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//===-- CodeGen/MachineJumpTableInfo.h - Abstract Jump Tables --*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// The MachineJumpTableInfo class keeps track of jump tables referenced by
// lowered switch instructions in the MachineFunction.
// Instructions reference the address of these jump tables through the use of
// MO_JumpTableIndex values. When emitting assembly or machine code, these
// virtual address references are converted to refer to the address of the
// function jump tables.
#include "llvm/Support/Printable.h"
#include <cassert>
#include <vector>
namespace llvm {
class MachineBasicBlock;
class DataLayout;
class raw_ostream;
/// MachineJumpTableEntry - One jump table in the jump table info.
struct MachineJumpTableEntry {
/// MBBs - The vector of basic blocks from which to create the jump table.
std::vector<MachineBasicBlock*> MBBs;
explicit MachineJumpTableEntry(const std::vector<MachineBasicBlock*> &M)
: MBBs(M) {}
class MachineJumpTableInfo {
/// JTEntryKind - This enum indicates how each entry of the jump table is
/// represented and emitted.
enum JTEntryKind {
/// EK_BlockAddress - Each entry is a plain address of block, e.g.:
/// .word LBB123
/// EK_GPRel64BlockAddress - Each entry is an address of block, encoded
/// with a relocation as gp-relative, e.g.:
/// .gpdword LBB123
/// EK_GPRel32BlockAddress - Each entry is an address of block, encoded
/// with a relocation as gp-relative, e.g.:
/// .gprel32 LBB123
/// EK_LabelDifference32 - Each entry is the address of the block minus
/// the address of the jump table. This is used for PIC jump tables where
/// gprel32 is not supported. e.g.:
/// .word LBB123 - LJTI1_2
/// If the .set directive is supported, this is emitted as:
/// .set L4_5_set_123, LBB123 - LJTI1_2
/// .word L4_5_set_123
/// EK_Inline - Jump table entries are emitted inline at their point of
/// use. It is the responsibility of the target to emit the entries.
/// EK_Custom32 - Each entry is a 32-bit value that is custom lowered by the
/// TargetLowering::LowerCustomJumpTableEntry hook.
JTEntryKind EntryKind;
std::vector<MachineJumpTableEntry> JumpTables;
explicit MachineJumpTableInfo(JTEntryKind Kind): EntryKind(Kind) {}
JTEntryKind getEntryKind() const { return EntryKind; }
/// getEntrySize - Return the size of each entry in the jump table.
unsigned getEntrySize(const DataLayout &TD) const;
/// getEntryAlignment - Return the alignment of each entry in the jump table.
unsigned getEntryAlignment(const DataLayout &TD) const;
/// createJumpTableIndex - Create a new jump table.
unsigned createJumpTableIndex(const std::vector<MachineBasicBlock*> &DestBBs);
/// isEmpty - Return true if there are no jump tables.
bool isEmpty() const { return JumpTables.empty(); }
const std::vector<MachineJumpTableEntry> &getJumpTables() const {
return JumpTables;
/// RemoveJumpTable - Mark the specific index as being dead. This will
/// prevent it from being emitted.
void RemoveJumpTable(unsigned Idx) {
/// ReplaceMBBInJumpTables - If Old is the target of any jump tables, update
/// the jump tables to branch to New instead.
bool ReplaceMBBInJumpTables(MachineBasicBlock *Old, MachineBasicBlock *New);
/// ReplaceMBBInJumpTable - If Old is a target of the jump tables, update
/// the jump table to branch to New instead.
bool ReplaceMBBInJumpTable(unsigned Idx, MachineBasicBlock *Old,
MachineBasicBlock *New);
/// print - Used by the MachineFunction printer to print information about
/// jump tables. Implemented in MachineFunction.cpp
void print(raw_ostream &OS) const;
/// dump - Call to stderr.
void dump() const;
/// Prints a jump table entry reference.
/// The format is:
/// %jump-table.5 - a jump table entry with index == 5.
/// Usage: OS << printJumpTableEntryReference(Idx) << '\n';
Printable printJumpTableEntryReference(unsigned Idx);
} // End llvm namespace