379 lines
12 KiB
C++
379 lines
12 KiB
C++
#include "compiler/build_tables/build_parse_table.h"
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#include <algorithm>
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#include <map>
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#include <set>
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#include <string>
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#include <unordered_map>
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#include <utility>
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#include "compiler/parse_table.h"
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#include "compiler/build_tables/parse_conflict_manager.h"
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#include "compiler/build_tables/remove_duplicate_states.h"
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#include "compiler/build_tables/parse_item.h"
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#include "compiler/build_tables/item_set_closure.h"
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#include "compiler/lexical_grammar.h"
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#include "compiler/syntax_grammar.h"
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#include "compiler/rules/symbol.h"
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#include "compiler/rules/built_in_symbols.h"
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namespace tree_sitter {
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namespace build_tables {
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using std::find;
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using std::pair;
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using std::vector;
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using std::set;
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using std::map;
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using std::string;
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using std::to_string;
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using std::unordered_map;
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using std::make_shared;
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using rules::Symbol;
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class ParseTableBuilder {
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const SyntaxGrammar grammar;
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const LexicalGrammar lexical_grammar;
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ParseConflictManager conflict_manager;
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unordered_map<ParseItemSet, ParseStateId, ParseItemSet::Hash> parse_state_ids;
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vector<pair<ParseItemSet, ParseStateId>> item_sets_to_process;
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ParseTable parse_table;
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std::set<string> conflicts;
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ParseItemSet null_item_set;
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std::set<const Production *> fragile_productions;
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public:
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ParseTableBuilder(const SyntaxGrammar &grammar,
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const LexicalGrammar &lex_grammar)
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: grammar(grammar), lexical_grammar(lex_grammar) {}
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pair<ParseTable, CompileError> build() {
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Symbol start_symbol = Symbol(0, grammar.variables.empty());
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Production start_production({
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ProductionStep(start_symbol, 0, rules::AssociativityNone),
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});
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add_parse_state(ParseItemSet({
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{
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ParseItem(rules::START(), start_production, 0),
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LookaheadSet({ rules::END_OF_INPUT() }),
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},
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}));
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while (!item_sets_to_process.empty()) {
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auto pair = item_sets_to_process.back();
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ParseItemSet item_set = item_set_closure(pair.first, grammar);
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ParseStateId state_id = pair.second;
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item_sets_to_process.pop_back();
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add_reduce_actions(item_set, state_id);
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add_shift_actions(item_set, state_id);
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if (!conflicts.empty())
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return { parse_table,
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CompileError(TSCompileErrorTypeParseConflict,
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"Unresolved conflict.\n\n" + *conflicts.begin()) };
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}
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for (ParseStateId state = 0; state < parse_table.states.size(); state++) {
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add_shift_extra_actions(state);
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add_reduce_extra_actions(state);
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}
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mark_fragile_actions();
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remove_duplicate_parse_states();
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parse_table.symbols.insert({ rules::ERROR(), {} });
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return { parse_table, CompileError::none() };
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}
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private:
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ParseStateId add_parse_state(const ParseItemSet &item_set) {
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auto pair = parse_state_ids.find(item_set);
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if (pair == parse_state_ids.end()) {
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ParseStateId state_id = parse_table.add_state();
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parse_state_ids[item_set] = state_id;
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item_sets_to_process.push_back({ item_set, state_id });
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return state_id;
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} else {
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return pair->second;
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}
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}
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void add_shift_actions(const ParseItemSet &item_set, ParseStateId state_id) {
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for (const auto &transition : item_set.transitions()) {
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const Symbol &symbol = transition.first;
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const ParseItemSet &next_item_set = transition.second.first;
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const PrecedenceRange &precedence = transition.second.second;
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ParseAction *new_action = add_action(
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state_id, symbol, ParseAction::Shift(0, precedence), item_set);
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if (new_action)
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new_action->state_index = add_parse_state(next_item_set);
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}
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}
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void add_reduce_actions(const ParseItemSet &item_set, ParseStateId state_id) {
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for (const auto &pair : item_set.entries) {
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const ParseItem &item = pair.first;
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const auto &lookahead_symbols = pair.second;
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ParseItem::CompletionStatus status = item.completion_status();
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if (status.is_done) {
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ParseAction action =
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(item.lhs() == rules::START())
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? ParseAction::Accept()
