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From: "wouter.vermaelen at scarlet dot be" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/50385] New: missed-optimization: jump to __builtin_unreachable() not removed Date: Tue, 13 Sep 2011 15:21:00 -0000 [thread overview] Message-ID: <bug-50385-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50385 Bug #: 50385 Summary: missed-optimization: jump to __builtin_unreachable() not removed Classification: Unclassified Product: gcc Version: 4.7.0 Status: UNCONFIRMED Severity: enhancement Priority: P3 Component: tree-optimization AssignedTo: unassigned@gcc.gnu.org ReportedBy: wouter.vermaelen@scarlet.be I'm not sure, but this issue might be the same as bug 49054 (if so, feel free to delete this one). #include <vector> struct S { int a, b; }; std::vector<S> v; int search_1(int a) { for (auto it = v.begin(); /**/; ++it) if (it->a == a) return it->b; } int search_2(int a) { for (auto& e : v) if (e.a == a) return e.b; __builtin_unreachable(); } I expected to see the same generated code for both functions. Instead the 2nd one still contains some useless comparisons and jumps past the end of the function. Since such a (conditional) jump is anyway undefined behavior it can as well be removed (including the instructions required to calculate the condition). Tested with SVN revision 178775 (20110912) on Linux x86_64.
next reply other threads:[~2011-09-13 15:07 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-09-13 15:21 wouter.vermaelen at scarlet dot be [this message] 2011-11-11 1:39 ` [Bug middle-end/50385] " pinskia at gcc dot gnu.org 2013-09-08 8:10 ` glisse at gcc dot gnu.org 2015-02-24 20:54 ` law at redhat dot com
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