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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - clang issues aligned vptr loads for packed structs"
href="https://bugs.llvm.org/show_bug.cgi?id=37274">37274</a>
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<th>Summary</th>
<td>clang issues aligned vptr loads for packed structs
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>richard-llvm@metafoo.co.uk
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<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
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<p>
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<pre>Testcase:
struct [[gnu::packed]] B { virtual void f(); };
static_assert(alignof(B) == 1);
void f(B &b) { b.f(); }
The static_assert passes, and yet Clang generates an aligned vptr load:
%3 = load %struct.B*, %struct.B** %2, align 8, !dbg !14
GCC appears to correctly handle this case:
<a href="https://godbolt.org/g/GJkafy">https://godbolt.org/g/GJkafy</a></pre>
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