diff --git a/Makefile b/Makefile
index d565ead16..4aae25c3c 100644
--- a/Makefile
+++ b/Makefile
@@ -44,7 +44,12 @@ LINK_ABC := 0
 # Needed for environments that can't run executables (i.e. emscripten, wasm)
 DISABLE_SPAWN := 0
 # Needed for environments that don't have proper thread support (i.e. emscripten, wasm--for now)
+ENABLE_THREADS := 1
+ifeq ($(ENABLE_THREADS),1)
 DISABLE_ABC_THREADS := 0
+else
+DISABLE_ABC_THREADS := 1
+endif
 
 # clang sanitizers
 SANITIZER =
@@ -300,6 +305,7 @@ DISABLE_SPAWN := 1
 
 ifeq ($(ENABLE_ABC),1)
 LINK_ABC := 1
+ENABLE_THREADS := 0
 DISABLE_ABC_THREADS := 1
 endif
 
@@ -457,6 +463,11 @@ CXXFLAGS := -Og -DDEBUG $(filter-out $(OPT_LEVEL),$(CXXFLAGS))
 STRIP :=
 endif
 
+ifeq ($(ENABLE_THREADS),1)
+CXXFLAGS += -DYOSYS_ENABLE_THREADS
+LIBS += -lpthread
+endif
+
 ifeq ($(ENABLE_ABC),1)
 CXXFLAGS += -DYOSYS_ENABLE_ABC
 ifeq ($(LINK_ABC),1)
@@ -612,6 +623,7 @@ $(eval $(call add_include_file,kernel/satgen.h))
 $(eval $(call add_include_file,kernel/scopeinfo.h))
 $(eval $(call add_include_file,kernel/sexpr.h))
 $(eval $(call add_include_file,kernel/sigtools.h))
+$(eval $(call add_include_file,kernel/threading.h))
 $(eval $(call add_include_file,kernel/timinginfo.h))
 $(eval $(call add_include_file,kernel/utils.h))
 $(eval $(call add_include_file,kernel/yosys.h))
@@ -638,7 +650,7 @@ OBJS += kernel/log_compat.o
 endif
 OBJS += kernel/binding.o kernel/tclapi.o
 OBJS += kernel/cellaigs.o kernel/celledges.o kernel/cost.o kernel/satgen.o kernel/scopeinfo.o kernel/qcsat.o kernel/mem.o kernel/ffmerge.o kernel/ff.o kernel/yw.o kernel/json.o kernel/fmt.o kernel/sexpr.o
-OBJS += kernel/drivertools.o kernel/functional.o
+OBJS += kernel/drivertools.o kernel/functional.o kernel/threading.o
 ifeq ($(ENABLE_ZLIB),1)
 OBJS += kernel/fstdata.o
 endif
diff --git a/kernel/threading.cc b/kernel/threading.cc
new file mode 100644
index 000000000..49fddaa7c
--- /dev/null
+++ b/kernel/threading.cc
@@ -0,0 +1,45 @@
+#include "kernel/yosys_common.h"
+#include "kernel/threading.h"
+
+YOSYS_NAMESPACE_BEGIN
+
+void DeferredLogs::flush()
+{
+	for (auto &m : logs)
+		if (m.error)
+			YOSYS_NAMESPACE_PREFIX log_error("%s", m.text.c_str());
+		else
+			YOSYS_NAMESPACE_PREFIX log("%s", m.text.c_str());
+}
+
+int ThreadPool::pool_size(int reserved_cores, int max_threads)
+{
+#ifdef YOSYS_ENABLE_THREADS
+	int num_threads = std::min<int>(std::thread::hardware_concurrency() - reserved_cores, max_threads);
+        return std::max(0, num_threads);
+#else
+        return 0;
+#endif
+}
+
+ThreadPool::ThreadPool(int pool_size, std::function<void(int)> b)
+	: body(std::move(b))
+{
+#ifdef YOSYS_ENABLE_THREADS
+        threads.reserve(pool_size);
+        for (int i = 0; i < pool_size; i++)
+                threads.emplace_back([i, this]{ body(i); });
+#else
+        log_assert(pool_size == 0);
+#endif
+}
+
+ThreadPool::~ThreadPool()
+{
+#ifdef YOSYS_ENABLE_THREADS
+	for (auto &t : threads)
+		t.join();
+#endif
+}
+
+YOSYS_NAMESPACE_END
diff --git a/kernel/threading.h b/kernel/threading.h
new file mode 100644
index 000000000..c34abf850
--- /dev/null
+++ b/kernel/threading.h
@@ -0,0 +1,186 @@
+#include <deque>
+
+#ifdef YOSYS_ENABLE_THREADS
+#include <condition_variable>
+#include <mutex>
+#include <thread>
+#endif
+
+#include "kernel/yosys_common.h"
+#include "kernel/log.h"
+
+#ifndef YOSYS_THREADING_H
+#define YOSYS_THREADING_H
+
+YOSYS_NAMESPACE_BEGIN
+
+// Concurrent queue implementation. Not fast, but simple.
+// Multi-producer, multi-consumer, optionally bounded.
+// When YOSYS_ENABLE_THREADS is not defined, this is just a non-thread-safe non-blocking deque.
+template <typename T>
+class ConcurrentQueue
+{
+public:
+	ConcurrentQueue(int capacity = INT_MAX)
+		: capacity(capacity) {}
+	// Push an element into the queue. If it's at capacity, block until there is room.
+	void push_back(T t)
+	{
+#ifdef YOSYS_ENABLE_THREADS
+		std::unique_lock<std::mutex> lock(mutex);
+		not_full_condition.wait(lock, [this] { return static_cast<int>(contents.size()) < capacity; });
+		if (contents.empty())
+			not_empty_condition.notify_one();
+#endif
+		log_assert(!closed);
+		contents.push_back(std::move(t));
+#ifdef YOSYS_ENABLE_THREADS
+		if (static_cast<int>(contents.size()) < capacity)
+			not_full_condition.notify_one();
+#endif
+	}
+	// Signal that no more elements will be produced. `pop_front()` will return nullopt.
+	void close()
+	{
+#ifdef YOSYS_ENABLE_THREADS
+		std::unique_lock<std::mutex> lock(mutex);
+		not_empty_condition.notify_all();
+#endif
+		closed = true;
+	}
+	// Pop an element from the queue. Blocks until an element is available
+	// or the queue is closed and empty.
+	std::optional<T> pop_front()
+	{
+		return pop_front_internal(true);
+	}
+	// Pop an element from the queue. Does not block, just returns nullopt if the
+	// queue is empty.
+	std::optional<T> try_pop_front()
+	{
+		return pop_front_internal(false);
+	}
+private:
+#ifdef YOSYS_ENABLE_THREADS
+	std::optional<T> pop_front_internal(bool wait)
+	{
+		std::unique_lock<std::mutex> lock(mutex);
+		if (wait) {
+			not_empty_condition.wait(lock, [this] { return !contents.empty() || closed; });
+		}
+#else
+	std::optional<T> pop_front_internal(bool)
+	{
+#endif
+		if (contents.empty())
+			return std::nullopt;
+#ifdef YOSYS_ENABLE_THREADS
+		if (static_cast<int>(contents.size()) == capacity)
+			not_full_condition.notify_one();
+#endif
+		T result = std::move(contents.front());
+		contents.pop_front();
+#ifdef YOSYS_ENABLE_THREADS
+		if (!contents.empty())
+			not_empty_condition.notify_one();
+#endif
+		return std::move(result);
+	}
+
+#ifdef YOSYS_ENABLE_THREADS
+	std::mutex mutex;
+	// Signals one waiter thread when the queue changes and is not full.
+	std::condition_variable not_full_condition;
+	// Signals one waiter thread when the queue changes and is not empty.
+	std::condition_variable not_empty_condition;
+#endif
+	std::deque<T> contents;
+	int capacity;
+	bool closed = false;
+};
+
+class DeferredLogs
+{
+public:
+	template <typename... Args>
+	void log(FmtString<TypeIdentity<Args>...> fmt, Args... args)
+	{
+		logs.push_back({fmt.format(args...), false});
+	}
+	template <typename... Args>
+	void log_error(FmtString<TypeIdentity<Args>...> fmt, Args... args)
+	{
+		logs.push_back({fmt.format(args...), true});
+	}
+	void flush();
+private:
+	struct Message
+	{
+		std::string text;
+		bool error;
+	};
+	std::vector<Message> logs;
+};
+
+class ThreadPool
+{
+public:
+	// Computes the number of worker threads to use.
+	// `reserved_cores` cores are set aside for other threads (e.g. work on the main thread).
+	// `max_threads` --- don't return more workers than this.
+	// The result may be 0.
+	static int pool_size(int reserved_cores, int max_threads);
+
+	// Create a pool of threads running the given closure (parameterized by thread number).
+	// `pool_size` must be the result of a `pool_size()` call.
+	ThreadPool(int pool_size, std::function<void(int)> b);
+	ThreadPool(ThreadPool &&other) = delete;
+	// Waits for all threads to terminate. Make sure those closures return!
+	~ThreadPool();
+
+	// Return the number of threads in the pool.
+	int num_threads() const
+	{
+#ifdef YOSYS_ENABLE_THREADS
+		return threads.size();
+#else
+		return 0;
+#endif
+	}
+private:
+	std::function<void(int)> body;
+#ifdef YOSYS_ENABLE_THREADS
+	std::vector<std::thread> threads;
+#endif
+};
+
+template <class T>
+class ConcurrentStack
+{
+public:
+	void push_back(T &&t) {
+#ifdef YOSYS_ENABLE_THREADS
+		std::lock_guard<std::mutex> lock(mutex);
+#endif
+		contents.push_back(std::move(t));
+	}
+	std::optional<T> try_pop_back() {
+#ifdef YOSYS_ENABLE_THREADS
+		std::lock_guard<std::mutex> lock(mutex);
+#endif
+		if (contents.empty())
+			return std::nullopt;
+		T result = std::move(contents.back());
+		contents.pop_back();
+		return result;
+	}
+private:
+#ifdef YOSYS_ENABLE_THREADS
+	std::mutex mutex;
+#endif
+	std::vector<T> contents;
+};
+
+YOSYS_NAMESPACE_END
+
+#endif // YOSYS_THREADING_H
diff --git a/kernel/yosys.cc b/kernel/yosys.cc
index dc640fae9..95beca75c 100644
--- a/kernel/yosys.cc
+++ b/kernel/yosys.cc
@@ -177,7 +177,7 @@ int run_command(const std::string &command, std::function<void(const std::string
 
