[NFC]: Fix PVS Studio warning in LoopNestAnalysis

[etiotto]

Summary

This patch fixes the following warnings uncovered by PVS Studio:

/home/xbolva00/LLVM/llvm-project/llvm/lib/Analysis/LoopCacheAnalysis.cpp 353 warn V612 An unconditional 'return' within a loop.
/home/xbolva00/LLVM/llvm-project/llvm/lib/Analysis/LoopCacheAnalysis.cpp 456 err V502 Perhaps the '?:' operator works in a different way than it was expected. The '?:' operator has a lower priority than the '==' operator.

[xbolva00]

Looks fine.

[Whitney]

llvm/lib/Analysis/LoopCacheAnalysis.cpp

345

return false?

llvm/lib/Analysis/LoopCacheAnalysis.cpp

bool IndexedReference::delinearize(const LoopInfo &LI) {
   assert(Subscripts.empty() && "Subscripts should be empty");
   assert(Sizes.empty() && "Sizes should be empty");
   assert(!IsValid && "Should be called once from the constructor");
   LLVM_DEBUG(dbgs() << "Delinearizing: " << StoreOrLoadInst << "\n");
 
   const SCEV *ElemSize = SE.getElementSize(&StoreOrLoadInst);
   const BasicBlock *BB = StoreOrLoadInst.getParent();
 
-  for (Loop *L = LI.getLoopFor(BB); L != nullptr; L = L->getParentLoop()) {
+  if (Loop *L = LI.getLoopFor(BB)) {
     const SCEV *AccessFn =
         SE.getSCEVAtScope(getPointerOperand(&StoreOrLoadInst), L);
 
     BasePointer = dyn_cast<SCEVUnknown>(SE.getPointerBase(AccessFn));
     if (BasePointer == nullptr) {
       LLVM_DEBUG(
           dbgs().indent(2)
           << "ERROR: failed to delinearize, can't identify base pointer\n");
if (Subscripts.empty() || Sizes.empty() ||
         Subscripts.size() != Sizes.size()) {
       // Attempt to determine whether we have a single dimensional array access.
       // before giving up.
       if (!isOneDimensionalArray(*AccessFn, *ElemSize, *L, SE)) {
         LLVM_DEBUG(dbgs().indent(2)
                    << "ERROR: failed to delinearize reference\n");
         Subscripts.clear();
         Sizes.clear();
-        break;
+        return false;
       }
 
       const SCEV *Div = SE.getUDivExactExpr(AccessFn, ElemSize);
       Subscripts.push_back(Div);
       Sizes.push_back(ElemSize);
     }
 
     return all_of(Subscripts, [&](const SCEV *Subscript) {
raw_ostream &llvm::operator<<(raw_ostream &OS, const CacheCost &CC) {
   return OS;
 }
 
 CacheCost::CacheCost(const LoopVectorTy &Loops, const LoopInfo &LI,
                      ScalarEvolution &SE, TargetTransformInfo &TTI,
                      AliasAnalysis &AA, DependenceInfo &DI,
                      Optional<unsigned> TRT)
     : Loops(Loops), TripCounts(), LoopCosts(),
-      TRT(TRT == None ? Optional<unsigned>(TemporalReuseThreshold) : TRT),
+      TRT((TRT == None) ? Optional<unsigned>(TemporalReuseThreshold) : TRT),
       LI(LI), SE(SE), TTI(TTI), AA(AA), DI(DI) {
   assert(!Loops.empty() && "Expecting a non-empty loop vector.");
 
   for (const Loop *L : Loops) {
     unsigned TripCount = SE.getSmallConstantTripCount(L);
     TripCount = (TripCount == 0) ? DefaultTripCount : TripCount;
     TripCounts.push_back({L, TripCount});
   }