kernel: call hierarchy for abstract modules automatically.

Whenever there are abstract modules in the netlist and the pass does not
declare that it supports them, call `hierarchy -auto-top` or `hierarchy`
(depending on whether there is a module marked `top`) to instantiate
them first. This makes several CLI workflows much more usable, including
one as basic as:

    $ yosys file.v -o file.il

kernel/register.cc

@@ -151,6 +151,22 @@ Pass::~Pass()
 
 Pass::pre_post_exec_state_t Pass::pre_execute()
 {
+	if (!abstract_modules_ok) {
+		bool has_top = false;
+		bool has_abstract = false;
+		for (auto mod : yosys_design->modules()) {
+			if (mod->get_bool_attribute(ID::top))
+				has_top = true;
+			if (mod->name.begins_with("$abstract"))
+				has_abstract = true;
+		}
+		if (has_abstract) {
+			std::string command = has_top ? "hierarchy" : "hierarchy -auto-top";
+			log_warning("Pass `%s` does not accept abstract modules; running `%s` first!\n", pass_name.c_str(), command.c_str());
+			run_pass(command);
+		}
+	}
+
 	pre_post_exec_state_t state;
 	call_counter++;
 	state.begin_ns = PerformanceTimer::query();
@@ -443,6 +459,7 @@ Frontend::Frontend(std::string name, std::string short_help) :
 		Pass(name.rfind("=", 0) == 0 ? name.substr(1) : "read_" + name, short_help),
 		frontend_name(name.rfind("=", 0) == 0 ? name.substr(1) : name)
 {
+	abstract_modules_ok = true;
 }
 
 void Frontend::run_register()

kernel/register.h

@@ -37,6 +37,7 @@ struct Pass
 	int call_counter;
 	int64_t runtime_ns;
 	bool experimental_flag = false;
+	bool abstract_modules_ok = false;
 
 	void experimental() {
 		experimental_flag = true;
@@ -78,7 +79,11 @@ struct ScriptPass : Pass
 	RTLIL::Design *active_design;
 	std::string active_run_from, active_run_to;
 
-	ScriptPass(std::string name, std::string short_help = "** document me **") : Pass(name, short_help) { }
+	ScriptPass(std::string name, std::string short_help = "** document me **") : Pass(name, short_help) {
+		// Either the script pass will include an explicit `hierarchy` invocation or one of the passes called inside will
+		// trigger the check for abstract modules.
+		abstract_modules_ok = true;
+	}
 
 	virtual void script() = 0;
 

passes/hierarchy/hierarchy.cc

@@ -716,7 +716,7 @@ RTLIL::Wire *find_implicit_port_wire(Module *module, Cell *cell, const std::stri
 }
 
 struct HierarchyPass : public Pass {
-	HierarchyPass() : Pass("hierarchy", "check, expand and clean up design hierarchy") { }
+	HierarchyPass() : Pass("hierarchy", "check, expand and clean up design hierarchy") { abstract_modules_ok = true; }
 	void help() override
 	{
 		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|