[LAA] Move runtime-check generation to Transforms/Utils/loopUtils (NFC)

[fhahn]

Summary

Currently LAA's uses of ScalarEvolutionExpander blocks moving the
expander from Analysis to Transforms. Conceptually the expander does not
fit into Analysis (it is only used for code generation) and
runtime-check generation also seems to be better suited as a
transformation utility.

[fhahn]

ping

[fhahn]

Ping. Rebased after 616657b39c81

[fhahn]

ping :)

[Ayal]

This analysis/utils refactoring looks good to me, thanks! Just adding some nits to clarify some presumably "add-on" parts, and possible alternatives/follow-ups.

llvm/include/llvm/Transforms/Utils/LoopUtils.h

48

nit: may be worthwhile to have a typdef for SmallVectorImpl<RuntimePointerCheck> as well.

435

nit: would be good to retain some of the original explanation of the abandoned addRuntimeChecks():

/// Add code that checks at runtime if the accessed arrays overlap.

llvm/lib/Transforms/Utils/LoopUtils.cpp

1556

nit: is there a reason to swap the order of getFirstInst() and struct PointerBounds?

1563

Just to clarify: using CG->ReCheck to save passing PtrRtChecking parameter here and through the other expandBounds() could have been done as a preparatory patch, right?

Seems like CG should provide an API for retrieving the desired Ptr of its first member.

llvm/lib/Transforms/Utils/LoopVersioning.cpp

65

Seems strange to call getRuntimePointerChecking() only for its getSE(). Perhaps pass RtPtrChecking, as commented below for LV, and have addRuntimeChecks() retrieve both AliasChecks and SE from there. This would require modifying the way (not) UseLAIChecks is handled.

Moreover, perhaps LoopVersioning's additional use of AliasChecks to annotate insns with no alias, should be shared with LV, or in general be taken care of by addRuntimeChecks()?

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

2801

Just to clarify: inlining addRuntimeChecks(Insn)'s call to RtPtrChecking.Need and discarding the former could have been done as a preparatory patch, right?

OTOH, instead of passing both RtPtrChecking.getChecks() and RtPtrChecking.getSE(), and potentially also RtPtrChecking.Need, perhaps pass only RtPtrChecking. This early-exit check for Need could also apply to LoopVersioning, right?

[fhahn]

Thanks Ayal! Comments should be addressed.

llvm/include/llvm/Transforms/Utils/LoopUtils.h

435

I've reworded the first line with the more descriptive message, thanks!

llvm/lib/Transforms/Utils/LoopUtils.cpp

1556

I've moved it into a lambda in the single function using it.

1563

Just to clarify: using CG->ReCheck to save passing PtrRtChecking parameter here and through the other expandBounds() could have been done as a preparatory patch, right?

I've pushed 57fb56b30e85c8e9662075c671d02fbdc37d8f3b doing exactly that, thanks.

Seems like CG should provide an API for retrieving the desired Ptr of its first member.

Can do that as a follow up.

llvm/lib/Transforms/Utils/LoopVersioning.cpp

65

Seems strange to call getRuntimePointerChecking() only for its getSE(). Perhaps pass RtPtrChecking, as commented below for LV, and have addRuntimeChecks() retrieve both AliasChecks and SE from there. This would require modifying the way (not) UseLAIChecks is handled.

I tried that, but it seems the LoopVersioning stores the checks on purpose. When using getChecks() directly, there are some test failures, although I did not spot the places that changes the checks on a quick look. I think unifying them would be better as a follow-up patch, if possible.

Moreover, perhaps LoopVersioning's additional use of AliasChecks to annotate insns with no alias, should be shared with LV, or in general be taken care of by addRuntimeChecks()?

+1. Not sure if there is a reason for the split, but I can take a look as a follow-up/

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

2801

Just to clarify: inlining addRuntimeChecks(Insn)'s call to RtPtrChecking.Need and discarding the former could have been done as a preparatory patch, right?

