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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 - [DebugInfo] Bloated dwarf for single location variable in nested scope"
href="https://bugs.llvm.org/show_bug.cgi?id=45889">45889</a>
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<th>Summary</th>
<td>[DebugInfo] Bloated dwarf for single location variable in nested scope
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Common Code Generator Code
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>orlando.hyams@sony.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=23476" name="attach_23476" title="XFAIL llvm-lit test">attachment 23476</a> <a href="attachment.cgi?id=23476&action=edit" title="XFAIL llvm-lit test">[details]</a></span>
XFAIL llvm-lit test
We get bloated dwarf for a variable location in a nested scope if it also has a
location tracked outside of that scope. I've attached a test case which fails
with llvm built at 72edb7986a8 (12th May 2020).
$ llc -start-after=livedebugvalues --filetype=obj test.mir -o - |
llvm-dwarfdump -
...
DW_TAG_lexical_block
DW_AT_low_pc (0x0000000000000002)
DW_AT_high_pc (0x0000000000000003)
DW_TAG_variable
DW_AT_location (0x00000000:
[0x0000000000000000, 0x0000000000000002): DW_OP_reg5 RDI
[0x0000000000000002, 0x0000000000000003): DW_OP_reg0 RAX)
DW_AT_name ("local")
...
Despite the fact that we have a location (DW_OP_reg0 RAX) which covers the
entire lexical block [0x0000000000000002, 0x0000000000000003) in which the
variable lives, we emit a location list. I think we could emit this instead:
DW_TAG_lexical_block
DW_AT_low_pc (0x0000000000000002)
DW_AT_high_pc (0x0000000000000003)
DW_TAG_variable
DW_AT_location (DW_OP_reg0 RAX)
DW_AT_name ("local")</pre>
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