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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [DTU] DomTreeUpdater's Eager strategy fails to update DomTree, Lazy strategy works OK"
href="https://bugs.llvm.org/show_bug.cgi?id=40528">40528</a>
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<th>Summary</th>
<td>[DTU] DomTreeUpdater's Eager strategy fails to update DomTree, Lazy strategy works OK
</td>
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<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>max.kazantsev@azul.com
</td>
</tr>
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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</tr></table>
<p>
<div>
<pre>I wrote a unit test <a href="https://reviews.llvm.org/D57448">https://reviews.llvm.org/D57448</a> which demonstrates that DTU
with Eager strategy fails to update the DomTree properly. Apply the patch and
run unit tests. The failure looks like:
1 FAILED TEST
DominatorTree is different than a freshly computed one!
Current:
=============================--------------------------------
Inorder Dominator Tree: DFSNumbers invalid: 0 slow queries.
[1] %BB {4294967295,4294967295} [0]
[2] %BB1 {4294967295,4294967295} [1]
[3] %BB17 {4294967295,4294967295} [2]
[3] %BB2 {4294967295,4294967295} [2]
[4] %Split {4294967295,4294967295} [3]
[5] %BB3 {4294967295,4294967295} [4]
[6] %BB4 {4294967295,4294967295} [5]
[7] %BB5 {4294967295,4294967295} [6]
[8] %BB16 {4294967295,4294967295} [7]
[8] %BB15 {4294967295,4294967295} [7]
[8] %BB14 {4294967295,4294967295} [7]
[8] %BB13 {4294967295,4294967295} [7]
[8] %BB12 {4294967295,4294967295} [7]
[8] %BB11 {4294967295,4294967295} [7]
[8] %BB8 {4294967295,4294967295} [7]
[9] %BB28 {4294967295,4294967295} [8]
[9] %BB27 {4294967295,4294967295} [8]
[9] %BB26 {4294967295,4294967295} [8]
[9] %BB23 {4294967295,4294967295} [8]
[9] %BB24 {4294967295,4294967295} [8]
[9] %BB25 {4294967295,4294967295} [8]
[9] %BB29 {4294967295,4294967295} [8]
[9] %BB22 {4294967295,4294967295} [8]
[9] %BB20 {4294967295,4294967295} [8]
[9] %BB21 {4294967295,4294967295} [8]
[8] %BB10 {4294967295,4294967295} [7]
[8] %BB9 {4294967295,4294967295} [7]
[8] %BB7 {4294967295,4294967295} [7]
[4] %BB19 {4294967295,4294967295} [3]
Freshly computed tree:
=============================--------------------------------
Inorder Dominator Tree: DFSNumbers invalid: 0 slow queries.
[1] %BB {4294967295,4294967295} [0]
[2] %BB1 {4294967295,4294967295} [1]
[3] %BB17 {4294967295,4294967295} [2]
[3] %BB2 {4294967295,4294967295} [2]
[4] %Split {4294967295,4294967295} [3]
[5] %BB3 {4294967295,4294967295} [4]
[6] %BB4 {4294967295,4294967295} [5]
[7] %BB5 {4294967295,4294967295} [6]
[8] %BB16 {4294967295,4294967295} [7]
[8] %BB15 {4294967295,4294967295} [7]
[8] %BB14 {4294967295,4294967295} [7]
[8] %BB13 {4294967295,4294967295} [7]
[8] %BB12 {4294967295,4294967295} [7]
[8] %BB11 {4294967295,4294967295} [7]
[8] %BB8 {4294967295,4294967295} [7]
[9] %BB28 {4294967295,4294967295} [8]
[9] %BB27 {4294967295,4294967295} [8]
[9] %BB26 {4294967295,4294967295} [8]
[9] %BB23 {4294967295,4294967295} [8]
[9] %BB24 {4294967295,4294967295} [8]
[9] %BB25 {4294967295,4294967295} [8]
[9] %BB29 {4294967295,4294967295} [8]
[10] %BB6 {4294967295,4294967295} [9]
[9] %BB22 {4294967295,4294967295} [8]
[9] %BB20 {4294967295,4294967295} [8]
[9] %BB21 {4294967295,4294967295} [8]
[8] %BB10 {4294967295,4294967295} [7]
[8] %BB9 {4294967295,4294967295} [7]
[8] %BB7 {4294967295,4294967295} [7]
[4] %BB19 {4294967295,4294967295} [3]
If we use Lazy update strategy instead of Eager, the very same tests passes.
I stepped over it while working on improving LoopSimplifyCFG. I worked this bug
around by patch <a href="https://reviews.llvm.org/D57316">https://reviews.llvm.org/D57316</a>. But it seems that it is a very
fundamental problem that compromises the DomTree updater.</pre>
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