[LoopIterator] Add const qualifier to LoopInfo (NFC)

Loop iteration utilities do not change LoopInfo.

Author: nikic

llvm/include/llvm/Analysis/LoopIterator.h

@@ -120,7 +120,7 @@ class LoopBlocksDFS {
   Loop *getLoop() const { return L; }
 
   /// Traverse the loop blocks and store the DFS result.
-  void perform(LoopInfo *LI);
+  void perform(const LoopInfo *LI);
 
   /// Return true if postorder numbers are assigned to all loop blocks.
   bool isComplete() const { return PostBlocks.size() == L->getNumBlocks(); }
@@ -177,7 +177,7 @@ class LoopBlocksRPO {
   LoopBlocksRPO(Loop *Container) : DFS(Container) {}
 
   /// Traverse the loop blocks and store the DFS result.
-  void perform(LoopInfo *LI) {
+  void perform(const LoopInfo *LI) {
     DFS.perform(LI);
   }
 
@@ -204,10 +204,10 @@ class LoopBlocksTraversal {
 
 private:
   LoopBlocksDFS &DFS;
-  LoopInfo *LI;
+  const LoopInfo *LI;
 
 public:
-  LoopBlocksTraversal(LoopBlocksDFS &Storage, LoopInfo *LInfo) :
+  LoopBlocksTraversal(LoopBlocksDFS &Storage, const LoopInfo *LInfo) :
     DFS(Storage), LI(LInfo) {}
 
   /// Postorder traversal over the graph. This only needs to be done once.

llvm/lib/Analysis/LoopInfo.cpp

@@ -1218,7 +1218,7 @@ PreservedAnalyses LoopVerifierPass::run(Function &F,
 /// Traverse the loop blocks and store the DFS result.
 /// Useful for clients that just want the final DFS result and don't need to
 /// visit blocks during the initial traversal.
-void LoopBlocksDFS::perform(LoopInfo *LI) {
+void LoopBlocksDFS::perform(const LoopInfo *LI) {
   LoopBlocksTraversal Traversal(*this, LI);
   for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(),
                                         POE = Traversal.end();