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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Confusing misaligned atomic operation warning"
href="https://bugs.llvm.org/show_bug.cgi?id=46947">46947</a>
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<th>Summary</th>
<td>Confusing misaligned atomic operation warning
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Frontend
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>schuett@gmail.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>For the following code, I get an error:
repro.cpp:13:3: warning: misaligned atomic operation may incur significant
performance penalty [-Watomic-alignment]
__atomic_load(&foo->bar, &dummy, __ATOMIC_RELAXED);
clang believes that the pointer is 8 byte aligned, but foo->bar is actually 16
byte aligned.
#include <cstdint>
struct Foo {
struct Bar {
uint64_t a;
uint64_t b;
};
Bar bar;
};
void braz(Foo *foo) {
Foo::Bar dummy;
__atomic_load(&foo->bar, &dummy, __ATOMIC_RELAXED);
}</pre>
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