[LLVMdev] MachineBasicBlock insertion

[Bin Zeng]

  Hi all,

I am really stumped on a problem for long. I could not figure out why. 
That is why i am here. OK, here is the problem:
I tried to insert a MachineBasicBlock into a function. Here is the code 
snippet:

// insert a machine basic block with the error_label into MF and before I
// Pred is the predecessor of the block to be inserted
// the new basic block is inserted right before I
void X86CFIOptPass::insertBasicBlockBefore(MachineFunction &MF,
                        MachineBasicBlock *Pred,
                        MachineFunction::iterator I){
   const BasicBlock* LLVM_BB = Pred->getBasicBlock();
   MachineBasicBlock * MBB = MF.CreateMachineBasicBlock(LLVM_BB); // 
create a MBB
   MBB->setNumber(19880616); // set the number of MBB to be 19880616 
which is used as an ID

   Pred->addSuccessor(MBB);
   const TargetInstrInfo *TII = MF.getTarget().getInstrInfo();
   DebugLoc dl;
   // CALLpcrel32 abort
   BuildMI(MBB,dl,TII->get(X86::CALLpcrel32)).addExternalSymbol("abort");
   // JNE_4 error_label
   BuildMI(MBB,dl,TII->get(X86::JNE_4)).addExternalSymbol("error_label");
   // MOV32ri %eax, 0
   BuildMI(MBB,dl,TII->get(X86::MOV32ri),X86::EAX).addImm(0);
   // CALL32r %eax
   // BuildMI(MBB,dl,TII->get(X86::CALL32r)).addReg(X86::EAX);
   MF.insert(I,MBB);
}

When I tried to dump the code after the insertion, the program enters an 
infinite loop
in the while loop inside MachineRegisterInfo.h:defusechain_iterator 
&operator++().
Basically, the CALLpcrel32 instruction has a register operand that 
points to itself, that is,
Contents.Reg.Next stores the address of itself. Does anyone knows how to 
insert a MachineBasicBlock
into a function? Any advice will be appreciated. Thanks in advance.

~Bin