The overrides of `Instruction.getOperandMemoryAccess` did not relate
`this` to any of its other parameters, which made it attempt to compute
the Cartesian product of `Instruction` and `TPhiOperand`. This happened
only during computation of aliased SSA. Perhaps the optimizer was able
to eliminate the CP for the non-aliased SSA computation.
With this change, I'm able to compute aliased SSA for medium-sized
snapshots.
e0c073360b