Crash on AU.addRequired<LoopInfo>(); in LLVM pass - llvm

Question

I have a simple Function pass, and I am trying to get loop info in the code. But when I try to add AU.addRequired() in getAnalysisUsage(), the module crashes. This happens even before getAnalysis() is called. It is a dynamically loaded pass (.so).
namespace
{
class TestPass : public FunctionPass
{
public:
static char ID;
TestPass() : FunctionPass(ID) {}
virtual void getAnalysisUsage(AnalysisUsage &AU) const
{
AU.addRequired<LoopInfo>();
AU.setPreservesAll();
}
bool runOnFunction(Function &F) override
{
errs() << F.getName() << " : " << F.getBasicBlockList().size() << "\n";
// LoopInfo &LI = getAnalysis<LoopInfo>();
return false;
}
};
}
char TestPass::ID = 0;
static RegisterPass<TestPass> X("TestPass", "Test pass");
// register pass for clang use
static void registerTestPassPass(const PassManagerBuilder &, PassManagerBase &PM)
{
PM.add(new TestPass());
}
static RegisterStandardPasses RegisterTestPassPass(PassManagerBuilder::EP_EarlyAsPossible , registerTestPassPass);
Here is the stack trace.
[armeabi-v7a] Compile thumb : test <= test.c
Pass 'Test pass' is not initialized.
Verify if there is a pass dependency cycle.
Required Passes:
0 clang 0x0000000001492ec2 llvm::sys::PrintStackTrace(_IO_FILE*) + 34
1 clang 0x0000000001490f61
2 libpthread.so.0 0x00002b15cbb4e340
3 clang 0x00000000011c86f7 llvm::PMTopLevelManager::schedulePass(llvm::Pass*) + 343
4 clang 0x00000000019c0401 llvm::PassManagerBuilder::addExtensionsToPM(llvm::PassManagerBuilder::ExtensionPointTy, llvm::legacy::PassManagerBase&) const + 225
5 clang 0x00000000019c054a llvm::PassManagerBuilder::populateFunctionPassManager(llvm::legacy::FunctionPassManager&) + 26
6 clang 0x0000000001837de3 clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::CodeGenOptions const&, clang::TargetOptions const&, clang::LangOptions const&, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::raw_ostream*) + 1171
7 clang 0x000000000182a47f
8 clang 0x0000000001bdf043 clang::ParseAST(clang::Sema&, bool, bool) + 483
9 clang 0x0000000001603ba6 clang::FrontendAction::Execute() + 118
10 clang 0x00000000015e47b8 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) + 280
11 clang 0x0000000001673b41 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) + 1921
12 clang 0x0000000000820358 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) + 1320
13 clang 0x00000000007fceaa main + 8298
14 libc.so.6 0x00002b15cc7b6ec5 __libc_start_main + 245
15 clang 0x000000000081e5d9
Am I missing something? Any help would be appreciated.

Answer 1

Found the solution. The code was missing creation of a new LoopInfo() object in order to call the LoopInfo pass.
// register pass for clang use
static void registerTestPassPass(const PassManagerBuilder &, PassManagerBase &PM)
{
PM.add(new LoopInfo());
PM.add(new TestPass());
}