<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Mar 30, 2016 at 3:47 PM, Mehdi Amini 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"><span class=""><br>
> On Mar 30, 2016, at 3:34 PM, Pete Cooper via llvm-commits <<a href="mailto:llvm-commits@lists.llvm.org">llvm-commits@lists.llvm.org</a>> wrote:<br>
><br>
> Author: pete<br>
> Date: Wed Mar 30 17:34:37 2016<br>
> New Revision: 264945<br>
><br>
> URL: <a href="http://llvm.org/viewvc/llvm-project?rev=264945&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project?rev=264945&view=rev</a><br>
> Log:<br>
> Remove useless unreachable.  Switch coverage already gives us this.  NFC<br>
<br>
</span>Does the optimizer has a notion of the switch coverage here? Or is the front-end generating an unreachable after your change?<br></blockquote><div><br></div><div>In GCC, the issue is that they are pessimistic about enum values - they assume (technically correct, of course) that an enum can have any of its representable values, which means that it could contain a value that isn't one of the enumerators & thus the switch could be bypassed entirely and so a return after the switch is needed.<br><br>Clang avoids the possible false positive by being optimistic and assuming that the enum will only contain enumerator values.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Also it is not totally NFC as llvm_unreachable is lowered to a real check in an assert build.<br></blockquote><div><br></div><div>I think that still qualifies under what I'd consider NFC. An assertion firing isn't functionality, as such - just bugs.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<span class="HOEnZb"><font color="#888888"><br>
--<br>
Mehdi<br>
</font></span><div class="HOEnZb"><div class="h5"><br>
<br>
<br>
><br>
> Modified:<br>
>    lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp<br>
><br>
> Modified: lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp<br>
> URL: <a href="http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp?rev=264945&r1=264944&r2=264945&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp?rev=264945&r1=264944&r2=264945&view=diff</a><br>
> ==============================================================================<br>
> --- lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp (original)<br>
> +++ lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp Wed Mar 30 17:34:37 2016<br>
> @@ -865,7 +865,6 @@ std::error_code Util::getSymbolTableRegi<br>
>     }<br>
>     break;<br>
>   }<br>
> -  llvm_unreachable("atom->scope() unknown enum value");<br>
> }<br>
><br>
> std::error_code Util::addSymbols(const lld::File &atomFile,<br>
><br>
><br>
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