swift234

Teach DI to remove destroy_addrs on paths where the memory is always uninitialized.

Doing this exposed that the dataflow analysis in DI was pretty fundamentaly broken:
it was trying to compute blocks where the (tuple elements of the) memory were either
initialized, uninitialized, or partially initialized (initialized only on some paths)
but it conflated partial with its unknown state, causing it to get the wrong results
a lot of the time.  Rewrite things so that it is correct.



Swift SVN r10594