 	int ret = pclose(f);
 	if (ret < 0)
-		return -1;
+		return -2;
 #ifdef _WIN32
 	return ret;
 #else
diff --git a/misc/create_vcxsrc.sh b/misc/create_vcxsrc.sh
index d6800d15e..228003bad 100644
--- a/misc/create_vcxsrc.sh
+++ b/misc/create_vcxsrc.sh
@@ -38,6 +38,7 @@ popd
 } > "$vcxsrc"/YosysVS/YosysVS.vcxproj.new
 
 sed -i 's,</AdditionalIncludeDirectories>,</AdditionalIncludeDirectories>\n      <LanguageStandard>stdcpp17</LanguageStandard>\n      <AdditionalOptions>/Zc:__cplusplus %(AdditionalOptions)</AdditionalOptions>,g' "$vcxsrc"/YosysVS/YosysVS.vcxproj.new
+sed -i 's,<PreprocessorDefinitions>,<PreprocessorDefinitions>YOSYS_ENABLE_THREADS;,g' "$vcxsrc"/YosysVS/YosysVS.vcxproj.new
 if [ -f "/usr/include/FlexLexer.h" ] ; then
 	sed -i 's,</AdditionalIncludeDirectories>,;..\\yosys\\libs\\flex</AdditionalIncludeDirectories>,g' "$vcxsrc"/YosysVS/YosysVS.vcxproj.new
 fi
diff --git a/passes/techmap/abc.cc b/passes/techmap/abc.cc
index 7d81b52d2..82a5124ae 100644
--- a/passes/techmap/abc.cc
+++ b/passes/techmap/abc.cc
@@ -48,6 +48,7 @@
 #include "kernel/ff.h"
 #include "kernel/cost.h"
 #include "kernel/log.h"
+#include "kernel/threading.h"
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
@@ -55,8 +56,14 @@
 #include <cerrno>
 #include <sstream>
 #include <climits>
+#include <memory>
 #include <vector>
 
+#ifdef __linux__
+#  include <fcntl.h>
+#  include <spawn.h>
+#  include <sys/wait.h>
+#endif
 #ifndef _WIN32
 #  include <unistd.h>
 #  include <dirent.h>
@@ -104,8 +111,10 @@ struct gate_t
 	gate_type_t type;
 	int in1, in2, in3, in4;
 	bool is_port;
-	RTLIL::SigBit bit;
+	bool bit_is_wire;
+	bool bit_is_1;
 	RTLIL::State init;
+	std::string bit_str;
 };
 
 bool map_mux4;
@@ -119,6 +128,7 @@ bool cmos_cost;
 
 struct AbcConfig
 {
+	std::string global_tempdir_name;
 	std::string script_file;
 	std::string exe_file;
 	std::vector<std::string> liberty_files;
@@ -148,31 +158,158 @@ struct AbcSigVal {
 	}
 };
 
