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_LabelDifference64 - Each entry is the address of the block minus
71 /// the address of the jump table. This is used for PIC jump tables where
72 /// gprel64 is not supported. e.g.:
73 /// .quad LBB123 - LJTI1_2
74 EK_LabelDifference64,
75
76 /// EK_Inline - Jump table entries are emitted inline at their point of
77 /// use. It is the responsibility of the target to emit the entries.
78 EK_Inline,
79
80 /// EK_Custom32 - Each entry is a 32-bit value that is custom lowered by the
81 /// TargetLowering::LowerCustomJumpTableEntry hook.
82 EK_Custom32
83 };
84
85private:
86 JTEntryKind EntryKind;
87 std::vector<MachineJumpTableEntry> JumpTables;
88public:
89 explicit MachineJumpTableInfo(JTEntryKind Kind): EntryKind(Kind) {}
90
91 JTEntryKind getEntryKind() const { return EntryKind; }
92
93 /// getEntrySize - Return the size of each entry in the jump table.
94 unsigned getEntrySize(const DataLayout &TD) const;
95 /// getEntryAlignment - Return the alignment of each entry in the jump table.
96 unsigned getEntryAlignment(const DataLayout &TD) const;
97
98 /// createJumpTableIndex - Create a new jump table.
99 ///
100 unsigned createJumpTableIndex(const std::vector<MachineBasicBlock*> &DestBBs);
101
102 /// isEmpty - Return true if there are no jump tables.
103 ///
104 bool isEmpty() const { return JumpTables.empty(); }
105
106 const std::vector<MachineJumpTableEntry> &getJumpTables() const {
107 return JumpTables;
108 }
109
110 /// RemoveJumpTable - Mark the specific index as being dead. This will
111 /// prevent it from being emitted.
112 void RemoveJumpTable(unsigned Idx) {
113 JumpTables[Idx].MBBs.clear();
114 }
115
116 /// RemoveMBBFromJumpTables - If MBB is present in any jump tables, remove it.
117 bool RemoveMBBFromJumpTables(MachineBasicBlock *MBB);
118
119 /// ReplaceMBBInJumpTables - If Old is the target of any jump tables, update
120 /// the jump tables to branch to New instead.
121 bool ReplaceMBBInJumpTables(MachineBasicBlock *Old, MachineBasicBlock *New);
122
123 /// ReplaceMBBInJumpTable - If Old is a target of the jump tables, update
124 /// the jump table to branch to New instead.
125 bool ReplaceMBBInJumpTable(unsigned Idx, MachineBasicBlock *Old,
126 MachineBasicBlock *New);
127
128 /// print - Used by the MachineFunction printer to print information about
129 /// jump tables. Implemented in MachineFunction.cpp
130 ///
131 void print(raw_ostream &OS) const;
132
133 /// dump - Call to stderr.
134 ///
135 void dump() const;
136};
137
138
139/// Prints a jump table entry reference.
140///
141/// The format is:
142/// %jump-table.5 - a jump table entry with index == 5.
143///
144/// Usage: OS << printJumpTableEntryReference(Idx) << '\n';
145Printable printJumpTableEntryReference(unsigned Idx);
146
147} // End llvm namespace
148
149#endif
150