[LoopAccesses] Factor out RuntimePointerCheck::needsChecking

[anemet]

Summary

Will be used by the new RuntimePointerCheck::print.

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

[hfinkel]

LGTM.

[anemet]

r229629

include/llvm/Analysis/LoopAccessAnalysis.h

void reset() {
       DependencySetId.clear();
       AliasSetId.clear();
     }
 
     /// Insert a pointer and calculate the start and end SCEVs.
     void insert(ScalarEvolution *SE, Loop *Lp, Value *Ptr, bool WritePtr,
                 unsigned DepSetId, unsigned ASId, ValueToValueMap &Strides);
 
+    /// \brief Decide whether we need to issue a run-time check for pointer at
+    /// index \p I and \p J to prove their independence.
+    bool needsChecking(unsigned I, unsigned J) const;
+
     /// This flag indicates if we need to add the runtime check.
     bool Need;
     /// Holds the pointers that we need to check.
     SmallVector<TrackingVH<Value>, 2> Pointers;
     /// Holds the pointer value at the beginning of the loop.
     SmallVector<const SCEV*, 2> Starts;
     /// Holds the pointer value at the end of the loop.
     SmallVector<const SCEV*, 2> Ends;

lib/Analysis/LoopAccessAnalysis.cpp

void LoopAccessInfo::RuntimePointerCheck::insert(ScalarEvolution *SE, Loop *Lp,
   Pointers.push_back(Ptr);
   Starts.push_back(AR->getStart());
   Ends.push_back(ScEnd);
   IsWritePtr.push_back(WritePtr);
   DependencySetId.push_back(DepSetId);
   AliasSetId.push_back(ASId);
 }
 
+bool LoopAccessInfo::RuntimePointerCheck::needsChecking(unsigned I,
+                                                        unsigned J) const {
+  // No need to check if two readonly pointers intersect.
+  if (!IsWritePtr[I] && !IsWritePtr[J])
+    return false;
+
+  // Only need to check pointers between two different dependency sets.
+  if (DependencySetId[I] == DependencySetId[J])
+    return false;
+
+  // Only need to check pointers in the same alias set.
+  if (AliasSetId[I] != AliasSetId[J])
+    return false;
+
+  return true;
+}
+
 namespace {
 /// \brief Analyses memory accesses in a loop.
 ///
 /// Checks whether run time pointer checks are needed and builds sets for data
 /// dependence checking.
 class AccessAnalysis {
 public:
   /// \brief Read or write access location.
for (unsigned i = 0; i < NumPointers; ++i) {
     }
   }
 
   IRBuilder<> ChkBuilder(Loc);
   // Our instructions might fold to a constant.
   Value *MemoryRuntimeCheck = nullptr;
   for (unsigned i = 0; i < NumPointers; ++i) {
     for (unsigned j = i+1; j < NumPointers; ++j) {
-      // No need to check if two readonly pointers intersect.
-      if (!PtrRtCheck.IsWritePtr[i] && !PtrRtCheck.IsWritePtr[j])
-        continue;
-
-      // Only need to check pointers between two different dependency sets.
-      if (PtrRtCheck.DependencySetId[i] == PtrRtCheck.DependencySetId[j])
-       continue;
-      // Only need to check pointers in the same alias set.
-      if (PtrRtCheck.AliasSetId[i] != PtrRtCheck.AliasSetId[j])
+      if (!PtrRtCheck.needsChecking(i, j))
         continue;
 
       unsigned AS0 = Starts[i]->getType()->getPointerAddressSpace();
       unsigned AS1 = Starts[j]->getType()->getPointerAddressSpace();
 
       assert((AS0 == Ends[j]->getType()->getPointerAddressSpace()) &&
              (AS1 == Ends[i]->getType()->getPointerAddressSpace()) &&
              "Trying to bounds check pointers with different address spaces");