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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [coroutines] CoroSplit fails to add musttaill under -O2"
href="https://bugs.llvm.org/show_bug.cgi?id=43070">43070</a>
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<th>Summary</th>
<td>[coroutines] CoroSplit fails to add musttaill under -O2
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Transformation Utilities
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>gornishanov@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<pre>Created <span class=""><a href="attachment.cgi?id=22405" name="attach_22405" title="repro of a failure to add musttail to symmetric coroutine transfer">attachment 22405</a> <a href="attachment.cgi?id=22405&action=edit" title="repro of a failure to add musttail to symmetric coroutine transfer">[details]</a></span>
repro of a failure to add musttail to symmetric coroutine transfer
CoroSplit.cpp:simplifyTerminatorLeadingToRet function is deficient and does not
add musttail under -O2 for this simple example (also see attached musttail.ll
reproducer).
<a href="https://godbolt.org/z/7T_YnR">https://godbolt.org/z/7T_YnR</a>
// -O2 -stdlib=libc++ -std=c++2a -fstack-protector-all
// <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Need to add product version numbers"
href="show_bug.cgi?id=1">Bug#1</a>, fails to insert musttail under -O2 (this-bug)
// <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Customize Bugzilla to have some LLVM flavah"
href="show_bug.cgi?id=2">Bug#2</a>, fstack-protector-all interactions prevent tail call ([coroutines]
musttail and -fstack-protector-all interactions don't mix well)
#include <experimental/coroutine>
using namespace std::experimental;
struct coro {
struct promise_type {
suspend_always initial_suspend() { return {}; }
suspend_always final_suspend() { return {}; }
void return_void() {}
void unhandled_exception(){}
coro get_return_object() { return{};}
};
};
coroutine_handle<> h;
struct sym {
bool await_ready() { return false; }
void await_resume() {}
auto await_suspend(coroutine_handle<>) { return h; }
};
coro f() { co_await sym{}; }</pre>
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