ext: In sst, don't assume existing imports in python blobs.

When executing blobs of python code in the gem5 sst integration, don't
assume previous blobs have already imported modules. Import them
explicitly instead.

Change-Id: I3aa008ffa092cf8ad82ad057eb73bc9de4bf77c5
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/54308
Maintainer: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

ext/sst/gem5.cc

diff --git a/ext/sst/gem5.cc b/ext/sst/gem5.cc
index 286f519..01ea3eb 100644
--- a/ext/sst/gem5.cc
+++ b/ext/sst/gem5.cc
@@ -194,6 +194,7 @@
         initPython(args.size(), &args[0]);
 
         const std::vector<std::string> m5_instantiate_commands = {
+            "import m5",
             "m5.instantiate()"
         };
         execPythonCommands(m5_instantiate_commands);
@@ -201,7 +202,10 @@
         // calling SimObject.startup()
         const std::vector<std::string> simobject_setup_commands = {
             "import atexit",
-            "import _m5",
+            "import _m5.core",
+            "import m5",
+            "import m5.stats",
+            "import m5.objects.Root",
             "root = m5.objects.Root.getInstance()",
             "for obj in root.descendants(): obj.startup()",
             "atexit.register(m5.stats.dump)",
@@ -258,6 +262,7 @@
         );
         // output gem5 stats
         const std::vector<std::string> output_stats_commands = {
+            "import m5.stats"
             "m5.stats.dump()"
         };
         execPythonCommands(output_stats_commands);