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 38 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_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 }; 78 private: 79 JTEntryKind EntryKind; 80 std::vector<MachineJumpTableEntry> JumpTables; 81 public: 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'; 138 Printable printJumpTableEntryReference(unsigned Idx); 139 140 } // End llvm namespace 141 142 #endif 143