python: Use PyBind11 instead of SWIG for Python wrappers

Use the PyBind11 wrapping infrastructure instead of SWIG to generate
wrappers for functionality that needs to be exported to Python. This
has several benefits:

  * PyBind11 can be redistributed with gem5, which means that we have
    full control of the version used. This avoid a large number of
    hard-to-debug SWIG issues we have seen in the past.

  * PyBind11 doesn't rely on a custom C++ parser, instead it relies on
    wrappers being explicitly declared in C++. The leads to slightly
    more boiler-plate code in manually created wrappers, but doesn't
    doesn't increase the overall code size. A big benefit is that this
    avoids strange compilation errors when SWIG doesn't understand
    modern language features.

  * Unlike SWIG, there is no risk that the wrapper code incorporates
    incorrect type casts (this has happened on numerous occasions in
    the past) since these will result in compile-time errors.

As a part of this change, the mechanism to define exported methods has
been redesigned slightly. New methods can be exported either by
declaring them in the SimObject declaration and decorating them with
the cxxMethod decorator or by adding an instance of
PyBindMethod/PyBindProperty to the cxx_exports class variable. The
decorator has the added benefit of making it possible to add a
docstring and naming the method's parameters.

The new wrappers have the following known issues:

  * Global events can't be memory managed correctly. This was the
    case in SWIG as well.

Change-Id: I88c5a95b6cf6c32fa9e1ad31dfc08b2e8199a763
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Andreas Hansson <andreas.hansson@arm.com>
Reviewed-by: Andrew Bardsley <andrew.bardsley@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2231
Reviewed-by: Tony Gutierrez <anthony.gutierrez@amd.com>
Reviewed-by: Pierre-Yves Péneau <pierre-yves.peneau@lirmm.fr>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

3 files changed, 19 insertions, 52 deletions

diff --git a/src/unittest/SConscript b/src/unittest/SConscript
index 2737be8f5..1f723ed2a 100644
--- a/src/unittest/SConscript
+++ b/src/unittest/SConscript
@@ -46,8 +46,7 @@ UnitTest('strnumtest', 'strnumtest.cc')
 UnitTest('trietest', 'trietest.cc')
 
 stattest_py = PySource('m5', 'stattestmain.py', skip_lib=True)
-stattest_swig = SwigSource('_m5', 'stattest.i', skip_lib=True)
-UnitTest('stattest', 'stattest.cc', stattest_py, stattest_swig, main=True)
+UnitTest('stattest', 'stattest.cc', stattest_py, main=True)
 
 UnitTest('symtest', 'symtest.cc')
 UnitTest('tokentest', 'tokentest.cc')
diff --git a/src/unittest/stattest.cc b/src/unittest/stattest.cc
index 20f2fd548..e3722204b 100644
--- a/src/unittest/stattest.cc
+++ b/src/unittest/stattest.cc
@@ -28,6 +28,8 @@
  * Authors: Nathan Binkert
  */
 
+#include "pybind11/pybind11.h"
+
 #include <iomanip>
 #include <iostream>
 #include <string>
@@ -37,8 +39,11 @@
 #include "base/statistics.hh"
 #include "base/types.hh"
 #include "sim/core.hh"
+#include "sim/init.hh"
 #include "sim/stat_control.hh"
 
+namespace py = pybind11;
+
 // override the default main() code for this unittest
 const char *m5MainCommands[] = {
     "import m5.stattestmain",
@@ -52,8 +57,6 @@ using namespace Stats;
 double testfunc();
 struct StatTest;
 StatTest & __stattest();
-void stattest_init();
-void stattest_run();
 
 
 double
@@ -123,18 +126,6 @@ __stattest()
 }
 
 void
-stattest_init()
-{
-    __stattest().init();
-}
-
-void
-stattest_run()
-{
-    __stattest().run();
-}
-
-void
 StatTest::init()
 {
     EventQueue *q = getEventQueue(0);
@@ -680,3 +671,16 @@ StatTest::run()
     s20[1] = 1;
 
 }
+
+static void
+stattest_init_pybind(py::module &m_internal)
+{
+    py::module m = m_internal.def_submodule("stattest");
+
+    m
+        .def("stattest_init", []() { __stattest().init(); })
+        .def("stattest_run", []() { __stattest().run(); })
+        ;
+}
+
+static EmbeddedPyBind embed_("stattest", stattest_init_pybind);
diff --git a/src/unittest/stattest.i b/src/unittest/stattest.i
deleted file mode 100644
index 66990689f..000000000
--- a/src/unittest/stattest.i
+++ /dev/null
@@ -1,36 +0,0 @@
-/*
- * Copyright (c) 2010 The Hewlett-Packard Development Company
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met: redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer;
- * redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution;
- * neither the name of the copyright holders nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * Authors: Nathan Binkert
- */
-
-%module(package="_m5") stattest
-
-%inline %{
-extern void stattest_init();
-extern void stattest_run();
-%}