1//===-- CodeGen/MachineJumpTableInfo.h - Abstract Jump Tables  --*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// The MachineJumpTableInfo class keeps track of jump tables referenced by
10// lowered switch instructions in the MachineFunction.
11//
12// Instructions reference the address of these jump tables through the use of
13// MO_JumpTableIndex values.  When emitting assembly or machine code, these
14// virtual address references are converted to refer to the address of the
15// function jump tables.
16//
17//===----------------------------------------------------------------------===//
18
19#ifndef LLVM_CODEGEN_MACHINEJUMPTABLEINFO_H
20#define LLVM_CODEGEN_MACHINEJUMPTABLEINFO_H
21
22#include "llvm/Support/Printable.h"
23#include <cassert>
24#include <vector>
25
26namespace llvm {
27
28class MachineBasicBlock;
29class DataLayout;
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_GPRel64BlockAddress - Each entry is an address of block, encoded
52    /// with a relocation as gp-relative, e.g.:
53    ///     .gpdword LBB123
54    EK_GPRel64BlockAddress,
55
56    /// EK_GPRel32BlockAddress - Each entry is an address of block, encoded
57    /// with a relocation as gp-relative, e.g.:
58    ///     .gprel32 LBB123
59    EK_GPRel32BlockAddress,
60
61    /// EK_LabelDifference32 - Each entry is the address of the block minus
62    /// the address of the jump table.  This is used for PIC jump tables where
63    /// gprel32 is not supported.  e.g.:
64    ///      .word LBB123 - LJTI1_2
65    /// If the .set directive is supported, this is emitted as:
66    ///      .set L4_5_set_123, LBB123 - LJTI1_2
67    ///      .word L4_5_set_123
68    EK_LabelDifference32,
69
70    /// EK_Inline - Jump table entries are emitted inline at their point of
71    /// use. It is the responsibility of the target to emit the entries.
72    EK_Inline,
73
74    /// EK_Custom32 - Each entry is a 32-bit value that is custom lowered by the
75    /// TargetLowering::LowerCustomJumpTableEntry hook.
76    EK_Custom32
77  };
78private:
79  JTEntryKind EntryKind;
80  std::vector<MachineJumpTableEntry> JumpTables;
81public:
82  explicit MachineJumpTableInfo(JTEntryKind Kind): EntryKind(Kind) {}
83
84  JTEntryKind getEntryKind() const { return EntryKind; }
85
86  /// getEntrySize - Return the size of each entry in the jump table.
87  unsigned getEntrySize(const DataLayout &TD) const;
88  /// getEntryAlignment - Return the alignment of each entry in the jump table.
89  unsigned getEntryAlignment(const DataLayout &TD) const;
90
91  /// createJumpTableIndex - Create a new jump table.
92  ///
93  unsigned createJumpTableIndex(const std::vector<MachineBasicBlock*> &DestBBs);
94
95  /// isEmpty - Return true if there are no jump tables.
96  ///
97  bool isEmpty() const { return JumpTables.empty(); }
98
99  const std::vector<MachineJumpTableEntry> &getJumpTables() const {
100    return JumpTables;
101  }
102
103  /// RemoveJumpTable - Mark the specific index as being dead.  This will
104  /// prevent it from being emitted.
105  void RemoveJumpTable(unsigned Idx) {
106    JumpTables[Idx].MBBs.clear();
107  }
108
109  /// ReplaceMBBInJumpTables - If Old is the target of any jump tables, update
110  /// the jump tables to branch to New instead.
111  bool ReplaceMBBInJumpTables(MachineBasicBlock *Old, MachineBasicBlock *New);
112
113  /// ReplaceMBBInJumpTable - If Old is a target of the jump tables, update
114  /// the jump table to branch to New instead.
115  bool ReplaceMBBInJumpTable(unsigned Idx, MachineBasicBlock *Old,
116                             MachineBasicBlock *New);
117
118  /// print - Used by the MachineFunction printer to print information about
119  /// jump tables.  Implemented in MachineFunction.cpp
120  ///
121  void print(raw_ostream &OS) const;
122
123  /// dump - Call to stderr.
124  ///
125  void dump() const;
126};
127
128
129/// Prints a jump table entry reference.
130///
131/// The format is:
132///   %jump-table.5       - a jump table entry with index == 5.
133///
134/// Usage: OS << printJumpTableEntryReference(Idx) << '\n';
135Printable printJumpTableEntryReference(unsigned Idx);
136
137} // End llvm namespace
138
139#endif
140