tracked. Instead of trying to manually keep track of these locations
while doing complex modifications, just recompute them when they're needed.
This fixes a bug in which the TopMBB and BotMBB were not correctly updated,
leading to invalid transformations.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84598 91177308-0d34-0410-b5e6-96231b3b80d8
