[LLVMdev] write a simple MachineFunctionPass

Alexandru Ionut Diaconescu alexandruionutdiaconescu at gmail.com
Fri Mar 15 05:30:23 PDT 2013

Hello everyone,

I have written several complex passes till now, but I cannot write a
MachineFunctionPass pass. It just gives me segfault. Hence I reduced the
pass to the following form :

using namespace llvm;

namespace {
  class CFGexplorator : public MachineFunctionPass {
    static char ID; // Pass identification, replacement for typeid
    CFGexplorator() : MachineFunctionPass(ID) {

    virtual bool runOnMachineFunction(MachineFunction &MF);

    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
} // end anonymous namespace

char CFGexplorator::ID = 0;
static RegisterPass<CFGexplorator> Y("mycfg", "mycfg", false, false);

bool CFGexplorator::runOnMachineFunction(MachineFunction &MF) {
return false;

I get the error :
Pass 'mycfg' is not initialized.
Verify if there is a pass dependency cycle.
Required Passes:
opt: PassManager.cpp:638: void
llvm::PMTopLevelManager::schedulePass(llvm::Pass*): Assertion `PI &&
"Expected required passes to be initialized"' failed.

So I have to initialize the pass. But in my all other passes I did not any
initialization and I don't want to use INITIALIZE_PASS since I have to
recompile the llvm file that is keeping the pass registration... Is there a
way to keep using static RegisterPass for a MachineFunctionPass ? I mention
that if I change to FunctionPass, I have no problems and that is weird..

Thank you for any advice !
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130315/3262431e/attachment.html>

More information about the llvm-dev mailing list