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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - AddDiscriminators and DILocation::computeNewDiscriminator() modifies the LLVMContext inappropriately"
href="https://llvm.org/bugs/show_bug.cgi?id=23200">23200</a>
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<th>Summary</th>
<td>AddDiscriminators and DILocation::computeNewDiscriminator() modifies the LLVMContext inappropriately
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>DebugInfo
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>dexonsmith@apple.com
</td>
</tr>
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<th>CC</th>
<td>aprantl@apple.com, dblaikie@gmail.com, dnovillo@google.com, llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>`DILocation::computeNewDiscriminator()` modifies a table in the LLVMContext
indexed by filename/line. This will changes results in other modules created
in the same context, and the table doesn't get serialized to bitcode/assembly
(so roundtripping will change the results of `computeNewDiscriminator()`).
Although it doesn't cause problems for `clang` in practice, this is fairly
broken.
Fortunately, the fix is simple: move the table (and logic) into
`AddDiscriminators::runOnFunction()` and stop modifying the LLVMContext. This
table is discriminating between adjacent basic blocks, so it doesn't need
global state.
I'll add FIXMEs and tag this PR when I move the function over to MDLocation,
and hopefully circle back to fix it soon after (if no one beats me to it).</pre>
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</p>
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