This is useful for debugging issues in the BlockFrequency implementation
since one can easily visualize where probability mass and other errors
occur in the propagation.
This is the MI version of r194654.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196183 91177308-0d34-0410-b5e6-96231b3b80d8