Done, I've put up D79679

OTOH, instead of passing both RtPtrChecking.getChecks() and RtPtrChecking.getSE(), and potentially also RtPtrChecking.Need, perhaps pass only RtPtrChecking. This early-exit check for Need could also apply to LoopVersioning, right?

It looks like there's an issue with passing RtPtrchecking directly for LoopVersioning. I can look into what is going on there, but I think it would be better as follow-up, because it seems a bit more risky.

[Ayal]

This looks good to me, thanks!
Noting a minor nit.
Follow-ups could be noted in TODO's.

llvm/lib/Transforms/Utils/LoopUtils.cpp

1628

Is this the indentation of this lambda right?

[fhahn]

Thanks Ayal, I fixed the formatting and added the TODOs

llvm/include/llvm/Analysis/LoopAccessAnalysis.h

public:
   /// index \p I and \p J to prove their independence.
   bool needsChecking(unsigned I, unsigned J) const;
 
   /// Return PointerInfo for pointer at index \p PtrIdx.
   const PointerInfo &getPointerInfo(unsigned PtrIdx) const {
     return Pointers[PtrIdx];
   }
 
+  ScalarEvolution *getSE() const { return SE; }
+
 private:
   /// Groups pointers such that a single memcheck is required
   /// between two different groups. This will clear the CheckingGroups vector
   /// and re-compute it. We will only group dependecies if \p UseDependencies
   /// is true, otherwise we will create a separate group for each pointer.
   void groupChecks(MemoryDepChecker::DepCandidates &DepCands,
                    bool UseDependencies);
 
public:
 
   /// Returns true if the value V is uniform within the loop.
   bool isUniform(Value *V) const;
 
   uint64_t getMaxSafeDepDistBytes() const { return MaxSafeDepDistBytes; }
   unsigned getNumStores() const { return NumStores; }
   unsigned getNumLoads() const { return NumLoads;}
 
-  /// Add code that checks at runtime if the accessed arrays \in p PointerChecks
-  /// 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 *> addRuntimeChecks(
-      Instruction *Loc,
-      const SmallVectorImpl<RuntimePointerCheck> &PointerChecks) const;
-
   /// The diagnostics report generated for the analysis.  E.g. why we
   /// couldn't analyze the loop.
   const OptimizationRemarkAnalysis *getReport() const { return Report.get(); }
 
   /// the Memory Dependence Checker which can determine the
   /// loop-independent and loop-carried dependences between memory accesses.
   const MemoryDepChecker &getDepChecker() const { return *DepChecker; }
 

llvm/include/llvm/Transforms/Utils/LoopUtils.h

 class PredIteratorCache;
 class ScalarEvolution;
 class SCEV;
 class SCEVExpander;
 class TargetLibraryInfo;
 class TargetTransformInfo;
 class LPPassManager;
 class Instruction;
+struct RuntimeCheckingPtrGroup;
+typedef std::pair<const RuntimeCheckingPtrGroup *,
+                  const RuntimeCheckingPtrGroup *>
+    RuntimePointerCheck;
 
 template <typename T> class Optional;
 template <typename T, unsigned N> class SmallSetVector;
 template <typename T, unsigned N> class SmallVector;
 template <typename T> class SmallVectorImpl;
 template <typename T, unsigned N> class SmallPriorityWorklist;
 
 BasicBlock *InsertPreheaderForLoop(Loop *L, DominatorTree *DT, LoopInfo *LI,
                                    MemorySSAUpdater *MSSAU, bool PreserveLCSSA);

 /// FIXME: Consider changing the order in LoopInfo.
 void appendLoopsToWorklist(LoopInfo &, SmallPriorityWorklist<Loop *, 4> &);
 
 /// Recursively clone the specified loop and all of its children,
 /// mapping the blocks with the specified map.
 Loop *cloneLoop(Loop *L, Loop *PL, ValueToValueMapTy &VM,
                 LoopInfo *LI, LPPassManager *LPM);
 
