Fix non-deterministic behavior.

We use CSEBlocks to initialize a worklist:

SmallVector<BasicBlock *, 8> CSEWorkList(CSEBlocks.begin(), CSEBlocks.end());

so it must have a deterministic order.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196520 91177308-0d34-0410-b5e6-96231b3b80d8