IR: Change PointerType to derive from Type rather than SequentialType.

As proposed on llvm-dev:
http://lists.llvm.org/pipermail/llvm-dev/2016-October/106640.html

This is for a couple of reasons:

- Values of type PointerType are unlike the other SequentialTypes (arrays
  and vectors) in that they do not hold values of the element type. By moving
  PointerType we can unify certain aspects of how the other SequentialTypes
  are handled.
- PointerType will have no place in the SequentialType hierarchy once
  pointee types are removed, so this is a necessary step towards removing
  pointee types.

Differential Revision: https://reviews.llvm.org/D26595

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288462 91177308-0d34-0410-b5e6-96231b3b80d8

docs/ProgrammersManual.rst

@@ -3278,7 +3278,7 @@ Important Derived Types
   * ``unsigned getBitWidth() const``: Get the bit width of an integer type.
 
 ``SequentialType``
-  This is subclassed by ArrayType, PointerType and VectorType.
+  This is subclassed by ArrayType and VectorType.
 
   * ``const Type * getElementType() const``: Returns the type of each
     of the elements in the sequential type.
@@ -3291,7 +3291,7 @@ Important Derived Types
     in the array.
 
 ``PointerType``
-  Subclass of SequentialType for pointer types.
+  Subclass of Type for pointer types.
 
 ``VectorType``
   Subclass of SequentialType for vector types.  A vector type is similar to an

include/llvm/IR/DerivedTypes.h

@@ -153,7 +153,7 @@ unsigned Type::getFunctionNumParams() const {
   return cast<FunctionType>(this)->getNumParams();
 }
 
-/// Common super class of ArrayType, StructType, PointerType and VectorType.
+/// Common super class of ArrayType, StructType and VectorType.
 class CompositeType : public Type {
 protected:
   explicit CompositeType(LLVMContext &C, TypeID tid) : Type(C, tid) {}
@@ -169,7 +169,6 @@ class CompositeType : public Type {
   static inline bool classof(const Type *T) {
     return T->getTypeID() == ArrayTyID ||
            T->getTypeID() == StructTyID ||
-           T->getTypeID() == PointerTyID ||
            T->getTypeID() == VectorTyID;
   }
 };
@@ -306,12 +305,12 @@ Type *Type::getStructElementType(unsigned N) const {
   return cast<StructType>(this)->getElementType(N);
 }
 
-/// This is the superclass of the array, pointer and vector type classes.
-/// All of these represent "arrays" in memory. The array type represents a
-/// specifically sized array, pointer types are unsized/unknown size arrays,
-/// vector types represent specifically sized arrays that allow for use of SIMD
-/// instructions. SequentialType holds the common features of all, which stem
-/// from the fact that all three lay their components out in memory identically.
+/// This is the superclass of the array and vector type classes. Both of these
+/// represent "arrays" in memory. The array type represents a specifically sized
+/// array, and the vector type represents a specifically sized array that allows
+/// for use of SIMD instructions. SequentialType holds the common features of
+/// both, which stem from the fact that both lay their components out in memory
+/// identically.
 class SequentialType : public CompositeType {
   Type *ContainedType;               ///< Storage for the single contained type.
   SequentialType(const SequentialType &) = delete;
@@ -329,9 +328,7 @@ class SequentialType : public CompositeType {
 
   /// Methods for support type inquiry through isa, cast, and dyn_cast.
   static inline bool classof(const Type *T) {
-    return T->getTypeID() == ArrayTyID ||
-           T->getTypeID() == PointerTyID ||
-           T->getTypeID() == VectorTyID;
+    return T->getTypeID() == ArrayTyID || T->getTypeID() == VectorTyID;
   }
 };
 
@@ -441,11 +438,13 @@ unsigned Type::getVectorNumElements() const {
 }
 
 /// Class to represent pointers.
-class PointerType : public SequentialType {
+class PointerType : public Type {
   PointerType(const PointerType &) = delete;
   const PointerType &operator=(const PointerType &) = delete;
   explicit PointerType(Type *ElType, unsigned AddrSpace);
 
+  Type *PointeeTy;
+
 public:
   /// This constructs a pointer to an object of the specified type in a numbered
   /// address space.
@@ -457,6 +456,8 @@ class PointerType : public SequentialType {
     return PointerType::get(ElementType, 0);
   }
 
+  Type *getElementType() const { return PointeeTy; }
+
   /// Return true if the specified type is valid as a element type.
   static bool isValidElementType(Type *ElemTy);
 

include/llvm/IR/Instructions.h

@@ -898,11 +898,6 @@ class GetElementPtrInst : public Instruction {
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
-  // getType - Overload to return most specific sequential type.
-  SequentialType *getType() const {
-    return cast<SequentialType>(Instruction::getType());
-  }
-
   Type *getSourceElementType() const { return SourceElementType; }
 
   void setSourceElementType(Type *Ty) { SourceElementType = Ty; }

include/llvm/IR/Type.h

@@ -110,7 +110,7 @@ class Type {
   Type * const *ContainedTys;
 
   static bool isSequentialType(TypeID TyID) {
-    return TyID == ArrayTyID || TyID == PointerTyID || TyID == VectorTyID;
+    return TyID == ArrayTyID || TyID == VectorTyID;
   }
 
 public:

lib/Analysis/ScalarEvolution.cpp

@@ -3057,9 +3057,9 @@ ScalarEvolution::getGEPExpr(GEPOperator *GEP,
                                              : SCEV::FlagAnyWrap;
 
