pyosys: rewrite using pybind11

- Rewrite all Python features to use the pybind11 library instead of boost::python.
  Unlike boost::python, pybind11 is a header-only library that is just included by Pyosys code, saving a lot of compile time on wheels.
- Factor out as much "translation" code from the generator into proper C++ files
- Fix running the embedded interpreter not supporting "from pyosys import libyosys as ys" like wheels
- Move Python-related elements to `pyosys` directory at the root of the repo
- Slight shift in bridging semantics:
  - Containers are declared as "opaque types" and are passed by reference to Python - many methods have been implemented to make them feel right at home without the overhead/ambiguity of copying to Python and then copying back after mutation
  - Monitor/Pass use "trampoline" pattern to support virual methods overridable in Python: virtual methods no longer require `py_` prefix
- Create really short test set for pyosys that just exercises basic functionality

kernel/driver.cc

@@ -92,8 +92,9 @@ int main(int argc, char **argv)
 	yosys_banner();
 	yosys_setup();
 #ifdef WITH_PYTHON
-	PyRun_SimpleString(("sys.path.append(\""+proc_self_dirname()+"\")").c_str());
-	PyRun_SimpleString(("sys.path.append(\""+proc_share_dirname()+"plugins\")").c_str());
+	py::object sys = py::module_::import("sys");
+	sys.attr("path").attr("append")(proc_self_dirname());
+	sys.attr("path").attr("append")(proc_share_dirname());
 #endif
 
 	if (argc == 2)
@@ -516,8 +517,9 @@ int main(int argc, char **argv)
 
 	yosys_setup();
 #ifdef WITH_PYTHON
-	PyRun_SimpleString(("sys.path.append(\""+proc_self_dirname()+"\")").c_str());
-	PyRun_SimpleString(("sys.path.append(\""+proc_share_dirname()+"plugins\")").c_str());
+	py::object sys = py::module_::import("sys");
+	sys.attr("path").attr("append")(proc_self_dirname());
+	sys.attr("path").attr("append")(proc_share_dirname());
 #endif
 	log_error_atexit = yosys_atexit;
 
@@ -567,21 +569,18 @@ int main(int argc, char **argv)
 #endif
 		} else if (scriptfile_python) {
 #ifdef WITH_PYTHON
-			PyObject *sys = PyImport_ImportModule("sys");
+			py::list new_argv;
 			int py_argc = special_args.size() + 1;
-			PyObject *new_argv = PyList_New(py_argc);
-			PyList_SetItem(new_argv, 0, PyUnicode_FromString(scriptfile.c_str()));
+			new_argv.append(scriptfile);
 			for (int i = 1; i < py_argc; ++i)
-				PyList_SetItem(new_argv, i, PyUnicode_FromString(special_args[i - 1].c_str()));
+				new_argv.append(special_args[i - 1]);
 
-			PyObject *old_argv = PyObject_GetAttrString(sys, "argv");
-			PyObject_SetAttrString(sys, "argv", new_argv);
-			Py_DECREF(old_argv);
+			py::setattr(sys, "argv", new_argv);
 
-			PyObject *py_path = PyUnicode_FromString(scriptfile.c_str());
-			PyObject_SetAttrString(sys, "_yosys_script_path", py_path);
-			Py_DECREF(py_path);
-			PyRun_SimpleString("import os, sys; sys.path.insert(0, os.path.dirname(os.path.abspath(sys._yosys_script_path)))");
+			py::object Path = py::module_::import("pathlib").attr("Path");
+			py::object scriptfile_python_path = Path(scriptfile).attr("parent");
+
+			sys.attr("path").attr("insert")(0, py::str(scriptfile_python_path));
 
 			FILE *scriptfp = fopen(scriptfile.c_str(), "r");
 			if (scriptfp == nullptr) {

kernel/yosys.cc

@@ -64,13 +64,8 @@
 #endif
 
 #ifdef WITH_PYTHON
-#if PY_MAJOR_VERSION >= 3
-#   define INIT_MODULE PyInit_libyosys
-    extern "C" PyObject* INIT_MODULE();
-#else
-#   define INIT_MODULE initlibyosys
-	extern "C" void INIT_MODULE();
-#endif
+extern "C" PyObject* PyInit_libyosys();
+extern "C" PyObject* PyInit_pyosys();
 #include <signal.h>
 #endif
 
@@ -189,6 +184,17 @@ int run_command(const std::string &command, std::function<void(const std::string
 bool already_setup = false;
 bool already_shutdown = false;
 
+#ifdef WITH_PYTHON
+// Include pyosys as a module so 'from pyosys import libyosys' also works
+// in interpreter mode.
+//
+// This should not affect using wheels as the dylib has to actually be called
+// pyosys.so for this module to be interacted with at all.
+PYBIND11_MODULE(pyosys, m) {
+	m.add_object("libyosys", m.import("libyosys"));
+}
+#endif
+
 void yosys_setup()
 {
 	if(already_setup)
@@ -199,11 +205,12 @@ void yosys_setup()
 	IdString::ensure_prepopulated();
 
 #ifdef WITH_PYTHON
-	// With Python 3.12, calling PyImport_AppendInittab on an already
+	// Starting Python 3.12, calling PyImport_AppendInittab on an already
 	// initialized platform fails (such as when libyosys is imported
 	// from a Python interpreter)
 	if (!Py_IsInitialized()) {
-		PyImport_AppendInittab((char*)"libyosys", INIT_MODULE);
+		PyImport_AppendInittab((char*)"libyosys", PyInit_libyosys);
+		PyImport_AppendInittab((char*)"pyosys", PyInit_pyosys);
 		Py_Initialize();
 		PyRun_SimpleString("import sys");
 		signal(SIGINT, SIG_DFL);

kernel/yosys_common.h

@@ -55,6 +55,9 @@
 
 #ifdef WITH_PYTHON
 #include <Python.h>
+#include <pybind11/pybind11.h>
+
+namespace py = pybind11;
 #endif
 
 #ifndef _YOSYS_