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<head>
<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - failed assertion in Live Variable Analysis with callbr w/ outputs"
href="https://bugs.llvm.org/show_bug.cgi?id=45565">45565</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>failed assertion in Live Variable Analysis with callbr w/ outputs
</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>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Global Analyses
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>ndesaulniers@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>efriedma@quicinc.com, isanbard@gmail.com, llvm-bugs@lists.llvm.org, srhines@google.com
</td>
</tr>
<tr>
<th>Blocks</th>
<td>4068
</td>
</tr></table>
<p>
<div>
<pre>llc -O2 futex.ll:
```
@c = dso_local local_unnamed_addr global i32 0, align 4
@a = dso_local local_unnamed_addr global i32 0, align 4
define dso_local i32 @b(i32* nocapture %f) #0 {
entry:
%0 = callbr i32 asm "", "=r,X,~{dirflag},~{fpsr},~{flags}"(i8*
blockaddress(@b, %e))
to label %asm.fallthrough [label %e]
asm.fallthrough: ; preds = %entry
store i32 %0, i32* %f, align 4
br label %e
e: ; preds = %asm.fallthrough,
%entry
ret i32 undef
}
define dso_local i32 @futex_lock_pi_atomic() local_unnamed_addr {
entry:
%0 = callbr i32 asm "", "=r,X,~{dirflag},~{fpsr},~{flags}"(i8*
blockaddress(@futex_lock_pi_atomic, %b.exit)) #2
to label %asm.fallthrough.i [label %b.exit]
asm.fallthrough.i: ; preds = %entry
br label %b.exit
b.exit: ; preds = %entry,
%asm.fallthrough.i
%1 = load i32, i32* @c, align 4
%2 = tail call { i32, i32 } asm "",
"=r,={ax},1,0,~{dirflag},~{fpsr},~{flags}"(i32 %0, i32 %1)
%asmresult = extractvalue { i32, i32 } %2, 0
%asmresult1 = extractvalue { i32, i32 } %2, 1
store i32 %asmresult, i32* @c, align 4
store i32 %asmresult1, i32* @a, align 4
ret i32 undef
}
```
llc: ../lib/CodeGen/LiveVariables.cpp:114: void
llvm::LiveVariables::MarkVirtRegAliveInBlock(llvm::LiveVariables::VarInfo &,
llvm::MachineBasicBlock *, llvm::MachineBasicBlock *,
std::vector<MachineBasicBlock *> &): Assertion `MBB != &MF->front() && "Can't
find reaching def for virtreg"' failed.
1. Running pass 'Function Pass Manager' on module 'futex.ll'.
2. Running pass 'Live Variable Analysis' on function
'@futex_lock_pi_atomic'
...
#9 0x00000000035d4d1e llvm::LiveVariables::HandleVirtRegUse(unsigned int,
llvm::MachineBasicBlock*, llvm::MachineInstr&)
(/android0/llvm-project/llvm/build/bin/llc+0x35d4d1e)
#10 0x00000000035d746e llvm::LiveVariables::runOnInstr(llvm::MachineInstr&,
llvm::SmallVectorImpl<unsigned int>&)
(/android0/llvm-project/llvm/build/bin/llc+0x35d746e)
#11 0x00000000035d7a4c
llvm::LiveVariables::runOnBlock(llvm::MachineBasicBlock*, unsigned int)
(/android0/llvm-project/llvm/build/bin/llc+0x35d7a4c)
#12 0x00000000035d82a1
llvm::LiveVariables::runOnMachineFunction(llvm::MachineFunction&)
(/android0/llvm-project/llvm/build/bin/llc+0x35d82a1)
#13 0x000000000363fd0a
llvm::MachineFunctionPass::runOnFunction(llvm::Function&)
(/android0/llvm-project/llvm/build/bin/llc+0x363fd0a)
#14 0x0000000003a1cc74 llvm::FPPassManager::runOnFunction(llvm::Function&)
(/android0/llvm-project/llvm/build/bin/llc+0x3a1cc74)
#15 0x0000000003a1cf28 llvm::FPPassManager::runOnModule(llvm::Module&)
(/android0/llvm-project/llvm/build/bin/llc+0x3a1cf28)
#16 0x0000000003a1d57d llvm::legacy::PassManagerImpl::run(llvm::Module&)
(/android0/llvm-project/llvm/build/bin/llc+0x3a1d57d)
#17 0x00000000022b9618 main
(/android0/llvm-project/llvm/build/bin/llc+0x22b9618)
...</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 - [Meta] Compiling the Linux kernel with clang"
href="https://bugs.llvm.org/show_bug.cgi?id=4068">Bug 4068</a>] [Meta] Compiling the Linux kernel with clang
</li>
</ul>
</div>
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