include/llvm/CodeGen/MachineJumpTableInfo.h

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