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, 18 insertions, 0 deletions

diff --git a/src/mem/packet.cc b/src/mem/packet.cc
index dc5ff4362..cea65cea0 100644
--- a/src/mem/packet.cc
+++ b/src/mem/packet.cc
@@ -316,6 +316,24 @@ Packet::checkFunctional(Printable *obj, Addr addr, int size, uint8_t *data)
 }
 
 void
+Packet::pushSenderState(Packet::SenderState *sender_state)
+{
+    assert(sender_state != NULL);
+    sender_state->predecessor = senderState;
+    senderState = sender_state;
+}
+
+Packet::SenderState *
+Packet::popSenderState()
+{
+    assert(senderState != NULL);
+    SenderState *sender_state = senderState;
+    senderState = sender_state->predecessor;
+    sender_state->predecessor = NULL;
+    return sender_state;
+}
+
+void
 Packet::print(ostream &o, const int verbosity, const string &prefix) const
 {
     ccprintf(o, "%s[%x:%x] %s\n", prefix,