IR: Add ConstantData, for operand-less Constants

Add a common parent `ConstantData` to the constants that have no
operands.  These are guaranteed to represent abstract data that is in no
way tied to a specific Module.

This is a good cleanup on its own.  It also makes it simpler to disallow
RAUW (and factor away use-lists) on these constants in the future.  (I
have some experimental patches that make RAUW illegal on ConstantData,
and they seem to catch a bunch of bugs...)

llvm-svn: 261464

llvm/include/llvm/IR/Constants.h

@@ -40,26 +40,47 @@ class SequentialType;
 struct ConstantExprKeyType;
 template <class ConstantClass> struct ConstantAggrKeyType;
 
+/// Base class for constants with no operands.
+///
+/// These constants have no operands; they represent their data directly.
+/// Since they can be in use by unrelated modules (and are never based on
+/// GlobalValues), it never makes sensee to RAUW them.
+class ConstantData : public Constant {
+  void anchor() override;
+  void *operator new(size_t, unsigned) = delete;
+  ConstantData() = delete;
+  ConstantData(const ConstantData &) = delete;
+
+  friend class Constant;
+  Value *handleOperandChangeImpl(Value *From, Value *To) {
+    llvm_unreachable("Constant data does not have operands!");
+  }
+
+protected:
+  explicit ConstantData(Type *Ty, ValueTy VT) : Constant(Ty, VT, nullptr, 0) {}
+  void *operator new(size_t s) { return User::operator new(s, 0); }
+
+public:
+  /// Methods to support type inquiry through isa, cast, and dyn_cast.
+  static bool classof(const Value *V) {
+    return V->getValueID() >= ConstantDataFirstVal &&
+           V->getValueID() <= ConstantDataLastVal;
+  }
+};
+
 //===----------------------------------------------------------------------===//
 /// This is the shared class of boolean and integer constants. This class
 /// represents both boolean and integral constants.
 /// @brief Class for constant integers.
-class ConstantInt : public Constant {
+class ConstantInt : public ConstantData {
   void anchor() override;
-  void *operator new(size_t, unsigned) = delete;
   ConstantInt(const ConstantInt &) = delete;
   ConstantInt(IntegerType *Ty, const APInt& V);
   APInt Val;
 
   friend class Constant;
   void destroyConstantImpl();
-  Value *handleOperandChangeImpl(Value *From, Value *To);
 
-protected:
-  // allocate space for exactly zero operands
-  void *operator new(size_t s) {
-    return User::operator new(s, 0);
-  }
 public:
   static ConstantInt *getTrue(LLVMContext &Context);
   static ConstantInt *getFalse(LLVMContext &Context);
@@ -230,24 +251,17 @@ public:
 //===----------------------------------------------------------------------===//
 /// ConstantFP - Floating Point Values [float, double]
 ///
-class ConstantFP : public Constant {
+class ConstantFP : public ConstantData {
   APFloat Val;
   void anchor() override;
-  void *operator new(size_t, unsigned) = delete;
   ConstantFP(const ConstantFP &) = delete;
-  friend class LLVMContextImpl;
 
   friend class Constant;
   void destroyConstantImpl();
-  Value *handleOperandChangeImpl(Value *From, Value *To);
 
 protected:
   ConstantFP(Type *Ty, const APFloat& V);
-protected:
-  // allocate space for exactly zero operands
-  void *operator new(size_t s) {
-    return User::operator new(s, 0);
-  }
+
 public:
   /// Floating point negation must be implemented with f(x) = -0.0 - x. This
   /// method returns the negative zero constant for floating point or vector
@@ -304,22 +318,16 @@ public:
 //===----------------------------------------------------------------------===//
 /// All zero aggregate value
 ///
-class ConstantAggregateZero : public Constant {
-  void *operator new(size_t, unsigned) = delete;
+class ConstantAggregateZero : public ConstantData {
   ConstantAggregateZero(const ConstantAggregateZero &) = delete;
 
   friend class Constant;
   void destroyConstantImpl();
-  Value *handleOperandChangeImpl(Value *From, Value *To);
 
 protected:
-  explicit ConstantAggregateZero(Type *ty)
-    : Constant(ty, ConstantAggregateZeroVal, nullptr, 0) {}
-protected:
-  // allocate space for exactly zero operands
-  void *operator new(size_t s) {
-    return User::operator new(s, 0);
-  }
+  explicit ConstantAggregateZero(Type *Ty)
+      : ConstantData(Ty, ConstantAggregateZeroVal) {}
+
 public:
   static ConstantAggregateZero *get(Type *Ty);
 
@@ -503,24 +511,16 @@ DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ConstantVector, Constant)
 //===----------------------------------------------------------------------===//
 /// A constant pointer value that points to null
 ///
-class ConstantPointerNull : public Constant {
-  void *operator new(size_t, unsigned) = delete;
+class ConstantPointerNull : public ConstantData {
   ConstantPointerNull(const ConstantPointerNull &) = delete;
 
   friend class Constant;
   void destroyConstantImpl();
-  Value *handleOperandChangeImpl(Value *From, Value *To);
 
 protected:
   explicit ConstantPointerNull(PointerType *T)
-    : Constant(T,
-               Value::ConstantPointerNullVal, nullptr, 0) {}
+      : ConstantData(T, Value::ConstantPointerNullVal) {}
 
