[Analysis] Remove unused fields in MemorySSA.cpp (NFC)

[kazu]

Summary

The last uses of AR were removed on July 28, 2022 in commit
f96ea53e892e0dfc1ee778868c1ed33616b95a82.

llvm/lib/Analysis/MemorySSA.cpp

struct UpwardsMemoryQuery {
   bool IsCall = false;
   // The pointer location we started the query with. This will be empty if
   // IsCall is true.
   MemoryLocation StartingLoc;
   // This is the instruction we were querying about.
   const Instruction *Inst = nullptr;
   // The MemoryAccess we actually got called with, used to test local domination
   const MemoryAccess *OriginalAccess = nullptr;
-  Optional<AliasResult> AR = AliasResult(AliasResult::MayAlias);
   bool SkipSelfAccess = false;
 
   UpwardsMemoryQuery() = default;
 
   UpwardsMemoryQuery(const Instruction *Inst, const MemoryAccess *Access)
       : IsCall(isa<CallBase>(Inst)), Inst(Inst), OriginalAccess(Access) {
     if (!IsCall)
       StartingLoc = MemoryLocation::get(Inst);
struct MemlocStackInfo {
     // the place the last stack walk ended.
     // Note: Correctness depends on this being initialized to 0, which densemap
     // does
     unsigned long LowerBound;
     const BasicBlock *LowerBoundBlock;
     // This is where the last walk for this memory location ended.
     unsigned long LastKill;
     bool LastKillValid;
-    Optional<AliasResult> AR;
   };
 
   void optimizeUsesInBlock(const BasicBlock *, unsigned long &, unsigned long &,
                            SmallVectorImpl<MemoryAccess *> &,
                            DenseMap<MemoryLocOrCall, MemlocStackInfo> &);
 
   MemorySSA *MSSA;
   CachingWalker<BatchAAResults> *Walker;
while (UpperBound > LocInfo.LowerBound) {
       MemoryDef *MD = cast<MemoryDef>(VersionStack[UpperBound]);
       if (instructionClobbersQuery(MD, MU, UseMLOC, *AA)) {
         FoundClobberResult = true;
         break;
       }
       --UpperBound;
     }
 
-    // Note: Phis always have AliasResult AR set to MayAlias ATM.
-
     // At the end of this loop, UpperBound is either a clobber, or lower bound
     // PHI walking may cause it to be < LowerBound, and in fact, < LastKill.
     if (FoundClobberResult || UpperBound < LocInfo.LastKill) {
       MU->setDefiningAccess(VersionStack[UpperBound], true);
       LocInfo.LastKill = UpperBound;
     } else {
       // Otherwise, we checked all the new ones, and now we know we can get to
       // LastKill.