"getFixedStack" on the MachinePointerInfo class. While
this isn't the problem I'm setting out to solve, it is the
right way to eliminate PseudoSourceValue, so lets go with it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114406 91177308-0d34-0410-b5e6-96231b3b80d8