+#if defined(__linux__) && !defined(YOSYS_DISABLE_SPAWN)
+struct AbcProcess
+{
+	pid_t pid;
+	int to_child_pipe;
+	int from_child_pipe;
+
+	AbcProcess() : pid(0), to_child_pipe(-1), from_child_pipe(-1) {}
+	AbcProcess(AbcProcess &&other) {
+		pid = other.pid;
+		to_child_pipe = other.to_child_pipe;
+		from_child_pipe = other.from_child_pipe;
+		other.pid = 0;
+		other.to_child_pipe = other.from_child_pipe = -1;
+	}
+	AbcProcess &operator=(AbcProcess &&other) {
+		if (this != &other) {
+			pid = other.pid;
+			to_child_pipe = other.to_child_pipe;
+			from_child_pipe = other.from_child_pipe;
+			other.pid = 0;
+			other.to_child_pipe = other.from_child_pipe = -1;
+		}
+		return *this;
+	}
+	~AbcProcess() {
+		if (pid == 0)
+			return;
+		if (to_child_pipe >= 0)
+			close(to_child_pipe);
+		int status;
+		int ret = waitpid(pid, &status, 0);
+		if (ret != pid) {
+			log_error("waitpid(%d) failed", pid);
+		}
+		if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+			log_error("ABC failed with status %X", status);
+		}
+		if (from_child_pipe >= 0)
+			close(from_child_pipe);
+	}
+};
+
+std::optional<AbcProcess> spawn_abc(const char* abc_exe, DeferredLogs &logs) {
+	// Open pipes O_CLOEXEC so we don't leak any of the fds into racing
+	// fork()s.
+	int to_child_pipe[2];
+	if (pipe2(to_child_pipe, O_CLOEXEC) != 0) {
+		logs.log_error("pipe failed");
+		return std::nullopt;
+	}
+	int from_child_pipe[2];
+	if (pipe2(from_child_pipe, O_CLOEXEC) != 0) {
+		logs.log_error("pipe failed");
+		return std::nullopt;
+	}
+
+	AbcProcess result;
+	result.to_child_pipe = to_child_pipe[1];
+	result.from_child_pipe = from_child_pipe[0];
+	// Allow the child side of the pipes to be inherited.
+	fcntl(to_child_pipe[0], F_SETFD, 0);
+	fcntl(from_child_pipe[1], F_SETFD, 0);
+
+	posix_spawn_file_actions_t file_actions;
+	if (posix_spawn_file_actions_init(&file_actions) != 0) {
+		logs.log_error("posix_spawn_file_actions_init failed");
+		return std::nullopt;
+	}
+
+	if (posix_spawn_file_actions_addclose(&file_actions, to_child_pipe[1]) != 0) {
+		logs.log_error("posix_spawn_file_actions_addclose failed");
+		return std::nullopt;
+	}
+	if (posix_spawn_file_actions_addclose(&file_actions, from_child_pipe[0]) != 0) {
+		logs.log_error("posix_spawn_file_actions_addclose failed");
+		return std::nullopt;
+	}
+	if (posix_spawn_file_actions_adddup2(&file_actions, to_child_pipe[0], STDIN_FILENO) != 0) {
+		logs.log_error("posix_spawn_file_actions_adddup2 failed");
+		return std::nullopt;
+	}
+	if (posix_spawn_file_actions_adddup2(&file_actions, from_child_pipe[1], STDOUT_FILENO) != 0) {
+		logs.log_error("posix_spawn_file_actions_adddup2 failed");
+		return std::nullopt;
+	}
+	if (posix_spawn_file_actions_adddup2(&file_actions, from_child_pipe[1], STDERR_FILENO) != 0) {
+		logs.log_error("posix_spawn_file_actions_adddup2 failed");
+		return std::nullopt;
+	}
+	if (posix_spawn_file_actions_addclose(&file_actions, to_child_pipe[0]) != 0) {
+		logs.log_error("posix_spawn_file_actions_addclose failed");
+		return std::nullopt;
+	}
+	if (posix_spawn_file_actions_addclose(&file_actions, from_child_pipe[1]) != 0) {
+		logs.log_error("posix_spawn_file_actions_addclose failed");
+		return std::nullopt;
+	}
+
+	char arg1[] = "-s";
+	char* argv[] = { strdup(abc_exe), arg1, nullptr };
+	if (0 != posix_spawn(&result.pid, abc_exe, &file_actions, nullptr, argv, environ)) {
+		logs.log_error("posix_spawn %s failed", abc_exe);
+		return std::nullopt;
+	}
+	free(argv[0]);
+	posix_spawn_file_actions_destroy(&file_actions);
+	close(to_child_pipe[0]);
+	close(from_child_pipe[1]);
+	return result;
+}
+#else
+struct AbcProcess {};
+#endif
+
 using AbcSigMap = SigValMap<AbcSigVal>;
 
-struct AbcModuleState {
+// Used by off-main-threads. Contains no direct or indirect access to RTLIL.
+struct RunAbcState {
 	const AbcConfig &config;
 
-	int map_autoidx = 0;
+	std::string tempdir_name;
 	std::vector<gate_t> signal_list;
+	bool did_run = false;
+	bool err = false;
+	DeferredLogs logs;
+	dict<int, std::string> pi_map, po_map;
+
+	RunAbcState(const AbcConfig &config) : config(config) {}
+	void run(ConcurrentStack<AbcProcess> &process_pool);
+};
+
+struct AbcModuleState {
+	RunAbcState run_abc;
+
+	int map_autoidx = 0;
+	std::vector<RTLIL::SigBit> signal_bits;
 	dict<RTLIL::SigBit, int> signal_map;
 	FfInitVals &initvals;
 	bool had_init = false;
-	bool did_run_abc = false;
 
 	bool clk_polarity = false;
 	bool en_polarity = false;
 	bool arst_polarity = false;
 	bool srst_polarity = false;
 	RTLIL::SigSpec clk_sig, en_sig, arst_sig, srst_sig;
-	dict<int, std::string> pi_map, po_map;
 
 	int undef_bits_lost = 0;
 
-	std::string tempdir_name;
-
 	AbcModuleState(const AbcConfig &config, FfInitVals &initvals)
-		: config(config), initvals(initvals) {}
+		: run_abc(config), initvals(initvals) {}
+	AbcModuleState(AbcModuleState&&) = delete;
 
 	int map_signal(const AbcSigMap &assign_map, RTLIL::SigBit bit, gate_type_t gate_type = G(NONE), int in1 = -1, int in2 = -1, int in3 = -1, int in4 = -1);
 	void mark_port(const AbcSigMap &assign_map, RTLIL::SigSpec sig);
@@ -180,7 +317,7 @@ struct AbcModuleState {
 	std::string remap_name(RTLIL::IdString abc_name, RTLIL::Wire **orig_wire = nullptr);
 	void dump_loop_graph(FILE *f, int &nr, dict<int, pool<int>> &edges, pool<int> &workpool, std::vector<int> &in_counts);
 	void handle_loops(AbcSigMap &assign_map, RTLIL::Module *module);
-	void abc_module(RTLIL::Design *design, RTLIL::Module *module, AbcSigMap &assign_map, const std::vector<RTLIL::Cell*> &cells,
+	void prepare_module(RTLIL::Design *design, RTLIL::Module *module, AbcSigMap &assign_map, const std::vector<RTLIL::Cell*> &cells,
 		bool dff_mode, std::string clk_str);
 	void extract(AbcSigMap &assign_map, RTLIL::Design *design, RTLIL::Module *module);
 	void finish();
@@ -195,20 +332,23 @@ int AbcModuleState::map_signal(const AbcSigMap &assign_map, RTLIL::SigBit bit, g
 
 	if (signal_map.count(bit) == 0) {
 		gate_t gate;
-		gate.id = signal_list.size();
+		gate.id = run_abc.signal_list.size();
 		gate.type = G(NONE);
 		gate.in1 = -1;
 		gate.in2 = -1;
 		gate.in3 = -1;
 		gate.in4 = -1;
 		gate.is_port = bit.wire != nullptr && val.is_port;
-		gate.bit = bit;
+		gate.bit_is_wire = bit.wire != nullptr;
+		gate.bit_is_1 = bit == State::S1;
 		gate.init = initvals(bit);
-		signal_list.push_back(gate);
+		gate.bit_str = std::string(log_signal(bit));
 		signal_map[bit] = gate.id;
+		run_abc.signal_list.push_back(std::move(gate));
+		signal_bits.push_back(bit);
 	}
 
