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Record in parse table which actions can hide splits

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Suppose a parse state S has multiple actions for a terminal lookahead symbol A.
Then during incremental parsing, while in state S, the parser should not
reuse a non-terminal lookahead B where FIRST(B) contains A, because reusing B
might prematurely discard one of the possible actions that a batch parser
would have attempted in state S, upon seeing A as a lookahead.
This commit is contained in:
Max Brunsfeld 2015-12-17 12:48:55 -08:00
parent 7fbb628c78
commit c495076adb
19 changed files with 58613 additions and 60661 deletions
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42
src/compiler/build_tables/build_parse_table.cc
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@ -79,7 +79,7 @@ class ParseTableBuilder {
add_reduce_extra_actions(state);
}
mark_fragile_reductions();
mark_fragile_actions();
remove_duplicate_states();
parse_table.symbols.insert({ rules::ERROR(), {} });
@ -134,9 +134,9 @@ class ParseTableBuilder {
}
void add_shift_extra_actions(ParseStateId state_id) {
ParseAction action = ParseAction::ShiftExtra();
for (const Symbol &ubiquitous_symbol : grammar.ubiquitous_tokens)
add_action(state_id, ubiquitous_symbol, ParseAction::ShiftExtra(),
null_item_set);
add_action(state_id, ubiquitous_symbol, action, null_item_set);
}
void add_reduce_extra_actions(ParseStateId state_id) {
@ -148,7 +148,7 @@ class ParseTableBuilder {
continue;
for (const ParseAction &action : actions_for_symbol->second)
if (action.type == ParseActionTypeShift) {
if (action.type == ParseActionTypeShift && !action.extra) {
size_t dest_state_id = action.state_index;
ParseAction reduce_extra = ParseAction::ReduceExtra(ubiquitous_symbol);
for (const auto &pair : state.actions)
@ -157,14 +157,36 @@ class ParseTableBuilder {
}
}
void mark_fragile_reductions() {
void mark_fragile_actions() {
for (ParseState &state : parse_table.states) {
set<Symbol> symbols_with_multiple_actions;
for (auto &entry : state.actions) {
if (entry.second.size() > 1)
symbols_with_multiple_actions.insert(entry.first);
for (ParseAction &action : entry.second) {
if (action.type == ParseActionTypeReduce) {
if (action.type == ParseActionTypeReduce && !action.extra) {
if (has_fragile_production(action.production))
action.type = ParseActionTypeReduceFragile;
action.fragile = true;
action.production = NULL;
action.precedence_range = PrecedenceRange();
action.associativity = rules::AssociativityNone;
}
}
}
if (!symbols_with_multiple_actions.empty()) {
for (auto &entry : state.actions) {
if (!entry.first.is_token) {
set<Symbol> first_set = get_first_set(entry.first);
for (const Symbol &symbol : symbols_with_multiple_actions) {
if (first_set.count(symbol)) {
entry.second[0].can_hide_split = true;
break;
}
}
}
}
}
@ -175,6 +197,7 @@ class ParseTableBuilder {
bool done = false;
while (!done) {
done = true;
map<ParseStateId, ParseStateId> replacements;
for (size_t i = 0, size = parse_table.states.size(); i < size; i++) {
for (size_t j = 0; j < i; j++) {
@ -210,9 +233,8 @@ class ParseTableBuilder {
}
}
for (auto replacement = replacements.rbegin(); replacement != replacements.rend(); ++replacement) {
parse_table.states.erase(parse_table.states.begin() + replacement->first);
}
for (auto i = replacements.rbegin(); i != replacements.rend(); ++i)
parse_table.states.erase(parse_table.states.begin() + i->first);
}
}