<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Mar 30, 2016, at 3:49 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com" class="">dblaikie@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><br class="Apple-interchange-newline"><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><div class="gmail_quote" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">On Wed, Mar 30, 2016 at 3:47 PM, Mehdi Amini via llvm-commits<span class="Apple-converted-space"> </span><span dir="ltr" class=""><<a href="mailto:llvm-commits@lists.llvm.org" target="_blank" class="">llvm-commits@lists.llvm.org</a>></span><span class="Apple-converted-space"> </span>wrote:<br class=""><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><span class=""><br class="">> On Mar 30, 2016, at 3:34 PM, Pete Cooper via llvm-commits <<a href="mailto:llvm-commits@lists.llvm.org" class="">llvm-commits@lists.llvm.org</a>> wrote:<br class="">><br class="">> Author: pete<br class="">> Date: Wed Mar 30 17:34:37 2016<br class="">> New Revision: 264945<br class="">><br class="">> URL:<span class="Apple-converted-space"> </span><a href="http://llvm.org/viewvc/llvm-project?rev=264945&view=rev" rel="noreferrer" target="_blank" class="">http://llvm.org/viewvc/llvm-project?rev=264945&view=rev</a><br class="">> Log:<br class="">> Remove useless unreachable. Switch coverage already gives us this. NFC<br class=""><br class=""></span>Does the optimizer has a notion of the switch coverage here? Or is the front-end generating an unreachable after your change?<br class=""></blockquote><div class=""><br class=""></div><div class="">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 class=""><br class="">Clang avoids the possible false positive by being optimistic and assuming that the enum will only contain enumerator values.</div></div></div></blockquote><div><br class=""></div><div>Clang could be more aggressive and generate an unreachable in the default-generated block of the switch instruction in this case.</div><div><br class=""></div><div>-- </div><div>Mehdi</div><div><br class=""></div><div><br class=""></div><br class=""><blockquote type="cite" class=""><div class=""><div class="gmail_quote" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div class=""> </div><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;">Also it is not totally NFC as llvm_unreachable is lowered to a real check in an assert build.<br class=""></blockquote><div class=""><br class=""></div><div class="">I think that still qualifies under what I'd consider NFC. An assertion firing isn't functionality, as such - just bugs.</div><div class=""> </div><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><span class="HOEnZb"><font color="#888888" class=""><br class="">--<br class="">Mehdi<br class=""></font></span><div class="HOEnZb"><div class="h5"><br class=""><br class=""><br class="">><br class="">> Modified:<br class="">> lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp<br class="">><br class="">> Modified: lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp<br class="">> URL:<span class="Apple-converted-space"> </span><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" class="">http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp?rev=264945&r1=264944&r2=264945&view=diff</a><br class="">> ==============================================================================<br class="">> --- lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp (original)<br class="">> +++ lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp Wed Mar 30 17:34:37 2016<br class="">> @@ -865,7 +865,6 @@ std::error_code Util::getSymbolTableRegi<br class="">> }<br class="">> break;<br class="">> }<br class="">> - llvm_unreachable("atom->scope() unknown enum value");<br class="">> }<br class="">><br class="">> std::error_code Util::addSymbols(const lld::File &atomFile,<br class="">><br class="">><br class="">> _______________________________________________<br class="">> llvm-commits mailing list<br class="">><span class="Apple-converted-space"> </span><a href="mailto:llvm-commits@lists.llvm.org" class="">llvm-commits@lists.llvm.org</a><br class="">><span class="Apple-converted-space"> </span><a href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits" rel="noreferrer" target="_blank" class="">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits</a><br class=""><br class="">_______________________________________________<br class="">llvm-commits mailing list<br class=""><a href="mailto:llvm-commits@lists.llvm.org" class="">llvm-commits@lists.llvm.org</a><br class=""><a href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits" rel="noreferrer" target="_blank" class="">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits</a></div></div></blockquote></div></div></blockquote></div><br class=""></body></html>