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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missing DSE opportunity when second store is done in inline assembly"
href="https://bugs.llvm.org/show_bug.cgi?id=44913">44913</a>
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<th>Summary</th>
<td>Missing DSE opportunity when second store is done in inline assembly
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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>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>Scalar Optimizations
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>glider@google.com
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<th>CC</th>
<td>florian_hahn@apple.com, llvm-bugs@lists.llvm.org, llvm-bugzilla@jfbastien.com, vitalybuka@google.com
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<p>
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<pre>As reported by Daniel Colascione, Clang fails to remove the dead store in the
following program:
extern int foo(int* bar);
int bar()
{
int x = 5;
asm("nop\n\tnop\n\tnop" : "=m" (x));
return foo(&x);
}
see <a href="https://gcc.godbolt.org/z/c2fMNH">https://gcc.godbolt.org/z/c2fMNH</a> (bad, clang) vs.
<a href="https://gcc.godbolt.org/z/a_biz5">https://gcc.godbolt.org/z/a_biz5</a> (good, GCC).
This probably prevents it from deleting redundant initialization before
copy_from_user() in the Linux kernel.</pre>
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