-	gate_t &gate = signal_list[signal_map[bit]];
+	gate_t &gate = run_abc.signal_list[signal_map[bit]];
 
 	if (gate_type != G(NONE))
 		gate.type = gate_type;
@@ -228,7 +368,7 @@ void AbcModuleState::mark_port(const AbcSigMap &assign_map, RTLIL::SigSpec sig)
 {
 	for (auto &bit : assign_map(sig))
 		if (bit.wire != nullptr && signal_map.count(bit) > 0)
-			signal_list[signal_map[bit]].is_port = true;
+			run_abc.signal_list[signal_map[bit]].is_port = true;
 }
 
 bool AbcModuleState::extract_cell(const AbcSigMap &assign_map, RTLIL::Module *module, RTLIL::Cell *cell, bool keepff)
@@ -307,7 +447,7 @@ bool AbcModuleState::extract_cell(const AbcSigMap &assign_map, RTLIL::Module *mo
 		if (keepff) {
 			SigBit bit = ff.sig_q;
 			if (assign_map(bit).wire != nullptr) {
-				signal_list[gate_id].is_port = true;
+				run_abc.signal_list[gate_id].is_port = true;
 			}
 			if (bit.wire != nullptr)
 				bit.wire->attributes[ID::keep] = 1;
@@ -459,19 +599,19 @@ std::string AbcModuleState::remap_name(RTLIL::IdString abc_name, RTLIL::Wire **o
 			size_t postfix_start = abc_sname.find_first_not_of("0123456789");
 			std::string postfix = postfix_start != std::string::npos ? abc_sname.substr(postfix_start) : "";
 
-			if (sid < GetSize(signal_list))
+			if (sid < GetSize(run_abc.signal_list))
 			{
-				auto sig = signal_list.at(sid);
-				if (sig.bit.wire != nullptr)
+				const auto &bit = signal_bits.at(sid);
+				if (bit.wire != nullptr)
 				{
-					std::string s = stringf("$abc$%d$%s", map_autoidx, sig.bit.wire->name.c_str()+1);
-					if (sig.bit.wire->width != 1)
-						s += stringf("[%d]", sig.bit.offset);
+					std::string s = stringf("$abc$%d$%s", map_autoidx, bit.wire->name.c_str()+1);
+					if (bit.wire->width != 1)
+						s += stringf("[%d]", bit.offset);
 					if (isnew)
 						s += "_new";
 					s += postfix;
 					if (orig_wire != nullptr)
-						*orig_wire = sig.bit.wire;
+						*orig_wire = bit.wire;
 					return s;
 				}
 			}
@@ -499,7 +639,7 @@ void AbcModuleState::dump_loop_graph(FILE *f, int &nr, dict<int, pool<int>> &edg
 	}
 
 	for (auto n : nodes)
-		fprintf(f, "  ys__n%d [label=\"%s\\nid=%d, count=%d\"%s];\n", n, log_signal(signal_list[n].bit),
+		fprintf(f, "  ys__n%d [label=\"%s\\nid=%d, count=%d\"%s];\n", n, run_abc.signal_list[n].bit_str.c_str(),
 				n, in_counts[n], workpool.count(n) ? ", shape=box" : "");
 
 	for (auto &e : edges)
@@ -521,7 +661,7 @@ void AbcModuleState::handle_loops(AbcSigMap &assign_map, RTLIL::Module *module)
 	// (Kahn, Arthur B. (1962), "Topological sorting of large networks")
 
 	dict<int, pool<int>> edges;
-	std::vector<int> in_edges_count(signal_list.size());
+	std::vector<int> in_edges_count(run_abc.signal_list.size());
 	pool<int> workpool;
 
 	FILE *dot_f = nullptr;
@@ -530,7 +670,7 @@ void AbcModuleState::handle_loops(AbcSigMap &assign_map, RTLIL::Module *module)
 	// uncomment for troubleshooting the loop detection code
 	// dot_f = fopen("test.dot", "w");
 
-	for (auto &g : signal_list) {
+	for (auto &g : run_abc.signal_list) {
 		if (g.type == G(NONE) || g.type == G(FF) || g.type == G(FF0) || g.type == G(FF1)) {
 			workpool.insert(g.id);
 		} else {
@@ -560,7 +700,7 @@ void AbcModuleState::handle_loops(AbcSigMap &assign_map, RTLIL::Module *module)
 		int id = *workpool.begin();
 		workpool.erase(id);
 
-		// log("Removing non-loop node %d from graph: %s\n", id, log_signal(signal_list[id].bit));
+		// log("Removing non-loop node %d from graph: %s\n", id, signal_list[id].bit_str);
 
 		for (int id2 : edges[id]) {
 			log_assert(in_edges_count[id2] > 0);
@@ -580,8 +720,8 @@ void AbcModuleState::handle_loops(AbcSigMap &assign_map, RTLIL::Module *module)
 
 			for (auto &edge_it : edges) {
 				int id2 = edge_it.first;
-				RTLIL::Wire *w1 = signal_list[id1].bit.wire;
-				RTLIL::Wire *w2 = signal_list[id2].bit.wire;
+				RTLIL::Wire *w1 = signal_bits[id1].wire;
+				RTLIL::Wire *w2 = signal_bits[id2].wire;
 				if (w1 == nullptr)
 					id1 = id2;
 				else if (w2 == nullptr)
@@ -603,7 +743,7 @@ void AbcModuleState::handle_loops(AbcSigMap &assign_map, RTLIL::Module *module)
 				continue;
 			}
 
-			log_assert(signal_list[id1].bit.wire != nullptr);
+			log_assert(signal_bits[id1].wire != nullptr);
 
 			std::stringstream sstr;
 			sstr << "$abcloop$" << (autoidx++);
@@ -613,33 +753,33 @@ void AbcModuleState::handle_loops(AbcSigMap &assign_map, RTLIL::Module *module)
 			for (int id2 : edges[id1]) {
 				if (first_line)
 					log("Breaking loop using new signal %s: %s -> %s\n", log_signal(RTLIL::SigSpec(wire)),
-							log_signal(signal_list[id1].bit), log_signal(signal_list[id2].bit));
+							run_abc.signal_list[id1].bit_str, run_abc.signal_list[id2].bit_str);
 				else
 					log("                               %*s  %s -> %s\n", int(strlen(log_signal(RTLIL::SigSpec(wire)))), "",
-							log_signal(signal_list[id1].bit), log_signal(signal_list[id2].bit));
+							run_abc.signal_list[id1].bit_str, run_abc.signal_list[id2].bit_str);
 				first_line = false;
 			}
 
 			int id3 = map_signal(assign_map, RTLIL::SigSpec(wire));
-			signal_list[id1].is_port = true;
-			signal_list[id3].is_port = true;
+			run_abc.signal_list[id1].is_port = true;
+			run_abc.signal_list[id3].is_port = true;
 			log_assert(id3 == int(in_edges_count.size()));
 			in_edges_count.push_back(0);
 			workpool.insert(id3);
 
 			for (int id2 : edges[id1]) {
-				if (signal_list[id2].in1 == id1)
-					signal_list[id2].in1 = id3;
-				if (signal_list[id2].in2 == id1)
-					signal_list[id2].in2 = id3;
-				if (signal_list[id2].in3 == id1)
-					signal_list[id2].in3 = id3;
-				if (signal_list[id2].in4 == id1)
-					signal_list[id2].in4 = id3;
+				if (run_abc.signal_list[id2].in1 == id1)
+					run_abc.signal_list[id2].in1 = id3;
+				if (run_abc.signal_list[id2].in2 == id1)
+					run_abc.signal_list[id2].in2 = id3;
+				if (run_abc.signal_list[id2].in3 == id1)
+					run_abc.signal_list[id2].in3 = id3;
+				if (run_abc.signal_list[id2].in4 == id1)
+					run_abc.signal_list[id2].in4 = id3;
 			}
 			edges[id1].swap(edges[id3]);
 
-			connect(assign_map, module, RTLIL::SigSig(signal_list[id3].bit, signal_list[id1].bit));
+			connect(assign_map, module, RTLIL::SigSig(signal_bits[id3], signal_bits[id1]));
 			dump_loop_graph(dot_f, dot_nr, edges, workpool, in_edges_count);
 		}
 	}
@@ -716,14 +856,14 @@ std::string replace_tempdir(std::string text, std::string tempdir_name, bool sho
 
 struct abc_output_filter
 {
-	const AbcModuleState &state;
+	RunAbcState &state;
 	bool got_cr;
 	int escape_seq_state;
 	std::string linebuf;
 	std::string tempdir_name;
 	bool show_tempdir;
 
