cpu: Support exit when any one Trace CPU completes replay

This change adds a Trace CPU param to exit simulation early,
i.e. when the first (any one) trace execution is complete. With
this change the user gets a choice to configure exit as either
when the last CPU finishes (default) or first CPU finishes
replay. Configuring an early exit enables simulating and
measuring stats strictly when memory-system resources are being
stressed by all Trace CPUs.

Change-Id: I3998045fdcc5cd343e1ca92d18dd7f7ecdba8f1d
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>

src/cpu/trace/TraceCPU.py

@@ -75,3 +75,8 @@ class TraceCPU(BaseCPU):
     # frequency as was used for generating the traces.
     freqMultiplier = Param.Float(1.0, "Multiplier scale the Trace CPU "\
                                  "frequency up or down")
+
+    # Enable exiting when any one Trace CPU completes execution which is set to
+    # false by default
+    enableEarlyExit = Param.Bool(False, "Exit when any one Trace CPU "\
+                                 "completes execution")

src/cpu/trace/trace_cpu.cc

@@ -61,7 +61,8 @@ TraceCPU::TraceCPU(TraceCPUParams *params)
         dcacheNextEvent(this),
         oneTraceComplete(false),
         traceOffset(0),
-        execCompleteEvent(nullptr)
+        execCompleteEvent(nullptr),
+        enableEarlyExit(params->enableEarlyExit)
 {
     // Increment static counter for number of Trace CPUs.
     ++TraceCPU::numTraceCPUs;
@@ -137,12 +138,18 @@ TraceCPU::init()
     // events using a relative tick delta
     dcacheGen.adjustInitTraceOffset(traceOffset);
 
-    // The static counter for number of Trace CPUs is correctly set at this
-    // point so create an event and pass it.
+    // If the Trace CPU simulation is configured to exit on any one trace
+    // completion then we don't need a counted event to count down all Trace
+    // CPUs in the system. If not then instantiate a counted event.
+    if (!enableEarlyExit) {
+        // The static counter for number of Trace CPUs is correctly set at
+        // this point so create an event and pass it.
         execCompleteEvent = new CountedExitEvent("end of all traces reached.",
                                                  numTraceCPUs);
     }
 
+}
+
 void
 TraceCPU::schedIcacheNext()
 {
@@ -191,9 +198,17 @@ TraceCPU::checkAndSchedExitEvent()
         // Schedule event to indicate execution is complete as both
         // instruction and data access traces have been played back.
         inform("%s: Execution complete.\n", name());
+        // If the replay is configured to exit early, that is when any one
+        // execution is complete then exit immediately and return. Otherwise,
+        // schedule the counted exit that counts down completion of each Trace
+        // CPU.
+        if (enableEarlyExit) {
+            exitSimLoop("End of trace reached");
+        } else {
             schedule(*execCompleteEvent, curTick());
         }
     }
+}
 
 void
 TraceCPU::regStats()

src/cpu/trace/trace_cpu.hh

@@ -1116,6 +1116,12 @@ class TraceCPU : public BaseCPU
     */
     CountedExitEvent *execCompleteEvent;
 
+    /**
+     * Exit when any one Trace CPU completes its execution. If this is
+     * configured true then the execCompleteEvent is not scheduled.
+     */
+    const bool enableEarlyExit;
+
     Stats::Scalar numSchedDcacheEvent;
     Stats::Scalar numSchedIcacheEvent;