Semantic tests for memory invalidation at statepoints

These are simply a collection of tests intended to show that information about the contents of gc references in the heap is lost at a statepoint. I've tried to write them so that they don't disallow correct transformations, while still being fairly easy to understand.

p.s. Ideas for additional tests are welcome.

Differential Revision: http://reviews.llvm.org/D6491



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224971 91177308-0d34-0410-b5e6-96231b3b80d8