-	abc_output_filter(const AbcModuleState& state, std::string tempdir_name, bool show_tempdir)
+	abc_output_filter(RunAbcState& state, std::string tempdir_name, bool show_tempdir)
 		: state(state), tempdir_name(tempdir_name), show_tempdir(show_tempdir)
 	{
 		got_cr = false;
@@ -751,7 +891,7 @@ struct abc_output_filter
 			return;
 		}
 		if (ch == '\n') {
-			log("ABC: %s\n", replace_tempdir(linebuf, tempdir_name, show_tempdir));
+			state.logs.log("ABC: %s\n", replace_tempdir(linebuf, tempdir_name, show_tempdir));
 			got_cr = false, linebuf.clear();
 			return;
 		}
@@ -764,7 +904,7 @@ struct abc_output_filter
 	{
 		int pi, po;
 		if (sscanf(line.c_str(), "Start-point = pi%d.  End-point = po%d.", &pi, &po) == 2) {
-			log("ABC: Start-point = pi%d (%s).  End-point = po%d (%s).\n",
+			state.logs.log("ABC: Start-point = pi%d (%s).  End-point = po%d (%s).\n",
 					pi, state.pi_map.count(pi) ? state.pi_map.at(pi).c_str() : "???",
 					po, state.po_map.count(po) ? state.po_map.at(po).c_str() : "???");
 			return;
@@ -775,7 +915,7 @@ struct abc_output_filter
 	}
 };
 
-void AbcModuleState::abc_module(RTLIL::Design *design, RTLIL::Module *module, AbcSigMap &assign_map, const std::vector<RTLIL::Cell*> &cells,
+void AbcModuleState::prepare_module(RTLIL::Design *design, RTLIL::Module *module, AbcSigMap &assign_map, const std::vector<RTLIL::Cell*> &cells,
 	bool dff_mode, std::string clk_str)
 {
 	map_autoidx = autoidx++;
@@ -850,16 +990,17 @@ void AbcModuleState::abc_module(RTLIL::Design *design, RTLIL::Module *module, Ab
 	if (dff_mode && clk_sig.empty())
 		log_cmd_error("Clock domain %s not found.\n", clk_str.c_str());
 
+	const AbcConfig &config = run_abc.config;
 	if (config.cleanup)
-		tempdir_name = get_base_tmpdir() + "/";
+		run_abc.tempdir_name = get_base_tmpdir() + "/";
 	else
-		tempdir_name = "_tmp_";
-	tempdir_name += proc_program_prefix() + "yosys-abc-XXXXXX";
-	tempdir_name = make_temp_dir(tempdir_name);
+		run_abc.tempdir_name = "_tmp_";
+	run_abc.tempdir_name += proc_program_prefix() + "yosys-abc-XXXXXX";
+	run_abc.tempdir_name = make_temp_dir(run_abc.tempdir_name);
 	log_header(design, "Extracting gate netlist of module `%s' to `%s/input.blif'..\n",
-			module->name.c_str(), replace_tempdir(tempdir_name, tempdir_name, config.show_tempdir).c_str());
+			module->name.c_str(), replace_tempdir(run_abc.tempdir_name, run_abc.tempdir_name, config.show_tempdir).c_str());
 
-	std::string abc_script = stringf("read_blif \"%s/input.blif\"; ", tempdir_name);
+	std::string abc_script = stringf("read_blif \"%s/input.blif\"; ", run_abc.tempdir_name);
 
 	if (!config.liberty_files.empty() || !config.genlib_files.empty()) {
 		std::string dont_use_args;
@@ -877,9 +1018,9 @@ void AbcModuleState::abc_module(RTLIL::Design *design, RTLIL::Module *module, Ab
 			abc_script += stringf("read_constr -v \"%s\"; ", config.constr_file);
 	} else
 	if (!config.lut_costs.empty())
-		abc_script += stringf("read_lut %s/lutdefs.txt; ", tempdir_name);
+		abc_script += stringf("read_lut %s/lutdefs.txt; ", config.global_tempdir_name);
 	else
-		abc_script += stringf("read_library %s/stdcells.genlib; ", tempdir_name);
+		abc_script += stringf("read_library %s/stdcells.genlib; ", config.global_tempdir_name);
 
 	if (!config.script_file.empty()) {
 		const std::string &script_file = config.script_file;
@@ -925,15 +1066,15 @@ void AbcModuleState::abc_module(RTLIL::Design *design, RTLIL::Module *module, Ab
 	for (size_t pos = abc_script.find("{S}"); pos != std::string::npos; pos = abc_script.find("{S}", pos))
 		abc_script = abc_script.substr(0, pos) + config.lutin_shared + abc_script.substr(pos+3);
 	if (config.abc_dress)
-		abc_script += stringf("; dress \"%s/input.blif\"", tempdir_name);
-	abc_script += stringf("; write_blif %s/output.blif", tempdir_name);
+		abc_script += stringf("; dress \"%s/input.blif\"", run_abc.tempdir_name);
+	abc_script += stringf("; write_blif %s/output.blif", run_abc.tempdir_name);
 	abc_script = add_echos_to_abc_cmd(abc_script);
 
 	for (size_t i = 0; i+1 < abc_script.size(); i++)
 		if (abc_script[i] == ';' && abc_script[i+1] == ' ')
 			abc_script[i+1] = '\n';
 
-	std::string buffer = stringf("%s/abc.script", tempdir_name);
+	std::string buffer = stringf("%s/abc.script", run_abc.tempdir_name);
 	FILE *f = fopen(buffer.c_str(), "wt");
 	if (f == nullptr)
 		log_error("Opening %s for writing failed: %s\n", buffer, strerror(errno));
@@ -987,11 +1128,52 @@ void AbcModuleState::abc_module(RTLIL::Design *design, RTLIL::Module *module, Ab
 		mark_port(assign_map, srst_sig);
 
 	handle_loops(assign_map, module);
+}
 
-	buffer = stringf("%s/input.blif", tempdir_name);
-	f = fopen(buffer.c_str(), "wt");
-	if (f == nullptr)
-		log_error("Opening %s for writing failed: %s\n", buffer, strerror(errno));
+bool read_until_abc_done(abc_output_filter &filt, int fd, DeferredLogs &logs) {
+	std::string line;
+	char buf[1024];
+	while (true) {
+		int ret = read(fd, buf, sizeof(buf) - 1);
+		if (ret < 0) {
+			logs.log_error("Failed to read from ABC, errno=%d", errno);
+			return false;
+		}
+		if (ret == 0) {
+			logs.log_error("ABC exited prematurely");
+			return false;
+		}
+		char *start = buf;
+		char *end = buf + ret;
+		while (start < end) {
+			char *p = static_cast<char*>(memchr(start, '\n', end - start));
+			if (p == nullptr) {
+				break;
+			}
+			line.append(start, p + 1 - start);
+			// ABC seems to actually print "ABC_DONE \n", but we probably shouldn't
+			// rely on that extra space being output.
+			if (line.substr(0, 8) == "ABC_DONE") {
+				// Ignore any leftover output, there should only be a prompt perhaps
+				return true;
+			}
+			filt.next_line(line);
+			line.clear();
+			start = p + 1;
+		}
+		line.append(start, end - start);
+	}
+}
+
+void RunAbcState::run(ConcurrentStack<AbcProcess> &process_pool)
+{
+	std::string buffer = stringf("%s/input.blif", tempdir_name);
+	FILE *f = fopen(buffer.c_str(), "wt");
+	if (f == nullptr) {
+		logs.log("Opening %s for writing failed: %s\n", buffer, strerror(errno));
+		err = true;
+		return;
+	}
 
 	fprintf(f, ".model netlist\n");
 
