<html>
<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [DebugInfo@O2] LiveDebugValues: Spill restores don't check location discriminator"
href="https://bugs.llvm.org/show_bug.cgi?id=43058">43058</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[DebugInfo@O2] LiveDebugValues: Spill restores don't check location discriminator
</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>
<tr>
<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>
<tr>
<th>Component</th>
<td>Common Code Generator Code
</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>aprantl@apple.com, 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, vsk@apple.com
</td>
</tr>
<tr>
<th>Blocks</th>
<td>31268
</td>
</tr></table>
<p>
<div>
<pre>Carrot Wei writes in the llvm-commits discussion for r368339, here:
<a href="http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20190819/685357.html">http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20190819/685357.html</a>
There are following code in
function LiveDebugValues::transferSpillOrRestoreInst,
854 } else if (TKind == TransferKind::TransferRestore &&
855 VarLocIDs[ID].Loc.SpillLocation == *Loc) {
856 LLVM_DEBUG(dbgs() << "Restoring Register " << printReg(Reg,
TRI) << '('
857 << VarLocIDs[ID].Var.getVar()->getName() <<
")\n");
There is no checking of VarLocIDs[ID].Kind before the usage of
VarLocIDs[ID].Loc.SpillLocation, is this another bug?
This is certainly a bug, and one we should fix: the VarLoc discriminator should
be checked to ensure the "Loc" union contains data of the expected type. As
it's a one-liner and obviously broken, I was just going to drop a commit in
that fixed this; however comparing a clang-3.4 build with/without that change
based on r369117, the "scope bytes covered" statistic from `llvm-dwarfdump
--statistics` jumps from 46% to 54%, which is too good to be true.
My hunch is that this bug is masking the effects of <a class="bz_bug_link
bz_status_NEW "
title="NEW - [DebugInfo@O2] LiveDebugValues misses stack restores, creates immortal variable locations"
href="show_bug.cgi?id=42772">bug 42772</a>, which would
explain the sudden increase in code coverage; only 15% confidence though.
Additional investigation of what effect this change has is needed IMO.</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_CONFIRMED "
title="CONFIRMED - Umbrella: debug info for optimized code"
href="https://bugs.llvm.org/show_bug.cgi?id=31268">Bug 31268</a>] Umbrella: debug info for optimized code
</li>
</ul>
</div>
<br>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>