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: ParseAction::Reduce(Symbol(item.variable_index), item.step_index,
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status.precedence, status.associativity,
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*item.production);
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for (const auto &lookahead_sym : *lookahead_symbols.entries)
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add_action(state_id, lookahead_sym, action, item_set);
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}
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}
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}
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void add_shift_extra_actions(ParseStateId state_id) {
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ParseAction action = ParseAction::ShiftExtra();
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for (const Symbol &extra_symbol : grammar.extra_tokens)
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add_action(state_id, extra_symbol, action, null_item_set);
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}
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void add_reduce_extra_actions(ParseStateId state_id) {
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const ParseState &state = parse_table.states[state_id];
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for (const Symbol &extra_symbol : grammar.extra_tokens) {
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const auto &actions_for_symbol = state.actions.find(extra_symbol);
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if (actions_for_symbol == state.actions.end())
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continue;
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for (const ParseAction &action : actions_for_symbol->second)
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if (action.type == ParseActionTypeShift && !action.extra) {
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size_t dest_state_id = action.state_index;
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ParseAction reduce_extra = ParseAction::ReduceExtra(extra_symbol);
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for (const auto &pair : state.actions)
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add_action(dest_state_id, pair.first, reduce_extra, null_item_set);
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}
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}
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}
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void mark_fragile_actions() {
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for (ParseState &state : parse_table.states) {
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set<Symbol> symbols_with_multiple_actions;
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for (auto &entry : state.actions) {
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if (entry.second.size() > 1)
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symbols_with_multiple_actions.insert(entry.first);
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for (ParseAction &action : entry.second) {
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if (action.type == ParseActionTypeReduce && !action.extra) {
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if (has_fragile_production(action.production))
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action.fragile = true;
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action.production = NULL;
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action.precedence_range = PrecedenceRange();
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action.associativity = rules::AssociativityNone;
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}
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}
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}
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if (!symbols_with_multiple_actions.empty()) {
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for (auto &entry : state.actions) {
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if (!entry.first.is_token) {
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set<Symbol> first_set = get_first_set(entry.first);
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for (const Symbol &symbol : symbols_with_multiple_actions) {
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if (first_set.count(symbol)) {
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entry.second[0].can_hide_split = true;
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break;
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}
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}
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}
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}
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}
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}
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}
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void remove_duplicate_parse_states() {
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remove_duplicate_states<ParseState, ParseAction, ParseActionTypeShift>(
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&parse_table.states);
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}
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ParseAction *add_action(ParseStateId state_id, Symbol lookahead,
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const ParseAction &new_action,
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const ParseItemSet &item_set) {
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const auto ¤t_actions = parse_table.states[state_id].actions;
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const auto ¤t_entry = current_actions.find(lookahead);
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if (current_entry == current_actions.end())
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return &parse_table.set_action(state_id, lookahead, new_action);
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const ParseAction old_action = current_entry->second[0];
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auto resolution = conflict_manager.resolve(new_action, old_action);
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switch (resolution.second) {
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case ConflictTypeNone:
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if (resolution.first)
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return &parse_table.set_action(state_id, lookahead, new_action);
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break;
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case ConflictTypeResolved: {
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if (resolution.first) {
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if (old_action.type == ParseActionTypeReduce)
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fragile_productions.insert(old_action.production);
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return &parse_table.set_action(state_id, lookahead, new_action);
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} else {
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if (new_action.type == ParseActionTypeReduce)
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fragile_productions.insert(new_action.production);
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break;
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}
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}
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case ConflictTypeUnresolved: {
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if (handle_unresolved_conflict(item_set, lookahead)) {
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if (old_action.type == ParseActionTypeReduce)
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fragile_productions.insert(old_action.production);
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if (new_action.type == ParseActionTypeReduce)
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fragile_productions.insert(new_action.production);
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return &parse_table.add_action(state_id, lookahead, new_action);
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}
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break;
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}
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}
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return nullptr;
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}
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bool handle_unresolved_conflict(const ParseItemSet &item_set,
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const Symbol &lookahead) {
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set<Symbol> involved_symbols;
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set<ParseItem> reduce_items;
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set<ParseItem> core_shift_items;
