public void startBlock(TypeList catches) {
    this.catches = catches;

    insns.clear();
    catchesUsed = false;
    returns = false;
    primarySuccessorIndex = 0;
    extraBlockCount = 0;
    blockCanThrow = false;
    hasJsr = false;
    returnAddress = null;
  }
Gets ready to start working on a new block. This will clear the {@link #insns} list, set {@link
#catches}, reset whether it has been used, reset whether the block contains a {@code return},
and reset {@link #primarySuccessorIndex}.
android/android_framework/dex-maker/src/main/java/com/android/dx/cf/code/RopperMachine.java