`ProvenanceAnalysis::related()` was assuming that the order of parameters for `relatedCheck()` was not affecting
the result but this was not the case when both parameters were `PHINode`s.
Due to this assumption `ProvenanceAnalysis::related()` was ordering the parameters based on pointer value which resulted in
non-deterministic behavior.
To address this change `relatedPHI()` so that it gives the same result independent of the parameter order.
rdar://100325456
Differential Revision: https://reviews.llvm.org/D135376
d877e3fe71