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 /// RemoveMBBFromJumpTables - If MBB is present in any jump tables, remove it.
110 bool RemoveMBBFromJumpTables(MachineBasicBlock *MBB);
111
112 /// ReplaceMBBInJumpTables - If Old is the target of any jump tables, update
113 /// the jump tables to branch to New instead.
114 bool ReplaceMBBInJumpTables(MachineBasicBlock *Old, MachineBasicBlock *New);
115
116 /// ReplaceMBBInJumpTable - If Old is a target of the jump tables, update
117 /// the jump table to branch to New instead.
118 bool ReplaceMBBInJumpTable(unsigned Idx, MachineBasicBlock *Old,
119 MachineBasicBlock *New);
120
121 /// print - Used by the MachineFunction printer to print information about
122 /// jump tables. Implemented in MachineFunction.cpp
123 ///
124 void print(raw_ostream &OS) const;
125
126 /// dump - Call to stderr.
127 ///
128 void dump() const;
129};
130
131
132/// Prints a jump table entry reference.
133///
134/// The format is:
135/// %jump-table.5 - a jump table entry with index == 5.
136///
137/// Usage: OS << printJumpTableEntryReference(Idx) << '\n';
138Printable printJumpTableEntryReference(unsigned Idx);
139
140} // End llvm namespace
141
142#endif
143