big arrays [was Re: bug found]

[Stephen Weeks]

> The only thing we need to do is to distinguish between array lengths
> and object headers.  So, if we make array lengths two words, the first
> of which will always be all zero, and the second containing the
> length, as it does now, we can have lengths up to 2G, which is the max
> we can hope for with 32 bit ints anyways.  There is no additional cost
> for bounds checking.  The only cost is an added word of space per
> array.

Although I'm hard pressed to argue that this is better than my other
proposal of reworking object headers so that only arrays have a top
zero bit.  That also has no additional cost for bounds checking.  The
only cost may be in a slightly more complex gc.