-protected:
-  // allocate space for exactly zero operands
-  void *operator new(size_t s) {
-    return User::operator new(s, 0);
-  }
 public:
   /// Static factory methods - Return objects of the specified value
   static ConstantPointerNull *get(PointerType *T);
@@ -546,7 +546,7 @@ public:
 ///
 /// This is the common base class of ConstantDataArray and ConstantDataVector.
 ///
-class ConstantDataSequential : public Constant {
+class ConstantDataSequential : public ConstantData {
   friend class LLVMContextImpl;
   /// A pointer to the bytes underlying this constant (which is owned by the
   /// uniquing StringMap).
@@ -557,27 +557,19 @@ class ConstantDataSequential : public Constant {
   /// element array of i8, or a 1-element array of i32.  They'll both end up in
   /// the same StringMap bucket, linked up.
   ConstantDataSequential *Next;
-  void *operator new(size_t, unsigned) = delete;
   ConstantDataSequential(const ConstantDataSequential &) = delete;
 
   friend class Constant;
   void destroyConstantImpl();
-  Value *handleOperandChangeImpl(Value *From, Value *To);
 
 protected:
   explicit ConstantDataSequential(Type *ty, ValueTy VT, const char *Data)
-    : Constant(ty, VT, nullptr, 0), DataElements(Data), Next(nullptr) {}
+      : ConstantData(ty, VT), DataElements(Data), Next(nullptr) {}
   ~ConstantDataSequential() override { delete Next; }
 
   static Constant *getImpl(StringRef Bytes, Type *Ty);
 
-protected:
-  // Allocate space for exactly zero operands.
-  void *operator new(size_t s) {
-    return User::operator new(s, 0);
-  }
 public:
-
   /// Return true if a ConstantDataSequential can be formed with a vector or
   /// array of the specified element type.
   /// ConstantDataArray only works with normal float and int types that are
@@ -780,19 +772,15 @@ public:
 //===----------------------------------------------------------------------===//
 /// A constant token which is empty
 ///
-class ConstantTokenNone : public Constant {
-  void *operator new(size_t, unsigned) = delete;
+class ConstantTokenNone : public ConstantData {
   ConstantTokenNone(const ConstantTokenNone &) = delete;
 
   friend class Constant;
   void destroyConstantImpl();
-  Value *handleOperandChangeImpl(Value *From, Value *To);
 
 protected:
   explicit ConstantTokenNone(LLVMContext &Context)
-      : Constant(Type::getTokenTy(Context), ConstantTokenNoneVal, nullptr, 0) {}
-  // allocate space for exactly zero operands
-  void *operator new(size_t s) { return User::operator new(s, 0); }
+      : ConstantData(Type::getTokenTy(Context), ConstantTokenNoneVal) {}
 
 public:
   /// Return the ConstantTokenNone.
@@ -1223,21 +1211,15 @@ DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ConstantExpr, Constant)
 /// can appear to have different bit patterns at each use. See
 /// LangRef.html#undefvalues for details.
 ///
-class UndefValue : public Constant {
-  void *operator new(size_t, unsigned) = delete;
+class UndefValue : public ConstantData {
   UndefValue(const UndefValue &) = delete;
 
   friend class Constant;
   void destroyConstantImpl();
-  Value *handleOperandChangeImpl(Value *From, Value *To);
 
 protected:
-  explicit UndefValue(Type *T) : Constant(T, UndefValueVal, nullptr, 0) {}
-protected:
-  // allocate space for exactly zero operands
-  void *operator new(size_t s) {
-    return User::operator new(s, 0);
-  }
+  explicit UndefValue(Type *T) : ConstantData(T, UndefValueVal) {}
+
 public:
   /// Static factory methods - Return an 'undef' object of the specified type.
   static UndefValue *get(Type *T);

llvm/include/llvm/IR/Value.def

@@ -61,17 +61,19 @@ HANDLE_VALUE(MemoryPhi)
 HANDLE_GLOBAL_VALUE(Function)
 HANDLE_GLOBAL_VALUE(GlobalAlias)
 HANDLE_GLOBAL_VALUE(GlobalVariable)
-HANDLE_CONSTANT(UndefValue)
 HANDLE_CONSTANT(BlockAddress)
 HANDLE_CONSTANT(ConstantExpr)
+HANDLE_CONSTANT(ConstantArray)
+HANDLE_CONSTANT(ConstantStruct)
+HANDLE_CONSTANT(ConstantVector)
+
+// ConstantData.
+HANDLE_CONSTANT(UndefValue)
 HANDLE_CONSTANT(ConstantAggregateZero)
 HANDLE_CONSTANT(ConstantDataArray)
 HANDLE_CONSTANT(ConstantDataVector)
 HANDLE_CONSTANT(ConstantInt)
 HANDLE_CONSTANT(ConstantFP)
-HANDLE_CONSTANT(ConstantArray)
-HANDLE_CONSTANT(ConstantStruct)
-HANDLE_CONSTANT(ConstantVector)
 HANDLE_CONSTANT(ConstantPointerNull)
 HANDLE_CONSTANT(ConstantTokenNone)
 
