MEM: Remove the Broadcast destination from the packet

This patch simplifies the packet by removing the broadcast flag and
instead more firmly relying on (and enforcing) the semantics of
transactions in the classic memory system, i.e. request packets are
routed from a master to a slave based on the address, and when they
are created they have neither a valid source, nor destination. On
their way to the slave, the request packet is updated with a source
field for all modules that multiplex packets from multiple master
(e.g. a bus). When a request packet is turned into a response packet
(at the final slave), it moves the potentially populated source field
to the destination field, and the response packet is routed through
any multiplexing components back to the master based on the
destination field.

Modules that connect multiplexing components, such as caches and
bridges store any existing source and destination field in the sender
state as a stack (just as before).

The packet constructor is simplified in that there is no longer a need
to pass the Packet::Broadcast as the destination (this was always the
case for the classic memory system). In the case of Ruby, rather than
using the parameter to the constructor we now rely on setDest, as
there is already another three-argument constructor in the packet
class.

In many places where the packet information was printed as part of
DPRINTFs, request packets would be printed with a numeric "dest" that
would always be -1 (Broadcast) and that field is now removed from the
printing.

1 files changed, 25 insertions, 31 deletions

diff --git a/src/mem/bus.cc b/src/mem/bus.cc
index eb26e268b..daf69c6df 100644
--- a/src/mem/bus.cc
+++ b/src/mem/bus.cc
@@ -213,24 +213,21 @@ Bus::recvTiming(PacketPtr pkt)
     // test if the bus should be considered occupied for the current
     // packet, and exclude express snoops from the check
     if (!pkt->isExpressSnoop() && isOccupied(pkt, src_port)) {
-        DPRINTF(Bus, "recvTiming: src %d dst %d %s 0x%x BUSY\n",
-                src_id, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
+        DPRINTF(Bus, "recvTiming: src %s %s 0x%x BUSY\n",
+                src_port->name(), pkt->cmdString(), pkt->getAddr());
         return false;
     }
 
-    DPRINTF(Bus, "recvTiming: src %d dst %d %s 0x%x\n",
-            src_id, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
+    DPRINTF(Bus, "recvTiming: src %s %s 0x%x\n",
+            src_port->name(), pkt->cmdString(), pkt->getAddr());
 
     Tick headerFinishTime = pkt->isExpressSnoop() ? 0 : calcPacketTiming(pkt);
     Tick packetFinishTime = pkt->isExpressSnoop() ? 0 : pkt->finishTime;
 
     // decide what to do based on the direction
     if (pkt->isRequest()) {
-        // the packet is a memory-mapped request and should be broadcasted to
-        // our snoopers
-        assert(pkt->getDest() == Packet::Broadcast);
-
-        // forward to all snoopers but the source
+        // the packet is a memory-mapped request and should be
+        // broadcasted to our snoopers but the source
         forwardTiming(pkt, src_id);
 
         // remember if we add an outstanding req so we can undo it if
@@ -262,8 +259,8 @@ Bus::recvTiming(PacketPtr pkt)
             if (add_outstanding)
                 outstandingReq.erase(pkt->req);
 
-            DPRINTF(Bus, "recvTiming: src %d dst %d %s 0x%x RETRY\n",
-                    src_id, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
+            DPRINTF(Bus, "recvTiming: src %s %s 0x%x RETRY\n",
+                    src_port->name(), pkt->cmdString(), pkt->getAddr());
 
             addToRetryList(src_port);
             occupyBus(headerFinishTime);
@@ -299,12 +296,11 @@ Bus::recvTimingSnoop(PacketPtr pkt)
     Packet::NodeID src_id = pkt->getSrc();
 
     if (pkt->isRequest()) {
-        DPRINTF(Bus, "recvTimingSnoop: src %d dst %d %s 0x%x\n",
-                src_id, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
+        DPRINTF(Bus, "recvTimingSnoop: src %d %s 0x%x\n",
+                src_id, pkt->cmdString(), pkt->getAddr());
 
         // the packet is an express snoop request and should be
         // broadcasted to our snoopers
-        assert(pkt->getDest() == Packet::Broadcast);
         assert(pkt->isExpressSnoop());
 
