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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Improve optimized debug info for escaped variables that live in memory"
href="https://bugs.llvm.org/show_bug.cgi?id=34136">34136</a>
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<th>Summary</th>
<td>Improve optimized debug info for escaped variables that live in memory
</td>
</tr>
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<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>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>DebugInfo
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>rnk@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Consider:
int getint(void);
void alias(char *);
void crash(void);
void f() {
int x = getint();
int y = getint();
int z = getint();
alias((char*)&x);
alias((char*)&y);
alias((char*)&z);
crash();
}
InstCombine runs LowerDbgDeclares on this code, and we end up with very poor
debug info. We basically say that x, y, and z live in EAX after each call to
getint, and they are immediately clobbered, never to be available again.
Those casts to char* also prevent the transform from adding more dbg.values
that would extend the range.
This was reduced from <a href="http://crbug.com/753934">http://crbug.com/753934</a></pre>
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