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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - VirtualBox miscompiled after LLVM r345163 / 18bfb3a5ec41"
href="https://bugs.llvm.org/show_bug.cgi?id=45334">45334</a>
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<th>Summary</th>
<td>VirtualBox miscompiled after LLVM r345163 / 18bfb3a5ec41
</td>
</tr>
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<th>Product</th>
<td>new-bugs
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>FreeBSD
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>kevans@FreeBSD.org
</td>
</tr>
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>After r345163 ("[CodeGen] skip lifetime end marker in isInTailCallPosition"),
LLVM 8.0+ no longer compile VirtualBox 5.2.x correctly -- notably, new machines
result in failure/segfault.
Both reverting this commit (see diff at the end of this e-mail) and building a
Debug build (so no more -O2) fix the observed behavior.
I'm still trying to work out where the problem's actually happening so that I
can produce a minimal reproducer... the code involved in the problematic area
(New VM wizard -> actual machine creation) is a twisty maze of C++ with various
bits like local variables that manage an object and then set a pointer in their
dtor and other fun lifetime-related tricks.
--- lib/CodeGen/Analysis.cpp.orig 2020-03-26 15:48:08 UTC
+++ lib/CodeGen/Analysis.cpp
@@ -538,11 +538,10 @@ bool llvm::isInTailCallPosition(ImmutableCallSite CS,
// Debug info intrinsics do not get in the way of tail call
optimization.
if (isa<DbgInfoIntrinsic>(BBI))
continue;
- // A lifetime end or assume intrinsic should not stop tail call
+ // An assume intrinsic should not stop tail call
// optimization.
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
- if (II->getIntrinsicID() == Intrinsic::lifetime_end ||
- II->getIntrinsicID() == Intrinsic::assume)
+ if (II->getIntrinsicID() == Intrinsic::assume)
continue;
if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
!isSafeToSpeculativelyExecute(&*BBI))</pre>
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