JumpThreading.cpp

  // us to simplify any PHI nodes in BB.
  TerminatorInst *PredTerm = PredBB->getTerminator();
  for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i)
    if (PredTerm->getSuccessor(i) == BB) {
      BB->removePredecessor(PredBB);
      PredTerm->setSuccessor(i, NewBB);
    }
  
  // At this point, the IR is fully up to date and consistent.  Do a quick scan
  // over the new instructions and zap any that are constants or dead.  This
  // frequently happens because of phi translation.
  BI = NewBB->begin();
  for (BasicBlock::iterator E = NewBB->end(); BI != E; ) {
    Instruction *Inst = BI++;
    if (Constant *C = ConstantFoldInstruction(Inst, BB->getContext(), TD)) {
      Inst->replaceAllUsesWith(C);
      Inst->eraseFromParent();
      continue;
    }
    
    RecursivelyDeleteTriviallyDeadInstructions(Inst);
  }
  
  // Threaded an edge!
  ++NumThreads;
  return true;
}