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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [CodeGenPrepare] Unreported IR changes in OptimizeExtractBits"
href="https://bugs.llvm.org/show_bug.cgi?id=47503">47503</a>
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<th>Summary</th>
<td>[CodeGenPrepare] Unreported IR changes in OptimizeExtractBits
</td>
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<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Common Code Generator Code
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>dmajor@mozilla.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<pre>Created <span class=""><a href="attachment.cgi?id=23950" name="attach_23950" title="OptimizeExtractBits.ll">attachment 23950</a> <a href="attachment.cgi?id=23950&action=edit" title="OptimizeExtractBits.ll">[details]</a></span>
OptimizeExtractBits.ll
With expensive checks enabled:
opt -codegenprepare -S OptimizeExtractBits.ll
Pass modifies its input and doesn't report it: CodeGen Prepare
The reproducer is not quite as reduced as it could be, but I need to get to a
stopping point for the week.
The `MadeChange =` should be `MadeChange |=` at
<a href="https://github.com/llvm/llvm-project/blob/06e356c81e0fce90c9a21f9f5fb7567efa51ee0f/llvm/lib/CodeGen/CodeGenPrepare.cpp#L1847">https://github.com/llvm/llvm-project/blob/06e356c81e0fce90c9a21f9f5fb7567efa51ee0f/llvm/lib/CodeGen/CodeGenPrepare.cpp#L1847</a>
This apparently dates back to LLVM 3.5:
<a href="https://github.com/llvm/llvm-project/commit/d069f6393a7c">https://github.com/llvm/llvm-project/commit/d069f6393a7c</a>
I haven't tested, but by inspection, this other use of `MadeChange =` also
looks suspicious:
<a href="https://github.com/llvm/llvm-project/blob/06e356c81e0fce90c9a21f9f5fb7567efa51ee0f/llvm/lib/CodeGen/CodeGenPrepare.cpp#L1153">https://github.com/llvm/llvm-project/blob/06e356c81e0fce90c9a21f9f5fb7567efa51ee0f/llvm/lib/CodeGen/CodeGenPrepare.cpp#L1153</a></pre>
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