[Analysis] Avoid repeated hash lookups (NFC) (#131421)

Author: kazutakahirata

llvm/lib/Analysis/LoopAccessAnalysis.cpp

@@ -2287,8 +2287,9 @@ bool MemoryDepChecker::areDepsSafe(const DepCandidates &AccessSets,
           (AIIsWrite ? AI : std::next(AI));
       while (OI != AE) {
         // Check every accessing instruction pair in program order.
-        for (std::vector<unsigned>::iterator I1 = Accesses[*AI].begin(),
-             I1E = Accesses[*AI].end(); I1 != I1E; ++I1)
+        auto &Acc = Accesses[*AI];
+        for (std::vector<unsigned>::iterator I1 = Acc.begin(), I1E = Acc.end();
+             I1 != I1E; ++I1)
           // Scan all accesses of another equivalence class, but only the next
           // accesses of the same equivalent class.
           for (std::vector<unsigned>::iterator