[MemorySSA] Remove dominator umbering

[davide]

Summary

Apparently this was originally used in the phi placement algorithm, but now it's pretty much dead.
I wasn't sure if you planned to use for something else in the future, hence this review.

[• dberlin]

No, this is definitely dead now i believe :)

include/llvm/Transforms/Utils/MemorySSA.h

 
   void
   determineInsertionPoint(const SmallPtrSetImpl<BasicBlock *> &DefiningBlocks);
-  void computeDomLevels(DenseMap<DomTreeNode *, unsigned> &DomLevels);
   void markUnreachableAsLiveOnEntry(BasicBlock *BB);
   bool dominatesUse(const MemoryAccess *, const MemoryAccess *) const;
   MemoryPhi *createMemoryPhi(BasicBlock *BB);

lib/Transforms/Utils/MemorySSA.cpp

   }
 }
 
-/// \brief Compute dominator levels, used by the phi insertion algorithm above.
-void MemorySSA::computeDomLevels(DenseMap<DomTreeNode *, unsigned> &DomLevels) {
-  for (auto DFI = df_begin(DT->getRootNode()), DFE = df_end(DT->getRootNode());
-       DFI != DFE; ++DFI)
-    DomLevels[*DFI] = DFI.getPathLength() - 1;
-}
-
 /// \brief This handles unreachable block accesses by deleting phi nodes in
 /// unreachable blocks, and marking all other unreachable MemoryAccess's as
 /// being uses of the live on entry definition.