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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - missing nop after branch"
href="http://llvm.org/bugs/show_bug.cgi?id=17111">17111</a>
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<th>Summary</th>
<td>missing nop after branch
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<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>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Backend: PowerPC
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>nlewycky@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Testcase:
class Base {
protected:
Base() {}
public:
virtual ~Base();
virtual void BaseMethod() {}
};
struct Derived : public Base {
~Derived() {
DerivedMethod();
}
void DerivedMethod();
virtual void BaseMethod();
};
void Derived::DerivedMethod() {}
void Derived::BaseMethod() {}
The bug is in the assembly generated for the destructor. Here's a snippet:
.Ltmp4:
std 5, 120(31)
bl _ZN7Derived13DerivedMethodEv
.Ltmp5:
b .LBB4_1
That doesn't leave enough space for the linker to insert the TOC reload when
resolving the R_PPC64_REL24 relocation. There needs to be a nop after the
branch+link instruction.
Reproduce with:
clang -target powerpc64-pc-linux-gnu -fpic testcase.cc -S -o -
Ultimately the symptom is a failure when linking:
error: call lacks nop, can't restore toc; recompile with -fPIC</pre>
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</p>
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