[NFC}[LoopSimplify] modernize for loops over LoopInfo

[tammela]

Summary

This patch modifies two for loops to use the range based syntax.
Since they are equivalent, this patch is tagged NFC.

[dmgreen]

LGTM!

llvm/lib/Transforms/Utils/LoopSimplify.cpp

if (MSSAAnalysis) {
       MSSA = &MSSAAnalysis->getMSSA();
       MSSAU = std::make_unique<MemorySSAUpdater>(MSSA);
     }
   }
 
   bool PreserveLCSSA = mustPreserveAnalysisID(LCSSAID);
 
   // Simplify each loop nest in the function.
-  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
-    Changed |= simplifyLoop(*I, DT, LI, SE, AC, MSSAU.get(), PreserveLCSSA);
+  for (auto *L : *LI)
+    Changed |= simplifyLoop(L, DT, LI, SE, AC, MSSAU.get(), PreserveLCSSA);
 
 #ifndef NDEBUG
   if (PreserveLCSSA) {
     bool InLCSSA = all_of(
         *LI, [&](Loop *L) { return L->isRecursivelyLCSSAForm(*DT, *LI); });
     assert(InLCSSA && "LCSSA is broken after loop-simplify.");
   }
 #endif
PreservedAnalyses LoopSimplifyPass::run(Function &F,
   if (MSSAAnalysis) {
     auto *MSSA = &MSSAAnalysis->getMSSA();
     MSSAU = std::make_unique<MemorySSAUpdater>(MSSA);
   }
 
 
   // Note that we don't preserve LCSSA in the new PM, if you need it run LCSSA
   // after simplifying the loops. MemorySSA is preserved if it exists.
-  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
+  for (auto *L : *LI)
     Changed |=
-        simplifyLoop(*I, DT, LI, SE, AC, MSSAU.get(), /*PreserveLCSSA*/ false);
+        simplifyLoop(L, DT, LI, SE, AC, MSSAU.get(), /*PreserveLCSSA*/ false);
 
   if (!Changed)
     return PreservedAnalyses::all();
 
   PreservedAnalyses PA;
   PA.preserve<DominatorTreeAnalysis>();
   PA.preserve<LoopAnalysis>();
   PA.preserve<BasicAA>();