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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - ThinLTO on Aarch64 fails to handle aliases to overridden weak functions"
href="https://bugs.llvm.org/show_bug.cgi?id=42542">42542</a>
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<th>Summary</th>
<td>ThinLTO on Aarch64 fails to handle aliases to overridden weak functions
</td>
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<th>Product</th>
<td>new-bugs
</td>
</tr>
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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>Linux
</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
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>samitolvanen@google.com
</td>
</tr>
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>C code that defines an alias to a weak function, which is then referred to in
assembly code that also overrides the same weak function, fails to compile with
-flto=thin on Aarch64:
$ cat alias.c
__attribute__((__weak__)) int __a(int n)
{
return n;
}
int a(int n) __attribute__((__alias__("__a")));
int main()
{
return __a(0);
}
$ cat alias.s
.arch armv8-a
__a:
b a
.globl __a
$ clang -flto=thin -fvisibility=hidden -fuse-ld=lld --target=aarch64-linux-gnu-
alias.s alias.c
Alias must point to a definition
i32 (i32)* @a
LLVM ERROR: Broken module found, compilation aborted!
clang-9: error: linker command failed with exit code 1 (use -v to see
invocation)
Using -flto instead of -flto=thin works.
This bug prevents us from compiling the Linux kernel with ThinLTO, as explained
here:
<a href="https://github.com/ClangBuiltLinux/linux/issues/509">https://github.com/ClangBuiltLinux/linux/issues/509</a></pre>
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