if (optIterator != null) optIterator.newStackWalk(thread);
if (VM.BuildForOptCompiler) { optIterator.newStackWalk(thread); }
  public void newStackWalk(VM_Thread thread, Address registerLocation) {     for (int i = 0; i < VM_Constants.NUM_GPRS; ++i) {      registerLocations.set(i, registerLocation.toWord());      registerLocation = registerLocation.plus(BYTES_IN_ADDRESS);    }    baselineIterator.newStackWalk(thread);    if (optIterator != null) optIterator.newStackWalk(thread);    hardwareTrapIterator.newStackWalk(thread);    jniIterator.newStackWalk(thread);  }