[LAA] Remove RuntimeCheckingPtrGroup::RtCheck member (NFC).

[fhahn]

Summary

This patch removes RtCheck from RuntimeCheckingPtrGroup to make it
possible to construct RuntimeCheckingPtrGroup objects without a
RuntimePointerChecking object. This should make it easier to
re-use the code to generate runtime checks, e.g. in D102834.

RtCheck was only used to access the pointer info for a given index.
Instead, the start and end expressions can be passed directly.

For code-gen, we also need to know the address space to use. This can
also be explicitly passed at construction.

[efriedma]

LGTM

[fhahn]

rebase

llvm/include/llvm/Analysis/LoopAccessAnalysis.h

 class RuntimePointerChecking;
 /// A grouping of pointers. A single memcheck is required between
 /// two groups.
 struct RuntimeCheckingPtrGroup {
   /// Create a new pointer checking group containing a single
   /// pointer, with index \p Index in RtCheck.
   RuntimeCheckingPtrGroup(unsigned Index, RuntimePointerChecking &RtCheck);
 
+  RuntimeCheckingPtrGroup(unsigned Index, const SCEV *Start, const SCEV *End,
+                          unsigned AS)
+      : High(End), Low(Start), AddressSpace(AS) {
+    Members.push_back(Index);
+  }
+
   /// Tries to add the pointer recorded in RtCheck at index
   /// \p Index to this pointer checking group. We can only add a pointer
   /// to a checking group if we will still be able to get
   /// the upper and lower bounds of the check. Returns true in case
   /// of success, false otherwise.
-  bool addPointer(unsigned Index);
+  bool addPointer(unsigned Index, RuntimePointerChecking &RtCheck);
+  bool addPointer(unsigned Index, const SCEV *Start, const SCEV *End,
+                  unsigned AS, ScalarEvolution &SE);
 
-  /// Constitutes the context of this pointer checking group. For each
-  /// pointer that is a member of this group we will retain the index
-  /// at which it appears in RtCheck.
-  RuntimePointerChecking &RtCheck;
   /// The SCEV expression which represents the upper bound of all the
   /// pointers in this group.
   const SCEV *High;
   /// The SCEV expression which represents the lower bound of all the
   /// pointers in this group.
   const SCEV *Low;
   /// Indices of all the pointers that constitute this grouping.
   SmallVector<unsigned, 2> Members;
+  /// Address space of the involved pointers.
+  unsigned AddressSpace;
 };
 
 /// A memcheck which made up of a pair of grouped pointers.
 typedef std::pair<const RuntimeCheckingPtrGroup *,
                   const RuntimeCheckingPtrGroup *>
     RuntimePointerCheck;
 
 /// Holds information about the memory runtime legality checks to verify

llvm/lib/Analysis/LoopAccessAnalysis.cpp

const SCEV *llvm::replaceSymbolicStrideSCEV(PredicatedScalarEvolution &PSE,
 
   LLVM_DEBUG(dbgs() << "LAA: Replacing SCEV: " << *OrigSCEV
        << " by: " << *Expr << "\n");
   return Expr;
 }
 
 RuntimeCheckingPtrGroup::RuntimeCheckingPtrGroup(
     unsigned Index, RuntimePointerChecking &RtCheck)
-    : RtCheck(RtCheck), High(RtCheck.Pointers[Index].End),
-      Low(RtCheck.Pointers[Index].Start) {
+    : High(RtCheck.Pointers[Index].End), Low(RtCheck.Pointers[Index].Start),
+      AddressSpace(RtCheck.Pointers[Index]
+                       .PointerValue->getType()
+                       ->getPointerAddressSpace()) {
   Members.push_back(Index);
 }
 
 /// Calculate Start and End points of memory access.
 /// Let's assume A is the first access and B is a memory access on N-th loop
 /// iteration. Then B is calculated as:
 ///   B = A + Step*N .
 /// Step value may be positive or negative.
static const SCEV *getMinFromExprs(const SCEV *I, const SCEV *J,
 
   if (!C)
     return nullptr;
   if (C->getValue()->isNegative())
     return J;
   return I;
 }
 
