1 //===-- CodeGen/MachineConstantPool.h - Abstract Constant Pool --*- 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 /// @file 11 /// This file declares the MachineConstantPool class which is an abstract 12 /// constant pool to keep track of constants referenced by a function. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #ifndef LLVM_CODEGEN_MACHINECONSTANTPOOL_H 17 #define LLVM_CODEGEN_MACHINECONSTANTPOOL_H 18 19 #include "llvm/ADT/DenseSet.h" 20 #include <cassert> 21 #include <climits> 22 #include <vector> 23 24 namespace llvm { 25 26 class Constant; 27 class FoldingSetNodeID; 28 class DataLayout; 29 class TargetMachine; 30 class Type; 31 class MachineConstantPool; 32 class raw_ostream; 33 34 /// Abstract base class for all machine specific constantpool value subclasses. 35 /// 36 class MachineConstantPoolValue { 37 virtual void anchor(); 38 Type *Ty; 39 40 public: 41 explicit MachineConstantPoolValue(Type *ty) : Ty(ty) {} 42 virtual ~MachineConstantPoolValue() {} 43 44 /// getType - get type of this MachineConstantPoolValue. 45 /// 46 Type *getType() const { return Ty; } 47 48 49 /// getRelocationInfo - This method classifies the entry according to 50 /// whether or not it may generate a relocation entry. This must be 51 /// conservative, so if it might codegen to a relocatable entry, it should say 52 /// so. The return values are the same as Constant::getRelocationInfo(). 53 virtual unsigned getRelocationInfo() const = 0; 54 55 virtual int getExistingMachineCPValue(MachineConstantPool *CP, 56 unsigned Alignment) = 0; 57 58 virtual void addSelectionDAGCSEId(FoldingSetNodeID &ID) = 0; 59 60 /// print - Implement operator<< 61 virtual void print(raw_ostream &O) const = 0; 62 }; 63 64 inline raw_ostream &operator<<(raw_ostream &OS, 65 const MachineConstantPoolValue &V) { 66 V.print(OS); 67 return OS; 68 } 69 70 71 /// This class is a data container for one entry in a MachineConstantPool. 72 /// It contains a pointer to the value and an offset from the start of 73 /// the constant pool. 74 /// @brief An entry in a MachineConstantPool 75 class MachineConstantPoolEntry { 76 public: 77 /// The constant itself. 78 union { 79 const Constant *ConstVal; 80 MachineConstantPoolValue *MachineCPVal; 81 } Val; 82 83 /// The required alignment for this entry. The top bit is set when Val is 84 /// a target specific MachineConstantPoolValue. 85 unsigned Alignment; 86 87 MachineConstantPoolEntry(const Constant *V, unsigned A) 88 : Alignment(A) { 89 Val.ConstVal = V; 90 } 91 MachineConstantPoolEntry(MachineConstantPoolValue *V, unsigned A) 92 : Alignment(A) { 93 Val.MachineCPVal = V; 94 Alignment |= 1U << (sizeof(unsigned)*CHAR_BIT-1); 95 } 96 97 /// isMachineConstantPoolEntry - Return true if the MachineConstantPoolEntry 98 /// is indeed a target specific constantpool entry, not a wrapper over a 99 /// Constant. 100 bool isMachineConstantPoolEntry() const { 101 return (int)Alignment < 0; 102 } 103 104 int getAlignment() const { 105 return Alignment & ~(1 << (sizeof(unsigned)*CHAR_BIT-1)); 106 } 107 108 Type *getType() const; 109 110 /// getRelocationInfo - This method classifies the entry according to 111 /// whether or not it may generate a relocation entry. This must be 112 /// conservative, so if it might codegen to a relocatable entry, it should say 113 /// so. The return values are: 114 /// 115 /// 0: This constant pool entry is guaranteed to never have a relocation 116 /// applied to it (because it holds a simple constant like '4'). 117 /// 1: This entry has relocations, but the entries are guaranteed to be 118 /// resolvable by the static linker, so the dynamic linker will never see 119 /// them. 120 /// 2: This entry may have arbitrary relocations. 121 unsigned getRelocationInfo() const; 122 }; 123 124 /// The MachineConstantPool class keeps track of constants referenced by a 125 /// function which must be spilled to memory. This is used for constants which 126 /// are unable to be used directly as operands to instructions, which typically 127 /// include floating point and large integer constants. 128 /// 129 /// Instructions reference the address of these constant pool constants through 130 /// the use of MO_ConstantPoolIndex values. When emitting assembly or machine 131 /// code, these virtual address references are converted to refer to the 132 /// address of the function constant pool values. 133 /// @brief The machine constant pool. 134 class MachineConstantPool { 135 const TargetMachine &TM; ///< The target machine. 136 unsigned PoolAlignment; ///< The alignment for the pool. 137 std::vector<MachineConstantPoolEntry> Constants; ///< The pool of constants. 138 /// MachineConstantPoolValues that use an existing MachineConstantPoolEntry. 139 DenseSet<MachineConstantPoolValue*> MachineCPVsSharingEntries; 140 141 const DataLayout *getDataLayout() const; 142 public: 143 /// @brief The only constructor. 144 explicit MachineConstantPool(const TargetMachine &TM) 145 : TM(TM), PoolAlignment(1) {} 146 ~MachineConstantPool(); 147 148 /// getConstantPoolAlignment - Return the alignment required by 149 /// the whole constant pool, of which the first element must be aligned. 150 unsigned getConstantPoolAlignment() const { return PoolAlignment; } 151 152 /// getConstantPoolIndex - Create a new entry in the constant pool or return 153 /// an existing one. User must specify the minimum required alignment for 154 /// the object. 155 unsigned getConstantPoolIndex(const Constant *C, unsigned Alignment); 156 unsigned getConstantPoolIndex(MachineConstantPoolValue *V,unsigned Alignment); 157 158 /// isEmpty - Return true if this constant pool contains no constants. 159 bool isEmpty() const { return Constants.empty(); } 160 161 const std::vector<MachineConstantPoolEntry> &getConstants() const { 162 return Constants; 163 } 164 165 /// print - Used by the MachineFunction printer to print information about 166 /// constant pool objects. Implemented in MachineFunction.cpp 167 /// 168 void print(raw_ostream &OS) const; 169 170 /// dump - Call print(cerr) to be called from the debugger. 171 void dump() const; 172 }; 173 174 } // End llvm namespace 175 176 #endif 177