+/// Add code that checks at runtime if the accessed arrays in \p PointerChecks
+/// 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 *>
+addRuntimeChecks(Instruction *Loc, Loop *TheLoop,
+                 const SmallVectorImpl<RuntimePointerCheck> &PointerChecks,
+                 ScalarEvolution *SE);
+
 } // end namespace llvm
 
 #endif // LLVM_TRANSFORMS_UTILS_LOOPUTILS_H

llvm/lib/Analysis/LoopAccessAnalysis.cpp

 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
-#include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/Value.h"
 #include "llvm/IR/ValueHandle.h"
bool LoopAccessInfo::isUniform(Value *V) const {
   // never considered uniform.
   // TODO: Is this really what we want? Even without FP SCEV, we may want some
   // trivially loop-invariant FP values to be considered uniform.
   if (!SE->isSCEVable(V->getType()))
     return false;
   return (SE->isLoopInvariant(SE->getSCEV(V), TheLoop));
 }
 
-// FIXME: this function is currently a duplicate of the one in
-// LoopVectorize.cpp.
-static Instruction *getFirstInst(Instruction *FirstInst, Value *V,
-                                 Instruction *Loc) {
-  if (FirstInst)
-    return FirstInst;
-  if (Instruction *I = dyn_cast<Instruction>(V))
-    return I->getParent() == Loc->getParent() ? I : nullptr;
-  return nullptr;
-}
-
-namespace {
-
-/// IR Values for the lower and upper bounds of a pointer evolution.  We
-/// need to use value-handles because SCEV expansion can invalidate previously
-/// expanded values.  Thus expansion of a pointer can invalidate the bounds for
-/// a previous one.
-struct PointerBounds {
-  TrackingVH<Value> Start;
-  TrackingVH<Value> End;
-};
-
-} // end anonymous namespace
-
-/// 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, ScalarEvolution *SE) {
-  Value *Ptr = CG->RtCheck.Pointers[CG->Members[0]].PointerValue;
-
-  const SCEV *Sc = SE->getSCEV(Ptr);
-
-  unsigned AS = Ptr->getType()->getPointerAddressSpace();
-  LLVMContext &Ctx = Loc->getContext();
-
-  // Use this type for pointer arithmetic.
-  Type *PtrArithTy = Type::getInt8PtrTy(Ctx, AS);
-
-  if (SE->isLoopInvariant(Sc, TheLoop)) {
-    LLVM_DEBUG(dbgs() << "LAA: Adding RT check for a loop invariant ptr:"
-                      << *Ptr << "\n");
-    // Ptr could be in the loop body. If so, expand a new one at the correct
-    // location.
-    Instruction *Inst = dyn_cast<Instruction>(Ptr);
-    Value *NewPtr = (Inst && TheLoop->contains(Inst))
-                        ? Exp.expandCodeFor(Sc, PtrArithTy, Loc)
-                        : Ptr;
-    // We must return a half-open range, which means incrementing Sc.
-    const SCEV *ScPlusOne = SE->getAddExpr(Sc, SE->getOne(PtrArithTy));
-    Value *NewPtrPlusOne = Exp.expandCodeFor(ScPlusOne, PtrArithTy, Loc);
-    return {NewPtr, NewPtrPlusOne};
-  } else {
-    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};
-  }
-}
-
-/// Turns a collection of checks into a collection of expanded upper and
-/// lower bounds for both pointers in the check.
-static SmallVector<std::pair<PointerBounds, PointerBounds>, 4>
-expandBounds(const SmallVectorImpl<RuntimePointerCheck> &PointerChecks, Loop *L,
-             Instruction *Loc, ScalarEvolution *SE, SCEVExpander &Exp) {
-  SmallVector<std::pair<PointerBounds, PointerBounds>, 4> ChecksWithBounds;
-
-  // Here we're relying on the SCEV Expander's cache to only emit code for the
-  // same bounds once.
-  transform(
-      PointerChecks, std::back_inserter(ChecksWithBounds),
-      [&](const RuntimePointerCheck &Check) {
-        PointerBounds
-          First = expandBounds(Check.first, L, Loc, Exp, SE),
