public void clear() {
    throwIfImmutable();

    for (int i = 0; i < stackPtr; i++) {
      stack[i] = null;
      local[i] = false;
    }

    stackPtr = 0;
  }
Clears the stack. (That is, this method pops everything off.)
android/android_framework/dex-maker/src/main/java/com/android/dx/cf/code/ExecutionStack.java