IR: Change the gep_type_iterator API to avoid always exposing the "current" type.

[pcc]

Summary

Instead, expose whether the current type is an array or a struct, if an array
what the upper bound is, and if a struct the struct type itself. This is
in preparation for a later change which will make PointerType derive from
Type rather than SequentialType.

[dblaikie]

I'm not quite following why this change is necessary - could you provide more detail?

What would happen/what doesn't work if we try to have generic_gep_type_iterator::operator* keep returning the Type* of the current type?

llvm/include/llvm/IR/GetElementPtrTypeIterator.h

57–58

presumably this'd be a bit better as a dyn_cast?

[pcc]

I think we could in principle continue to provide a way to access the "current type", but it would make the gep_type_iterator implementation even harder to follow once we move PointerType (for example, we would probably have to add type switches in the two places where we have CompositeType::getTypeAtIndex now). gep_type_iterator was already getting rather complicated as a result of supporting operator* (e.g. it takes an address space) and I would prefer not to add to that.

[dblaikie]

Seems odd to have an iterator-like thing without any op*, though.

Should we make op* return 'getIndexedType' (I realize this is a subtle API break to change the semantics of an existing operation - perhaps better to leave that as a cleanup a version or two from now (leave a FIXME)?)

I think you've stared at this code a fair bit more than I have (certainly more than I have recently - I'm probably the one to blame for the AddressSpace parameter being plumbed through a year ago or something) - could you summarize/explain why the need for such a variety of member functions on the iterator now? (getArray, isArray, isBoundedArray, getArrayBound, isStruct, getStruct, getStructOrNull)

It'd be nice if there were some more unifying API - currently this diversity seems a bit awkward.

[pcc]

In D26594#602867, @dblaikie wrote:

Seems odd to have an iterator-like thing without any op*, though.

Should we make op* return 'getIndexedType' (I realize this is a subtle API break to change the semantics of an existing operation - perhaps better to leave that as a cleanup a version or two from now (leave a FIXME)?)

Yes, it was the semantics break I was concerned about. Good idea to add the FIXME, will do.

I think you've stared at this code a fair bit more than I have (certainly more than I have recently - I'm probably the one to blame for the AddressSpace parameter being plumbed through a year ago or something) - could you summarize/explain why the need for such a variety of member functions on the iterator now? (getArray, isArray, isBoundedArray, getArrayBound, isStruct, getStruct, getStructOrNull)

It'd be nice if there were some more unifying API - currently this diversity seems a bit awkward.

Basically these are convenience functions around a small set of internal states (struct, unbounded array, bounded array) to help with readability at call sites.

In an earlier version of the patch [1] I had just two APIs: getStructType (which would return null for arrays) and getArrayBound (which could return a sentinel value meaning "unbounded"). Using those two functions, you can figure out which state you are in and effectively get the rest of the API, but that came at the cost of some readability (e.g. you would have to remember that "!getStructType" means "this is an array"). On balance it seemed better to have more API in gep_type_iterator.

Relatedly, I found that we only care about the array "boundedness" in relatively few places, which suggests to me that maybe we should look more closely at whether it is really necessary to expose that property and see if we can remove some of the API surface here. However, that seems like an orthogonal change to me.

[1] https://github.com/llvm-project/llvm-project/compare/master...pcc:pointertype

[pcc]

• Formatting, address review comments, fix bug I introduced in NaryReassociate

[dblaikie]

I'd probably be inclined to add some comments about how this API's a bit weird and could be more offset-focussed (including the gotchas/places where that doesn't quite hold (you were saying about the outer structness being interesting - though I couldn't quite follow how/why)) in a non-doc comment at the top of the class.

But if not, people might still find this discussion in the code review. Thanks for your patience.

[haicheng]

llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h

516 ↗

(On Diff #80016)

Hi Peter,

Would you please take a look at D27357 ?

Should I change this line to fix the bug in the baseline?

Thank you,

Haicheng

[pcc]

llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h

516 ↗

(On Diff #80016)

Yes please, sorry about the conflict. This would appear to be the right code change for D27357:

diff --git a/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h b/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
index 2934e9c..7bc6415 100644
--- a/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
+++ b/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
@@ -483,7 +483,9 @@ public:
     int64_t Scale = 0;
 
     auto GTI = gep_type_begin(PointeeType, Operands);
+    Type *TargetType;
     for (auto I = Operands.begin(); I != Operands.end(); ++I, ++GTI) {
+      TargetType = GTI.getIndexedType();
       // We assume that the cost of Scalar GEP with constant index and the
       // cost of Vector GEP with splat constant index are the same.
       const ConstantInt *ConstIdx = dyn_cast<ConstantInt>(*I);
@@ -513,9 +515,8 @@ public:
     unsigned AS =
         (Ptr == nullptr ? 0 : Ptr->getType()->getPointerAddressSpace());
     if (static_cast<T *>(this)->isLegalAddressingMode(
-            PointerType::get(Type::getInt8Ty(PointeeType->getContext()), AS),
-            const_cast<GlobalValue *>(BaseGV),
-            BaseOffset, HasBaseReg, Scale, AS)) {
+            TargetType, const_cast<GlobalValue *>(BaseGV), BaseOffset,
+            HasBaseReg, Scale, AS)) {
       return TTI::TCC_Free;
     }
     return TTI::TCC_Basic;

[haicheng]

llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h

516 ↗

(On Diff #80016)

Thank you. I will use your code.

llvm/include/llvm/Analysis/TargetTransformInfoImpl.h

if (Ptr != nullptr) {
                  PointeeType &&
              "explicit pointee type doesn't match operand's pointee type");
       BaseGV = dyn_cast<GlobalValue>(Ptr->stripPointerCasts());
     }
     bool HasBaseReg = (BaseGV == nullptr);
     int64_t BaseOffset = 0;
     int64_t Scale = 0;
 
-    // Assumes the address space is 0 when Ptr is nullptr.
-    unsigned AS =
-        (Ptr == nullptr ? 0 : Ptr->getType()->getPointerAddressSpace());
-    auto GTI = gep_type_begin(PointeeType, AS, Operands);
+    auto GTI = gep_type_begin(PointeeType, Operands);
     for (auto I = Operands.begin(); I != Operands.end(); ++I, ++GTI) {
       // We assume that the cost of Scalar GEP with constant index and the
       // cost of Vector GEP with splat constant index are the same.
       const ConstantInt *ConstIdx = dyn_cast<ConstantInt>(*I);
       if (!ConstIdx)
         if (auto Splat = getSplatValue(*I))
           ConstIdx = dyn_cast<ConstantInt>(Splat);
-      if (isa<SequentialType>(*GTI)) {
+      if (StructType *STy = GTI.getStructTypeOrNull()) {
+        // For structures the index is always splat or scalar constant
+        assert(ConstIdx && "Unexpected GEP index");
+        uint64_t Field = ConstIdx->getZExtValue();
+        BaseOffset += DL.getStructLayout(STy)->getElementOffset(Field);
+      } else {
         int64_t ElementSize = DL.getTypeAllocSize(GTI.getIndexedType());
         if (ConstIdx)
           BaseOffset += ConstIdx->getSExtValue() * ElementSize;
         else {
           // Needs scale register.
           if (Scale != 0)
             // No addressing mode takes two scale registers.
             return TTI::TCC_Basic;
           Scale = ElementSize;
         }
-      } else {
-        StructType *STy = cast<StructType>(*GTI);
-        // For structures the index is always splat or scalar constant
-        assert(ConstIdx && "Unexpected GEP index");
-        uint64_t Field = ConstIdx->getZExtValue();
-        BaseOffset += DL.getStructLayout(STy)->getElementOffset(Field);
       }
     }
 
+    // Assumes the address space is 0 when Ptr is nullptr.
+    unsigned AS =
+        (Ptr == nullptr ? 0 : Ptr->getType()->getPointerAddressSpace());
     if (static_cast<T *>(this)->isLegalAddressingMode(
-            PointerType::get(*GTI, AS), const_cast<GlobalValue *>(BaseGV),
+            PointerType::get(Type::getInt8Ty(PointeeType->getContext()), AS),
+            const_cast<GlobalValue *>(BaseGV),
             BaseOffset, HasBaseReg, Scale, AS)) {
       return TTI::TCC_Free;
     }
     return TTI::TCC_Basic;
   }
 
   using BaseT::getIntrinsicCost;
 

llvm/include/llvm/IR/GetElementPtrTypeIterator.h

 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_IR_GETELEMENTPTRTYPEITERATOR_H
 #define LLVM_IR_GETELEMENTPTRTYPEITERATOR_H
 
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/User.h"
-#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/PointerUnion.h"
 
 namespace llvm {
   template<typename ItTy = User::const_op_iterator>
   class generic_gep_type_iterator
     : public std::iterator<std::forward_iterator_tag, Type *, ptrdiff_t> {
     typedef std::iterator<std::forward_iterator_tag,
                           Type *, ptrdiff_t> super;
 
     ItTy OpIt;
-    PointerIntPair<Type *, 1> CurTy;
-    unsigned AddrSpace;
+    PointerUnion<StructType *, Type *> CurTy;
+    enum { Unbounded = -1ull };
+    uint64_t ArrayBound = Unbounded;
     generic_gep_type_iterator() {}
   public:
 
-    static generic_gep_type_iterator begin(Type *Ty, unsigned AddrSpace,
-                                           ItTy It) {
+    static generic_gep_type_iterator begin(Type *Ty, ItTy It) {
       generic_gep_type_iterator I;
-      I.CurTy.setPointer(Ty);
-      I.CurTy.setInt(true);
-      I.AddrSpace = AddrSpace;
+      I.CurTy = Ty;
       I.OpIt = It;
       return I;
     }
     static generic_gep_type_iterator end(ItTy It) {
       generic_gep_type_iterator I;
       I.OpIt = It;
       return I;
     }
 
     bool operator==(const generic_gep_type_iterator& x) const {
       return OpIt == x.OpIt;
     }
     bool operator!=(const generic_gep_type_iterator& x) const {
       return !operator==(x);
     }
 
-    Type *operator*() const {
-      if (CurTy.getInt())
-        return CurTy.getPointer()->getPointerTo(AddrSpace);
-      return CurTy.getPointer();
+    Type *getIndexedType() const {
+      if (CurTy.is<Type *>())
+        return CurTy.get<Type *>();
+      return CurTy.get<StructType *>()->getTypeAtIndex(getOperand());
     }
 
-    Type *getIndexedType() const {
-      if (CurTy.getInt())
-        return CurTy.getPointer();
-      CompositeType *CT = cast<CompositeType>(CurTy.getPointer());
-      return CT->getTypeAtIndex(getOperand());
+    bool isStruct() const {
+      return CurTy.is<StructType *>();
+    }
+
+    StructType *getStructType() const {
+      return CurTy.get<StructType *>();
     }
 
-    // This is a non-standard operator->.  It allows you to call methods on the
-    // current type directly.
-    Type *operator->() const { return operator*(); }
+    StructType *getStructTypeOrNull() const {
+      return CurTy.dyn_cast<StructType *>();
+    }
 
     Value *getOperand() const { return const_cast<Value *>(&**OpIt); }
 
-    generic_gep_type_iterator& operator++() {   // Preincrement
-      if (CurTy.getInt()) {
-        CurTy.setInt(false);
-      } else if (CompositeType *CT =
-                     dyn_cast<CompositeType>(CurTy.getPointer())) {
-        CurTy.setPointer(CT->getTypeAtIndex(getOperand()));
-      } else {
-        CurTy.setPointer(nullptr);
-      }
+    bool isArray() const {
+      return CurTy.is<Type *>();
+
+    bool isBoundedArray() const {
+      return isArray() && ArrayBound != Unbounded;
+    }
+
+    uint64_t getArrayBound() const {
+      assert(isBoundedArray());
+      return ArrayBound;
+    }
+
+    generic_gep_type_iterator& operator++() {   // Preincrement
+      Type *Ty = getIndexedType();
+      if (auto *ATy = dyn_cast<ArrayType>(Ty)) {
+        CurTy = ATy->getElementType();
+        ArrayBound = ATy->getNumElements();
+      } else if (auto *VTy = dyn_cast<VectorType>(Ty)) {
+        CurTy = VTy->getElementType();
+        ArrayBound = VTy->getNumElements();
+      } else
+        CurTy = dyn_cast<StructType>(Ty);
       ++OpIt;
       return *this;
     }
 
     generic_gep_type_iterator operator++(int) { // Postincrement
       generic_gep_type_iterator tmp = *this; ++*this; return tmp;
     }
   };
 
   typedef generic_gep_type_iterator<> gep_type_iterator;
 
   inline gep_type_iterator gep_type_begin(const User *GEP) {
     auto *GEPOp = cast<GEPOperator>(GEP);
     return gep_type_iterator::begin(
         GEPOp->getSourceElementType(),
-        cast<PointerType>(GEPOp->getPointerOperandType()->getScalarType())
-            ->getAddressSpace(),
         GEP->op_begin() + 1);
   }
   inline gep_type_iterator gep_type_end(const User *GEP) {
     return gep_type_iterator::end(GEP->op_end());
   }
   inline gep_type_iterator gep_type_begin(const User &GEP) {
     auto &GEPOp = cast<GEPOperator>(GEP);
     return gep_type_iterator::begin(
         GEPOp.getSourceElementType(),
-        cast<PointerType>(GEPOp.getPointerOperandType()->getScalarType())
-            ->getAddressSpace(),
         GEP.op_begin() + 1);
   }
   inline gep_type_iterator gep_type_end(const User &GEP) {
     return gep_type_iterator::end(GEP.op_end());
   }
 
   template<typename T>
   inline generic_gep_type_iterator<const T *>
-  gep_type_begin(Type *Op0, unsigned AS, ArrayRef<T> A) {
-    return generic_gep_type_iterator<const T *>::begin(Op0, AS, A.begin());
+  gep_type_begin(Type *Op0, ArrayRef<T> A) {
+    return generic_gep_type_iterator<const T *>::begin(Op0, A.begin());
   }
 
   template<typename T>
   inline generic_gep_type_iterator<const T *>
-  gep_type_end(Type * /*Op0*/, unsigned /*AS*/, ArrayRef<T> A) {
+  gep_type_end(Type * /*Op0*/, ArrayRef<T> A) {
     return generic_gep_type_iterator<const T *>::end(A.end());
   }
 } // end namespace llvm
 
 #endif

llvm/include/llvm/Transforms/Utils/Local.h

for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
        ++i, ++GTI) {
     Value *Op = *i;
     uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
     if (Constant *OpC = dyn_cast<Constant>(Op)) {
       if (OpC->isZeroValue())
         continue;
 
       // Handle a struct index, which adds its field offset to the pointer.
-      if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+      if (StructType *STy = GTI.getStructTypeOrNull()) {
         if (OpC->getType()->isVectorTy())
           OpC = OpC->getSplatValue();
 
         uint64_t OpValue = cast<ConstantInt>(OpC)->getZExtValue();
         Size = DL.getStructLayout(STy)->getElementOffset(OpValue);
 
         if (Size)
           Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size),

llvm/lib/Analysis/BasicAliasAnalysis.cpp

do {
 
     unsigned AS = GEPOp->getPointerAddressSpace();
     // Walk the indices of the GEP, accumulating them into BaseOff/VarIndices.
     gep_type_iterator GTI = gep_type_begin(GEPOp);
     unsigned PointerSize = DL.getPointerSizeInBits(AS);
     // Assume all GEP operands are constants until proven otherwise.
     bool GepHasConstantOffset = true;
     for (User::const_op_iterator I = GEPOp->op_begin() + 1, E = GEPOp->op_end();
-         I != E; ++I) {
+         I != E; ++I, ++GTI) {
       const Value *Index = *I;
       // Compute the (potentially symbolic) offset in bytes for this index.
-      if (StructType *STy = dyn_cast<StructType>(*GTI++)) {
+      if (StructType *STy = GTI.getStructTypeOrNull()) {
         // For a struct, add the member offset.
         unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
         if (FieldNo == 0)
           continue;
 
         Decomposed.StructOffset +=
           DL.getStructLayout(STy)->getElementOffset(FieldNo);
         continue;
       }
 
       // For an array/pointer, add the element offset, explicitly scaled.
       if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
         if (CIdx->isZero())
           continue;
         Decomposed.OtherOffset +=
-          DL.getTypeAllocSize(*GTI) * CIdx->getSExtValue();
+          DL.getTypeAllocSize(GTI.getIndexedType()) * CIdx->getSExtValue();
         continue;
       }
 
       GepHasConstantOffset = false;
 
-      uint64_t Scale = DL.getTypeAllocSize(*GTI);
+      uint64_t Scale = DL.getTypeAllocSize(GTI.getIndexedType());
       unsigned ZExtBits = 0, SExtBits = 0;
 
       // If the integer type is smaller than the pointer size, it is implicitly
       // sign extended to pointer size.
       unsigned Width = Index->getType()->getIntegerBitWidth();
       if (PointerSize > Width)
         SExtBits += PointerSize - Width;
 

llvm/lib/Analysis/InlineCost.cpp

if (!OpC)
       if (Constant *SimpleOp = SimplifiedValues.lookup(GTI.getOperand()))
         OpC = dyn_cast<ConstantInt>(SimpleOp);
     if (!OpC)
       return false;
     if (OpC->isZero())
       continue;
 
     // Handle a struct index, which adds its field offset to the pointer.
-    if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+    if (StructType *STy = GTI.getStructTypeOrNull()) {
       unsigned ElementIdx = OpC->getZExtValue();
       const StructLayout *SL = DL.getStructLayout(STy);
       Offset += APInt(IntPtrWidth, SL->getElementOffset(ElementIdx));
       continue;
     }
 
     APInt TypeSize(IntPtrWidth, DL.getTypeAllocSize(GTI.getIndexedType()));
     Offset += OpC->getValue().sextOrTrunc(IntPtrWidth) * TypeSize;

llvm/lib/Analysis/ValueTracking.cpp

case Instruction::GetElementPtr: {
     APInt LocalKnownZero(BitWidth, 0), LocalKnownOne(BitWidth, 0);
     computeKnownBits(I->getOperand(0), LocalKnownZero, LocalKnownOne, Depth + 1,
                      Q);
     unsigned TrailZ = LocalKnownZero.countTrailingOnes();
 
     gep_type_iterator GTI = gep_type_begin(I);
     for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i, ++GTI) {
       Value *Index = I->getOperand(i);
-      if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+      if (StructType *STy = GTI.getStructTypeOrNull()) {
         // Handle struct member offset arithmetic.
 
         // Handle case when index is vector zeroinitializer
         Constant *CIndex = cast<Constant>(Index);
         if (CIndex->isZeroValue())
           continue;
 
         if (CIndex->getType()->isVectorTy())
if (isKnownNonZero(GEP->getPointerOperand(), Depth, Q))
     return true;
 
   // Walk the GEP operands and see if any operand introduces a non-zero offset.
   // If so, then the GEP cannot produce a null pointer, as doing so would
   // inherently violate the inbounds contract within address space zero.
   for (gep_type_iterator GTI = gep_type_begin(GEP), GTE = gep_type_end(GEP);
        GTI != GTE; ++GTI) {
     // Struct types are easy -- they must always be indexed by a constant.
-    if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+    if (StructType *STy = GTI.getStructTypeOrNull()) {
       ConstantInt *OpC = cast<ConstantInt>(GTI.getOperand());
       unsigned ElementIdx = OpC->getZExtValue();
       const StructLayout *SL = Q.DL.getStructLayout(STy);
       uint64_t ElementOffset = SL->getElementOffset(ElementIdx);
       if (ElementOffset > 0)
         return true;
       continue;
     }

llvm/lib/Analysis/VectorUtils.cpp

unsigned llvm::getGEPInductionOperand(const GetElementPtrInst *Gep) {
   const DataLayout &DL = Gep->getModule()->getDataLayout();
   unsigned LastOperand = Gep->getNumOperands() - 1;
   unsigned GEPAllocSize = DL.getTypeAllocSize(Gep->getResultElementType());
 
   // Walk backwards and try to peel off zeros.
   while (LastOperand > 1 && match(Gep->getOperand(LastOperand), m_Zero())) {
     // Find the type we're currently indexing into.
     gep_type_iterator GEPTI = gep_type_begin(Gep);
-    std::advance(GEPTI, LastOperand - 1);
+    std::advance(GEPTI, LastOperand - 2);
 
     // If it's a type with the same allocation size as the result of the GEP we
     // can peel off the zero index.
-    if (DL.getTypeAllocSize(*GEPTI) != GEPAllocSize)
+    if (DL.getTypeAllocSize(GEPTI.getIndexedType()) != GEPAllocSize)
       break;
     --LastOperand;
   }
 
   return LastOperand;
 }
 
 /// \brief If the argument is a GEP, then returns the operand identified by

llvm/lib/CodeGen/CodeGenPrepare.cpp

case Instruction::GetElementPtr: {
     // Scan the GEP.  We check it if it contains constant offsets and at most
     // one variable offset.
     int VariableOperand = -1;
     unsigned VariableScale = 0;
 
     int64_t ConstantOffset = 0;
     gep_type_iterator GTI = gep_type_begin(AddrInst);
     for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) {
-      if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+      if (StructType *STy = GTI.getStructTypeOrNull()) {
         const StructLayout *SL = DL.getStructLayout(STy);
         unsigned Idx =
           cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue();
         ConstantOffset += SL->getElementOffset(Idx);
       } else {
         uint64_t TypeSize = DL.getTypeAllocSize(GTI.getIndexedType());
         if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) {
           ConstantOffset += CI->getSExtValue()*TypeSize;

llvm/lib/CodeGen/SelectionDAG/FastISel.cpp

bool FastISel::selectGetElementPtr(const User *I) {
   // into a single N = N + TotalOffset.
   uint64_t TotalOffs = 0;
   // FIXME: What's a good SWAG number for MaxOffs?
   uint64_t MaxOffs = 2048;
   MVT VT = TLI.getPointerTy(DL);
   for (gep_type_iterator GTI = gep_type_begin(I), E = gep_type_end(I);
        GTI != E; ++GTI) {
     const Value *Idx = GTI.getOperand();
-    if (auto *StTy = dyn_cast<StructType>(*GTI)) {
+    if (StructType *StTy = GTI.getStructTypeOrNull()) {
       uint64_t Field = cast<ConstantInt>(Idx)->getZExtValue();
       if (Field) {
         // N = N + Offset
         TotalOffs += DL.getStructLayout(StTy)->getElementOffset(Field);
         if (TotalOffs >= MaxOffs) {
           N = fastEmit_ri_(VT, ISD::ADD, N, NIsKill, TotalOffs, VT);
           if (!N) // Unhandled operand. Halt "fast" selection and bail.
             return false;

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

if (VectorWidth && !N.getValueType().isVector()) {
     LLVMContext &Context = *DAG.getContext();
     EVT VT = EVT::getVectorVT(Context, N.getValueType(), VectorWidth);
     SmallVector<SDValue, 16> Ops(VectorWidth, N);
     N = DAG.getNode(ISD::BUILD_VECTOR, dl, VT, Ops);
   }
   for (gep_type_iterator GTI = gep_type_begin(&I), E = gep_type_end(&I);
        GTI != E; ++GTI) {
     const Value *Idx = GTI.getOperand();
-    if (StructType *StTy = dyn_cast<StructType>(*GTI)) {
+    if (StructType *StTy = GTI.getStructTypeOrNull()) {
       unsigned Field = cast<Constant>(Idx)->getUniqueInteger().getZExtValue();
       if (Field) {
         // N = N + Offset
         uint64_t Offset = DL->getStructLayout(StTy)->getElementOffset(Field);
 
         // In an inbouds GEP with an offset that is nonnegative even when
         // interpreted as signed, assume there is no unsigned overflow.
         SDNodeFlags Flags;

llvm/lib/ExecutionEngine/Interpreter/Execution.cpp

GenericValue Interpreter::executeGEPOperation(Value *Ptr, gep_type_iterator I,
                                               gep_type_iterator E,
                                               ExecutionContext &SF) {
   assert(Ptr->getType()->isPointerTy() &&
          "Cannot getElementOffset of a nonpointer type!");
 
   uint64_t Total = 0;
 
   for (; I != E; ++I) {
-    if (StructType *STy = dyn_cast<StructType>(*I)) {
+    if (StructType *STy = I.getStructTypeOrNull()) {
       const StructLayout *SLO = getDataLayout().getStructLayout(STy);
 
       const ConstantInt *CPU = cast<ConstantInt>(I.getOperand());
       unsigned Index = unsigned(CPU->getZExtValue());
 
       Total += SLO->getElementOffset(Index);
     } else {
-      SequentialType *ST = cast<SequentialType>(*I);
       // Get the index number for the array... which must be long type...
       GenericValue IdxGV = getOperandValue(I.getOperand(), SF);
 
       int64_t Idx;
       unsigned BitWidth = 
         cast<IntegerType>(I.getOperand()->getType())->getBitWidth();
       if (BitWidth == 32)
         Idx = (int64_t)(int32_t)IdxGV.IntVal.getZExtValue();
       else {
         assert(BitWidth == 64 && "Invalid index type for getelementptr");
         Idx = (int64_t)IdxGV.IntVal.getZExtValue();
       }
-      Total += getDataLayout().getTypeAllocSize(ST->getElementType()) * Idx;
+      Total += getDataLayout().getTypeAllocSize(I.getIndexedType()) * Idx;
     }
   }
 
   GenericValue Result;
   Result.PointerVal = ((char*)getOperandValue(Ptr, SF).PointerVal) + Total;
   DEBUG(dbgs() << "GEP Index " << Total << " bytes.\n");
   return Result;
 }

llvm/lib/IR/ConstantFold.cpp

if (!cast<ConstantInt>(Idxs[0])->isOne())
     return false;
   for (unsigned i = 1, e = Idxs.size(); i != e; ++i)
     if (!cast<Constant>(Idxs[i])->isNullValue())
       return false;
   return true;
 }
 
 /// Test whether a given ConstantInt is in-range for a SequentialType.
-static bool isIndexInRangeOfSequentialType(SequentialType *STy,
-                                           const ConstantInt *CI) {
-  // And indices are valid when indexing along a pointer
-  if (isa<PointerType>(STy))
-    return true;
-
-  uint64_t NumElements = 0;
-  // Determine the number of elements in our sequential type.
-  if (auto *ATy = dyn_cast<ArrayType>(STy))
-    NumElements = ATy->getNumElements();
-  else if (auto *VTy = dyn_cast<VectorType>(STy))
-    NumElements = VTy->getNumElements();
-
-  assert((isa<ArrayType>(STy) || NumElements > 0) &&
-         "didn't expect non-array type to have zero elements!");
-
+static bool isIndexInRangeOfArrayType(uint64_t NumElements,
   // We cannot bounds check the index if it doesn't fit in an int64_t.
   if (CI->getValue().getActiveBits() > 64)
     return false;
 
   // A negative index or an index past the end of our sequential type is
   // considered out-of-range.
   int64_t IndexVal = CI->getSExtValue();
   if (IndexVal < 0 || (NumElements > 0 && (uint64_t)IndexVal >= NumElements))
Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C,
   }
 
   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
     // Combine Indices - If the source pointer to this getelementptr instruction
     // is a getelementptr instruction, combine the indices of the two
     // getelementptr instructions into a single instruction.
     //
     if (CE->getOpcode() == Instruction::GetElementPtr) {
-      Type *LastTy = nullptr;
+      gep_type_iterator LastI = gep_type_end(CE);
       for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
            I != E; ++I)
-        LastTy = *I;
+        LastI = I;
 
