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<div class="moz-cite-prefix">On 1/30/2018 6:26 AM, Martin J.
O'Riordan via cfe-dev wrote:<br>
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<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">Hi CFE-Devs,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">I am investigating a number of
regressions in my out-of-tree target since I migrated from
LLVM v4 to v5. They have been there a while, but waiting
for me to have time to analyse. In all cases the enabling
of the loop-unroller seems to cause the problem.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">There are 14 failures are in ‘</span><span
style="font-size:12.0pt;font-family:"Courier New"">tests/std/containers/unord/unord[multimap]</span><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">’ and 1 other ‘</span><span
style="font-size:12.0pt;font-family:"Courier New"">tests/src/utilities/exchange/exchange.pass.cpp</span><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">’. All appear to be to do with the
list constructors and the list iteration. I can’t see any
particular issue with my backend, except that it is for
non-interlocked VLIW so scheduling tends to be more
sensitive to tiny differences in dependencies than for more
traditional targets.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">Disabling unrolling, or disabling
function inlining seems to fix the problem.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif"><o:p> </o:p></span></p>
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<br>
I would generally assume this indicates an optimization bug. (That
isn't always true; the source code could have undefined behavior.
But if the test doesn't have any asan or ubsan failures, there isn't
any good way to track down undefined behavior anyway.)<br>
<br>
You probably want to start with
<a class="moz-txt-link-freetext" href="https://llvm.org/docs/OptBisect.html">https://llvm.org/docs/OptBisect.html</a>.<br>
<br>
-Eli<br>
<pre class="moz-signature" cols="72">--
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project</pre>
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