[objc-arc] Make sure that multiple owners is propogated correctly through the pass via the usage of a global data structure.

rdar://13750319

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182669 91177308-0d34-0410-b5e6-96231b3b80d8
[objc-arc] KnownSafe does not imply that it is safe to perform code motion across CFG edges since even if it is safe to remove RR pairs, we may still be able to move a retain/release into a loop.

rdar://13949644

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182670 91177308-0d34-0410-b5e6-96231b3b80d8