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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [DebugInfo@O2] SimplifyCFG sink splitting drops a variable location"
href="https://bugs.llvm.org/show_bug.cgi?id=41881">41881</a>
</td>
</tr>
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<th>Summary</th>
<td>[DebugInfo@O2] SimplifyCFG sink splitting drops a variable location
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Keywords</th>
<td>wrong-debug
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>jeremy.morse.llvm@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>chackz0x12@gmail.com, greg.bedwell@sony.com, llvm-bugs@lists.llvm.org, orlando.hyams@sony.com, paul.robinson@am.sony.com, stephen.tozer@sony.com
</td>
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<th>Blocks</th>
<td>38768
</td>
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<p>
<div>
<pre>With llvm/clang r359863, running "clang -emit-llvm -O2 -g -S" on the code
below, the dbg.value representing the assignment of "local = q" is dropped by
SimplifyCFG. From the names of the basic blocks, it would appear to be the
SinkCommonCodeFromPredecessors function that does the dropping.
--------8<--------
volatile int g, *x;
int baz(int p, int q) {
int local;
local = p;
switch (g) {
case 1:
x[1] = local;
g += p;
break;
case 2:
x[1] += p;
break;
case 3:
local = q;
g++;
break;
}
return 4 + q;
}
-------->8--------
In this particular test case the impact of dropping the "local=q" assignment is
that the "local=p" assignment dominates all blocks, and an incorrect location
for "local" is produce in the "case 3" and exit block. (Didn't test this as far
as a debugger because I believe the error is fairly clear).</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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