-bool RuntimeCheckingPtrGroup::addPointer(unsigned Index) {
-  const SCEV *Start = RtCheck.Pointers[Index].Start;
-  const SCEV *End = RtCheck.Pointers[Index].End;
+bool RuntimeCheckingPtrGroup::addPointer(unsigned Index,
+                                         RuntimePointerChecking &RtCheck) {
+  return addPointer(
+      Index, RtCheck.Pointers[Index].Start, RtCheck.Pointers[Index].End,
+      RtCheck.Pointers[Index].PointerValue->getType()->getPointerAddressSpace(),
+      *RtCheck.SE);
+}
+
+bool RuntimeCheckingPtrGroup::addPointer(unsigned Index, const SCEV *Start,
+                                         const SCEV *End, unsigned AS,
+                                         ScalarEvolution &SE) {
+  assert(AddressSpace == AS &&
+         "all pointers in a checking group must be in the same address space");
 
   // Compare the starts and ends with the known minimum and maximum
   // of this set. We need to know how we compare against the min/max
   // of the set in order to be able to emit memchecks.
-  const SCEV *Min0 = getMinFromExprs(Start, Low, RtCheck.SE);
+  const SCEV *Min0 = getMinFromExprs(Start, Low, &SE);
   if (!Min0)
     return false;
 
-  const SCEV *Min1 = getMinFromExprs(End, High, RtCheck.SE);
+  const SCEV *Min1 = getMinFromExprs(End, High, &SE);
   if (!Min1)
     return false;
 
   // Update the low bound  expression if we've found a new min value.
   if (Min0 == Start)
     Low = Start;
 
   // Update the high bound expression if we've found a new max value.
for (auto MI = DepCands.member_begin(LeaderI), ME = DepCands.member_end();
         // This should limit the cost of grouping the pointers to something
         // reasonable.  If we do end up hitting this threshold, the algorithm
         // will create separate groups for all remaining pointers.
         if (TotalComparisons > MemoryCheckMergeThreshold)
           break;
 
         TotalComparisons++;
 
-        if (Group.addPointer(Pointer)) {
+        if (Group.addPointer(Pointer, *this)) {
           Merged = true;
           break;
         }
       }
 
       if (!Merged)
         // We couldn't add this pointer to any existing set or the threshold
         // for the number of comparisons has been reached. Create a new group

llvm/lib/Transforms/Utils/LoopUtils.cpp

struct PointerBounds {
   TrackingVH<Value> End;
 };
 
 /// Expand code for the lower and upper bound of the pointer group \p CG
 /// in \p TheLoop.  \return the values for the bounds.
 static PointerBounds expandBounds(const RuntimeCheckingPtrGroup *CG,
                                   Loop *TheLoop, Instruction *Loc,
                                   SCEVExpander &Exp) {
-  // TODO: Add helper to retrieve pointers to CG.
-  Value *Ptr = CG->RtCheck.Pointers[CG->Members[0]].PointerValue;
-
-  unsigned AS = Ptr->getType()->getPointerAddressSpace();
   LLVMContext &Ctx = Loc->getContext();
-
-  // Use this type for pointer arithmetic.
-  Type *PtrArithTy = Type::getInt8PtrTy(Ctx, AS);
+  Type *PtrArithTy = Type::getInt8PtrTy(Ctx, CG->AddressSpace);
 
   Value *Start = nullptr, *End = nullptr;
   LLVM_DEBUG(dbgs() << "LAA: Adding RT check for range:\n");
   Start = Exp.expandCodeFor(CG->Low, PtrArithTy, Loc);
   End = Exp.expandCodeFor(CG->High, PtrArithTy, Loc);
   LLVM_DEBUG(dbgs() << "Start: " << *CG->Low << " End: " << *CG->High << "\n");
   return {Start, End};
 }