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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Volatile stores of undef values are deleted"
href="https://llvm.org/bugs/show_bug.cgi?id=27309">27309</a>
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<th>Summary</th>
<td>Volatile stores of undef values are deleted
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>koriakin@0x04.net
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</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>All stores of undef values are deleted at the moment - including volatile
stores:
define void @f(i32 *%p) {
store volatile i32 undef, i32 *%p;
ret void;
}
Compiles to:
f: retq
In theory, the pointer could point to a hardware device where the store has
some side-effects like increasing a queue pointer. A driver that wants to
write dummy data could reasonably store an undef and need it to be actually
performed.
Bug found when browsing idly through the code, I don't actually have a
real-world case for it.</pre>
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</p>
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