pattern reduce

state <IdString> portname
udata <vector<pair<Cell*, IdString>>> chain longest_chain
udata <pool<Cell*>> non_first_cells
udata <SigSpec> leaves

code
	non_first_cells.clear();
	subpattern(setup);
endcode

match first
	select first->type.in($_AND_, $_OR_, $_XOR_)
	filter !non_first_cells.count(first)
generate
	SigSpec A = module->addWire(NEW_ID);
	SigSpec B = module->addWire(NEW_ID);
	SigSpec Y = module->addWire(NEW_ID);
	switch (rng(3))
	{
	case 0:
		module->addAndGate(NEW_ID, A, B, Y);
		break;
	case 1:
		module->addOrGate(NEW_ID, A, B, Y);
		break;
	case 2:
		module->addXorGate(NEW_ID, A, B, Y);
		break;
	}
endmatch

code
	leaves = SigSpec();
	longest_chain.clear();
	chain.push_back(make_pair(first, \A));
	subpattern(tail);
	chain.back().second = \B;
	subpattern(tail);
finally
	chain.pop_back();
	log_assert(chain.empty());
	if (GetSize(longest_chain) > 1)
		accept;
endcode

// ------------------------------------------------------------------

subpattern setup

match first
	select first->type.in($_AND_, $_OR_, $_XOR_)
endmatch

code portname
	portname = \A;
	branch;
	portname = \B;
endcode

match next
	select nusers(port(next, \Y)) == 2
	select next->type.in($_AND_, $_OR_, $_XOR_)
	index <IdString> next->type === first->type
	index <SigSpec> port(next, \Y) === port(first, portname)
endmatch

code
	non_first_cells.insert(next);
endcode

// ------------------------------------------------------------------

subpattern tail
arg first

match next
	semioptional
	select nusers(port(next, \Y)) == 2
	select next->type.in($_AND_, $_OR_, $_XOR_)
	index <IdString> next->type === chain.back().first->type
	index <SigSpec> port(next, \Y) === port(chain.back().first, chain.back().second)
generate 10
	SigSpec A = module->addWire(NEW_ID);
	SigSpec B = module->addWire(NEW_ID);
	SigSpec Y = port(chain.back().first, chain.back().second);
	Cell *c = module->addAndGate(NEW_ID, A, B, Y);
	c->type = chain.back().first->type;
endmatch

code
	if (next) {
		chain.push_back(make_pair(next, \A));
		subpattern(tail);
		chain.back().second = \B;
		subpattern(tail);
	} else {
		if (GetSize(chain) > GetSize(longest_chain))
			longest_chain = chain;
		leaves.append(port(chain.back().first, chain.back().second));
	}
finally
	if (next)
		chain.pop_back();
endcode