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 26 namespace llvm { 27 28 class MachineBasicBlock; 29 class DataLayout; 30 class raw_ostream; 31 32 /// MachineJumpTableEntry - One jump table in the jump table info. 33 /// 34 struct MachineJumpTableEntry { 35 /// MBBs - The vector of basic blocks from which to create the jump table. 36 std::vector<MachineBasicBlock*> MBBs; 37 MachineJumpTableEntryMachineJumpTableEntry38 explicit MachineJumpTableEntry(const std::vector<MachineBasicBlock*> &M) 39 : MBBs(M) {} 40 }; 41 42 class MachineJumpTableInfo { 43 public: 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 85 private: 86 JTEntryKind EntryKind; 87 std::vector<MachineJumpTableEntry> JumpTables; 88 public: MachineJumpTableInfo(JTEntryKind Kind)89 explicit MachineJumpTableInfo(JTEntryKind Kind): EntryKind(Kind) {} 90 getEntryKind()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 /// isEmpty()104 bool isEmpty() const { return JumpTables.empty(); } 105 getJumpTables()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. RemoveJumpTable(unsigned Idx)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'; 145 Printable printJumpTableEntryReference(unsigned Idx); 146 147 } // End llvm namespace 148 149 #endif 150