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set<ParseItem> other_shift_items;
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for (const auto &pair : item_set.entries) {
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const ParseItem &item = pair.first;
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const LookaheadSet &lookahead_set = pair.second;
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if (item.step_index == item.production->size()) {
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if (lookahead_set.contains(lookahead)) {
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involved_symbols.insert(item.lhs());
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reduce_items.insert(item);
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}
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} else {
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Symbol next_symbol = item.production->at(item.step_index).symbol;
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if (item.step_index > 0) {
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set<Symbol> first_set = get_first_set(next_symbol);
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if (first_set.count(lookahead)) {
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involved_symbols.insert(item.lhs());
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core_shift_items.insert(item);
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}
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} else if (next_symbol == lookahead) {
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other_shift_items.insert(item);
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}
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}
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}
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for (const auto &conflict_set : grammar.expected_conflicts)
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if (involved_symbols == conflict_set)
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return true;
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string description = "Lookahead symbol: " + symbol_name(lookahead) + "\n";
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if (!reduce_items.empty()) {
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description += "Reduce items:\n";
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for (const ParseItem &item : reduce_items)
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description += " " + item_string(item) + "\n";
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}
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if (!core_shift_items.empty()) {
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description += "Core shift items:\n";
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for (const ParseItem &item : core_shift_items)
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description += " " + item_string(item) + "\n";
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}
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if (!other_shift_items.empty()) {
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description += "Other shift items:\n";
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for (const ParseItem &item : other_shift_items)
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description += " " + item_string(item) + "\n";
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}
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conflicts.insert(description);
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return false;
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}
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string item_string(const ParseItem &item) const {
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string result = symbol_name(item.lhs()) + " ->";
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size_t i = 0;
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for (const ProductionStep &step : *item.production) {
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if (i == item.step_index)
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result += " \u2022";
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result += " " + symbol_name(step.symbol);
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i++;
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}
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if (i == item.step_index)
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result += " \u2022";
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result += " (prec " + to_string(item.precedence());
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switch (item.associativity()) {
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case rules::AssociativityNone:
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result += ")";
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break;
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case rules::AssociativityLeft:
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result += ", assoc left)";
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break;
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case rules::AssociativityRight:
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result += ", assoc right)";
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break;
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}
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return result;
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}
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set<Symbol> get_first_set(const Symbol &start_symbol) {
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set<Symbol> result;
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vector<Symbol> symbols_to_process({ start_symbol });
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while (!symbols_to_process.empty()) {
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Symbol symbol = symbols_to_process.back();
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symbols_to_process.pop_back();
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if (result.insert(symbol).second)
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for (const Production &production : grammar.productions(symbol))
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if (!production.empty())
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symbols_to_process.push_back(production[0].symbol);
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}
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return result;
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}
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string symbol_name(const rules::Symbol &symbol) const {
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if (symbol.is_built_in()) {
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if (symbol == rules::ERROR())
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return "ERROR";
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else if (symbol == rules::END_OF_INPUT())
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return "END_OF_INPUT";
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else
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return "";
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} else if (symbol.is_token) {
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const Variable &variable = lexical_grammar.variables[symbol.index];
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if (variable.type == VariableTypeNamed)
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return variable.name;
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else
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return "'" + variable.name + "'";
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} else {
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return grammar.variables[symbol.index].name;
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}
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}
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bool has_fragile_production(const Production *production) {
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auto end = fragile_productions.end();
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return std::find(fragile_productions.begin(), end, production) != end;
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}
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};
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pair<ParseTable, CompileError> build_parse_table(
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const SyntaxGrammar &grammar, const LexicalGrammar &lex_grammar) {
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return ParseTableBuilder(grammar, lex_grammar).build();
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}
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} // namespace build_tables
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} // namespace tree_sitter
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