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