assigned to @lattner

The C source for this example is:

int main() { return 0; }

you just have to compile with -g to see the crash.

Here's a backtrace (different line numbers show that this tree is closer to
current CVS):

(gdb) bt
#​0 0xffffe405 in __kernel_vsyscall ()
#​1 0xf7d2f811 in raise () from /lib/tls/i686/cmov/libc.so.6
#​2 0xf7d30fb9 in abort () from /lib/tls/i686/cmov/libc.so.6
#​3 0xf7d28fbf in __assert_fail () from /lib/tls/i686/cmov/libc.so.6
#​4 0x08650883 in (anonymous namespace)::SelectionDAGLegalize::LegalizeOp (
this=0xffc7277c, Op={Val = 0x899c298, ResNo = 0}) at LegalizeDAG.cpp:876
#​5 0x08671be2 in (anonymous namespace)::SelectionDAGLegalize::HandleOp (
this=0xffc7277c, Op={Val = 0x899c298, ResNo = 0}) at LegalizeDAG.cpp:475
#​6 0x08671fdc in (anonymous namespace)::SelectionDAGLegalize::LegalizeDAG (
this=0xffc7277c) at LegalizeDAG.cpp:355
#​7 0x0867212d in llvm::SelectionDAG::Legalize (this=0xffc72934)
at LegalizeDAG.cpp:5639
#​8 0x0860ea1b in llvm::SelectionDAGISel::CodeGenAndEmitDAG (this=0x89a6798,
DAG=@0xffc72934) at SelectionDAGISel.cpp:4373
#​9 0x086221e1 in llvm::SelectionDAGISel::SelectBasicBlock (this=0x89a6798,
LLVMBB=0x89a4458, MF=@0x899cf70, FuncInfo=@0xffc72a98)
at SelectionDAGISel.cpp:4403
#​10 0x086237dd in llvm::SelectionDAGISel::runOnFunction (this=0x89a6798,
Fn=@0x899d390) at SelectionDAGISel.cpp:4088
#​11 0x084aa937 in (anonymous namespace)::PPCDAGToDAGISel::runOnFunction (
this=0x89a6798, Fn=@0x899d390) at PPCISelDAGToDAG.cpp:54
#​12 0x08806bc4 in llvm::FPPassManager::runOnFunction (this=0x8999478,
F=@0x899d390) at PassManager.cpp:991

The code in question is this:

case ISD::LABEL:
assert(Node->getNumOperands() == 2 && "Invalid LABEL node!");
switch (TLI.getOperationAction(ISD::LABEL, MVT::Other)) {
default: assert(0 && "This action is not supported yet!");
case TargetLowering::Legal:
Tmp1 = LegalizeOp(Node->getOperand(0)); // Legalize the chain.
Tmp2 = LegalizeOp(Node->getOperand(1)); // Legalize the label id.
Result = DAG.UpdateNodeOperands(Result, Tmp1, Tmp2);
break;
}
break;

gdb won't accept an expression with "ISD::LABEL" so I don't know what value it's
switching on.

Fixed, patch here:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070226/045464.html

However, you may now get undefined label errors when assembling the resultant .s file. If so, go into
PPCISelLowering.cpp, and delete this:

if (!TM.getSubtarget().isDarwin()) {
setOperationAction(ISD::LABEL, MVT::Other, Expand);

-Chris