public boolean areAllOperandsEqual() {
    if (operands.size() == 0) {
      // This should never happen.
      return true;
    }

    int firstReg = operands.get(0).regSpec.getReg();
    for (Operand o : operands) {
      if (firstReg != o.regSpec.getReg()) {
        return false;
      }
    }

    return true;
  }
@return true if all operands use the same register
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/PhiInsn.java