@@ -84,6 +86,8 @@ HANDLE_INSTRUCTION(Instruction)
 
 HANDLE_CONSTANT_MARKER(ConstantFirstVal, Function)
 HANDLE_CONSTANT_MARKER(ConstantLastVal, ConstantTokenNone)
+HANDLE_CONSTANT_MARKER(ConstantDataFirstVal, UndefValue)
+HANDLE_CONSTANT_MARKER(ConstantDataLastVal, ConstantTokenNone)
 
 #undef HANDLE_GLOBAL_VALUE
 #undef HANDLE_CONSTANT

llvm/include/llvm/IR/Value.h

@@ -27,6 +27,7 @@ class Argument;
 class AssemblyAnnotationWriter;
 class BasicBlock;
 class Constant;
+class ConstantData;
 class DataLayout;
 class Function;
 class GlobalAlias;
@@ -685,6 +686,13 @@ template <> struct isa_impl<Constant, Value> {
   }
 };
 
+template <> struct isa_impl<ConstantData, Value> {
+  static inline bool doit(const Value &Val) {
+    return Val.getValueID() >= Value::ConstantDataFirstVal &&
+           Val.getValueID() <= Value::ConstantDataLastVal;
+  }
+};
+
 template <> struct isa_impl<Argument, Value> {
   static inline bool doit (const Value &Val) {
     return Val.getValueID() == Value::ArgumentVal;

llvm/lib/IR/Constants.cpp

@@ -42,6 +42,8 @@ using namespace llvm;
 
 void Constant::anchor() { }
 
+void ConstantData::anchor() {}
+
 bool Constant::isNegativeZeroValue() const {
   // Floating point values have an explicit -0.0 value.
   if (const ConstantFP *CFP = dyn_cast<ConstantFP>(this))
@@ -521,8 +523,8 @@ void Constant::removeDeadConstantUsers() const {
 
 void ConstantInt::anchor() { }
 
-ConstantInt::ConstantInt(IntegerType *Ty, const APInt& V)
-  : Constant(Ty, ConstantIntVal, nullptr, 0), Val(V) {
+ConstantInt::ConstantInt(IntegerType *Ty, const APInt &V)
+    : ConstantData(Ty, ConstantIntVal), Val(V) {
   assert(V.getBitWidth() == Ty->getBitWidth() && "Invalid constant for type");
 }
 
@@ -748,8 +750,8 @@ Constant *ConstantFP::getInfinity(Type *Ty, bool Negative) {
   return C;
 }
 
-ConstantFP::ConstantFP(Type *Ty, const APFloat& V)
-  : Constant(Ty, ConstantFPVal, nullptr, 0), Val(V) {
+ConstantFP::ConstantFP(Type *Ty, const APFloat &V)
+    : ConstantData(Ty, ConstantFPVal), Val(V) {
   assert(&V.getSemantics() == TypeToFloatSemantics(Ty) &&
          "FP type Mismatch");
 }
@@ -2816,34 +2818,6 @@ void Constant::handleOperandChange(Value *From, Value *To) {
   destroyConstant();
 }
 
-Value *ConstantInt::handleOperandChangeImpl(Value *From, Value *To) {
-  llvm_unreachable("Unsupported class for handleOperandChange()!");
-}
-
-Value *ConstantFP::handleOperandChangeImpl(Value *From, Value *To) {
-  llvm_unreachable("Unsupported class for handleOperandChange()!");
-}
-
-Value *ConstantTokenNone::handleOperandChangeImpl(Value *From, Value *To) {
-  llvm_unreachable("Unsupported class for handleOperandChange()!");
-}
-
-Value *UndefValue::handleOperandChangeImpl(Value *From, Value *To) {
-  llvm_unreachable("Unsupported class for handleOperandChange()!");
-}
-
-Value *ConstantPointerNull::handleOperandChangeImpl(Value *From, Value *To) {
-  llvm_unreachable("Unsupported class for handleOperandChange()!");
-}
-
-Value *ConstantAggregateZero::handleOperandChangeImpl(Value *From, Value *To) {
-  llvm_unreachable("Unsupported class for handleOperandChange()!");
-}
-
-Value *ConstantDataSequential::handleOperandChangeImpl(Value *From, Value *To) {
-  llvm_unreachable("Unsupported class for handleOperandChange()!");
-}
-
 Value *ConstantArray::handleOperandChangeImpl(Value *From, Value *To) {
   assert(isa<Constant>(To) && "Cannot make Constant refer to non-constant!");
   Constant *ToC = cast<Constant>(To);