Try to fix the atom buildbots by adding an explicit 'cpu' to the 'llc' command.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190541 91177308-0d34-0410-b5e6-96231b3b80d8
Add getUnrollingPreferences to TTI

Allow targets to customize the default behavior of the generic loop unrolling
transformation. This will be used by the PowerPC backend when targeting the A2
core (which is in-order with a deep pipeline), and using more aggressive
defaults is important.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190542 91177308-0d34-0410-b5e6-96231b3b80d8
Debug info: add more comments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190544 91177308-0d34-0410-b5e6-96231b3b80d8