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<div class="moz-cite-prefix">On 12/21/2016 03:36 PM, Sanjay Patel
via llvm-dev wrote:<br>
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<div>I would have replied to this thread sooner, but I was busy
adding more instcombines. :)</div>
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<div>The motivation for r289855 is in the commit msg (I'm out of
the office and can't look things up conveniently). Feel free to
revert that and the follow ups, however, if that patch caused a
noticeable slowdown, then it suggests we have a bigger
problem?...that's a simple matcher (no value tracking required).</div>
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<br>
I'd recommend against reverting this until we understand more about
the problem. This is not a critical compile-time regression, and we
don't yet know the cause (it might just be enabling more down-stream
transformations), or whether there have been any corresponding
benefits to code side, performance, etc. It definitely looks like a
pattern that we should catch.<br>
<br>
-Hal<br>
<br>
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<div>On Wed, Dec 21, 2016 at 12:12 PM Sean Silva <<a
moz-do-not-send="true" href="mailto:chisophugis@gmail.com">chisophugis@gmail.com</a>>
wrote:<br>
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<div class="gmail_quote gmail_msg">On Wed, Dec 21, 2016
at 8:07 AM, Davide Italiano via llvm-dev <span
class="gmail_msg"><<a moz-do-not-send="true"
href="mailto:llvm-dev@lists.llvm.org"
class="gmail_msg" target="_blank">llvm-dev@lists.llvm.org</a>></span>
wrote:<br class="gmail_msg">
<blockquote class="gmail_quote gmail_msg"
style="margin:0px 0px 0px 0.8ex;border-left:1px
solid rgb(204,204,204);padding-left:1ex"><span
class="m_3457995834792049705gmail- gmail_msg">On
Mon, Dec 19, 2016 at 4:24 PM, Mikhail Zolotukhin<br
class="gmail_msg">
<br>
<br>
<<a moz-do-not-send="true"
href="mailto:mzolotukhin@apple.com"
class="gmail_msg" target="_blank">mzolotukhin@apple.com</a>>
wrote:<br class="gmail_msg">
<br>
<br>
> Hi Davide,<br class="gmail_msg">
<br>
<br>
><br class="gmail_msg">
<br>
<br>
> Thanks for the analysis, it's really
interesting! And I'm really glad that we now put
more and more attention at the compile time!<br
class="gmail_msg">
<br>
<br>
><br class="gmail_msg">
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<br>
> Just recently I've been looking into
historical compile time data as well, and have had
similar conclusions. The regressions you've found
are probably caused by:<br class="gmail_msg">
<br>
<br>
> 1) r289813 and r289855 - new matchers in
InstCombine<br class="gmail_msg">
<br>
<br>
> 2) r286814 and r288024 - changes in Inlining
cost model<br class="gmail_msg">
<br>
<br>
><br class="gmail_msg">
<br>
<br>
<br class="gmail_msg">
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<br>
</span>Haven't looked at 2) yet, but I can confirm
for 1). Sanjay/Ehsan, can<br class="gmail_msg">
<br>
<br>
you please explain what's the motivation behind the
new<br class="gmail_msg">
<br>
<br>
transformations you introduced? I'm tempted to ask a
revert, but I'd<br class="gmail_msg">
<br>
<br>
like to understand the motivations first.<br
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<div class="gmail_msg">Both r289813 and r289855 add a
very small amount of matching (it seems?) compared
to the rest of the size of instcombine. How is it
that these checks are causing such a
disproportionate slowdown compared to the rest of
instcombine? (by "I can confirm for 1)" I assume you
mean these two patches have a pretty significant
impact on compile time; not "0.1%" each)</div>
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<div class="gmail_extra gmail_msg">
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</div>
<div class="gmail_msg">-- Sean Silva</div>
<div class="gmail_msg"> </div>
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<br>
<br>
--<br class="gmail_msg">
<br>
<br>
Davide<br class="gmail_msg">
<br>
<br>
<br class="gmail_msg">
<br>
<br>
"There are no solved problems; there are only
problems that are more<br class="gmail_msg">
<br>
<br>
or less solved" -- Henri Poincare<br
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<br>
_______________________________________________<br
class="gmail_msg">
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<pre wrap="">_______________________________________________
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<br>
<pre class="moz-signature" cols="72">--
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory</pre>
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