[ObjCARC] Pass the correct BasicBlock to fix assertion failure.

The BasicBlock passed to FindPredecessorRetainWithSafePath should be the
parent block of Autorelease. This fixes a crash that occurs in
FindDependencies when StartInst is not in StartBB.

rdar://problem/33866381

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312266 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed