Index: llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h
===================================================================
--- llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h
+++ llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h
@@ -482,10 +482,7 @@
     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.
@@ -493,7 +490,12 @@
       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;
@@ -504,17 +506,15 @@
             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;
     }
Index: llvm/trunk/include/llvm/IR/GetElementPtrTypeIterator.h
===================================================================
--- llvm/trunk/include/llvm/IR/GetElementPtrTypeIterator.h
+++ llvm/trunk/include/llvm/IR/GetElementPtrTypeIterator.h
@@ -16,7 +16,7 @@
 #define LLVM_IR_GETELEMENTPTRTYPEITERATOR_H
 
 #include "llvm/ADT/ArrayRef.h"
-#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/PointerUnion.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/User.h"
@@ -33,18 +33,15 @@
                           Type *, ptrdiff_t> super;
 
     ItTy OpIt;
-    PointerIntPair<Type *, 1> CurTy;
-    unsigned AddrSpace;
-
+    PointerUnion<StructType *, Type *> CurTy;
+    enum { Unbounded = -1ull };
+    uint64_t NumElements = Unbounded;
     generic_gep_type_iterator() = default;
 
   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;
     }
@@ -63,34 +60,28 @@
       return !operator==(x);
     }
 
-    Type *operator*() const {
-      if (CurTy.getInt())
-        return CurTy.getPointer()->getPointerTo(AddrSpace);
-      return CurTy.getPointer();
-    }
-
+    // FIXME: Make this the iterator's operator*() after the 4.0 release.
+    // operator*() had a different meaning in earlier releases, so we're
+    // temporarily not giving this iterator an operator*() to avoid a subtle
+    // semantics break.
     Type *getIndexedType() const {
-      if (CurTy.getInt())
-        return CurTy.getPointer();
-      CompositeType *CT = cast<CompositeType>(CurTy.getPointer());
-      return CT->getTypeAtIndex(getOperand());
+      if (auto *T = CurTy.dyn_cast<Type *>())
+        return T;
+      return CurTy.get<StructType *>()->getTypeAtIndex(getOperand());
     }
 
-    // This is a non-standard operator->.  It allows you to call methods on the
-    // current type directly.
-    Type *operator->() const { return operator*(); }
-
     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);
-      }
+      Type *Ty = getIndexedType();
+      if (auto *ATy = dyn_cast<ArrayType>(Ty)) {
+        CurTy = ATy->getElementType();
+        NumElements = ATy->getNumElements();
+      } else if (auto *VTy = dyn_cast<VectorType>(Ty)) {
+        CurTy = VTy->getElementType();
+        NumElements = VTy->getNumElements();
+      } else
+        CurTy = dyn_cast<StructType>(Ty);
       ++OpIt;
       return *this;
     }
@@ -98,6 +89,39 @@
     generic_gep_type_iterator operator++(int) { // Postincrement
       generic_gep_type_iterator tmp = *this; ++*this; return tmp;
     }
+
+    // All of the below API is for querying properties of the "outer type", i.e.
+    // the type that contains the indexed type. Most of the time this is just
+    // the type that was visited immediately prior to the indexed type, but for
+    // the first element this is an unbounded array of the GEP's source element
+    // type, for which there is no clearly corresponding IR type (we've
+    // historically used a pointer type as the outer type in this case, but
+    // pointers will soon lose their element type).
+    //
+    // FIXME: Most current users of this class are just interested in byte
+    // offsets (a few need to know whether the outer type is a struct because
+    // they are trying to replace a constant with a variable, which is only
+    // legal for arrays, e.g. canReplaceOperandWithVariable in SimplifyCFG.cpp);
+    // we should provide a more minimal API here that exposes not much more than
+    // that.
+
+    bool isStruct() const { return CurTy.is<StructType *>(); }
+    bool isSequential() const { return CurTy.is<Type *>(); }
+
+    StructType *getStructType() const { return CurTy.get<StructType *>(); }
+
+    StructType *getStructTypeOrNull() const {
+      return CurTy.dyn_cast<StructType *>();
+    }
+
+    bool isBoundedSequential() const {
+      return isSequential() && NumElements != Unbounded;
+    }
+
+    uint64_t getSequentialNumElements() const {
+      assert(isBoundedSequential());
+      return NumElements;
+    }
   };
 
   typedef generic_gep_type_iterator<> gep_type_iterator;
@@ -106,8 +130,6 @@
     auto *GEPOp = cast<GEPOperator>(GEP);
     return gep_type_iterator::begin(
         GEPOp->getSourceElementType(),
-        cast<PointerType>(GEPOp->getPointerOperandType()->getScalarType())
-            ->getAddressSpace(),
         GEP->op_begin() + 1);
   }
 
@@ -119,8 +141,6 @@
     auto &GEPOp = cast<GEPOperator>(GEP);
     return gep_type_iterator::begin(
         GEPOp.getSourceElementType(),
-        cast<PointerType>(GEPOp.getPointerOperandType()->getScalarType())
-            ->getAddressSpace(),
         GEP.op_begin() + 1);
   }
 
@@ -130,13 +150,13 @@
 
   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());
   }
 
Index: llvm/trunk/include/llvm/Transforms/Utils/Local.h
===================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/Local.h
+++ llvm/trunk/include/llvm/Transforms/Utils/Local.h
@@ -217,7 +217,7 @@
         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();
 
Index: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
===================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
@@ -412,10 +412,10 @@
     // 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)
@@ -431,13 +431,13 @@
         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
Index: llvm/trunk/lib/Analysis/InlineCost.cpp
===================================================================
--- llvm/trunk/lib/Analysis/InlineCost.cpp
+++ llvm/trunk/lib/Analysis/InlineCost.cpp
@@ -318,7 +318,7 @@
       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));
Index: llvm/trunk/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp
@@ -1231,7 +1231,7 @@
     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
@@ -1730,7 +1730,7 @@
   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);
Index: llvm/trunk/lib/Analysis/VectorUtils.cpp
===================================================================
--- llvm/trunk/lib/Analysis/VectorUtils.cpp
+++ llvm/trunk/lib/Analysis/VectorUtils.cpp
@@ -107,11 +107,11 @@
   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;
   }
Index: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
@@ -3261,7 +3261,7 @@
     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();
Index: llvm/trunk/lib/CodeGen/SelectionDAG/FastISel.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ llvm/trunk/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -488,7 +488,7 @@
   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
Index: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3274,7 +3274,7 @@
   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
Index: llvm/trunk/lib/ExecutionEngine/Interpreter/Execution.cpp
===================================================================
--- llvm/trunk/lib/ExecutionEngine/Interpreter/Execution.cpp
+++ llvm/trunk/lib/ExecutionEngine/Interpreter/Execution.cpp
@@ -999,7 +999,7 @@
   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());
@@ -1007,7 +1007,6 @@
 
       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);
 
@@ -1020,7 +1019,7 @@
         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;
     }
   }
 
Index: llvm/trunk/lib/IR/ConstantFold.cpp
===================================================================
--- llvm/trunk/lib/IR/ConstantFold.cpp
+++ llvm/trunk/lib/IR/ConstantFold.cpp
@@ -2019,22 +2019,8 @@
 }
 
 /// 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,
+                                      const ConstantInt *CI) {
   // We cannot bounds check the index if it doesn't fit in an int64_t.
   if (CI->getValue().getActiveBits() > 64)
     return false;
@@ -2089,10 +2075,10 @@
     // 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
@@ -2115,9 +2101,11 @@
       bool PerformFold = false;
       if (Idx0->isNullValue())
         PerformFold = true;
-      else if (SequentialType *STy = dyn_cast_or_null<SequentialType>(LastTy))
+      else if (LastI.isSequential())
         if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0))
-          PerformFold = isIndexInRangeOfSequentialType(STy, CI);
+          PerformFold =
+              !LastI.isBoundedSequential() ||
+              isIndexInRangeOfArrayType(LastI.getSequentialNumElements(), CI);
 
       if (PerformFold) {
         SmallVector<Value*, 16> NewIndices;
@@ -2228,7 +2216,10 @@
       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)) {
Index: llvm/trunk/lib/IR/Constants.cpp
===================================================================
--- llvm/trunk/lib/IR/Constants.cpp
+++ llvm/trunk/lib/IR/Constants.cpp
@@ -1073,19 +1073,14 @@
   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.isBoundedSequential() &&
+        (CI->getValue().getActiveBits() > 64 ||
+         CI->getZExtValue() >= GEPI.getSequentialNumElements()))
+      return false;
   }
 
   // All the indices checked out.
Index: llvm/trunk/lib/IR/DataLayout.cpp
===================================================================
--- llvm/trunk/lib/IR/DataLayout.cpp
+++ llvm/trunk/lib/IR/DataLayout.cpp
@@ -737,15 +737,12 @@
                                            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();
 
Index: llvm/trunk/lib/IR/Operator.cpp
===================================================================
--- llvm/trunk/lib/IR/Operator.cpp
+++ llvm/trunk/lib/IR/Operator.cpp
@@ -33,7 +33,7 @@
       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));
Index: llvm/trunk/lib/Target/AArch64/AArch64FastISel.cpp
===================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64FastISel.cpp
+++ llvm/trunk/lib/Target/AArch64/AArch64FastISel.cpp
@@ -557,7 +557,7 @@
     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);
@@ -4885,7 +4885,7 @@
   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)
Index: llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -7157,8 +7157,8 @@
     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:
Index: llvm/trunk/lib/Target/ARM/ARMFastISel.cpp
===================================================================
--- llvm/trunk/lib/Target/ARM/ARMFastISel.cpp
+++ llvm/trunk/lib/Target/ARM/ARMFastISel.cpp
@@ -733,7 +733,7 @@
       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);
Index: llvm/trunk/lib/Target/Mips/MipsFastISel.cpp
===================================================================
--- llvm/trunk/lib/Target/Mips/MipsFastISel.cpp
+++ llvm/trunk/lib/Target/Mips/MipsFastISel.cpp
@@ -445,7 +445,7 @@
     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);
Index: llvm/trunk/lib/Target/PowerPC/PPCFastISel.cpp
===================================================================
--- llvm/trunk/lib/Target/PowerPC/PPCFastISel.cpp
+++ llvm/trunk/lib/Target/PowerPC/PPCFastISel.cpp
@@ -358,7 +358,7 @@
       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);
Index: llvm/trunk/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
===================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
@@ -241,7 +241,7 @@
     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);
Index: llvm/trunk/lib/Target/X86/X86FastISel.cpp
===================================================================
--- llvm/trunk/lib/Target/X86/X86FastISel.cpp
+++ llvm/trunk/lib/Target/X86/X86FastISel.cpp
@@ -936,7 +936,7 @@
     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;
Index: llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
===================================================================
--- llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
+++ llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
@@ -371,14 +371,14 @@
   ++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.isSequential()) {
     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.isBoundedSequential() &&
+        Idx->getZExtValue() >= GEPI.getSequentialNumElements())
       return false;
 
     // We cannot scalar repl this level of the array unless any array
@@ -391,19 +391,13 @@
     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.isBoundedSequential() &&
+           IdxVal->getZExtValue() >= GEPI.getSequentialNumElements()))
         return false;
     }
   }
Index: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -517,7 +517,7 @@
       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());
@@ -547,7 +547,7 @@
     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());
Index: llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1389,7 +1389,7 @@
   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
@@ -1546,7 +1546,7 @@
     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.isSequential();
 
     // Can we combine the two pointer arithmetics offsets?
     if (EndsWithSequential) {
Index: llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -52,7 +52,7 @@
     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;
     }
Index: llvm/trunk/lib/Transforms/Scalar/NaryReassociate.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/NaryReassociate.cpp
+++ llvm/trunk/lib/Transforms/Scalar/NaryReassociate.cpp
@@ -281,9 +281,10 @@
     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)) {
+  for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
+    if (GTI.isSequential()) {
+      if (auto *NewGEP = tryReassociateGEPAtIndex(GEP, I - 1,
+                                                  GTI.getIndexedType())) {
         return NewGEP;
       }
     }
Index: llvm/trunk/lib/Transforms/Scalar/SROA.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/SROA.cpp
+++ llvm/trunk/lib/Transforms/Scalar/SROA.cpp
@@ -692,7 +692,7 @@
           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 +=
Index: llvm/trunk/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
+++ llvm/trunk/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
@@ -722,7 +722,7 @@
   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.isSequential()) {
       if ((*I)->getType() != IntPtrTy) {
         *I = CastInst::CreateIntegerCast(*I, IntPtrTy, true, "idxprom", GEP);
         Changed = true;
@@ -739,7 +739,7 @@
   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.isSequential()) {
       // Tries to extract a constant offset from this GEP index.
       int64_t ConstantOffset =
           ConstantOffsetExtractor::Find(GEP->getOperand(I), GEP, DT);
@@ -752,7 +752,7 @@
             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) {
@@ -787,7 +787,7 @@
   // 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.isSequential()) {
       Value *Idx = Variadic->getOperand(I);
       // Skip zero indices.
       if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx))
@@ -848,7 +848,7 @@
   // 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.isSequential()) {
       Value *Idx = Variadic->getOperand(I);
       // Skip zero indices.
       if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx))
@@ -928,7 +928,7 @@
   // 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.isSequential()) {
       // 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);
Index: llvm/trunk/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
+++ llvm/trunk/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
@@ -490,8 +490,8 @@
     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];
@@ -501,7 +501,7 @@
     // 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
Index: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1416,7 +1416,7 @@
     if (OpIdx == 0)
       return true;
     gep_type_iterator It = std::next(gep_type_begin(I), OpIdx - 1);
-    return !It->isStructTy();
+    return It.isSequential();
   }
 }