For code like this:

       0: bipush 9
       2: iconst_2
       3: multianewarray #2, 2 // class "[[QPoint;"
       7: astore_3
       8: aload_3
       9: iload_1
      10: aaload <<<<< should be loading from "[[QPoint;"
      11: iload_2
      12: aload_0
      13: aastore <<<<< should be storing to "[QPoint;"
      14: aload_3
      15: areturn

The multianewarray instruction at bci#3 throws away the type information. I.e., NewMultiArray::exact_type() returns NULL.

When we get to the aaload at bci#10, we only know that the operand is a T_OBJECT.

When we get to the aastore at bci#13, we only know that the operand is a T_OBJECT, so we don't know that the array is actually flattened.

The fix is to implement this function properly:

ciType* NewMultiArray::exact_type() const {
  return _klass;
}