stats: Provide a mechanism to get a callback when stats are dumped.

This mechanism is useful for dumping output that is correlated with stats
dumping, but isn't tracked by the gem5 statistics.

src/base/statistics.cc

@@ -433,6 +433,7 @@ Formula::str() const
     return root ? root->str() : "";
 }
 
+CallbackQueue dumpQueue;
 CallbackQueue resetQueue;
 
 void
@@ -458,6 +459,12 @@ enable()
     _enabled = true;
 }
 
+void
+registerDumpCallback(Callback *cb)
+{
+    dumpQueue.add(cb);
+}
+
 } // namespace Stats
 
 void

src/base/statistics.hh

@@ -3135,6 +3135,12 @@ bool enabled();
  */
 void registerResetCallback(Callback *cb);
 
+/**
+ * Register a callback that should be called whenever statistics are
+ * about to be dumped
+ */
+void registerDumpCallback(Callback *cb);
+
 std::list<Info *> &statsList();
 
 } // namespace Stats

src/python/m5/stats/__init__.py

@@ -103,6 +103,8 @@ def dump():
         return
     lastDump = curTick
 
+    internal.stats.processDumpQueue()
+
     prepare()
 
     for output in outputList:

src/python/swig/stats.i

@@ -71,6 +71,13 @@ processResetQueue()
     resetQueue.process();
 }
 
+inline void
+processDumpQueue()
+{
+    extern CallbackQueue dumpQueue;
+    dumpQueue.process();
+}
+
 inline char *
 PCC(const char *string)
 {
@@ -146,6 +153,7 @@ void schedStatEvent(bool dump, bool reset,
                     Tick when = curTick(), Tick repeat = 0);
 
 void processResetQueue();
+void processDumpQueue();
 void enable();
 bool enabled();