systemc: Track the scheduler status using an enum instead of bools.

The scheduler tracked whether it was paused or stopped with two bools
which are mutually exclusive. It's useful to be able to also check for
some other mutually exclusive states like what phase the scheduler is
currently running.

Rather than adding a bunch of additional bools, this change switches
those mutually exclusive states over to an enum, and adds some methods
to access and maintain that enum.

Change-Id: Ia9696b2853d1b122c1100c9df0e12b018fe9b84b
Reviewed-on: https://gem5-review.googlesource.com/c/12605
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/systemc/core/scheduler.cc

@@ -46,7 +46,7 @@ Scheduler::Scheduler() :
     stopEvent(this, false, StopPriority),
     scMain(nullptr), _throwToScMain(nullptr),
     starvationEvent(this, false, StarvationPriority),
-    _started(false), _paused(false), _stopped(false), _stopNow(false),
+    _started(false), _stopNow(false), _status(StatusOther),
     maxTickEvent(this, false, MaxTickPriority),
     _numCycles(0), _changeStamp(0), _current(nullptr), initDone(false),
     runOnce(false), readyList(nullptr)
@@ -123,10 +123,8 @@ Scheduler::initPhase()
         p->ready();
     }
 
-    update();
-
-    while (!deltas.empty())
-        deltas.front()->run();
+    runUpdate();
+    runDelta();
 
     for (auto ets: eventsToSchedule)
         eq->schedule(ets.first, ets.second);
@@ -139,6 +137,8 @@ Scheduler::initPhase()
     }
 
     initDone = true;
+
+    status(StatusOther);
 }
 
 void
@@ -311,23 +311,23 @@ Scheduler::runReady()
     if (_stopNow)
         return;
 
-    // The update phase.
-    update();
-
-    // The delta phase.
-    while (!deltas.empty())
-        deltas.front()->run();
+    runUpdate();
+    runDelta();
 
     if (!runToTime && starved())
         scheduleStarvationEvent();
 
     if (runOnce)
         schedulePause();
+
+    status(StatusOther);
 }
 
 void
-Scheduler::update()
+Scheduler::runUpdate()
 {
+    status(StatusUpdate);
+
     Channel *channel = updateList.getNext();
     while (channel) {
         channel->popListNode();
@@ -336,10 +336,18 @@ Scheduler::update()
     }
 }
 
+void
+Scheduler::runDelta()
+{
+    status(StatusDelta);
+    while (!deltas.empty())
+        deltas.front()->run();
+}
+
 void
 Scheduler::pause()
 {
-    _paused = true;
+    status(StatusPaused);
     kernel->status(::sc_core::SC_PAUSED);
     runOnce = false;
     if (scMain && !scMain->finished())
@@ -349,7 +357,7 @@ Scheduler::pause()
 void
 Scheduler::stop()
 {
-    _stopped = true;
+    status(StatusStopped);
     kernel->stop();
 
     clear();
@@ -367,8 +375,7 @@ Scheduler::start(Tick max_tick, bool run_to_time)
     scMain = Fiber::currentFiber();
 
     _started = true;
-    _paused = false;
-    _stopped = false;
+    status(StatusOther);
     runToTime = run_to_time;
 
     maxTick = max_tick;

src/systemc/core/scheduler.hh

@@ -318,7 +318,10 @@ class Scheduler
     }
 
     // Run scheduled channel updates.
-    void update();
+    void runUpdate();
+
+    // Run delta events.
+    void runDelta();
 
     void setScMainFiber(Fiber *sc_main) { scMain = sc_main; }
 
@@ -328,13 +331,29 @@ class Scheduler
     void schedulePause();
     void scheduleStop(bool finish_delta);
 
-    bool paused() { return _paused; }
-    bool stopped() { return _stopped; }
+    enum Status
+    {
+        StatusOther = 0,
+        StatusDelta,
+        StatusUpdate,
+        StatusTiming,
+        StatusPaused,
+        StatusStopped
+    };
+
+    bool paused() { return status() == StatusPaused; }
+    bool stopped() { return status() == StatusStopped; }
+    bool inDelta() { return status() == StatusDelta; }
+    bool inUpdate() { return status() == StatusUpdate; }
+    bool inTiming() { return status() == StatusTiming; }
 
     uint64_t changeStamp() { return _changeStamp; }
 
     void throwToScMain(const ::sc_core::sc_report *r=nullptr);
 
+    Status status() { return _status; }
+    void status(Status s) { _status = s; }
+
   private:
     typedef const EventBase::Priority Priority;
     static Priority DefaultPriority = EventBase::Default_Pri;
@@ -395,10 +414,10 @@ class Scheduler
     void scheduleStarvationEvent();
 
     bool _started;
-    bool _paused;
-    bool _stopped;
     bool _stopNow;
 
+    Status _status;
+
     Tick maxTick;
     Tick lastReadyTick;
     void
@@ -436,8 +455,12 @@ extern Scheduler scheduler;
 inline void
 Scheduler::TimeSlot::process()
 {
+    scheduler.status(StatusTiming);
+
     while (!events.empty())
         events.front()->run();
+
+    scheduler.status(StatusOther);
     scheduler.completeTimeSlot(this);
 }