MachineJumpTableInfo.h revision 203954 
1//===-- CodeGen/MachineJumpTableInfo.h - Abstract Jump Tables  --*- 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// The MachineJumpTableInfo class keeps track of jump tables referenced by
11// lowered switch instructions in the MachineFunction.
12//
13// Instructions reference the address of these jump tables through the use of
14// MO_JumpTableIndex values.  When emitting assembly or machine code, these
15// virtual address references are converted to refer to the address of the
16// function jump tables.
17//
18//===----------------------------------------------------------------------===//
19
20#ifndef LLVM_CODEGEN_MACHINEJUMPTABLEINFO_H
21#define LLVM_CODEGEN_MACHINEJUMPTABLEINFO_H
22
23#include <vector>
24#include <cassert>
25
26namespace llvm {
27
28class MachineBasicBlock;
29class TargetData;
30class raw_ostream;
31
32/// MachineJumpTableEntry - One jump table in the jump table info.
33///
34struct MachineJumpTableEntry {
35  /// MBBs - The vector of basic blocks from which to create the jump table.
36  std::vector<MachineBasicBlock*> MBBs;
37
38  explicit MachineJumpTableEntry(const std::vector<MachineBasicBlock*> &M)
39  : MBBs(M) {}
40};
41
42class MachineJumpTableInfo {
43public:
44  /// JTEntryKind - This enum indicates how each entry of the jump table is
45  /// represented and emitted.
46  enum JTEntryKind {
47    /// EK_BlockAddress - Each entry is a plain address of block, e.g.:
48    ///     .word LBB123
49    EK_BlockAddress,
50
51    /// EK_GPRel32BlockAddress - Each entry is an address of block, encoded
52    /// with a relocation as gp-relative, e.g.:
53    ///     .gprel32 LBB123
54    EK_GPRel32BlockAddress,
55
56    /// EK_LabelDifference32 - Each entry is the address of the block minus
57    /// the address of the jump table.  This is used for PIC jump tables where
58    /// gprel32 is not supported.  e.g.:
59    ///      .word LBB123 - LJTI1_2
60    /// If the .set directive is supported, this is emitted as:
61    ///      .set L4_5_set_123, LBB123 - LJTI1_2
62    ///      .word L4_5_set_123
63    EK_LabelDifference32,
64
65    /// EK_Custom32 - Each entry is a 32-bit value that is custom lowered by the
66    /// TargetLowering::LowerCustomJumpTableEntry hook.
67    EK_Custom32
68  };
69private:
70  JTEntryKind EntryKind;
71  std::vector<MachineJumpTableEntry> JumpTables;
72public:
73  MachineJumpTableInfo(JTEntryKind Kind): EntryKind(Kind) {}
74
75  JTEntryKind getEntryKind() const { return EntryKind; }
76
77  /// getEntrySize - Return the size of each entry in the jump table.
78  unsigned getEntrySize(const TargetData &TD) const;
79  /// getEntryAlignment - Return the alignment of each entry in the jump table.
80  unsigned getEntryAlignment(const TargetData &TD) const;
81
82  /// getJumpTableIndex - Create a new jump table or return an existing one.
83  ///
84  unsigned getJumpTableIndex(const std::vector<MachineBasicBlock*> &DestBBs);
85
86  /// isEmpty - Return true if there are no jump tables.
87  ///
88  bool isEmpty() const { return JumpTables.empty(); }
89
90  const std::vector<MachineJumpTableEntry> &getJumpTables() const {
91    return JumpTables;
92  }
93
94  /// RemoveJumpTable - Mark the specific index as being dead.  This will
95  /// prevent it from being emitted.
96  void RemoveJumpTable(unsigned Idx) {
97    JumpTables[Idx].MBBs.clear();
98  }
99
100  /// ReplaceMBBInJumpTables - If Old is the target of any jump tables, update
101  /// the jump tables to branch to New instead.
102  bool ReplaceMBBInJumpTables(MachineBasicBlock *Old, MachineBasicBlock *New);
103
104  /// ReplaceMBBInJumpTable - If Old is a target of the jump tables, update
105  /// the jump table to branch to New instead.
106  bool ReplaceMBBInJumpTable(unsigned Idx, MachineBasicBlock *Old,
107                             MachineBasicBlock *New);
108
109  /// print - Used by the MachineFunction printer to print information about
110  /// jump tables.  Implemented in MachineFunction.cpp
111  ///
112  void print(raw_ostream &OS) const;
113
114  /// dump - Call to stderr.
115  ///
116  void dump() const;
117};
118
119} // End llvm namespace
120
121#endif
122