@@ -1001,7 +1183,7 @@ void AbcModuleState::abc_module(RTLIL::Design *design, RTLIL::Module *module, Ab
 		if (!si.is_port || si.type != G(NONE))
 			continue;
 		fprintf(f, " ys__n%d", si.id);
-		pi_map[count_input++] = log_signal(si.bit);
+		pi_map[count_input++] = si.bit_str;
 	}
 	if (count_input == 0)
 		fprintf(f, " dummy_input\n");
@@ -1013,17 +1195,17 @@ void AbcModuleState::abc_module(RTLIL::Design *design, RTLIL::Module *module, Ab
 		if (!si.is_port || si.type == G(NONE))
 			continue;
 		fprintf(f, " ys__n%d", si.id);
-		po_map[count_output++] = log_signal(si.bit);
+		po_map[count_output++] = si.bit_str;
 	}
 	fprintf(f, "\n");
 
 	for (auto &si : signal_list)
-		fprintf(f, "# ys__n%-5d %s\n", si.id, log_signal(si.bit));
+		fprintf(f, "# ys__n%-5d %s\n", si.id, si.bit_str.c_str());
 
 	for (auto &si : signal_list) {
-		if (si.bit.wire == nullptr) {
+		if (!si.bit_is_wire) {
 			fprintf(f, ".names ys__n%d\n", si.id);
-			if (si.bit == RTLIL::State::S1)
+			if (si.bit_is_1)
 				fprintf(f, "1\n");
 		}
 	}
@@ -1106,19 +1288,112 @@ void AbcModuleState::abc_module(RTLIL::Design *design, RTLIL::Module *module, Ab
 	fprintf(f, ".end\n");
 	fclose(f);
 
-	log("Extracted %d gates and %d wires to a netlist network with %d inputs and %d outputs.\n",
+	logs.log("Extracted %d gates and %d wires to a netlist network with %d inputs and %d outputs.\n",
 			count_gates, GetSize(signal_list), count_input, count_output);
-	log_push();
 	if (count_output > 0)
 	{
-		log_header(design, "Executing ABC.\n");
+		std::string tmp_script_name = stringf("%s/abc.script", tempdir_name);
+		logs.log("Running ABC script: %s\n", replace_tempdir(tmp_script_name, tempdir_name, config.show_tempdir));
 
+		errno = 0;
+		abc_output_filter filt(*this, tempdir_name, config.show_tempdir);
+#ifdef YOSYS_LINK_ABC
+		string temp_stdouterr_name = stringf("%s/stdouterr.txt", tempdir_name);
+		FILE *temp_stdouterr_w = fopen(temp_stdouterr_name.c_str(), "w");
+		if (temp_stdouterr_w == NULL)
+			log_error("ABC: cannot open a temporary file for output redirection");
+		fflush(stdout);
+		fflush(stderr);
+		FILE *old_stdout = fopen(temp_stdouterr_name.c_str(), "r"); // need any fd for renumbering
+		FILE *old_stderr = fopen(temp_stdouterr_name.c_str(), "r"); // need any fd for renumbering
+#if defined(__wasm)
+#define fd_renumber(from, to) (void)__wasi_fd_renumber(from, to)
+#else
+#define fd_renumber(from, to) dup2(from, to)
+#endif
+		fd_renumber(fileno(stdout), fileno(old_stdout));
+		fd_renumber(fileno(stderr), fileno(old_stderr));
+		fd_renumber(fileno(temp_stdouterr_w), fileno(stdout));
+		fd_renumber(fileno(temp_stdouterr_w), fileno(stderr));
+		fclose(temp_stdouterr_w);
+		// These needs to be mutable, supposedly due to getopt
+		char *abc_argv[5];
+		abc_argv[0] = strdup(config.exe_file.c_str());
+		abc_argv[1] = strdup("-s");
+		abc_argv[2] = strdup("-f");
+		abc_argv[3] = strdup(tmp_script_name.c_str());
+		abc_argv[4] = 0;
+		int ret = abc::Abc_RealMain(4, abc_argv);
+		free(abc_argv[0]);
+		free(abc_argv[1]);
+		free(abc_argv[2]);
+		free(abc_argv[3]);
+		fflush(stdout);
+		fflush(stderr);
+		fd_renumber(fileno(old_stdout), fileno(stdout));
+		fd_renumber(fileno(old_stderr), fileno(stderr));
+		fclose(old_stdout);
+		fclose(old_stderr);
+		std::ifstream temp_stdouterr_r(temp_stdouterr_name);
+		for (std::string line; std::getline(temp_stdouterr_r, line); )
+			filt.next_line(line + "\n");
+		temp_stdouterr_r.close();
+#elif defined(__linux__) && !defined(YOSYS_DISABLE_SPAWN)
+		AbcProcess process;
+		if (std::optional<AbcProcess> process_opt = process_pool.try_pop_back()) {
+			process = std::move(process_opt.value());
+		} else if (std::optional<AbcProcess> process_opt = spawn_abc(config.exe_file.c_str(), logs)) {
+			process = std::move(process_opt.value());
+		} else {
+			return;
+		}
+		std::string cmd = stringf(
+				// This makes ABC switch stdout to line buffering, which we need
+				// to see our ABC_DONE message.
+				"set abcout /dev/stdout\n"
+				"empty\n"
+				"source %s\n"
+				"echo \"ABC_DONE\"\n", tmp_script_name);
+		int ret = write(process.to_child_pipe, cmd.c_str(), cmd.size());
+		if (ret != static_cast<int>(cmd.size())) {
+			logs.log_error("write failed");
+			return;
+		}
+		ret = read_until_abc_done(filt, process.from_child_pipe, logs) ? 0 : 1;
+		if (ret == 0) {
+			process_pool.push_back(std::move(process));
+		}
+#else
+		std::string cmd = stringf("\"%s\" -s -f %s/abc.script 2>&1", config.exe_file.c_str(), tempdir_name.c_str());
+		int ret = run_command(cmd, std::bind(&abc_output_filter::next_line, filt, std::placeholders::_1));
+#endif
+		if (ret != 0) {
+			logs.log_error("ABC: execution of script \"%s\" failed: return code %d (errno=%d).\n", tmp_script_name, ret, errno);
+			return;
+		}
+		did_run = true;
+		return;
+	}
+	log("Don't call ABC as there is nothing to map.\n");
+}
+
+void emit_global_input_files(const AbcConfig &config)
+{
+	if (!config.lut_costs.empty()) {
+		std::string buffer = stringf("%s/lutdefs.txt", config.global_tempdir_name.c_str());
+		FILE *f = fopen(buffer.c_str(), "wt");
+		if (f == nullptr)
+			log_error("Opening %s for writing failed: %s\n", buffer.c_str(), strerror(errno));
+		for (int i = 0; i < GetSize(config.lut_costs); i++)
+			fprintf(f, "%d %d.00 1.00\n", i+1, config.lut_costs.at(i));
+		fclose(f);
+	} else {
 		auto &cell_cost = cmos_cost ? CellCosts::cmos_gate_cost() : CellCosts::default_gate_cost();
 