         // forward to all snoopers
@@ -326,13 +322,13 @@ Bus::recvTimingSnoop(PacketPtr pkt)
         SlavePort* src_port = slavePorts[src_id];
 
         if (isOccupied(pkt, src_port)) {
-            DPRINTF(Bus, "recvTimingSnoop: src %d dst %d %s 0x%x BUSY\n",
-                    src_id, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
+            DPRINTF(Bus, "recvTimingSnoop: src %s %s 0x%x BUSY\n",
+                    src_port->name(), pkt->cmdString(), pkt->getAddr());
             return false;
         }
 
-        DPRINTF(Bus, "recvTimingSnoop: src %d dst %d %s 0x%x\n",
-                src_id, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
+        DPRINTF(Bus, "recvTimingSnoop: src %s %s 0x%x\n",
+                src_port->name(), pkt->cmdString(), pkt->getAddr());
 
         // get the destination from the packet
         Packet::NodeID dest = pkt->getDest();
@@ -532,11 +528,11 @@ Bus::findPort(Addr addr)
 Tick
 Bus::recvAtomic(PacketPtr pkt)
 {
-    DPRINTF(Bus, "recvAtomic: packet src %d dest %d addr 0x%x cmd %s\n",
-            pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
+    DPRINTF(Bus, "recvAtomic: packet src %s addr 0x%x cmd %s\n",
+            slavePorts[pkt->getSrc()]->name(), pkt->getAddr(),
+            pkt->cmdString());
 
     // we should always see a request routed based on the address
-    assert(pkt->getDest() == Packet::Broadcast);
     assert(pkt->isRequest());
 
     // forward to all snoopers but the source
@@ -566,11 +562,11 @@ Bus::recvAtomic(PacketPtr pkt)
 Tick
 Bus::recvAtomicSnoop(PacketPtr pkt)
 {
-    DPRINTF(Bus, "recvAtomicSnoop: packet src %d dest %d addr 0x%x cmd %s\n",
-            pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
+    DPRINTF(Bus, "recvAtomicSnoop: packet src %s addr 0x%x cmd %s\n",
+            masterPorts[pkt->getSrc()]->name(), pkt->getAddr(),
+            pkt->cmdString());
 
     // we should always see a request routed based on the address
-    assert(pkt->getDest() == Packet::Broadcast);
     assert(pkt->isRequest());
 
     // forward to all snoopers
@@ -621,7 +617,7 @@ Bus::forwardAtomic(PacketPtr pkt, int exclude_slave_port_id)
                 // restore original packet state for remaining snoopers
                 pkt->cmd = orig_cmd;
                 pkt->setSrc(orig_src_id);
-                pkt->setDest(Packet::Broadcast);
+                pkt->clearDest();
             }
         }
     }
@@ -637,13 +633,12 @@ Bus::recvFunctional(PacketPtr pkt)
     if (!pkt->isPrint()) {
         // don't do DPRINTFs on PrintReq as it clutters up the output
         DPRINTF(Bus,
-                "recvFunctional: packet src %d dest %d addr 0x%x cmd %s\n",
-                pkt->getSrc(), pkt->getDest(), pkt->getAddr(),
+                "recvFunctional: packet src %s addr 0x%x cmd %s\n",
+                slavePorts[pkt->getSrc()]->name(), pkt->getAddr(),
                 pkt->cmdString());
     }
 
     // we should always see a request routed based on the address
-    assert(pkt->getDest() == Packet::Broadcast);
     assert(pkt->isRequest());
 
     // forward to all snoopers but the source
@@ -664,13 +659,12 @@ Bus::recvFunctionalSnoop(PacketPtr pkt)
     if (!pkt->isPrint()) {
         // don't do DPRINTFs on PrintReq as it clutters up the output
         DPRINTF(Bus,
-                "recvFunctionalSnoop: packet src %d dest %d addr 0x%x cmd %s\n",
-                pkt->getSrc(), pkt->getDest(), pkt->getAddr(),
+                "recvFunctionalSnoop: packet src %s addr 0x%x cmd %s\n",
+                masterPorts[pkt->getSrc()]->name(), pkt->getAddr(),
                 pkt->cmdString());
     }
 
     // we should always see a request routed based on the address
-    assert(pkt->getDest() == Packet::Broadcast);
     assert(pkt->isRequest());
 
     // forward to all snoopers