default flip is mostly a
Clang default flip. But hopefully our doc updates will trigger
this being "perceived" as the default for other frontends, and
I'll try to reach out to other major frontends as well (Swift
and Rust are on my radar, and I've already started talking
with Philip Reames about their Falcon JIT).</div>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
LLVM Developers mailing list
<a class="moz-txt-link-abbreviated" href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>
<a class="moz-txt-link-freetext" href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a>
</pre>
</blockquote>
<br>
</body>
</html>