[LoopAccesses] Add missing const to APIs in VectorizationReport

[anemet]

Summary

When I split out LoopAccessReport from this, I need to create some temps
so constness becomes necessary.

This is part of the patchset that converts LoopAccessAnalysis into an
actual analysis pass.

[hfinkel]

LGTM.

[anemet]

r229896

include/llvm/Analysis/LoopAccessAnalysis.h

 class ScalarEvolution;
 class Loop;
 class SCEV;
 
 /// Optimization analysis message produced during vectorization. Messages inform
 /// the user why vectorization did not occur.
 class VectorizationReport {
   std::string Message;
-  Instruction *Instr;
+  const Instruction *Instr;
 
 public:
-  VectorizationReport(Instruction *I = nullptr)
+  VectorizationReport(const Instruction *I = nullptr)
       : Message("loop not vectorized: "), Instr(I) {}
 
   template <typename A> VectorizationReport &operator<<(const A &Value) {
     raw_string_ostream Out(Message);
     Out << Value;
     return *this;
   }
 
-  Instruction *getInstr() { return Instr; }
+  const Instruction *getInstr() const { return Instr; }
 
   std::string &str() { return Message; }
+  const std::string &str() const { return Message; }
   operator Twine() { return Message; }
 
   /// \brief Emit an analysis note with the debug location from the instruction
   /// in \p Message if available.  Otherwise use the location of \p TheLoop.
-  static void emitAnalysis(VectorizationReport &Message,
+  static void emitAnalysis(const VectorizationReport &Message,
                            const Function *TheFunction,
                            const Loop *TheLoop);
 };
 
 /// \brief Drive the analysis of memory accesses in the loop
 ///
 /// This class is responsible for analyzing the memory accesses of a loop.  It
 /// collects the accesses and then its main helper the AccessAnalysis class

lib/Analysis/LoopAccessAnalysis.cpp

 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Transforms/Utils/VectorUtils.h"
 using namespace llvm;
 
 #define DEBUG_TYPE "loop-accesses"
 
-void VectorizationReport::emitAnalysis(VectorizationReport &Message,
+void VectorizationReport::emitAnalysis(const VectorizationReport &Message,
                                        const Function *TheFunction,
                                        const Loop *TheLoop) {
   DebugLoc DL = TheLoop->getStartLoc();
-  if (Instruction *I = Message.getInstr())
+  if (const Instruction *I = Message.getInstr())
     DL = I->getDebugLoc();
   emitOptimizationRemarkAnalysis(TheFunction->getContext(), "loop-vectorize",
                                  *TheFunction, DL, Message.str());
 }
 
 Value *llvm::stripIntegerCast(Value *V) {
   if (CastInst *CI = dyn_cast<CastInst>(V))
     if (CI->getOperand(0)->getType()->isIntegerTy())

lib/Transforms/Vectorize/LoopVectorize.cpp

private:
   /// \brief Collect memory access with loop invariant strides.
   ///
   /// Looks for accesses like "a[i * StrideA]" where "StrideA" is loop
   /// invariant.
   void collectStridedAccess(Value *LoadOrStoreInst);
 
   /// Report an analysis message to assist the user in diagnosing loops that are
   /// not vectorized.
-  void emitAnalysis(VectorizationReport &Message) {
+  void emitAnalysis(const VectorizationReport &Message) {
     VectorizationReport::emitAnalysis(Message, TheFunction, TheLoop);
   }
 
   unsigned NumPredStores;
 
   /// The loop that we evaluate.
   Loop *TheLoop;
   /// Scev analysis.
private:
   static Type* ToVectorTy(Type *Scalar, unsigned VF);
 
   /// Returns whether the instruction is a load or store and will be a emitted
   /// as a vector operation.
   bool isConsecutiveLoadOrStore(Instruction *I);
 
   /// Report an analysis message to assist the user in diagnosing loops that are
   /// not vectorized.
-  void emitAnalysis(VectorizationReport &Message) {
+  void emitAnalysis(const VectorizationReport &Message) {
     VectorizationReport::emitAnalysis(Message, TheFunction, TheLoop);
   }
 
   /// Values used only by @llvm.assume calls.
   SmallPtrSet<const Value *, 32> EphValues;
 
   /// The loop that we evaluate.
   Loop *TheLoop;