-		buffer = stringf("%s/stdcells.genlib", tempdir_name);
-		f = fopen(buffer.c_str(), "wt");
+		std::string buffer = stringf("%s/stdcells.genlib", config.global_tempdir_name.c_str());
+		FILE *f = fopen(buffer.c_str(), "wt");
 		if (f == nullptr)
-			log_error("Opening %s for writing failed: %s\n", buffer, strerror(errno));
+			log_error("Opening %s for writing failed: %s\n", buffer.c_str(), strerror(errno));
 		fprintf(f, "GATE ZERO    1 Y=CONST0;\n");
 		fprintf(f, "GATE ONE     1 Y=CONST1;\n");
 		fprintf(f, "GATE BUF    %d Y=A;                  PIN * NONINV  1 999 1 0 1 0\n", cell_cost.at(ID($_BUF_)));
@@ -1158,92 +1433,28 @@ void AbcModuleState::abc_module(RTLIL::Design *design, RTLIL::Module *module, Ab
 		if (map_mux16)
 			fprintf(f, "GATE MUX16  %d Y=(!S*!T*!U*!V*A)+(S*!T*!U*!V*B)+(!S*T*!U*!V*C)+(S*T*!U*!V*D)+(!S*!T*U*!V*E)+(S*!T*U*!V*F)+(!S*T*U*!V*G)+(S*T*U*!V*H)+(!S*!T*!U*V*I)+(S*!T*!U*V*J)+(!S*T*!U*V*K)+(S*T*!U*V*L)+(!S*!T*U*V*M)+(S*!T*U*V*N)+(!S*T*U*V*O)+(S*T*U*V*P); PIN * UNKNOWN 1 999 1 0 1 0\n", 8*cell_cost.at(ID($_MUX_)));
 		fclose(f);
-
-		if (!config.lut_costs.empty()) {
-			buffer = stringf("%s/lutdefs.txt", tempdir_name);
-			f = fopen(buffer.c_str(), "wt");
-			if (f == nullptr)
-				log_error("Opening %s for writing failed: %s\n", buffer, strerror(errno));
-			for (int i = 0; i < GetSize(config.lut_costs); i++)
-				fprintf(f, "%d %d.00 1.00\n", i+1, config.lut_costs.at(i));
-			fclose(f);
-		}
-
-		buffer = stringf("\"%s\" -s -f %s/abc.script 2>&1", config.exe_file, tempdir_name);
-		log("Running ABC command: %s\n", replace_tempdir(buffer, tempdir_name, config.show_tempdir));
-
-#ifndef YOSYS_LINK_ABC
-		abc_output_filter filt(*this, tempdir_name, config.show_tempdir);
-		int ret = run_command(buffer, std::bind(&abc_output_filter::next_line, filt, std::placeholders::_1));
-#else
-		string temp_stdouterr_name = stringf("%s/stdouterr.txt", tempdir_name);
-		FILE *temp_stdouterr_w = fopen(temp_stdouterr_name.c_str(), "w");
-		if (temp_stdouterr_w == NULL)
-			log_error("ABC: cannot open a temporary file for output redirection");
-		fflush(stdout);
-		fflush(stderr);
-		FILE *old_stdout = fopen(temp_stdouterr_name.c_str(), "r"); // need any fd for renumbering
-		FILE *old_stderr = fopen(temp_stdouterr_name.c_str(), "r"); // need any fd for renumbering
-#if defined(__wasm)
-#define fd_renumber(from, to) (void)__wasi_fd_renumber(from, to)
-#else
-#define fd_renumber(from, to) dup2(from, to)
-#endif
-		fd_renumber(fileno(stdout), fileno(old_stdout));
-		fd_renumber(fileno(stderr), fileno(old_stderr));
-		fd_renumber(fileno(temp_stdouterr_w), fileno(stdout));
-		fd_renumber(fileno(temp_stdouterr_w), fileno(stderr));
-		fclose(temp_stdouterr_w);
-		// These needs to be mutable, supposedly due to getopt
-		char *abc_argv[5];
-		string tmp_script_name = stringf("%s/abc.script", tempdir_name);
-		abc_argv[0] = strdup(config.exe_file.c_str());
-		abc_argv[1] = strdup("-s");
-		abc_argv[2] = strdup("-f");
-		abc_argv[3] = strdup(tmp_script_name.c_str());
-		abc_argv[4] = 0;
-		int ret = abc::Abc_RealMain(4, abc_argv);
-		free(abc_argv[0]);
-		free(abc_argv[1]);
-		free(abc_argv[2]);
-		free(abc_argv[3]);
-		fflush(stdout);
-		fflush(stderr);
-		fd_renumber(fileno(old_stdout), fileno(stdout));
-		fd_renumber(fileno(old_stderr), fileno(stderr));
-		fclose(old_stdout);
-		fclose(old_stderr);
-		std::ifstream temp_stdouterr_r(temp_stdouterr_name);
-		abc_output_filter filt(*this, tempdir_name, config.show_tempdir);
-		for (std::string line; std::getline(temp_stdouterr_r, line); )
-			filt.next_line(line + "\n");
-		temp_stdouterr_r.close();
-#endif
-		if (ret != 0) {
-			log_error("ABC: execution of command \"%s\" failed: return code %d.\n", buffer, ret);
-			return;
-		}
-		did_run_abc = true;
-		return;
 	}
-	log("Don't call ABC as there is nothing to map.\n");
 }
 
 void AbcModuleState::extract(AbcSigMap &assign_map, RTLIL::Design *design, RTLIL::Module *module)
 {
-	if (!did_run_abc) {
+	log_push();
+	log_header(design, "Executed ABC.\n");
+	run_abc.logs.flush();
+	if (!run_abc.did_run) {
+		finish();
 		return;
 	}
 
-	std::string buffer = stringf("%s/%s", tempdir_name, "output.blif");
+	std::string buffer = stringf("%s/%s", run_abc.tempdir_name, "output.blif");
 	std::ifstream ifs;
 	ifs.open(buffer);
 	if (ifs.fail())
 		log_error("Can't open ABC output file `%s'.\n", buffer);
 
-	bool builtin_lib = config.liberty_files.empty() && config.genlib_files.empty();
+	bool builtin_lib = run_abc.config.liberty_files.empty() && run_abc.config.genlib_files.empty();
 	RTLIL::Design *mapped_design = new RTLIL::Design;
-	parse_blif(mapped_design, ifs, builtin_lib ? ID(DFF) : ID(_dff_), false, config.sop_mode);
+	parse_blif(mapped_design, ifs, builtin_lib ? ID(DFF) : ID(_dff_), false, run_abc.config.sop_mode);
 
 	ifs.close();
 
@@ -1492,37 +1703,37 @@ void AbcModuleState::extract(AbcSigMap &assign_map, RTLIL::Design *design, RTLIL
 	for (auto &it : cell_stats)
 		log("ABC RESULTS:   %15s cells: %8d\n", it.first, it.second);
 	int in_wires = 0, out_wires = 0;
-	for (auto &si : signal_list)
+	for (auto &si : run_abc.signal_list)
 		if (si.is_port) {
 			char buffer[100];
 			snprintf(buffer, 100, "\\ys__n%d", si.id);
 			RTLIL::SigSig conn;
 			if (si.type != G(NONE)) {
-				conn.first = si.bit;
+				conn.first = signal_bits[si.id];
 				conn.second = module->wire(remap_name(buffer));
 				out_wires++;
 			} else {
 				conn.first = module->wire(remap_name(buffer));
-				conn.second = si.bit;
+				conn.second = signal_bits[si.id];
 				in_wires++;
 			}
 			connect(assign_map, module, conn);
 		}
-	log("ABC RESULTS:        internal signals: %8d\n", int(signal_list.size()) - in_wires - out_wires);
+	log("ABC RESULTS:        internal signals: %8d\n", int(run_abc.signal_list.size()) - in_wires - out_wires);
 	log("ABC RESULTS:           input signals: %8d\n", in_wires);
 	log("ABC RESULTS:          output signals: %8d\n", out_wires);
 
 	delete mapped_design;
+	finish();
 }
 
 void AbcModuleState::finish()
 {
-	if (config.cleanup)
+	if (run_abc.config.cleanup)
 	{
 		log("Removing temp directory.\n");
-		remove_directory(tempdir_name);
+		remove_directory(run_abc.tempdir_name);
 	}
-
 	log_pop();
 }
 
