sim: print --debug-flag Event execution and instance ID

This makes it much easier to determine what event is causing something to
happen, especially when there are multiple events happening at the
same time.

Change-Id: I17378e16bd3de1d98e936a6252aab2cd8c303b23
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25383
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/sim/eventq.cc

@@ -81,11 +81,7 @@ Event::~Event()
 const std::string
 Event::name() const
 {
-#ifndef NDEBUG
-    return csprintf("Event_%d", instance);
-#else
-    return csprintf("Event_%x", (uintptr_t)this);
-#endif
+    return csprintf("Event_%s", instanceString());
 }
 
 
@@ -220,7 +216,8 @@ EventQueue::serviceOne()
     if (!event->squashed()) {
         // forward current cycle to the time when this event occurs.
         setCurTick(event->when());
-
+        if (DTRACE(Event))
+            event->trace("executed");
         event->process();
         if (event->isExitEvent()) {
             assert(!event->flags.isSet(Event::Managed) ||
@@ -388,8 +385,18 @@ Event::trace(const char *action)
     // more informative message in the trace, override this method on
     // the particular subclass where you have the information that
     // needs to be printed.
-    DPRINTF_UNCONDITIONAL(Event, "%s event %s @ %d\n",
-            description(), action, when());
+    DPRINTF_UNCONDITIONAL(Event, "%s %s %s @ %d\n",
+            description(), instanceString(), action, when());
+}
+
+const std::string
+Event::instanceString() const
+{
+#ifndef NDEBUG
+    return csprintf("%d", instance);
+#else
+    return csprintf("%#x", (uintptr_t)this);
+#endif
 }
 
 void

src/sim/eventq.hh

@@ -284,6 +284,9 @@ class Event : public EventBase, public Serializable
     // This function isn't really useful if TRACING_ON is not defined
     virtual void trace(const char *action);     //!< trace event activity
 
+    /// Return the instance number as a string.
+    const std::string instanceString() const;
+
   protected: /* Memory management */
     /**
      * @{