       // We cannot combine indices if doing so would take us outside of an
       // array or vector.  Doing otherwise could trick us if we evaluated such a
       // GEP as part of a load.
       //
       // e.g. Consider if the original GEP was:
       // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
       //                    i32 0, i32 0, i64 0)
       //
       // If we then tried to offset it by '8' to get to the third element,
       // an i8, we should *not* get:
       // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c,
       //                    i32 0, i32 0, i64 8)
       //
       // This GEP tries to index array element '8  which runs out-of-bounds.
       // Subsequent evaluation would get confused and produce erroneous results.
       //
       // The following prohibits such a GEP from being formed by checking to see
       // if the index is in-range with respect to an array or vector.
       bool PerformFold = false;
       if (Idx0->isNullValue())
         PerformFold = true;
-      else if (SequentialType *STy = dyn_cast_or_null<SequentialType>(LastTy))
+      else if (LastI.isArray())
         if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0))
-          PerformFold = isIndexInRangeOfSequentialType(STy, CI);
+          PerformFold = !LastI.isBoundedArray() ||
+                        isIndexInRangeOfArrayType(LastI.getArrayBound(), CI);
 
       if (PerformFold) {
         SmallVector<Value*, 16> NewIndices;
         NewIndices.reserve(Idxs.size() + CE->getNumOperands());
         NewIndices.append(CE->op_begin() + 1, CE->op_end() - 1);
 
         // Add the last index of the source with the first index of the new GEP.
         // Make sure to handle the case when they are actually different types.
if (isa<PointerType>(STy)) {
       Unknown = true;
       continue;
     }
     if (isa<VectorType>(STy)) {
       // There can be awkward padding in after a non-power of two vector.
       Unknown = true;
       continue;
     }
-    if (isIndexInRangeOfSequentialType(STy, CI))
+    if (isIndexInRangeOfArrayType(isa<ArrayType>(STy)
+                                      ? cast<ArrayType>(STy)->getNumElements()
+                                      : cast<VectorType>(STy)->getNumElements(),
+                                  CI))
       // It's in range, skip to the next index.
       continue;
     if (!isa<SequentialType>(Prev)) {
       // It's out of range, but the prior dimension is a struct
       // so we can't do anything about it.
       Unknown = true;
       continue;
     }

llvm/lib/IR/Constants.cpp

 }
 
 bool ConstantExpr::isGEPWithNoNotionalOverIndexing() const {
   if (getOpcode() != Instruction::GetElementPtr) return false;
 
   gep_type_iterator GEPI = gep_type_begin(this), E = gep_type_end(this);
   User::const_op_iterator OI = std::next(this->op_begin());
 
-  // Skip the first index, as it has no static limit.
-  ++GEPI;
-  ++OI;
-
   // The remaining indices must be compile-time known integers within the
   // bounds of the corresponding notional static array types.
   for (; GEPI != E; ++GEPI, ++OI) {
     ConstantInt *CI = dyn_cast<ConstantInt>(*OI);
-    if (!CI) return false;
-    if (ArrayType *ATy = dyn_cast<ArrayType>(*GEPI))
-      if (CI->getValue().getActiveBits() > 64 ||
-          CI->getZExtValue() >= ATy->getNumElements())
-        return false;
+    if (GEPI.isBoundedArray() &&
+         (CI->getValue().getActiveBits() > 64 ||
+          CI->getZExtValue() >= GEPI.getArrayBound()))
   }
 
   // All the indices checked out.
   return true;
 }
 
 bool ConstantExpr::hasIndices() const {
   return getOpcode() == Instruction::ExtractValue ||

llvm/lib/IR/DataLayout.cpp

unsigned DataLayout::getLargestLegalIntTypeSizeInBits() const {
   auto Max = std::max_element(LegalIntWidths.begin(), LegalIntWidths.end());
   return Max != LegalIntWidths.end() ? *Max : 0;
 }
 
 int64_t DataLayout::getIndexedOffsetInType(Type *ElemTy,
                                            ArrayRef<Value *> Indices) const {
   int64_t Result = 0;
 
-  // We can use 0 as the address space as we don't need
-  // to get pointer types back from gep_type_iterator.
-  unsigned AS = 0;
   generic_gep_type_iterator<Value* const*>
-    GTI = gep_type_begin(ElemTy, AS, Indices),
-    GTE = gep_type_end(ElemTy, AS, Indices);
+    GTI = gep_type_begin(ElemTy, Indices),
+    GTE = gep_type_end(ElemTy, Indices);
   for (; GTI != GTE; ++GTI) {
     Value *Idx = GTI.getOperand();
-    if (auto *STy = dyn_cast<StructType>(*GTI)) {
+    if (StructType *STy = GTI.getStructTypeOrNull()) {
       assert(Idx->getType()->isIntegerTy(32) && "Illegal struct idx");
       unsigned FieldNo = cast<ConstantInt>(Idx)->getZExtValue();
 
       // Get structure layout information...
       const StructLayout *Layout = getStructLayout(STy);
 
       // Add in the offset, as calculated by the structure layout info...
       Result += Layout->getElementOffset(FieldNo);

llvm/lib/IR/Operator.cpp

for (gep_type_iterator GTI = gep_type_begin(this), GTE = gep_type_end(this);
        GTI != GTE; ++GTI) {
     ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
     if (!OpC)
       return false;
     if (OpC->isZero())
       continue;
 
     // Handle a struct index, which adds its field offset to the pointer.
-    if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+    if (StructType *STy = GTI.getStructTypeOrNull()) {
       unsigned ElementIdx = OpC->getZExtValue();
       const StructLayout *SL = DL.getStructLayout(STy);
       Offset += APInt(Offset.getBitWidth(), SL->getElementOffset(ElementIdx));
       continue;
     }
 
     // For array or vector indices, scale the index by the size of the type.
     APInt Index = OpC->getValue().sextOrTrunc(Offset.getBitWidth());
     Offset += Index * APInt(Offset.getBitWidth(),
                             DL.getTypeAllocSize(GTI.getIndexedType()));
   }
   return true;
 }
 }

llvm/lib/Target/AArch64/AArch64FastISel.cpp

case Instruction::GetElementPtr: {
     Address SavedAddr = Addr;
     uint64_t TmpOffset = Addr.getOffset();
 
     // Iterate through the GEP folding the constants into offsets where
     // we can.
     for (gep_type_iterator GTI = gep_type_begin(U), E = gep_type_end(U);
          GTI != E; ++GTI) {
       const Value *Op = GTI.getOperand();
-      if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+      if (StructType *STy = GTI.getStructTypeOrNull()) {
         const StructLayout *SL = DL.getStructLayout(STy);
         unsigned Idx = cast<ConstantInt>(Op)->getZExtValue();
         TmpOffset += SL->getElementOffset(Idx);
       } else {
         uint64_t S = DL.getTypeAllocSize(GTI.getIndexedType());
         for (;;) {
           if (const ConstantInt *CI = dyn_cast<ConstantInt>(Op)) {
             // Constant-offset addressing.
bool AArch64FastISel::selectGetElementPtr(const Instruction *I) {
 
   // Keep a running tab of the total offset to coalesce multiple N = N + Offset
   // into a single N = N + TotalOffset.
   uint64_t TotalOffs = 0;
   MVT VT = TLI.getPointerTy(DL);
   for (gep_type_iterator GTI = gep_type_begin(I), E = gep_type_end(I);
        GTI != E; ++GTI) {
     const Value *Idx = GTI.getOperand();
-    if (auto *StTy = dyn_cast<StructType>(*GTI)) {
+    if (auto *StTy = GTI.getStructTypeOrNull()) {
       unsigned Field = cast<ConstantInt>(Idx)->getZExtValue();
       // N = N + Offset
       if (Field)
         TotalOffs += DL.getStructLayout(StTy)->getElementOffset(Field);
     } else {
       Type *Ty = GTI.getIndexedType();
 
       // If this is a constant subscript, handle it quickly.

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

for (const Use &U : Ext->uses()) {
     switch (Instr->getOpcode()) {
     case Instruction::Shl:
       if (!isa<ConstantInt>(Instr->getOperand(1)))
         return false;
       break;
     case Instruction::GetElementPtr: {
       gep_type_iterator GTI = gep_type_begin(Instr);
       auto &DL = Ext->getModule()->getDataLayout();
-      std::advance(GTI, U.getOperandNo());
-      Type *IdxTy = *GTI;
+      std::advance(GTI, U.getOperandNo()-1);
+      Type *IdxTy = GTI.getIndexedType();
       // This extension will end up with a shift because of the scaling factor.
       // 8-bit sized types have a scaling factor of 1, thus a shift amount of 0.
       // Get the shift amount based on the scaling factor:
       // log2(sizeof(IdxTy)) - log2(8).
       uint64_t ShiftAmt =
           countTrailingZeros(DL.getTypeStoreSizeInBits(IdxTy)) - 3;
       // Is the constant foldable in the shift of the addressing mode?
       // I.e., shift amount is between 1 and 4 inclusive.

llvm/lib/Target/ARM/ARMFastISel.cpp

case Instruction::GetElementPtr: {
       int TmpOffset = Addr.Offset;
 
       // Iterate through the GEP folding the constants into offsets where
       // we can.
       gep_type_iterator GTI = gep_type_begin(U);
       for (User::const_op_iterator i = U->op_begin() + 1, e = U->op_end();
            i != e; ++i, ++GTI) {
         const Value *Op = *i;
-        if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+        if (StructType *STy = GTI.getStructTypeOrNull()) {
           const StructLayout *SL = DL.getStructLayout(STy);
           unsigned Idx = cast<ConstantInt>(Op)->getZExtValue();
           TmpOffset += SL->getElementOffset(Idx);
         } else {
           uint64_t S = DL.getTypeAllocSize(GTI.getIndexedType());
           for (;;) {
             if (const ConstantInt *CI = dyn_cast<ConstantInt>(Op)) {
               // Constant-offset addressing.

llvm/lib/Target/Mips/MipsFastISel.cpp

case Instruction::GetElementPtr: {
     Address SavedAddr = Addr;
     uint64_t TmpOffset = Addr.getOffset();
     // Iterate through the GEP folding the constants into offsets where
     // we can.
     gep_type_iterator GTI = gep_type_begin(U);
     for (User::const_op_iterator i = U->op_begin() + 1, e = U->op_end(); i != e;
          ++i, ++GTI) {
       const Value *Op = *i;
-      if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+      if (StructType *STy = GTI.getStructTypeOrNull()) {
         const StructLayout *SL = DL.getStructLayout(STy);
         unsigned Idx = cast<ConstantInt>(Op)->getZExtValue();
         TmpOffset += SL->getElementOffset(Idx);
       } else {
         uint64_t S = DL.getTypeAllocSize(GTI.getIndexedType());
         for (;;) {
           if (const ConstantInt *CI = dyn_cast<ConstantInt>(Op)) {
             // Constant-offset addressing.

llvm/lib/Target/PowerPC/PPCFastISel.cpp

case Instruction::GetElementPtr: {
       long TmpOffset = Addr.Offset;
 
       // Iterate through the GEP folding the constants into offsets where
       // we can.
       gep_type_iterator GTI = gep_type_begin(U);
       for (User::const_op_iterator II = U->op_begin() + 1, IE = U->op_end();
            II != IE; ++II, ++GTI) {
         const Value *Op = *II;
-        if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+        if (StructType *STy = GTI.getStructTypeOrNull()) {
           const StructLayout *SL = DL.getStructLayout(STy);
           unsigned Idx = cast<ConstantInt>(Op)->getZExtValue();
           TmpOffset += SL->getElementOffset(Idx);
         } else {
           uint64_t S = DL.getTypeAllocSize(GTI.getIndexedType());
           for (;;) {
             if (const ConstantInt *CI = dyn_cast<ConstantInt>(Op)) {
               // Constant-offset addressing.

llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp

bool WebAssemblyFastISel::computeAddress(const Value *Obj, Address &Addr) {
   case Instruction::GetElementPtr: {
     Address SavedAddr = Addr;
     uint64_t TmpOffset = Addr.getOffset();
     // Iterate through the GEP folding the constants into offsets where
     // we can.
     for (gep_type_iterator GTI = gep_type_begin(U), E = gep_type_end(U);
          GTI != E; ++GTI) {
       const Value *Op = GTI.getOperand();
-      if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+      if (StructType *STy = GTI.getStructTypeOrNull()) {
         const StructLayout *SL = DL.getStructLayout(STy);
         unsigned Idx = cast<ConstantInt>(Op)->getZExtValue();
         TmpOffset += SL->getElementOffset(Idx);
       } else {
         uint64_t S = DL.getTypeAllocSize(GTI.getIndexedType());
         for (;;) {
           if (const ConstantInt *CI = dyn_cast<ConstantInt>(Op)) {
             // Constant-offset addressing.

llvm/lib/Target/X86/X86FastISel.cpp

case Instruction::GetElementPtr: {
     unsigned IndexReg = AM.IndexReg;
     unsigned Scale = AM.Scale;
     gep_type_iterator GTI = gep_type_begin(U);
     // Iterate through the indices, folding what we can. Constants can be
     // folded, and one dynamic index can be handled, if the scale is supported.
     for (User::const_op_iterator i = U->op_begin() + 1, e = U->op_end();
          i != e; ++i, ++GTI) {
       const Value *Op = *i;
-      if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+      if (StructType *STy = GTI.getStructTypeOrNull()) {
         const StructLayout *SL = DL.getStructLayout(STy);
         Disp += SL->getElementOffset(cast<ConstantInt>(Op)->getZExtValue());
         continue;
       }
 
       // A array/variable index is always of the form i*S where S is the
       // constant scale size.  See if we can push the scale into immediates.
       uint64_t S = DL.getTypeAllocSize(GTI.getIndexedType());

llvm/lib/Transforms/IPO/GlobalOpt.cpp

if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
       !cast<Constant>(U->getOperand(1))->isNullValue() ||
       !isa<ConstantInt>(U->getOperand(2)))
     return false;
 
   gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
   ++GEPI;  // Skip over the pointer index.
 
   // If this is a use of an array allocation, do a bit more checking for sanity.
-  if (ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
-    uint64_t NumElements = AT->getNumElements();
+  if (GEPI.isArray()) {
     ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
 
     // Check to make sure that index falls within the array.  If not,
     // something funny is going on, so we won't do the optimization.
     //
-    if (Idx->getZExtValue() >= NumElements)
+    if (GEPI.isBoundedArray() && Idx->getZExtValue() >= GEPI.getArrayBound())
       return false;
 
     // We cannot scalar repl this level of the array unless any array
     // sub-indices are in-range constants.  In particular, consider:
     // A[0][i].  We cannot know that the user isn't doing invalid things like
     // allowing i to index an out-of-range subscript that accesses A[1].
     //
     // Scalar replacing *just* the outer index of the array is probably not
     // going to be a win anyway, so just give up.
     for (++GEPI; // Skip array index.
          GEPI != E;
          ++GEPI) {
-      uint64_t NumElements;
-      if (ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
-        NumElements = SubArrayTy->getNumElements();
-      else if (VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI))
-        NumElements = SubVectorTy->getNumElements();
-      else {
-        assert((*GEPI)->isStructTy() &&
-               "Indexed GEP type is not array, vector, or struct!");
+      if (GEPI.isStruct())
         continue;
-      }
 
       ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
-      if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
+      if (!IdxVal || (GEPI.isBoundedArray() &&
+                      IdxVal->getZExtValue() >= GEPI.getArrayBound()))
         return false;
     }
   }
 
   for (User *UU : U->users())
     if (!isSafeSROAElementUse(UU))
       return false;
 

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

static Value *evaluateGEPOffsetExpression(User *GEP, InstCombiner &IC,
   unsigned i, e = GEP->getNumOperands();
   int64_t Offset = 0;
   for (i = 1; i != e; ++i, ++GTI) {
     if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
       // Compute the aggregate offset of constant indices.
       if (CI->isZero()) continue;
 
       // Handle a struct index, which adds its field offset to the pointer.
-      if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+      if (StructType *STy = GTI.getStructTypeOrNull()) {
         Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
       } else {
         uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
         Offset += Size*CI->getSExtValue();
       }
     } else {
       // Found our variable index.
       break;
static Value *evaluateGEPOffsetExpression(User *GEP, InstCombiner &IC,
   for (++i, ++GTI; i != e; ++i, ++GTI) {
     ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i));
     if (!CI) return nullptr;
 
     // Compute the aggregate offset of constant indices.
     if (CI->isZero()) continue;
 
     // Handle a struct index, which adds its field offset to the pointer.
-    if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+    if (StructType *STy = GTI.getStructTypeOrNull()) {
       Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
     } else {
       uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
       Offset += Size*CI->getSExtValue();
     }
   }
 
   // Okay, we know we have a single variable index, which must be a

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
   bool MadeChange = false;
   Type *IntPtrTy =
     DL.getIntPtrType(GEP.getPointerOperandType()->getScalarType());
 
   gep_type_iterator GTI = gep_type_begin(GEP);
   for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end(); I != E;
        ++I, ++GTI) {
     // Skip indices into struct types.
-    if (isa<StructType>(*GTI))
+    if (GTI.isStruct())
       continue;
 
     // Index type should have the same width as IntPtr
     Type *IndexTy = (*I)->getType();
     Type *NewIndexType = IndexTy->isVectorTy() ?
       VectorType::get(IntPtrTy, IndexTy->getVectorNumElements()) : IntPtrTy;
 
     // If the element type has zero size then any index over it is equivalent
if (GEPOperator *SrcGEP =
         return nullptr;   // Wait until our source is folded to completion.
 
     SmallVector<Value*, 8> Indices;
 
     // Find out whether the last index in the source GEP is a sequential idx.
     bool EndsWithSequential = false;
     for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src);
          I != E; ++I)
-      EndsWithSequential = !(*I)->isStructTy();
+      EndsWithSequential = I.isArray();
 
     // Can we combine the two pointer arithmetics offsets?
     if (EndsWithSequential) {
       // Replace: gep (gep %P, long B), long A, ...
       // With:    T = long A+B; gep %P, T, ...
       //
       Value *Sum;
       Value *SO1 = Src->getOperand(Src->getNumOperands()-1);

llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp

static int64_t GetOffsetFromIndex(const GEPOperator *GEP, unsigned Idx,
   int64_t Offset = 0;
   for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
     ConstantInt *OpC = dyn_cast<ConstantInt>(GEP->getOperand(i));
     if (!OpC)
       return VariableIdxFound = true;
     if (OpC->isZero()) continue;  // No offset.
 
     // Handle struct indices, which add their field offset to the pointer.
-    if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+    if (StructType *STy = GTI.getStructTypeOrNull()) {
       Offset += DL.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
       continue;
     }
 
     // Otherwise, we have a sequential type like an array or vector.  Multiply
     // the index by the ElementSize.
     uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
     Offset += Size*OpC->getSExtValue();

llvm/lib/Transforms/Scalar/NaryReassociate.cpp

 
 Instruction *NaryReassociatePass::tryReassociateGEP(GetElementPtrInst *GEP) {
   // Not worth reassociating GEP if it is foldable.
   if (isGEPFoldable(GEP, TTI))
     return nullptr;
 
   gep_type_iterator GTI = gep_type_begin(*GEP);
   for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I) {
-    if (isa<SequentialType>(*GTI++)) {
-      if (auto *NewGEP = tryReassociateGEPAtIndex(GEP, I - 1, *GTI)) {
+    if (GTI.isArray()) {
+      if (auto *NewGEP = tryReassociateGEPAtIndex(GEP, I - 1,
+                                                  GTI.getIndexedType())) {
         return NewGEP;
       }
     }
   }
   return nullptr;
 }
 
 bool NaryReassociatePass::requiresSignExtension(Value *Index,

llvm/lib/Transforms/Scalar/SROA.cpp

if (SROAStrictInbounds && GEPI.isInBounds()) {
       for (gep_type_iterator GTI = gep_type_begin(GEPI),
                              GTE = gep_type_end(GEPI);
            GTI != GTE; ++GTI) {
         ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
         if (!OpC)
           break;
 