@@ -1811,6 +2022,13 @@ struct AbcPass : public Pass {
 		config.show_tempdir = design->scratchpad_get_bool("abc.showtmp", false);
 		markgroups = design->scratchpad_get_bool("abc.markgroups", markgroups);
 
+		if (config.cleanup)
+			config.global_tempdir_name = get_base_tmpdir() + "/";
+		else
+			config.global_tempdir_name = "_tmp_";
+		config.global_tempdir_name += proc_program_prefix() + "yosys-abc-XXXXXX";
+		config.global_tempdir_name = make_temp_dir(config.global_tempdir_name);
+
 		if (design->scratchpad_get_bool("abc.debug")) {
 			config.cleanup = false;
 			config.show_tempdir = true;
@@ -2139,6 +2357,8 @@ struct AbcPass : public Pass {
 			// enabled_gates.insert("NMUX");
 		}
 
+		emit_global_input_files(config);
+
 		for (auto mod : design->selected_modules())
 		{
 			if (mod->processes.size() > 0) {
@@ -2163,9 +2383,10 @@ struct AbcPass : public Pass {
 				assign_cell_connection_ports(mod, {&cells}, assign_map);
 
 				AbcModuleState state(config, initvals);
-				state.abc_module(design, mod, assign_map, cells, dff_mode, clk_str);
+				state.prepare_module(design, mod, assign_map, cells, dff_mode, clk_str);
+				ConcurrentStack<AbcProcess> process_pool;
+				state.run_abc.run(process_pool);
 				state.extract(assign_map, design, mod);
-				state.finish();
 				continue;
 			}
 
@@ -2310,33 +2531,81 @@ struct AbcPass : public Pass {
 			}
 
 			log_header(design, "Summary of detected clock domains:\n");
-			for (auto &it : assigned_cells)
-				log("  %d cells in clk=%s%s, en=%s%s, arst=%s%s, srst=%s%s\n", GetSize(it.second),
-						std::get<0>(it.first) ? "" : "!", log_signal(std::get<1>(it.first)),
-						std::get<2>(it.first) ? "" : "!", log_signal(std::get<3>(it.first)),
-						std::get<4>(it.first) ? "" : "!", log_signal(std::get<5>(it.first)),
-						std::get<6>(it.first) ? "" : "!", log_signal(std::get<7>(it.first)));
-
 			{
 				std::vector<std::vector<RTLIL::Cell*>*> cell_sets;
-				for (auto &it : assigned_cells)
+				for (auto &it : assigned_cells) {
+					log("  %d cells in clk=%s%s, en=%s%s, arst=%s%s, srst=%s%s\n", GetSize(it.second),
+							std::get<0>(it.first) ? "" : "!", log_signal(std::get<1>(it.first)),
+							std::get<2>(it.first) ? "" : "!", log_signal(std::get<3>(it.first)),
+							std::get<4>(it.first) ? "" : "!", log_signal(std::get<5>(it.first)),
+							std::get<6>(it.first) ? "" : "!", log_signal(std::get<7>(it.first)));
 					cell_sets.push_back(&it.second);
+				}
 				assign_cell_connection_ports(mod, cell_sets, assign_map);
 			}
-			for (auto &it : assigned_cells) {
-				AbcModuleState state(config, initvals);
-				state.clk_polarity = std::get<0>(it.first);
-				state.clk_sig = assign_map(std::get<1>(it.first));
-				state.en_polarity = std::get<2>(it.first);
-				state.en_sig = assign_map(std::get<3>(it.first));
-				state.arst_polarity = std::get<4>(it.first);
-				state.arst_sig = assign_map(std::get<5>(it.first));
-				state.srst_polarity = std::get<6>(it.first);
-				state.srst_sig = assign_map(std::get<7>(it.first));
-				state.abc_module(design, mod, assign_map, it.second, !state.clk_sig.empty(), "$");
-				state.extract(assign_map, design, mod);
-				state.finish();
+
+			// Reserve one core for our main thread, and don't create more worker threads
+			// than ABC runs.
+			int max_threads = assigned_cells.size();
+			if (max_threads <= 1) {
+				// Just do everything on the main thread.
+				max_threads = 0;
 			}
+#ifdef YOSYS_LINK_ABC
+			// ABC does't support multithreaded calls so don't call it off the main thread.
+			max_threads = 0;
+#endif
+			int num_worker_threads = ThreadPool::pool_size(1, max_threads);
+			ConcurrentQueue<std::unique_ptr<AbcModuleState>> work_queue(num_worker_threads);
+			ConcurrentQueue<std::unique_ptr<AbcModuleState>> work_finished_queue;
+			int work_finished_count = 0;
+			ConcurrentStack<AbcProcess> process_pool;
+			ThreadPool worker_threads(num_worker_threads, [&](int){
+					while (std::optional<std::unique_ptr<AbcModuleState>> work =
+							work_queue.pop_front()) {
+						// Only the `run_abc` component is safe to touch here!
+						(*work)->run_abc.run(process_pool);
+						work_finished_queue.push_back(std::move(*work));
+					}
+				});
+			for (auto &it : assigned_cells) {
+				// Process ABC results that have already finished before queueing another ABC.
+				// This should keep our memory usage down.
+				while (std::optional<std::unique_ptr<AbcModuleState>> work =
+						work_finished_queue.try_pop_front()) {
+					(*work)->extract(assign_map, design, mod);
+					++work_finished_count;
+				}
+				std::unique_ptr<AbcModuleState> state = std::make_unique<AbcModuleState>(config, initvals);
+				state->clk_polarity = std::get<0>(it.first);
+				state->clk_sig = assign_map(std::get<1>(it.first));
+				state->en_polarity = std::get<2>(it.first);
+				state->en_sig = assign_map(std::get<3>(it.first));
+				state->arst_polarity = std::get<4>(it.first);
+				state->arst_sig = assign_map(std::get<5>(it.first));
+				state->srst_polarity = std::get<6>(it.first);
+				state->srst_sig = assign_map(std::get<7>(it.first));
+				state->prepare_module(design, mod, assign_map, it.second, !state->clk_sig.empty(), "$");
+				if (num_worker_threads > 0) {
+					work_queue.push_back(std::move(state));
+				} else {
+					// Just run everything on the main thread.
+					state->run_abc.run(process_pool);
+					work_finished_queue.push_back(std::move(state));
+				}
+			}
+			work_queue.close();
+			while (work_finished_count < static_cast<int>(assigned_cells.size())) {
+				std::optional<std::unique_ptr<AbcModuleState>> work =
+					work_finished_queue.pop_front();
+				(*work)->extract(assign_map, design, mod);
+				++work_finished_count;
+			}
+		}
+
+		if (config.cleanup) {
+			log("Removing global temp directory.\n");
+			remove_directory(config.global_tempdir_name);
 		}
 
 		log_pop();