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 "llvm/MC/SectionKind.h"
21#include <cassert>
22#include <climits>
23#include <vector>
24
25namespace llvm {
26
27class Constant;
28class FoldingSetNodeID;
29class DataLayout;
30class TargetMachine;
31class Type;
32class MachineConstantPool;
33class raw_ostream;
34
35/// Abstract base class for all machine specific constantpool value subclasses.
36///
37class MachineConstantPoolValue {
38  virtual void anchor();
39  Type *Ty;
40
41public:
42  explicit MachineConstantPoolValue(Type *ty) : Ty(ty) {}
43  virtual ~MachineConstantPoolValue() {}
44
45  /// getType - get type of this MachineConstantPoolValue.
46  ///
47  Type *getType() const { return Ty; }
48
49  virtual int getExistingMachineCPValue(MachineConstantPool *CP,
50                                        unsigned Alignment) = 0;
51
52  virtual void addSelectionDAGCSEId(FoldingSetNodeID &ID) = 0;
53
54  /// print - Implement operator<<
55  virtual void print(raw_ostream &O) const = 0;
56};
57
58inline raw_ostream &operator<<(raw_ostream &OS,
59                               const MachineConstantPoolValue &V) {
60  V.print(OS);
61  return OS;
62}
63
64/// This class is a data container for one entry in a MachineConstantPool.
65/// It contains a pointer to the value and an offset from the start of
66/// the constant pool.
67/// @brief An entry in a MachineConstantPool
68class MachineConstantPoolEntry {
69public:
70  /// The constant itself.
71  union {
72    const Constant *ConstVal;
73    MachineConstantPoolValue *MachineCPVal;
74  } Val;
75
76  /// The required alignment for this entry. The top bit is set when Val is
77  /// a target specific MachineConstantPoolValue.
78  unsigned Alignment;
79
80  MachineConstantPoolEntry(const Constant *V, unsigned A)
81    : Alignment(A) {
82    Val.ConstVal = V;
83  }
84  MachineConstantPoolEntry(MachineConstantPoolValue *V, unsigned A)
85      : Alignment(A) {
86    Val.MachineCPVal = V;
87    Alignment |= 1U << (sizeof(unsigned) * CHAR_BIT - 1);
88  }
89
90  /// isMachineConstantPoolEntry - Return true if the MachineConstantPoolEntry
91  /// is indeed a target specific constantpool entry, not a wrapper over a
92  /// Constant.
93  bool isMachineConstantPoolEntry() const {
94    return (int)Alignment < 0;
95  }
96
97  int getAlignment() const {
98    return Alignment & ~(1 << (sizeof(unsigned) * CHAR_BIT - 1));
99  }
100
101  Type *getType() const;
102
103  /// This method classifies the entry according to whether or not it may
104  /// generate a relocation entry.  This must be conservative, so if it might
105  /// codegen to a relocatable entry, it should say so.
106  bool needsRelocation() const;
107
108  SectionKind getSectionKind(const DataLayout *DL) const;
109};
110
111/// The MachineConstantPool class keeps track of constants referenced by a
112/// function which must be spilled to memory.  This is used for constants which
113/// are unable to be used directly as operands to instructions, which typically
114/// include floating point and large integer constants.
115///
116/// Instructions reference the address of these constant pool constants through
117/// the use of MO_ConstantPoolIndex values.  When emitting assembly or machine
118/// code, these virtual address references are converted to refer to the
119/// address of the function constant pool values.
120/// @brief The machine constant pool.
121class MachineConstantPool {
122  unsigned PoolAlignment;       ///< The alignment for the pool.
123  std::vector<MachineConstantPoolEntry> Constants; ///< The pool of constants.
124  /// MachineConstantPoolValues that use an existing MachineConstantPoolEntry.
125  DenseSet<MachineConstantPoolValue*> MachineCPVsSharingEntries;
126  const DataLayout &DL;
127
128  const DataLayout &getDataLayout() const { return DL; }
129
130public:
131  /// @brief The only constructor.
132  explicit MachineConstantPool(const DataLayout &DL)
133      : PoolAlignment(1), DL(DL) {}
134  ~MachineConstantPool();
135
136  /// getConstantPoolAlignment - Return the alignment required by
137  /// the whole constant pool, of which the first element must be aligned.
138  unsigned getConstantPoolAlignment() const { return PoolAlignment; }
139
140  /// getConstantPoolIndex - Create a new entry in the constant pool or return
141  /// an existing one.  User must specify the minimum required alignment for
142  /// the object.
143  unsigned getConstantPoolIndex(const Constant *C, unsigned Alignment);
144  unsigned getConstantPoolIndex(MachineConstantPoolValue *V,
145                                unsigned Alignment);
146
147  /// isEmpty - Return true if this constant pool contains no constants.
148  bool isEmpty() const { return Constants.empty(); }
149
150  const std::vector<MachineConstantPoolEntry> &getConstants() const {
151    return Constants;
152  }
153
154  /// print - Used by the MachineFunction printer to print information about
155  /// constant pool objects.  Implemented in MachineFunction.cpp
156  ///
157  void print(raw_ostream &OS) const;
158
159  /// dump - Call print(cerr) to be called from the debugger.
160  void dump() const;
161};
162
163} // End llvm namespace
164
165#endif
166