[SimplifyCFG] Merge together cleanuppads

Cleanuppads may be merged together if one is the only predecessor of the
other in which case a simple transform can be performed: replace the
a cleanupret with a branch and remove an unnecessary cleanuppad.

Differential Revision: http://reviews.llvm.org/D17459

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261390 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed