MachineModuleInfo.cpp

  assert(0 && "Personality function should be set!");
  return 0;
}

//===----------------------------------------------------------------------===//
/// DebugLabelFolding pass - This pass prunes out redundant labels.  This allows
/// a info consumer to determine if the range of two labels is empty, by seeing
/// if the labels map to the same reduced label.

namespace llvm {

struct DebugLabelFolder : public MachineFunctionPass {
  static char ID;
  DebugLabelFolder() : MachineFunctionPass(&ID) {}

  virtual bool runOnMachineFunction(MachineFunction &MF);
  virtual const char *getPassName() const { return "Label Folder"; }
};

char DebugLabelFolder::ID = 0;

bool DebugLabelFolder::runOnMachineFunction(MachineFunction &MF) {
  // Get machine module info.
  MachineModuleInfo *MMI = getAnalysisToUpdate<MachineModuleInfo>();
  if (!MMI) return false;
  
  // Track if change is made.
  bool MadeChange = false;
  // No prior label to begin.
  unsigned PriorLabel = 0;
  
  // Iterate through basic blocks.
  for (MachineFunction::iterator BB = MF.begin(), E = MF.end();
       BB != E; ++BB) {
    // Iterate through instructions.
    for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
      // Is it a label.
      if (I->isDebugLabel()) {
        // The label ID # is always operand #0, an immediate.
        unsigned NextLabel = I->getOperand(0).getImm();
        
        // If there was an immediate prior label.
        if (PriorLabel) {
          // Remap the current label to prior label.
          MMI->RemapLabel(NextLabel, PriorLabel);
          // Delete the current label.
          I = BB->erase(I);
          // Indicate a change has been made.
          MadeChange = true;
          continue;
        } else {
          // Start a new round.
          PriorLabel = NextLabel;
        }
       } else {
        // No consecutive labels.
        PriorLabel = 0;
      }
      
      ++I;
    }
  }
  
  return MadeChange;
}

FunctionPass *createDebugLabelFoldingPass() { return new DebugLabelFolder(); }

}