-          Second = expandBounds(Check.second, L, Loc, Exp, SE);
-        return std::make_pair(First, Second);
-      });
-
-  return ChecksWithBounds;
-}
-
-std::pair<Instruction *, Instruction *> LoopAccessInfo::addRuntimeChecks(
-    Instruction *Loc,
-    const SmallVectorImpl<RuntimePointerCheck> &PointerChecks) const {
-  const DataLayout &DL = TheLoop->getHeader()->getModule()->getDataLayout();
-  auto *SE = PSE->getSE();
-  SCEVExpander Exp(*SE, DL, "induction");
-  auto ExpandedChecks = expandBounds(PointerChecks, TheLoop, Loc, SE, Exp);
-
-  LLVMContext &Ctx = Loc->getContext();
-  Instruction *FirstInst = nullptr;
-  IRBuilder<> ChkBuilder(Loc);
-  // Our instructions might fold to a constant.
-  Value *MemoryRuntimeCheck = nullptr;
-
-  for (const auto &Check : ExpandedChecks) {
-    const PointerBounds &A = Check.first, &B = Check.second;
-    // Check if two pointers (A and B) conflict where conflict is computed as:
-    // start(A) <= end(B) && start(B) <= end(A)
-    unsigned AS0 = A.Start->getType()->getPointerAddressSpace();
-    unsigned AS1 = B.Start->getType()->getPointerAddressSpace();
-
-    assert((AS0 == B.End->getType()->getPointerAddressSpace()) &&
-           (AS1 == A.End->getType()->getPointerAddressSpace()) &&
-           "Trying to bounds check pointers with different address spaces");
-
-    Type *PtrArithTy0 = Type::getInt8PtrTy(Ctx, AS0);
-    Type *PtrArithTy1 = Type::getInt8PtrTy(Ctx, AS1);
-
-    Value *Start0 = ChkBuilder.CreateBitCast(A.Start, PtrArithTy0, "bc");
-    Value *Start1 = ChkBuilder.CreateBitCast(B.Start, PtrArithTy1, "bc");
-    Value *End0 =   ChkBuilder.CreateBitCast(A.End,   PtrArithTy1, "bc");
-    Value *End1 =   ChkBuilder.CreateBitCast(B.End,   PtrArithTy0, "bc");
-
-    // [A|B].Start points to the first accessed byte under base [A|B].
-    // [A|B].End points to the last accessed byte, plus one.
-    // There is no conflict when the intervals are disjoint:
-    // NoConflict = (B.Start >= A.End) || (A.Start >= B.End)
-    //
-    // bound0 = (B.Start < A.End)
-    // bound1 = (A.Start < B.End)
-    //  IsConflict = bound0 & bound1
-    Value *Cmp0 = ChkBuilder.CreateICmpULT(Start0, End1, "bound0");
-    FirstInst = getFirstInst(FirstInst, Cmp0, Loc);
-    Value *Cmp1 = ChkBuilder.CreateICmpULT(Start1, End0, "bound1");
-    FirstInst = getFirstInst(FirstInst, Cmp1, Loc);
-    Value *IsConflict = ChkBuilder.CreateAnd(Cmp0, Cmp1, "found.conflict");
-    FirstInst = getFirstInst(FirstInst, IsConflict, Loc);
-    if (MemoryRuntimeCheck) {
-      IsConflict =
-          ChkBuilder.CreateOr(MemoryRuntimeCheck, IsConflict, "conflict.rdx");
-      FirstInst = getFirstInst(FirstInst, IsConflict, Loc);
-    }
-    MemoryRuntimeCheck = IsConflict;
-  }
-
-  if (!MemoryRuntimeCheck)
-    return std::make_pair(nullptr, nullptr);
-
-  // We have to do this trickery because the IRBuilder might fold the check to a
-  // constant expression in which case there is no Instruction anchored in a
-  // the block.
-  Instruction *Check = BinaryOperator::CreateAnd(MemoryRuntimeCheck,
-                                                 ConstantInt::getTrue(Ctx));
-  ChkBuilder.Insert(Check, "memcheck.conflict");
-  FirstInst = getFirstInst(FirstInst, Check, Loc);
-  return std::make_pair(FirstInst, Check);
-}
-
 void LoopAccessInfo::collectStridedAccess(Value *MemAccess) {
   Value *Ptr = nullptr;
   if (LoadInst *LI = dyn_cast<LoadInst>(MemAccess))
     Ptr = LI->getPointerOperand();
   else if (StoreInst *SI = dyn_cast<StoreInst>(MemAccess))
     Ptr = SI->getPointerOperand();
   else
     return;

llvm/lib/Transforms/Utils/LoopUtils.cpp

if (LI->getLoopFor(*I) == L)
       New.addBasicBlockToLoop(cast<BasicBlock>(VM[*I]), *LI);
 
   // Add all of the subloops to the new loop.
   for (Loop *I : *L)
     cloneLoop(I, &New, VM, LI, LPM);
 
   return &New;
 }
+
+/// IR Values for the lower and upper bounds of a pointer evolution.  We
+/// need to use value-handles because SCEV expansion can invalidate previously
+/// expanded values.  Thus expansion of a pointer can invalidate the bounds for
+/// a previous one.
+struct PointerBounds {
+  TrackingVH<Value> Start;
+  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, ScalarEvolution *SE) {
+  // TODO: Add helper to retrieve pointers to CG.
+  Value *Ptr = CG->RtCheck.Pointers[CG->Members[0]].PointerValue;
+  const SCEV *Sc = SE->getSCEV(Ptr);
+
+  unsigned AS = Ptr->getType()->getPointerAddressSpace();
+  LLVMContext &Ctx = Loc->getContext();
+
+  // Use this type for pointer arithmetic.
+  Type *PtrArithTy = Type::getInt8PtrTy(Ctx, AS);
+
+  if (SE->isLoopInvariant(Sc, TheLoop)) {
+    LLVM_DEBUG(dbgs() << "LAA: Adding RT check for a loop invariant ptr:"
+                      << *Ptr << "\n");
+    // Ptr could be in the loop body. If so, expand a new one at the correct
+    // location.
+    Instruction *Inst = dyn_cast<Instruction>(Ptr);
+    Value *NewPtr = (Inst && TheLoop->contains(Inst))
+                        ? Exp.expandCodeFor(Sc, PtrArithTy, Loc)
+                        : Ptr;
+    // We must return a half-open range, which means incrementing Sc.
+    const SCEV *ScPlusOne = SE->getAddExpr(Sc, SE->getOne(PtrArithTy));
+    Value *NewPtrPlusOne = Exp.expandCodeFor(ScPlusOne, PtrArithTy, Loc);
+    return {NewPtr, NewPtrPlusOne};
+  } else {
+    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};
+  }
+}
+
+/// Turns a collection of checks into a collection of expanded upper and
+/// lower bounds for both pointers in the check.
+static SmallVector<std::pair<PointerBounds, PointerBounds>, 4>
+expandBounds(const SmallVectorImpl<RuntimePointerCheck> &PointerChecks, Loop *L,
+             Instruction *Loc, ScalarEvolution *SE, SCEVExpander &Exp) {
+  SmallVector<std::pair<PointerBounds, PointerBounds>, 4> ChecksWithBounds;
+
+  // Here we're relying on the SCEV Expander's cache to only emit code for the
+  // same bounds once.
+  transform(PointerChecks, std::back_inserter(ChecksWithBounds),
+            [&](const RuntimePointerCheck &Check) {
+              PointerBounds First = expandBounds(Check.first, L, Loc, Exp, SE),
+                            Second =
+                                expandBounds(Check.second, L, Loc, Exp, SE);
+              return std::make_pair(First, Second);
+            });
+
+  return ChecksWithBounds;
+}
+
+std::pair<Instruction *, Instruction *> llvm::addRuntimeChecks(
+    Instruction *Loc, Loop *TheLoop,
+    const SmallVectorImpl<RuntimePointerCheck> &PointerChecks,
+    ScalarEvolution *SE) {
+  // TODO: Move noalias annotation code from LoopVersioning here and share with LV if possible.
+  // TODO: Pass  RtPtrChecking instead of PointerChecks and SE separately, if possible
+  const DataLayout &DL = TheLoop->getHeader()->getModule()->getDataLayout();
+  SCEVExpander Exp(*SE, DL, "induction");
+  auto ExpandedChecks = expandBounds(PointerChecks, TheLoop, Loc, SE, Exp);
+
+  LLVMContext &Ctx = Loc->getContext();
+  Instruction *FirstInst = nullptr;
+  IRBuilder<> ChkBuilder(Loc);
+  // Our instructions might fold to a constant.
+  Value *MemoryRuntimeCheck = nullptr;
+
+  // FIXME: this helper is currently a duplicate of the one in
+  // LoopVectorize.cpp.
+  auto GetFirstInst = [](Instruction *FirstInst, Value *V,
+                         Instruction *Loc) -> Instruction * {
+    if (FirstInst)
+      return FirstInst;
+    if (Instruction *I = dyn_cast<Instruction>(V))
+      return I->getParent() == Loc->getParent() ? I : nullptr;
+    return nullptr;
+  };
+
+  for (const auto &Check : ExpandedChecks) {
+    const PointerBounds &A = Check.first, &B = Check.second;
+    // Check if two pointers (A and B) conflict where conflict is computed as:
+    // start(A) <= end(B) && start(B) <= end(A)
+    unsigned AS0 = A.Start->getType()->getPointerAddressSpace();
+    unsigned AS1 = B.Start->getType()->getPointerAddressSpace();
+
+    assert((AS0 == B.End->getType()->getPointerAddressSpace()) &&
+           (AS1 == A.End->getType()->getPointerAddressSpace()) &&
+           "Trying to bounds check pointers with different address spaces");
+
+    Type *PtrArithTy0 = Type::getInt8PtrTy(Ctx, AS0);
+    Type *PtrArithTy1 = Type::getInt8PtrTy(Ctx, AS1);
+
+    Value *Start0 = ChkBuilder.CreateBitCast(A.Start, PtrArithTy0, "bc");
+    Value *Start1 = ChkBuilder.CreateBitCast(B.Start, PtrArithTy1, "bc");
+    Value *End0 = ChkBuilder.CreateBitCast(A.End, PtrArithTy1, "bc");
+    Value *End1 = ChkBuilder.CreateBitCast(B.End, PtrArithTy0, "bc");
+
+    // [A|B].Start points to the first accessed byte under base [A|B].
+    // [A|B].End points to the last accessed byte, plus one.
+    // There is no conflict when the intervals are disjoint:
+    // NoConflict = (B.Start >= A.End) || (A.Start >= B.End)
+    //
+    // bound0 = (B.Start < A.End)
+    // bound1 = (A.Start < B.End)
+    //  IsConflict = bound0 & bound1
+    Value *Cmp0 = ChkBuilder.CreateICmpULT(Start0, End1, "bound0");
+    FirstInst = GetFirstInst(FirstInst, Cmp0, Loc);
+    Value *Cmp1 = ChkBuilder.CreateICmpULT(Start1, End0, "bound1");
+    FirstInst = GetFirstInst(FirstInst, Cmp1, Loc);
+    Value *IsConflict = ChkBuilder.CreateAnd(Cmp0, Cmp1, "found.conflict");
+    FirstInst = GetFirstInst(FirstInst, IsConflict, Loc);
+    if (MemoryRuntimeCheck) {
+      IsConflict =
+          ChkBuilder.CreateOr(MemoryRuntimeCheck, IsConflict, "conflict.rdx");
+      FirstInst = GetFirstInst(FirstInst, IsConflict, Loc);
+    }
+    MemoryRuntimeCheck = IsConflict;
+  }
+
+  if (!MemoryRuntimeCheck)
+    return std::make_pair(nullptr, nullptr);
+
+  // We have to do this trickery because the IRBuilder might fold the check to a
+  // constant expression in which case there is no Instruction anchored in a
+  // the block.
+  Instruction *Check =
+      BinaryOperator::CreateAnd(MemoryRuntimeCheck, ConstantInt::getTrue(Ctx));
+  ChkBuilder.Insert(Check, "memcheck.conflict");
+  FirstInst = GetFirstInst(FirstInst, Check, Loc);
+  return std::make_pair(FirstInst, Check);
+}

