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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - std::terminate() and abort() do not have __builtin_unreachable() semantics"
href="https://bugs.llvm.org/show_bug.cgi?id=45839">45839</a>
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<th>Summary</th>
<td>std::terminate() and abort() do not have __builtin_unreachable() semantics
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>All
</td>
</tr>
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<th>OS</th>
<td>All
</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>C++
</td>
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<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>s_bugzilla@nedprod.com
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>Consider the codegen from <a href="https://godbolt.org/z/Em3ZXP">https://godbolt.org/z/Em3ZXP</a>:
```
#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <exception>
void sum(uint32_t *__restrict a, const uint32_t *__restrict b, const uint32_t
*__restrict c, size_t count)
{
auto invoke_terminate = []{
#ifdef USE_UNREACHABLE
__builtin_unreachable();
#else
std::terminate();
#endif
};
if((((uintptr_t)a) & 15)!=0) invoke_terminate();
if((((uintptr_t)b) & 15)!=0) invoke_terminate();
if((((uintptr_t)c) & 15)!=0) invoke_terminate();
if((count & 15) != 0) invoke_terminate();
while(count != 0)
{
*a++ = *b++ + *c++;
count--;
}
}
```
It would seem that functions marked with both [[noreturn]] and noexcept do not
have the same improvements on codegen as __builtin_unreachable() has. This is
despite that [[noreturn]] functions returning is explicitly required to be UB
in the standard, and if they are noexcept then they cannot throw an exception
either.
Can noexcept functions marked [[noreturn]] please gain the same effects on
codegen as __builtin_unreachable() has please?</pre>
</div>
</p>
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