MachineJumpTableInfo.h revision 327952 
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 "llvm/Support/Printable.h"
24#include <cassert>
25#include <vector>
26
27namespace llvm {
28
29class MachineBasicBlock;
30class DataLayout;
31class raw_ostream;
32
33/// MachineJumpTableEntry - One jump table in the jump table info.
34///
35struct MachineJumpTableEntry {
36  /// MBBs - The vector of basic blocks from which to create the jump table.
37  std::vector<MachineBasicBlock*> MBBs;
38
39  explicit MachineJumpTableEntry(const std::vector<MachineBasicBlock*> &M)
40  : MBBs(M) {}
41};
42
43class MachineJumpTableInfo {
44public:
45  /// JTEntryKind - This enum indicates how each entry of the jump table is
46  /// represented and emitted.
47  enum JTEntryKind {
48    /// EK_BlockAddress - Each entry is a plain address of block, e.g.:
49    ///     .word LBB123
50    EK_BlockAddress,
51
52    /// EK_GPRel64BlockAddress - Each entry is an address of block, encoded
53    /// with a relocation as gp-relative, e.g.:
54    ///     .gpdword LBB123
55    EK_GPRel64BlockAddress,
56
57    /// EK_GPRel32BlockAddress - Each entry is an address of block, encoded
58    /// with a relocation as gp-relative, e.g.:
59    ///     .gprel32 LBB123
60    EK_GPRel32BlockAddress,
61
62    /// EK_LabelDifference32 - Each entry is the address of the block minus
63    /// the address of the jump table.  This is used for PIC jump tables where
64    /// gprel32 is not supported.  e.g.:
65    ///      .word LBB123 - LJTI1_2
66    /// If the .set directive is supported, this is emitted as:
67    ///      .set L4_5_set_123, LBB123 - LJTI1_2
68    ///      .word L4_5_set_123
69    EK_LabelDifference32,
70
71    /// EK_Inline - Jump table entries are emitted inline at their point of
72    /// use. It is the responsibility of the target to emit the entries.
73    EK_Inline,
74
75    /// EK_Custom32 - Each entry is a 32-bit value that is custom lowered by the
76    /// TargetLowering::LowerCustomJumpTableEntry hook.
77    EK_Custom32
78  };
79private:
80  JTEntryKind EntryKind;
81  std::vector<MachineJumpTableEntry> JumpTables;
82public:
83  explicit MachineJumpTableInfo(JTEntryKind Kind): EntryKind(Kind) {}
84
85  JTEntryKind getEntryKind() const { return EntryKind; }
86
87  /// getEntrySize - Return the size of each entry in the jump table.
88  unsigned getEntrySize(const DataLayout &TD) const;
89  /// getEntryAlignment - Return the alignment of each entry in the jump table.
90  unsigned getEntryAlignment(const DataLayout &TD) const;
91
92  /// createJumpTableIndex - Create a new jump table.
93  ///
94  unsigned createJumpTableIndex(const std::vector<MachineBasicBlock*> &DestBBs);
95
96  /// isEmpty - Return true if there are no jump tables.
97  ///
98  bool isEmpty() const { return JumpTables.empty(); }
99
100  const std::vector<MachineJumpTableEntry> &getJumpTables() const {
101    return JumpTables;
102  }
103
104  /// RemoveJumpTable - Mark the specific index as being dead.  This will
105  /// prevent it from being emitted.
106  void RemoveJumpTable(unsigned Idx) {
107    JumpTables[Idx].MBBs.clear();
108  }
109
110  /// ReplaceMBBInJumpTables - If Old is the target of any jump tables, update
111  /// the jump tables to branch to New instead.
112  bool ReplaceMBBInJumpTables(MachineBasicBlock *Old, MachineBasicBlock *New);
113
114  /// ReplaceMBBInJumpTable - If Old is a target of the jump tables, update
115  /// the jump table to branch to New instead.
116  bool ReplaceMBBInJumpTable(unsigned Idx, MachineBasicBlock *Old,
117                             MachineBasicBlock *New);
118
119  /// print - Used by the MachineFunction printer to print information about
120  /// jump tables.  Implemented in MachineFunction.cpp
121  ///
122  void print(raw_ostream &OS) const;
123
124  /// dump - Call to stderr.
125  ///
126  void dump() const;
127};
128
129
130/// Prints a jump table entry reference.
131///
132/// The format is:
133///   %jump-table.5       - a jump table entry with index == 5.
134///
135/// Usage: OS << printJumpTableEntryReference(Idx) << '\n';
136Printable printJumpTableEntryReference(unsigned Idx);
137
138} // End llvm namespace
139
140#endif
141