llvm/lib/Transforms/Utils/LoopVersioning.cpp

void LoopVersioning::versionLoop(
     const SmallVectorImpl<Instruction *> &DefsUsedOutside) {
   Instruction *FirstCheckInst;
   Instruction *MemRuntimeCheck;
   Value *SCEVRuntimeCheck;
   Value *RuntimeCheck = nullptr;
 
   // Add the memcheck in the original preheader (this is empty initially).
   BasicBlock *RuntimeCheckBB = VersionedLoop->getLoopPreheader();
+  const auto &RtPtrChecking = *LAI.getRuntimePointerChecking();
   std::tie(FirstCheckInst, MemRuntimeCheck) =
-      LAI.addRuntimeChecks(RuntimeCheckBB->getTerminator(), AliasChecks);
+      addRuntimeChecks(RuntimeCheckBB->getTerminator(), VersionedLoop,
+                       AliasChecks, RtPtrChecking.getSE());
 
   const SCEVUnionPredicate &Pred = LAI.getPSE().getUnionPredicate();
   SCEVExpander Exp(*SE, RuntimeCheckBB->getModule()->getDataLayout(),
                    "scev.check");
   SCEVRuntimeCheck =
       Exp.expandCodeForPredicate(&Pred, RuntimeCheckBB->getTerminator());
   auto *CI = dyn_cast<ConstantInt>(SCEVRuntimeCheck);
 

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

void InnerLoopVectorizer::emitMemRuntimeChecks(Loop *L, BasicBlock *Bypass) {
   // checks into a separate block to make the more common case of few elements
   // faster.
   auto *LAI = Legal->getLAI();
   const auto &RtPtrChecking = *LAI->getRuntimePointerChecking();
   if (!RtPtrChecking.Need)
     return;
   Instruction *FirstCheckInst;
   Instruction *MemRuntimeCheck;
-  std::tie(FirstCheckInst, MemRuntimeCheck) = LAI->addRuntimeChecks(
-      MemCheckBlock->getTerminator(), RtPtrChecking.getChecks());
+  std::tie(FirstCheckInst, MemRuntimeCheck) =
+      addRuntimeChecks(MemCheckBlock->getTerminator(), OrigLoop,
+                       RtPtrChecking.getChecks(), RtPtrChecking.getSE());
   if (!MemRuntimeCheck)
     return;
 
   if (MemCheckBlock->getParent()->hasOptSize()) {
     assert(Cost->Hints->getForce() == LoopVectorizeHints::FK_Enabled &&
            "Cannot emit memory checks when optimizing for size, unless forced "
            "to vectorize.");
     ORE->emit([&]() {
       return OptimizationRemarkAnalysis(DEBUG_TYPE, "VectorizationCodeSize",
                                         L->getStartLoc(), L->getHeader())
              << "Code-size may be reduced by not forcing "
                 "vectorization, or by source-code modifications "
                 "eliminating the need for runtime checks "