         // Handle a struct index, which adds its field offset to the pointer.
-        if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+        if (StructType *STy = GTI.getStructTypeOrNull()) {
           unsigned ElementIdx = OpC->getZExtValue();
           const StructLayout *SL = DL.getStructLayout(STy);
           GEPOffset +=
               APInt(Offset.getBitWidth(), SL->getElementOffset(ElementIdx));
         } else {
           // For array or vector indices, scale the index by the size of the
           // type.
           APInt Index = OpC->getValue().sextOrTrunc(Offset.getBitWidth());

llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp

 bool SeparateConstOffsetFromGEP::canonicalizeArrayIndicesToPointerSize(
     GetElementPtrInst *GEP) {
   bool Changed = false;
   Type *IntPtrTy = DL->getIntPtrType(GEP->getType());
   gep_type_iterator GTI = gep_type_begin(*GEP);
   for (User::op_iterator I = GEP->op_begin() + 1, E = GEP->op_end();
        I != E; ++I, ++GTI) {
     // Skip struct member indices which must be i32.
-    if (isa<SequentialType>(*GTI)) {
+    if (GTI.isArray()) {
       if ((*I)->getType() != IntPtrTy) {
         *I = CastInst::CreateIntegerCast(*I, IntPtrTy, true, "idxprom", GEP);
         Changed = true;
       }
     }
   }
   return Changed;
 }
 
 int64_t
 SeparateConstOffsetFromGEP::accumulateByteOffset(GetElementPtrInst *GEP,
                                                  bool &NeedsExtraction) {
   NeedsExtraction = false;
   int64_t AccumulativeByteOffset = 0;
   gep_type_iterator GTI = gep_type_begin(*GEP);
   for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
-    if (isa<SequentialType>(*GTI)) {
+    if (GTI.isArray()) {
       // Tries to extract a constant offset from this GEP index.
       int64_t ConstantOffset =
           ConstantOffsetExtractor::Find(GEP->getOperand(I), GEP, DT);
       if (ConstantOffset != 0) {
         NeedsExtraction = true;
         // A GEP may have multiple indices.  We accumulate the extracted
         // constant offset to a byte offset, and later offset the remainder of
         // the original GEP with this byte offset.
         AccumulativeByteOffset +=
             ConstantOffset * DL->getTypeAllocSize(GTI.getIndexedType());
       }
     } else if (LowerGEP) {
-      StructType *StTy = cast<StructType>(*GTI);
+      StructType *StTy = GTI.getStructType();
       uint64_t Field = cast<ConstantInt>(GEP->getOperand(I))->getZExtValue();
       // Skip field 0 as the offset is always 0.
       if (Field != 0) {
         NeedsExtraction = true;
         AccumulativeByteOffset +=
             DL->getStructLayout(StTy)->getElementOffset(Field);
       }
     }
void SeparateConstOffsetFromGEP::lowerToSingleIndexGEPs(
 
   if (ResultPtr->getType() != I8PtrTy)
     ResultPtr = Builder.CreateBitCast(ResultPtr, I8PtrTy);
 
   gep_type_iterator GTI = gep_type_begin(*Variadic);
   // Create an ugly GEP for each sequential index. We don't create GEPs for
   // structure indices, as they are accumulated in the constant offset index.
   for (unsigned I = 1, E = Variadic->getNumOperands(); I != E; ++I, ++GTI) {
-    if (isa<SequentialType>(*GTI)) {
+    if (GTI.isArray()) {
       Value *Idx = Variadic->getOperand(I);
       // Skip zero indices.
       if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx))
         if (CI->isZero())
           continue;
 
       APInt ElementSize = APInt(IntPtrTy->getIntegerBitWidth(),
                                 DL->getTypeAllocSize(GTI.getIndexedType()));
SeparateConstOffsetFromGEP::lowerToArithmetics(GetElementPtrInst *Variadic,
   Type *IntPtrTy = DL->getIntPtrType(Variadic->getType());
 
   Value *ResultPtr = Builder.CreatePtrToInt(Variadic->getOperand(0), IntPtrTy);
   gep_type_iterator GTI = gep_type_begin(*Variadic);
   // Create ADD/SHL/MUL arithmetic operations for each sequential indices. We
   // don't create arithmetics for structure indices, as they are accumulated
   // in the constant offset index.
   for (unsigned I = 1, E = Variadic->getNumOperands(); I != E; ++I, ++GTI) {
-    if (isa<SequentialType>(*GTI)) {
+    if (GTI.isArray()) {
       Value *Idx = Variadic->getOperand(I);
       // Skip zero indices.
       if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx))
         if (CI->isZero())
           continue;
 
       APInt ElementSize = APInt(IntPtrTy->getIntegerBitWidth(),
                                 DL->getTypeAllocSize(GTI.getIndexedType()));
bool SeparateConstOffsetFromGEP::splitGEP(GetElementPtrInst *GEP) {
   // computes the variadic base.
   // Notice that we don't remove struct field indices here. If LowerGEP is
   // disabled, a structure index is not accumulated and we still use the old
   // one. If LowerGEP is enabled, a structure index is accumulated in the
   // constant offset. LowerToSingleIndexGEPs or lowerToArithmetics will later
   // handle the constant offset and won't need a new structure index.
   gep_type_iterator GTI = gep_type_begin(*GEP);
   for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
-    if (isa<SequentialType>(*GTI)) {
+    if (GTI.isArray()) {
       // Splits this GEP index into a variadic part and a constant offset, and
       // uses the variadic part as the new index.
       Value *OldIdx = GEP->getOperand(I);
       User *UserChainTail;
       Value *NewIdx =
           ConstantOffsetExtractor::Extract(OldIdx, GEP, UserChainTail, DT);
       if (NewIdx != nullptr) {
         // Switches to the index with the constant offset removed.

llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp

void StraightLineStrengthReduce::allocateCandidatesAndFindBasisForGEP(
   if (GEP->getType()->isVectorTy())
     return;
 
   SmallVector<const SCEV *, 4> IndexExprs;
   for (auto I = GEP->idx_begin(); I != GEP->idx_end(); ++I)
     IndexExprs.push_back(SE->getSCEV(*I));
 
   gep_type_iterator GTI = gep_type_begin(GEP);
-  for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I) {
-    if (!isa<SequentialType>(*GTI++))
+  for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
+    if (GTI.isStruct())
       continue;
 
     const SCEV *OrigIndexExpr = IndexExprs[I - 1];
     IndexExprs[I - 1] = SE->getZero(OrigIndexExpr->getType());
 
     // The base of this candidate is GEP's base plus the offsets of all
     // indices except this current one.
     const SCEV *BaseExpr = SE->getGEPExpr(cast<GEPOperator>(GEP), IndexExprs);
     Value *ArrayIdx = GEP->getOperand(I);
-    uint64_t ElementSize = DL->getTypeAllocSize(*GTI);
+    uint64_t ElementSize = DL->getTypeAllocSize(GTI.getIndexedType());
     if (ArrayIdx->getType()->getIntegerBitWidth() <=
         DL->getPointerSizeInBits(GEP->getAddressSpace())) {
       // Skip factoring if ArrayIdx is wider than the pointer size, because
       // ArrayIdx is implicitly truncated to the pointer size.
       factorArrayIndex(ArrayIdx, BaseExpr, ElementSize, GEP);
     }
     // When ArrayIdx is the sext of a value, we try to factor that value as
     // well.  Handling this case is important because array indices are

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

case Instruction::InsertValue:
     // All operands apart from the first are constant.
     return OpIdx == 0;
   case Instruction::Alloca:
     return false;
   case Instruction::GetElementPtr:
     if (OpIdx == 0)
       return true;
     gep_type_iterator It = std::next(gep_type_begin(I), OpIdx - 1);
-    return !It->isStructTy();
+    return It.isArray();
   }
 }
 
 // All instructions in Insts belong to different blocks that all unconditionally
 // branch to a common successor. Analyze each instruction and return true if it
 // would be possible to sink them into their successor, creating one common
 // instruction instead. For every value that would be required to be provided by
 // PHI node (because an operand varies in each input block), add to PHIOperands.