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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - GlobalMerge optimization drops visibility attributes"
href="https://bugs.llvm.org/show_bug.cgi?id=39413">39413</a>
</td>
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<th>Summary</th>
<td>GlobalMerge optimization drops visibility attributes
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Common Code Generator Code
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>rprichard@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>The GlobalMerge optimization enabled with -Oz or -O3 appears to discard
visibility attributes from variables. The merged variables have default
visibility when they were declared as hidden or protected.
int somevar1 __attribute__((visibility("hidden"))) = 1;
int somevar2 __attribute__((visibility("hidden"))) = 2;
int somevar3 __attribute__((visibility("protected"))) = 1;
int somevar4 __attribute__((visibility("protected"))) = 2;
int get12() {
return somevar1 + somevar2;
}
int get34() {
return somevar3 + somevar4;
}
$ clang -target arm -Oz test.c -c && readelf -s test.o | grep somevar
11: 00000000 4 OBJECT GLOBAL DEFAULT 6 somevar1
12: 00000004 4 OBJECT GLOBAL DEFAULT 6 somevar2
13: 00000008 4 OBJECT GLOBAL DEFAULT 6 somevar3
14: 0000000c 4 OBJECT GLOBAL DEFAULT 6 somevar4
$ clang -target arm -Oz test.c -c -mno-global-merge && readelf -s test.o | grep
somevar
9: 00000000 4 OBJECT GLOBAL HIDDEN 6 somevar1
10: 00000004 4 OBJECT GLOBAL HIDDEN 6 somevar2
11: 00000008 4 OBJECT GLOBAL PROTECTED 6 somevar3
12: 0000000c 4 OBJECT GLOBAL PROTECTED 6 somevar4
This was originally reported against the Android NDK
(<a href="https://github.com/android-ndk/ndk/issues/829">https://github.com/android-ndk/ndk/issues/829</a>).</pre>
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