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      1 //===-- llvm/User.h - User class definition ---------------------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This class defines the interface that one who uses a Value must implement.
     11 // Each instance of the Value class keeps track of what User's have handles
     12 // to it.
     13 //
     14 //  * Instructions are the largest class of Users.
     15 //  * Constants may be users of other constants (think arrays and stuff)
     16 //
     17 //===----------------------------------------------------------------------===//
     18 
     19 #ifndef LLVM_IR_USER_H
     20 #define LLVM_IR_USER_H
     21 
     22 #include "llvm/ADT/iterator.h"
     23 #include "llvm/ADT/iterator_range.h"
     24 #include "llvm/IR/Value.h"
     25 #include "llvm/Support/ErrorHandling.h"
     26 
     27 namespace llvm {
     28 
     29 /// OperandTraits - Compile-time customization of
     30 /// operand-related allocators and accessors
     31 /// for use of the User class
     32 template <class>
     33 struct OperandTraits;
     34 
     35 class User : public Value {
     36   User(const User &) LLVM_DELETED_FUNCTION;
     37   void *operator new(size_t) LLVM_DELETED_FUNCTION;
     38   template <unsigned>
     39   friend struct HungoffOperandTraits;
     40   virtual void anchor();
     41 protected:
     42   /// NumOperands - The number of values used by this User.
     43   ///
     44   unsigned NumOperands;
     45 
     46   /// OperandList - This is a pointer to the array of Uses for this User.
     47   /// For nodes of fixed arity (e.g. a binary operator) this array will live
     48   /// prefixed to some derived class instance.  For nodes of resizable variable
     49   /// arity (e.g. PHINodes, SwitchInst etc.), this memory will be dynamically
     50   /// allocated and should be destroyed by the classes' virtual dtor.
     51   Use *OperandList;
     52 
     53   void *operator new(size_t s, unsigned Us);
     54   User(Type *ty, unsigned vty, Use *OpList, unsigned NumOps)
     55     : Value(ty, vty), NumOperands(NumOps), OperandList(OpList) {}
     56   Use *allocHungoffUses(unsigned) const;
     57   void dropHungoffUses() {
     58     Use::zap(OperandList, OperandList + NumOperands, true);
     59     OperandList = nullptr;
     60     // Reset NumOperands so User::operator delete() does the right thing.
     61     NumOperands = 0;
     62   }
     63 public:
     64   ~User() {
     65     Use::zap(OperandList, OperandList + NumOperands);
     66   }
     67   /// operator delete - free memory allocated for User and Use objects
     68   void operator delete(void *Usr);
     69   /// placement delete - required by std, but never called.
     70   void operator delete(void*, unsigned) {
     71     llvm_unreachable("Constructor throws?");
     72   }
     73   /// placement delete - required by std, but never called.
     74   void operator delete(void*, unsigned, bool) {
     75     llvm_unreachable("Constructor throws?");
     76   }
     77 protected:
     78   template <int Idx, typename U> static Use &OpFrom(const U *that) {
     79     return Idx < 0
     80       ? OperandTraits<U>::op_end(const_cast<U*>(that))[Idx]
     81       : OperandTraits<U>::op_begin(const_cast<U*>(that))[Idx];
     82   }
     83   template <int Idx> Use &Op() {
     84     return OpFrom<Idx>(this);
     85   }
     86   template <int Idx> const Use &Op() const {
     87     return OpFrom<Idx>(this);
     88   }
     89 public:
     90   Value *getOperand(unsigned i) const {
     91     assert(i < NumOperands && "getOperand() out of range!");
     92     return OperandList[i];
     93   }
     94   void setOperand(unsigned i, Value *Val) {
     95     assert(i < NumOperands && "setOperand() out of range!");
     96     assert((!isa<Constant>((const Value*)this) ||
     97             isa<GlobalValue>((const Value*)this)) &&
     98            "Cannot mutate a constant with setOperand!");
     99     OperandList[i] = Val;
    100   }
    101   const Use &getOperandUse(unsigned i) const {
    102     assert(i < NumOperands && "getOperandUse() out of range!");
    103     return OperandList[i];
    104   }
    105   Use &getOperandUse(unsigned i) {
    106     assert(i < NumOperands && "getOperandUse() out of range!");
    107     return OperandList[i];
    108   }
    109 
    110   unsigned getNumOperands() const { return NumOperands; }
    111 
    112   // ---------------------------------------------------------------------------
    113   // Operand Iterator interface...
    114   //
    115   typedef Use*       op_iterator;
    116   typedef const Use* const_op_iterator;
    117   typedef iterator_range<op_iterator> op_range;
    118   typedef iterator_range<const_op_iterator> const_op_range;
    119 
    120   inline op_iterator       op_begin()       { return OperandList; }
    121   inline const_op_iterator op_begin() const { return OperandList; }
    122   inline op_iterator       op_end()         { return OperandList+NumOperands; }
    123   inline const_op_iterator op_end()   const { return OperandList+NumOperands; }
    124   inline op_range operands() {
    125     return op_range(op_begin(), op_end());
    126   }
    127   inline const_op_range operands() const {
    128     return const_op_range(op_begin(), op_end());
    129   }
    130 
    131   /// Convenience iterator for directly iterating over the Values in the
    132   /// OperandList
    133   struct value_op_iterator
    134       : iterator_adaptor_base<value_op_iterator, op_iterator,
    135                               std::random_access_iterator_tag, Value *,
    136                               ptrdiff_t, Value *, Value *> {
    137     explicit value_op_iterator(Use *U = nullptr) : iterator_adaptor_base(U) {}
    138 
    139     Value *operator*() const { return *I; }
    140     Value *operator->() const { return operator*(); }
    141   };
    142 
    143   inline value_op_iterator value_op_begin() {
    144     return value_op_iterator(op_begin());
    145   }
    146   inline value_op_iterator value_op_end() {
    147     return value_op_iterator(op_end());
    148   }
    149   inline iterator_range<value_op_iterator> operand_values() {
    150     return iterator_range<value_op_iterator>(value_op_begin(), value_op_end());
    151   }
    152 
    153   // dropAllReferences() - This function is in charge of "letting go" of all
    154   // objects that this User refers to.  This allows one to
    155   // 'delete' a whole class at a time, even though there may be circular
    156   // references...  First all references are dropped, and all use counts go to
    157   // zero.  Then everything is deleted for real.  Note that no operations are
    158   // valid on an object that has "dropped all references", except operator
    159   // delete.
    160   //
    161   void dropAllReferences() {
    162     for (Use &U : operands())
    163       U.set(nullptr);
    164   }
    165 
    166   /// replaceUsesOfWith - Replaces all references to the "From" definition with
    167   /// references to the "To" definition.
    168   ///
    169   void replaceUsesOfWith(Value *From, Value *To);
    170 
    171   // Methods for support type inquiry through isa, cast, and dyn_cast:
    172   static inline bool classof(const Value *V) {
    173     return isa<Instruction>(V) || isa<Constant>(V);
    174   }
    175 };
    176 
    177 template<> struct simplify_type<User::op_iterator> {
    178   typedef Value* SimpleType;
    179   static SimpleType getSimplifiedValue(User::op_iterator &Val) {
    180     return Val->get();
    181   }
    182 };
    183 template<> struct simplify_type<User::const_op_iterator> {
    184   typedef /*const*/ Value* SimpleType;
    185   static SimpleType getSimplifiedValue(User::const_op_iterator &Val) {
    186     return Val->get();
    187   }
    188 };
    189 
    190 } // End llvm namespace
    191 
    192 #endif
    193