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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - AArch64-ios: Cannot scavenge register without an emergency spill slot"
href="https://llvm.org/bugs/show_bug.cgi?id=27717">27717</a>
</td>
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<th>Summary</th>
<td>AArch64-ios: Cannot scavenge register without an emergency spill slot
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Other
</td>
</tr>
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<th>OS</th>
<td>MacOS X
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Register Allocator
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>alina.sbirlea@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=16361" name="attach_16361" title="Test showing the failure.">attachment 16361</a> <a href="attachment.cgi?id=16361&action=edit" title="Test showing the failure.">[details]</a></span>
Test showing the failure.
Running "llc fail.ll" yields assertion failure "Cannot scavenge register
without an emergency spill slot" on aarch64-ios. See attached "fail.ll"
This is caused by not finding a register to scavenge, no architecture specific
handling and because on MachO there isn't an emergency spill slot added.
See line lib/Target/AArch64/AArch64FrameLowering.cpp:1127:
// MachO's compact unwind format relies on all registers being stored in
// pairs.
// FIXME: the usual format is actually better if unwinding isn't needed.
if (produceCompactUnwindFrame(MF) && !SavedRegs.test(PairedReg)) {
SavedRegs.set(PairedReg);
ExtraCSSpill = true;
}
Unsetting "ExtraCSSpill = true;"(AArch64FrameLowering.cpp:1129) resolves the
issue, but I am unsure this is the right solution.
Side note:
<a class="bz_bug_link
bz_status_NEW "
title="NEW --- - ARMv7 -O0: Cannot scavenge register without an emergency spill slot!"
href="show_bug.cgi?id=23444">Bug 23444</a> seemed to be a duplicate at first, but the problem does not reproduce
in the example provided (fn06.bc). <a class="bz_bug_link
bz_status_NEW "
title="NEW --- - ARMv7 -O0: Cannot scavenge register without an emergency spill slot!"
href="show_bug.cgi?id=23444">Bug 23444</a> may be fixed.</pre>
</div>
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