1 //===-- CodeGen/MachineConstantPool.h - Abstract Constant Pool --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 /// This file declares the MachineConstantPool class which is an abstract
12 /// constant pool to keep track of constants referenced by a function.
14 //===----------------------------------------------------------------------===//
16 #ifndef LLVM_CODEGEN_MACHINECONSTANTPOOL_H
17 #define LLVM_CODEGEN_MACHINECONSTANTPOOL_H
19 #include "llvm/ADT/DenseSet.h"
27 class FoldingSetNodeID;
31 class MachineConstantPool;
34 /// Abstract base class for all machine specific constantpool value subclasses.
36 class MachineConstantPoolValue {
37 virtual void anchor();
41 explicit MachineConstantPoolValue(Type *ty) : Ty(ty) {}
42 virtual ~MachineConstantPoolValue() {}
44 /// getType - get type of this MachineConstantPoolValue.
46 Type *getType() const { return Ty; }
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;
55 virtual int getExistingMachineCPValue(MachineConstantPool *CP,
56 unsigned Alignment) = 0;
58 virtual void addSelectionDAGCSEId(FoldingSetNodeID &ID) = 0;
60 /// print - Implement operator<<
61 virtual void print(raw_ostream &O) const = 0;
64 inline raw_ostream &operator<<(raw_ostream &OS,
65 const MachineConstantPoolValue &V) {
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 {
77 /// The constant itself.
79 const Constant *ConstVal;
80 MachineConstantPoolValue *MachineCPVal;
83 /// The required alignment for this entry. The top bit is set when Val is
84 /// a target specific MachineConstantPoolValue.
87 MachineConstantPoolEntry(const Constant *V, unsigned A)
91 MachineConstantPoolEntry(MachineConstantPoolValue *V, unsigned A)
94 Alignment |= 1U << (sizeof(unsigned)*CHAR_BIT-1);
97 /// isMachineConstantPoolEntry - Return true if the MachineConstantPoolEntry
98 /// is indeed a target specific constantpool entry, not a wrapper over a
100 bool isMachineConstantPoolEntry() const {
101 return (int)Alignment < 0;
104 int getAlignment() const {
105 return Alignment & ~(1 << (sizeof(unsigned)*CHAR_BIT-1));
108 Type *getType() const;
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:
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
120 /// 2: This entry may have arbitrary relocations.
121 unsigned getRelocationInfo() const;
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.
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 DataLayout *TD; ///< The machine's DataLayout.
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;
141 /// @brief The only constructor.
142 explicit MachineConstantPool(const DataLayout *td)
143 : TD(td), PoolAlignment(1) {}
144 ~MachineConstantPool();
146 /// getConstantPoolAlignment - Return the alignment required by
147 /// the whole constant pool, of which the first element must be aligned.
148 unsigned getConstantPoolAlignment() const { return PoolAlignment; }
150 /// getConstantPoolIndex - Create a new entry in the constant pool or return
151 /// an existing one. User must specify the minimum required alignment for
153 unsigned getConstantPoolIndex(const Constant *C, unsigned Alignment);
154 unsigned getConstantPoolIndex(MachineConstantPoolValue *V,unsigned Alignment);
156 /// isEmpty - Return true if this constant pool contains no constants.
157 bool isEmpty() const { return Constants.empty(); }
159 const std::vector<MachineConstantPoolEntry> &getConstants() const {
163 /// print - Used by the MachineFunction printer to print information about
164 /// constant pool objects. Implemented in MachineFunction.cpp
166 void print(raw_ostream &OS) const;
168 /// dump - Call print(cerr) to be called from the debugger.
172 } // End llvm namespace