1 //===--------------------- DfaEmitter.h -----------------------------------===// 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 // Defines a generic automaton builder. This takes a set of transitions and 9 // states that represent a nondeterministic finite state automaton (NFA) and 10 // emits a determinized DFA in a form that include/llvm/Support/Automaton.h can 11 // drive. 12 // 13 // See file llvm/TableGen/Automaton.td for the TableGen API definition. 14 // 15 //===----------------------------------------------------------------------===// 16 17 #ifndef LLVM_UTILS_TABLEGEN_DFAEMITTER_H 18 #define LLVM_UTILS_TABLEGEN_DFAEMITTER_H 19 20 #include "llvm/ADT/SmallVector.h" 21 #include "llvm/ADT/UniqueVector.h" 22 #include <map> 23 #include <set> 24 25 namespace llvm { 26 27 class raw_ostream; 28 class StringRef; 29 30 /// Construct a deterministic finite state automaton from possible 31 /// nondeterministic state and transition data. 32 /// 33 /// The state type is a 64-bit unsigned integer. The generated automaton is 34 /// invariant to the sparsity of the state representation - its size is only 35 /// a function of the cardinality of the set of states. 36 /// 37 /// The inputs to this emitter are considered to define a nondeterministic 38 /// finite state automaton (NFA). This is then converted to a DFA during 39 /// emission. The emitted tables can be used to by 40 /// include/llvm/Support/Automaton.h. 41 class DfaEmitter { 42 public: 43 // The type of an NFA state. The initial state is always zero. 44 using state_type = uint64_t; 45 // The type of an action. 46 using action_type = uint64_t; 47 48 DfaEmitter() = default; 49 virtual ~DfaEmitter() = default; 50 51 void addTransition(state_type From, state_type To, action_type A); 52 void emit(StringRef Name, raw_ostream &OS); 53 54 protected: 55 /// Emit the C++ type of an action to OS. 56 virtual void printActionType(raw_ostream &OS); 57 /// Emit the C++ value of an action A to OS. 58 virtual void printActionValue(action_type A, raw_ostream &OS); 59 60 private: 61 /// The state type of deterministic states. These are only used internally to 62 /// this class. This is an ID into the DfaStates UniqueVector. 63 using dfa_state_type = unsigned; 64 65 /// The actual representation of a DFA state, which is a union of one or more 66 /// NFA states. 67 using DfaState = SmallVector<state_type, 4>; 68 69 /// A DFA transition consists of a set of NFA states transitioning to a 70 /// new set of NFA states. The DfaTransitionInfo tracks, for every 71 /// transitioned-from NFA state, a set of valid transitioned-to states. 72 /// 73 /// Emission of this transition relation allows algorithmic determination of 74 /// the possible candidate NFA paths taken under a given input sequence to 75 /// reach a given DFA state. 76 using DfaTransitionInfo = SmallVector<std::pair<state_type, state_type>, 4>; 77 78 /// The set of all possible actions. 79 std::set<action_type> Actions; 80 81 /// The set of nondeterministic transitions. A state-action pair can 82 /// transition to multiple target states. 83 std::map<std::pair<state_type, action_type>, std::vector<state_type>> 84 NfaTransitions; 85 std::set<state_type> NfaStates; 86 unsigned NumNfaTransitions = 0; 87 88 /// The set of deterministic states. DfaStates.getId(DfaState) returns an ID, 89 /// which is dfa_state_type. Note that because UniqueVector reserves state 90 /// zero, the initial DFA state is always 1. 91 UniqueVector<DfaState> DfaStates; 92 /// The set of deterministic transitions. A state-action pair has only a 93 /// single target state. 94 std::map<std::pair<dfa_state_type, action_type>, 95 std::pair<dfa_state_type, DfaTransitionInfo>> 96 DfaTransitions; 97 98 /// Visit all NFA states and construct the DFA. 99 void constructDfa(); 100 /// Visit a single DFA state and construct all possible transitions to new DFA 101 /// states. 102 void visitDfaState(const DfaState &DS); 103 }; 104 105 } // namespace llvm 106 107 #endif 108