mem: Add predecessor to SenderState base class

This patch adds a predecessor field to the SenderState base class to
make the process of linking them up more uniform, and enable a
traversal of the stack without knowing the specific type of the
subclasses.

There are a number of simplifications done as part of changing the
SenderState, particularly in the RubyTest.

1 files changed, 4 insertions, 9 deletions

diff --git a/src/mem/comm_monitor.hh b/src/mem/comm_monitor.hh
index 271ae5fff..c3cb0d352 100644
--- a/src/mem/comm_monitor.hh
+++ b/src/mem/comm_monitor.hh
@@ -107,23 +107,18 @@ class CommMonitor : public MemObject
       public:
 
         /**
-         * Construct a new sender state and remember the original one
-         * so that we can implement a stack.
+         * Construct a new sender state and store the time so we can
+         * calculate round-trip latency.
          *
-         * @param _origSenderState Sender state to remember
          * @param _transmitTime Time of packet transmission
          */
-        CommMonitorSenderState(SenderState* _origSenderState,
-                               Tick _transmitTime)
-            : origSenderState(_origSenderState), transmitTime(_transmitTime)
+        CommMonitorSenderState(Tick _transmitTime)
+            : transmitTime(_transmitTime)
         { }
 
         /** Destructor */
         ~CommMonitorSenderState() { }
 
-        /** Pointer to old sender state of packet */
-        SenderState* origSenderState;
-
         /** Tick when request is transmitted */
         Tick transmitTime;