output_slr: collapse duplicate case branches

src/output_slr.cpp

@@ -33,20 +33,29 @@
 
 namespace solar {
 
-void output_slr_t::emit_state_shift(unsigned state, const symbol_t &token) {
-	auto it = generator->get_shifts().find(std::make_pair(state, token));
-	if (it == generator->get_shifts().end())
-		return;
+void output_slr_t::emit_state_shift(unsigned state) {
+	std::map<unsigned, std::set<symbol_t>> shifts;
 
-	std::fprintf(source_file, "\t\t\tcase %s:\n", symbol_case(token).c_str());
-	std::fprintf(source_file, "\t\t\t\tparser->stack[parser->top].value.token = *value;\n");
-	std::fprintf(source_file, "\t\t\t\tparser->stack[++parser->top].state = %u;\n", unsigned(it->second));
-	std::fprintf(source_file, "\t\t\t\treturn 1;\n\n");
+	for (const symbol_t &token : generator->get_terminals()) {
+		auto it = generator->get_shifts().find(std::make_pair(state, token));
+		if (it == generator->get_shifts().end())
+			continue;
+
+		std::set<symbol_t> &symbols = shifts.insert(std::make_pair(it->second, std::set<symbol_t>())).first->second;
+		symbols.insert(token);
+	}
+
+	for (const auto &entry : shifts) {
+		for (const symbol_t &sym : entry.second)
+			std::fprintf(source_file, "\t\t\tcase %s:\n", symbol_case(sym).c_str());
+
+		std::fprintf(source_file, "\t\t\t\tparser->stack[parser->top].value.token = *value;\n");
+		std::fprintf(source_file, "\t\t\t\tparser->stack[++parser->top].state = %u;\n", entry.first);
+		std::fprintf(source_file, "\t\t\t\treturn 1;\n\n");
+	}
 }
 
-void output_slr_t::emit_state_reduce(const item_t &item, const symbol_t &token, int rule_id) {
-	std::fprintf(source_file, "\t\t\tcase %s:\n", symbol_case(token).c_str());
-
+void output_slr_t::emit_state_reduce_code(const item_t &item, int rule_id) {
 	const auto &rhs = item.get_rhs();
 	if (rhs.size())
 		std::fprintf(source_file, "\t\t\t\tparser->top -= %u;\n", unsigned(rhs.size()));
@@ -114,19 +123,38 @@ void output_slr_t::emit_state_reduce(const item_t &item, const symbol_t &token,
 
 		std::fprintf(source_file, "\t\t\t\t}\n");
 	}
-
-	std::fprintf(source_file, "\t\t\t\tbreak;\n\n");
 }
 
-void output_slr_t::do_emit_state(unsigned state, const symbol_t &token) {
-	auto it = generator->get_reductions().find(std::make_pair(state, token));
-	if (it == generator->get_reductions().end()) {
-		emit_state_shift(state, token);
+bool output_slr_t::emit_state_reduce(unsigned state) {
+	std::map<unsigned, std::set<symbol_t>> reductions;
+
+	for (const symbol_t &token : generator->get_terminals()) {
+		auto it = generator->get_reductions().find(std::make_pair(state, token));
+		if (it == generator->get_reductions().end())
+			continue;
+
+		std::set<symbol_t> &symbols = reductions.insert(std::make_pair(it->second, std::set<symbol_t>())).first->second;
+		symbols.insert(token);
 	}
-	else {
-		const rule_t &rule = generator->get_grammar().rules[it->second];
-		emit_state_reduce(rule.item, token, rule.action.empty() ? -1 : it->second);
+
+	for (const auto &entry : reductions) {
+		if (reductions.size() == 1) {
+			std::fprintf(source_file, "\t\t\tdefault:\n");
+		}
+		else {
+			for (const symbol_t &sym : entry.second)
+				std::fprintf(source_file, "\t\t\tcase %s:\n", symbol_case(sym).c_str());
+		}
+
+		const rule_t &rule = generator->get_grammar().rules[entry.first];
+		emit_state_reduce_code(rule.item, rule.action.empty() ? -1 : entry.first);
+
+		if (reductions.size() != 1)
+			std::fprintf(source_file, "\t\t\t\tbreak;\n\n");
+
 	}
+
+	return (reductions.size() == 1);
 }
 
 void output_slr_t::emit_state(unsigned state) {
@@ -138,13 +166,14 @@ void output_slr_t::emit_state(unsigned state) {
 		std::fprintf(source_file, "\t\t\t\treturn 0;\n\n");
 	}
 
-	do_emit_state(state, symbol_t::empty());
+	emit_state_shift(state);
 
-	for (const symbol_t &token : generator->get_terminals())
-		do_emit_state(state, token);
+	bool def = emit_state_reduce(state);
 
-	std::fprintf(source_file, "\t\t\tdefault:\n");
-	std::fprintf(source_file, "\t\t\t\treturn -1;\n");
+	if (!def) {
+		std::fprintf(source_file, "\t\t\tdefault:\n");
+		std::fprintf(source_file, "\t\t\t\treturn -1;\n");
+	}
 
 	std::fprintf(source_file, "\t\t\t}\n");
 	std::fprintf(source_file, "\t\t\tbreak;\n\n");

src/output_slr.hpp

@@ -36,9 +36,11 @@ class output_slr_t : public output_t {
 private:
 	const generator_slr_t *generator;
 
-	void emit_state_shift(unsigned state, const symbol_t &token);
-	void emit_state_reduce(const item_t &item, const symbol_t &token, int rule_id);
-	void do_emit_state(unsigned state, const symbol_t &token);
+
+	void emit_state_shift(unsigned state);
+
+	void emit_state_reduce_code(const item_t &item, int rule_id);
+	bool emit_state_reduce(unsigned state);
 
 protected:
 	virtual const generator_t * get_generator() {