cpu: Get rid of the nextInstEventCount method.

This was only used by the KVM CPU, and it has access to all it needs to
figure out that value locally without requiring all the ThreadContexts
to implement an equivalent function.

Change-Id: I17a14ce669db2519edf129db761ebd8dc3bd4129
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22114
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/fastmodel/iris/thread_context.hh

@@ -96,7 +96,6 @@ class ThreadContext : public ::ThreadContext
     bool schedule(PCEvent *e) override { return false; }
     bool remove(PCEvent *e) override { return false; }
 
-    Tick nextInstEventCount() override { return MaxTick; }
     void scheduleInstCountEvent(Event *event, Tick count) override {}
     void descheduleInstCountEvent(Event *event) override {}
     Tick getCurrentInstCount() override;

src/cpu/checker/thread_context.hh

@@ -92,11 +92,6 @@ class CheckerThreadContext : public ThreadContext
     bool schedule(PCEvent *e) override { return actualTC->schedule(e); }
     bool remove(PCEvent *e) override { return actualTC->remove(e); }
 
-    Tick
-    nextInstEventCount() override
-    {
-        return actualTC->nextInstEventCount();
-    }
     void
     scheduleInstCountEvent(Event *event, Tick count) override
     {

src/cpu/kvm/base.cc

@@ -630,7 +630,9 @@ BaseKvmCPU::tick()
 
       case RunningServiceCompletion:
       case Running: {
-          const uint64_t nextInstEvent(tc->nextInstEventCount());
+          auto &queue = thread->comInstEventQueue;
+          const uint64_t nextInstEvent(
+                  queue.empty() ? MaxTick : queue.nextTick());
           // Enter into KVM and complete pending IO instructions if we
           // have an instruction event pending.
           const Tick ticksToExecute(
@@ -686,7 +688,7 @@ BaseKvmCPU::tick()
           // Service any pending instruction events. The vCPU should
           // have exited in time for the event using the instruction
           // counter configured by setupInstStop().
-          thread->comInstEventQueue.serviceEvents(ctrInsts);
+          queue.serviceEvents(ctrInsts);
 
           if (tryDrain())
               _status = Idle;
@@ -1346,10 +1348,10 @@ BaseKvmCPU::ioctlRun()
 void
 BaseKvmCPU::setupInstStop()
 {
-    Tick next = tc->nextInstEventCount();
-    if (next == MaxTick) {
+    if (thread->comInstEventQueue.empty()) {
         setupInstCounter(0);
     } else {
+        Tick next = thread->comInstEventQueue.nextTick();
         assert(next > ctrInsts);
         setupInstCounter(next - ctrInsts);
     }

src/cpu/o3/thread_context.hh

@@ -86,12 +86,6 @@ class O3ThreadContext : public ThreadContext
         return thread->pcEventQueue.remove(e);
     }
 
-    Tick
-    nextInstEventCount() override
-    {
-        return thread->comInstEventQueue.empty() ?
-            MaxTick : thread->comInstEventQueue.nextTick();
-    }
     void
     scheduleInstCountEvent(Event *event, Tick count) override
     {

src/cpu/simple_thread.hh

@@ -198,12 +198,6 @@ class SimpleThread : public ThreadState, public ThreadContext
     bool schedule(PCEvent *e) override { return pcEventQueue.schedule(e); }
     bool remove(PCEvent *e) override { return pcEventQueue.remove(e); }
 
-    Tick
-    nextInstEventCount() override
-    {
-        return comInstEventQueue.empty() ?
-            MaxTick : comInstEventQueue.nextTick();
-    }
     void
     scheduleInstCountEvent(Event *event, Tick count) override
     {

src/cpu/thread_context.hh

@@ -192,7 +192,6 @@ class ThreadContext : public PCEventScope
 
     virtual EndQuiesceEvent *getQuiesceEvent() = 0;
 
-    virtual Tick nextInstEventCount() = 0;
     virtual void scheduleInstCountEvent(Event *event, Tick count) = 0;
     virtual void descheduleInstCountEvent(Event *event) = 0;
     virtual Tick getCurrentInstCount() = 0;