MachineConstantPool.h revision 62ca32540f950d500227f1863b95cd08ad28099e 
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 This file declares the MachineConstantPool class which is an abstract
11/// constant pool to keep track of constants referenced by a function.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_CODEGEN_MACHINECONSTANTPOOL_H
16#define LLVM_CODEGEN_MACHINECONSTANTPOOL_H
17
18#include "llvm/ADT/FoldingSet.h"
19#include <cassert>
20#include <vector>
21
22namespace llvm {
23
24class AsmPrinter;
25class Constant;
26class TargetData;
27class TargetMachine;
28class Type;
29class MachineConstantPool;
30class raw_ostream;
31
32/// Abstract base class for all machine specific constantpool value subclasses.
33///
34class MachineConstantPoolValue {
35  const Type *Ty;
36
37public:
38  explicit MachineConstantPoolValue(const Type *ty) : Ty(ty) {}
39  virtual ~MachineConstantPoolValue() {}
40
41  /// getType - get type of this MachineConstantPoolValue.
42  ///
43  inline const Type *getType() const { return Ty; }
44
45  virtual int getExistingMachineCPValue(MachineConstantPool *CP,
46                                        unsigned Alignment) = 0;
47
48  virtual void AddSelectionDAGCSEId(FoldingSetNodeID &ID) = 0;
49
50  /// print - Implement operator<<
51  virtual void print(raw_ostream &O) const = 0;
52};
53
54inline raw_ostream &operator<<(raw_ostream &OS,
55                               const MachineConstantPoolValue &V) {
56  V.print(OS);
57  return OS;
58}
59
60
61/// This class is a data container for one entry in a MachineConstantPool.
62/// It contains a pointer to the value and an offset from the start of
63/// the constant pool.
64/// @brief An entry in a MachineConstantPool
65class MachineConstantPoolEntry {
66public:
67  /// The constant itself.
68  union {
69    Constant *ConstVal;
70    MachineConstantPoolValue *MachineCPVal;
71  } Val;
72
73  /// The offset of the constant from the start of the pool. The top bit is set
74  /// when Val is a MachineConstantPoolValue.
75  unsigned Offset;
76
77  MachineConstantPoolEntry(Constant *V, unsigned O)
78    : Offset(O) {
79    assert((int)Offset >= 0 && "Offset is too large");
80    Val.ConstVal = V;
81  }
82  MachineConstantPoolEntry(MachineConstantPoolValue *V, unsigned O)
83    : Offset(O){
84    assert((int)Offset >= 0 && "Offset is too large");
85    Val.MachineCPVal = V;
86    Offset |= 1 << (sizeof(unsigned)*8-1);
87  }
88
89  bool isMachineConstantPoolEntry() const {
90    return (int)Offset < 0;
91  }
92
93  int getOffset() const {
94    return Offset & ~(1 << (sizeof(unsigned)*8-1));
95  }
96
97  const Type *getType() const;
98};
99
100/// The MachineConstantPool class keeps track of constants referenced by a
101/// function which must be spilled to memory.  This is used for constants which
102/// are unable to be used directly as operands to instructions, which typically
103/// include floating point and large integer constants.
104///
105/// Instructions reference the address of these constant pool constants through
106/// the use of MO_ConstantPoolIndex values.  When emitting assembly or machine
107/// code, these virtual address references are converted to refer to the
108/// address of the function constant pool values.
109/// @brief The machine constant pool.
110class MachineConstantPool {
111  const TargetData *TD;   ///< The machine's TargetData.
112  unsigned PoolAlignment; ///< The alignment for the pool.
113  std::vector<MachineConstantPoolEntry> Constants; ///< The pool of constants.
114public:
115  /// @brief The only constructor.
116  explicit MachineConstantPool(const TargetData *td)
117    : TD(td), PoolAlignment(1) {}
118  ~MachineConstantPool();
119
120  /// getConstantPoolAlignment - Return the log2 of the alignment required by
121  /// the whole constant pool, of which the first element must be aligned.
122  unsigned getConstantPoolAlignment() const { return PoolAlignment; }
123
124  /// getConstantPoolIndex - Create a new entry in the constant pool or return
125  /// an existing one.  User must specify an alignment in bytes for the object.
126  unsigned getConstantPoolIndex(Constant *C, unsigned Alignment);
127  unsigned getConstantPoolIndex(MachineConstantPoolValue *V,unsigned Alignment);
128
129  /// isEmpty - Return true if this constant pool contains no constants.
130  bool isEmpty() const { return Constants.empty(); }
131
132  const std::vector<MachineConstantPoolEntry> &getConstants() const {
133    return Constants;
134  }
135
136  /// print - Used by the MachineFunction printer to print information about
137  /// constant pool objects.  Implemented in MachineFunction.cpp
138  ///
139  void print(raw_ostream &OS) const;
140
141  /// dump - Call print(cerr) to be called from the debugger.
142  void dump() const;
143};
144
145} // End llvm namespace
146
147#endif
148