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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [DebugInfo] Poor support for x87 variable locations"
href="https://bugs.llvm.org/show_bug.cgi?id=51033">51033</a>
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<th>Summary</th>
<td>[DebugInfo] Poor support for x87 variable locations
</td>
</tr>
<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>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Keywords</th>
<td>wrong-debug
</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>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>jeremy.morse.llvm@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Blocks</th>
<td>38768
</td>
</tr></table>
<p>
<div>
<pre>Observed over in <a href="https://reviews.llvm.org/D105657">https://reviews.llvm.org/D105657</a> , both our current variable
location implementation and the instruction referencing stuff I've been working
on are unable to cope with x87 variable locations. Both are unable to actually
express where in registers variable values go.
The root cause is the baroqueness of x87 itself: it refers to registers as a
stack, rather than just naming them directly. If we had a DBG_VALUE that
referred to $st(1), we might need to issue additional DBG_VALUEs as the stack
position of the value changed due to other FP instructions.
It's a significant pain in the neck, and VarLoc LiveDebugValues doesn't try to
solve it. InstrRef LiveDebugValues doesn't try either. I suspect that interest
in this matter is low (what with i386 processors being out of fashion for at
least a decade) but thought I'd open the ticket in case there's something out
there who this is relevant to.</pre>
</div>
</p>
<div id="referenced">
<hr style="border: 1px dashed #969696">
<b>Referenced Bugs:</b>
<ul>
<li>
[<a class="bz_bug_link
bz_status_NEW "
title="NEW - [meta][DebugInfo] Umbrella bug for poor debug experiences"
href="https://bugs.llvm.org/show_bug.cgi?id=38768">Bug 38768</a>] [meta][DebugInfo] Umbrella bug for poor debug experiences
</li>
</ul>
</div>
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