[LoopAccesses] Stash the report from the analysis rather than emitting it

[anemet]

Summary

The transformation passes will query this and then emit them as part of
their own report. The currently only user LV is modified to do just
that.

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

[hfinkel]

I imagine that, in the future, we might generate multiple report messages. I think that this is fine for now, however. LGTM.

lib/Analysis/LoopAccessAnalysis.cpp

1080

report -> reports

[anemet]

In D7681#124563, @hfinkel wrote:

I imagine that, in the future, we might generate multiple report messages. I think that this is fine for now, however. LGTM.

Yeah, initially I wrote this with a SmallVector. When later in the patchset I was writing the part to prepend "loop cannot be vectorized" to the report for the vectorizer I realized that there was no point making that a loop, etc since we only have reports with a single message in them.

[anemet]

229891

include/llvm/Analysis/LoopAccessAnalysis.h

 // was originally developed for the Loop Vectorizer.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
 #define LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
 
 #include "llvm/ADT/EquivalenceClasses.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/AliasSetTracker.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/Support/raw_ostream.h"
 
 namespace llvm {
struct RuntimePointerCheck {
     SmallVector<bool, 2> IsWritePtr;
     /// Holds the id of the set of pointers that could be dependent because of a
     /// shared underlying object.
     SmallVector<unsigned, 2> DependencySetId;
     /// Holds the id of the disjoint alias set to which this pointer belongs.
     SmallVector<unsigned, 2> AliasSetId;
   };
 
-  LoopAccessInfo(Function *F, Loop *L, ScalarEvolution *SE,
-                 const DataLayout *DL, const TargetLibraryInfo *TLI,
-                 AliasAnalysis *AA, DominatorTree *DT) :
-      TheFunction(F), TheLoop(L), SE(SE), DL(DL), TLI(TLI), AA(AA), DT(DT),
-      NumLoads(0), NumStores(0), MaxSafeDepDistBytes(-1U) {}
+  LoopAccessInfo(Loop *L, ScalarEvolution *SE, const DataLayout *DL,
+                 const TargetLibraryInfo *TLI, AliasAnalysis *AA,
+                 DominatorTree *DT) :
+      TheLoop(L), SE(SE), DL(DL), TLI(TLI), AA(AA), DT(DT), NumLoads(0),
+      NumStores(0), MaxSafeDepDistBytes(-1U) {}
 
   /// Return true we can analyze the memory accesses in the loop and there are
   /// no memory dependence cycles.  Replaces symbolic strides using Strides.
   bool canVectorizeMemory(ValueToValueMap &Strides);
 
   RuntimePointerCheck *getRuntimePointerCheck() { return &PtrRtCheck; }
 
   /// Return true if the block BB needs to be predicated in order for the loop
public:
 
   /// \brief Add code that checks at runtime if the accessed arrays overlap.
   ///
   /// Returns a pair of instructions where the first element is the first
   /// instruction generated in possibly a sequence of instructions and the
   /// second value is the final comparator value or NULL if no check is needed.
   std::pair<Instruction *, Instruction *> addRuntimeCheck(Instruction *Loc);
 
+  /// \brief The diagnostics report generated for the analysis.  E.g. why we
+  /// couldn't analyze the loop.
+  Optional<VectorizationReport> &getReport() { return Report; }
+
 private:
   void emitAnalysis(VectorizationReport &Message);
 
   /// We need to check that all of the pointers in this list are disjoint
   /// at runtime.
   RuntimePointerCheck PtrRtCheck;
-  Function *TheFunction;
   Loop *TheLoop;
   ScalarEvolution *SE;
   const DataLayout *DL;
   const TargetLibraryInfo *TLI;
   AliasAnalysis *AA;
   DominatorTree *DT;
 
   unsigned NumLoads;
   unsigned NumStores;
 
   unsigned MaxSafeDepDistBytes;
+
+  /// \brief The diagnostics report generated for the analysis.  E.g. why we
+  /// couldn't analyze the loop.
+  Optional<VectorizationReport> Report;
 };
 
 Value *stripIntegerCast(Value *V);
 
 ///\brief Return the SCEV corresponding to a pointer with the symbolic stride
 ///replaced with constant one.
 ///
 /// If \p OrigPtr is not null, use it to look up the stride value instead of \p

lib/Analysis/LoopAccessAnalysis.cpp

bool LoopAccessInfo::blockNeedsPredication(BasicBlock *BB)  {
   assert(TheLoop->contains(BB) && "Unknown block used");
 
   // Blocks that do not dominate the latch need predication.
   BasicBlock* Latch = TheLoop->getLoopLatch();
   return !DT->dominates(BB, Latch);
 }
 
 void LoopAccessInfo::emitAnalysis(VectorizationReport &Message) {
-  VectorizationReport::emitAnalysis(Message, TheFunction, TheLoop);
+  assert(!Report && "Multiple report generated");
+  Report = Message;
 }
 
 bool LoopAccessInfo::isUniform(Value *V) {
   return (SE->isLoopInvariant(SE->getSCEV(V), TheLoop));
 }
 
 // FIXME: this function is currently a duplicate of the one in
 // LoopVectorize.cpp.

lib/Transforms/Vectorize/LoopVectorize.cpp

 public:
   LoopVectorizationLegality(Loop *L, ScalarEvolution *SE, const DataLayout *DL,
                             DominatorTree *DT, TargetLibraryInfo *TLI,
                             AliasAnalysis *AA, Function *F,
                             const TargetTransformInfo *TTI)
       : NumPredStores(0), TheLoop(L), SE(SE), DL(DL),
         TLI(TLI), TheFunction(F), TTI(TTI), Induction(nullptr),
         WidestIndTy(nullptr),
-        LAI(F, L, SE, DL, TLI, AA, DT),
+        LAI(L, SE, DL, TLI, AA, DT),
         HasFunNoNaNAttr(false) {}
 
   /// This enum represents the kinds of reductions that we support.
   enum ReductionKind {
     RK_NoReduction, ///< Not a reduction.
     RK_IntegerAdd,  ///< Sum of integers.
     RK_IntegerMult, ///< Product of integers.
     RK_IntegerOr,   ///< Bitwise or logical OR of numbers.
while (!Worklist.empty()) {
     Uniforms.insert(I);
 
     // Insert all operands.
     Worklist.insert(Worklist.end(), I->op_begin(), I->op_end());
   }
 }
 
 bool LoopVectorizationLegality::canVectorizeMemory() {
-  return LAI.canVectorizeMemory(Strides);
+  bool Success = LAI.canVectorizeMemory(Strides);
+  auto &OptionalReport = LAI.getReport();
+  if (OptionalReport)
+    emitAnalysis(*OptionalReport);
+  return Success;
 }
 
 static bool hasMultipleUsesOf(Instruction *I,
                               SmallPtrSetImpl<Instruction *> &Insts) {
   unsigned NumUses = 0;
   for(User::op_iterator Use = I->op_begin(), E = I->op_end(); Use != E; ++Use) {
     if (Insts.count(dyn_cast<Instruction>(*Use)))
       ++NumUses;