   const SCEV *TotalOffset = getZero(IntPtrTy);
-  // The address space is unimportant. The first thing we do on CurTy is getting
+  // The array size is unimportant. The first thing we do on CurTy is getting
   // its element type.
-  Type *CurTy = PointerType::getUnqual(GEP->getSourceElementType());
+  Type *CurTy = ArrayType::get(GEP->getSourceElementType(), 0);
   for (const SCEV *IndexExpr : IndexExprs) {
     // Compute the (potentially symbolic) offset in bytes for this index.
     if (StructType *STy = dyn_cast<StructType>(CurTy)) {

lib/IR/ConstantFold.cpp

@@ -120,7 +120,6 @@ static Constant *FoldBitCast(Constant *V, Type *DestTy) {
             IdxList.push_back(Zero);
           } else if (SequentialType *STy =
                      dyn_cast<SequentialType>(ElTy)) {
-            if (ElTy->isPointerTy()) break;  // Can't index into pointers!
             ElTy = STy->getElementType();
             IdxList.push_back(Zero);
           } else {
@@ -2206,11 +2205,6 @@ Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C,
       continue;
     }
     auto *STy = cast<SequentialType>(Ty);
-    if (isa<PointerType>(STy)) {
-      // We don't know if it's in range or not.
-      Unknown = true;
-      continue;
-    }
     if (isa<VectorType>(STy)) {
       // There can be awkward padding in after a non-power of two vector.
       Unknown = true;
@@ -2222,7 +2216,7 @@ Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C,
                                   CI))
       // It's in range, skip to the next index.
       continue;
-    if (!isa<SequentialType>(Prev)) {
+    if (isa<StructType>(Prev)) {
       // It's out of range, but the prior dimension is a struct
       // so we can't do anything about it.
       Unknown = true;

lib/IR/Core.cpp

@@ -578,8 +578,11 @@ LLVMTypeRef LLVMVectorType(LLVMTypeRef ElementType, unsigned ElementCount) {
   return wrap(VectorType::get(unwrap(ElementType), ElementCount));
 }
 
-LLVMTypeRef LLVMGetElementType(LLVMTypeRef Ty) {
-  return wrap(unwrap<SequentialType>(Ty)->getElementType());
+LLVMTypeRef LLVMGetElementType(LLVMTypeRef WrappedTy) {
+  auto *Ty = unwrap<Type>(WrappedTy);
+  if (auto *PTy = dyn_cast<PointerType>(Ty))
+    return wrap(PTy->getElementType());
+  return wrap(cast<SequentialType>(Ty)->getElementType());
 }
 
 unsigned LLVMGetArrayLength(LLVMTypeRef ArrayTy) {

lib/IR/Type.cpp

@@ -673,7 +673,9 @@ PointerType *PointerType::get(Type *EltTy, unsigned AddressSpace) {
 
 
 PointerType::PointerType(Type *E, unsigned AddrSpace)
-  : SequentialType(PointerTyID, E) {
+  : Type(E->getContext(), PointerTyID), PointeeTy(E) {
+  ContainedTys = &PointeeTy;
+  NumContainedTys = 1;
   setSubclassData(AddrSpace);
 }
 

lib/Target/Hexagon/HexagonCommonGEP.cpp

@@ -178,6 +178,8 @@ namespace {
 
 
   Type *next_type(Type *Ty, Value *Idx) {
+    if (auto *PTy = dyn_cast<PointerType>(Ty))
+      return PTy->getElementType();
     // Advance the type.
     if (!Ty->isStructTy()) {
       Type *NexTy = cast<SequentialType>(Ty)->getElementType();

lib/Transforms/IPO/ArgumentPromotion.cpp

@@ -176,8 +176,7 @@ static bool isDenselyPacked(Type *type, const DataLayout &DL) {
 
   // For homogenous sequential types, check for padding within members.
   if (SequentialType *seqTy = dyn_cast<SequentialType>(type))
-    return isa<PointerType>(seqTy) ||
-           isDenselyPacked(seqTy->getElementType(), DL);
+    return isDenselyPacked(seqTy->getElementType(), DL);
 
   // Check for padding within and between elements of a struct.
   StructType *StructTy = cast<StructType>(type);
@@ -835,7 +834,10 @@ DoPromotion(Function *F, SmallPtrSetImpl<Argument *> &ArgsToPromote,
                     Type::getInt64Ty(F->getContext()));
               Ops.push_back(ConstantInt::get(IdxTy, II));
               // Keep track of the type we're currently indexing.
-              ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(II);
+              if (auto *ElPTy = dyn_cast<PointerType>(ElTy))
+                ElTy = ElPTy->getElementType();
+              else
+                ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(II);
             }
             // And create a GEP to extract those indices.
             V = GetElementPtrInst::Create(ArgIndex.first, V, Ops,

lib/Transforms/Scalar/SROA.cpp

@@ -3219,10 +3219,6 @@ static Type *getTypePartition(const DataLayout &DL, Type *Ty, uint64_t Offset,
     return nullptr;
 
   if (SequentialType *SeqTy = dyn_cast<SequentialType>(Ty)) {
-    // We can't partition pointers...
-    if (SeqTy->isPointerTy())
-      return nullptr;
-
     Type *ElementTy = SeqTy->getElementType();
     uint64_t ElementSize = DL.getTypeAllocSize(ElementTy);
     uint64_t NumSkippedElements = Offset / ElementSize;