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 enum class MachineFunctionDataHotness; 32 33 /// MachineJumpTableEntry - One jump table in the jump table info. 34 /// 35 struct MachineJumpTableEntry { 36 /// MBBs - The vector of basic blocks from which to create the jump table. 37 std::vector<MachineBasicBlock*> MBBs; 38 39 /// The hotness of MJTE is inferred from the hotness of the source basic 40 /// block(s) that reference it. 41 MachineFunctionDataHotness Hotness; 42 43 explicit MachineJumpTableEntry(const std::vector<MachineBasicBlock *> &M); 44 }; 45 46 class MachineJumpTableInfo { 47 public: 48 /// JTEntryKind - This enum indicates how each entry of the jump table is 49 /// represented and emitted. 50 enum JTEntryKind { 51 /// EK_BlockAddress - Each entry is a plain address of block, e.g.: 52 /// .word LBB123 53 EK_BlockAddress, 54 55 /// EK_GPRel64BlockAddress - Each entry is an address of block, encoded 56 /// with a relocation as gp-relative, e.g.: 57 /// .gpdword LBB123 58 EK_GPRel64BlockAddress, 59 60 /// EK_GPRel32BlockAddress - Each entry is an address of block, encoded 61 /// with a relocation as gp-relative, e.g.: 62 /// .gprel32 LBB123 63 EK_GPRel32BlockAddress, 64 65 /// EK_LabelDifference32 - Each entry is the address of the block minus 66 /// the address of the jump table. This is used for PIC jump tables where 67 /// gprel32 is not supported. e.g.: 68 /// .word LBB123 - LJTI1_2 69 /// If the .set directive is supported, this is emitted as: 70 /// .set L4_5_set_123, LBB123 - LJTI1_2 71 /// .word L4_5_set_123 72 EK_LabelDifference32, 73 74 /// EK_LabelDifference64 - Each entry is the address of the block minus 75 /// the address of the jump table. This is used for PIC jump tables where 76 /// gprel64 is not supported. e.g.: 77 /// .quad LBB123 - LJTI1_2 78 EK_LabelDifference64, 79 80 /// EK_Inline - Jump table entries are emitted inline at their point of 81 /// use. It is the responsibility of the target to emit the entries. 82 EK_Inline, 83 84 /// EK_Custom32 - Each entry is a 32-bit value that is custom lowered by the 85 /// TargetLowering::LowerCustomJumpTableEntry hook. 86 EK_Custom32 87 }; 88 89 private: 90 JTEntryKind EntryKind; 91 std::vector<MachineJumpTableEntry> JumpTables; 92 public: 93 explicit MachineJumpTableInfo(JTEntryKind Kind): EntryKind(Kind) {} 94 95 JTEntryKind getEntryKind() const { return EntryKind; } 96 97 /// getEntrySize - Return the size of each entry in the jump table. 98 unsigned getEntrySize(const DataLayout &TD) const; 99 /// getEntryAlignment - Return the alignment of each entry in the jump table. 100 unsigned getEntryAlignment(const DataLayout &TD) const; 101 102 /// createJumpTableIndex - Create a new jump table. 103 /// 104 unsigned createJumpTableIndex(const std::vector<MachineBasicBlock*> &DestBBs); 105 106 /// isEmpty - Return true if there are no jump tables. 107 /// 108 bool isEmpty() const { return JumpTables.empty(); } 109 110 const std::vector<MachineJumpTableEntry> &getJumpTables() const { 111 return JumpTables; 112 } 113 114 // Update machine jump table entry's hotness. Return true if the hotness is 115 // updated. 116 bool updateJumpTableEntryHotness(size_t JTI, 117 MachineFunctionDataHotness Hotness); 118 119 /// RemoveJumpTable - Mark the specific index as being dead. This will 120 /// prevent it from being emitted. 121 void RemoveJumpTable(unsigned Idx) { 122 JumpTables[Idx].MBBs.clear(); 123 } 124 125 /// RemoveMBBFromJumpTables - If MBB is present in any jump tables, remove it. 126 bool RemoveMBBFromJumpTables(MachineBasicBlock *MBB); 127 128 /// ReplaceMBBInJumpTables - If Old is the target of any jump tables, update 129 /// the jump tables to branch to New instead. 130 bool ReplaceMBBInJumpTables(MachineBasicBlock *Old, MachineBasicBlock *New); 131 132 /// ReplaceMBBInJumpTable - If Old is a target of the jump tables, update 133 /// the jump table to branch to New instead. 134 bool ReplaceMBBInJumpTable(unsigned Idx, MachineBasicBlock *Old, 135 MachineBasicBlock *New); 136 137 /// print - Used by the MachineFunction printer to print information about 138 /// jump tables. Implemented in MachineFunction.cpp 139 /// 140 void print(raw_ostream &OS) const; 141 142 /// dump - Call to stderr. 143 /// 144 void dump() const; 145 }; 146 147 148 /// Prints a jump table entry reference. 149 /// 150 /// The format is: 151 /// %jump-table.5 - a jump table entry with index == 5. 152 /// 153 /// Usage: OS << printJumpTableEntryReference(Idx) << '\n'; 154 Printable printJumpTableEntryReference(unsigned Idx); 155 156 } // End llvm namespace 157 158 #endif 159