George Burgess IV 0a451a3606 Fix bugs in the MemorySSA walker.
There are a few bugs in the walker that this patch addresses.
Primarily:
- Caching can break when we have multiple BBs without phis
- We weren't optimizing some phis properly
- Because of how the DFS iterator works, there were times where we
  wouldn't cache any results of our DFS

I left the test cases with FIXMEs in, because I'm not sure how much
effort it will take to get those to work (read: We'll probably
ultimately have to end up redoing the walker, or we'll have to come up
with some creative caching tricks), and more test coverage = better.

Differential Revision: http://reviews.llvm.org/D18065


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264180 91177308-0d34-0410-b5e6-96231b3b80d8
2016-03-23 18:31:55 +00:00
..
2016-03-23 14:00:28 +00:00