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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [ARM] crash while folding SP-update into vpush/vpop"
href="http://llvm.org/bugs/show_bug.cgi?id=19136">19136</a>
</td>
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<th>Summary</th>
<td>[ARM] crash while folding SP-update into vpush/vpop
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</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>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>weimingz@codeaurora.org
</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>Created <span class=""><a href="attachment.cgi?id=12230" name="attach_12230" title="llc < test.ll">attachment 12230</a> <a href="attachment.cgi?id=12230&action=edit" title="llc < test.ll">[details]</a></span>
llc < test.ll
When build LLVM with assertion on, it crashes:
*** Bad machine code: Using an undefined physical register ***
- function: test
- basic block: BB#2 exit (0x16e2ee0)
- instruction: %SP<def,tied1> = t2LDMIA_RET %SP<tied0>, pred:14, pred:%noreg,
%R4<def>, %PC<def>, %S0<imp-use,kill>
- operand 6: %S0<imp-use,kill>
LLVM ERROR: Found 1 machine code errors.
Without assertion, it output incorrect error.
Analysis:
Before Frame lowering:
vpush d8
sub sp, 64
....
...
s16= ....
s0 = ...
add sp, #64
vpop d8
(ret s0 implicitly)
When -Os is used, tryFoldSPUdateIntoPushPop() kicks in and tries to eliminate
"sub sp, 64" and "add sp, 64" by doing
vpush {d0-d8}, vpop {d0-d8}, which destroys s0.
The reason it uses MBB->computeRegisterLiveness() check the liveness D0.
However D0 is clobbered by S0 and assumed to be LQR_Dead.</pre>
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