mem: Add support for repopulating the flags of an MSHR TargetList

This patch adds support for repopulating the flags of an MSHR
TargetList. The added functionality makes it possible to remove
targets from a TargetList without leaving it in an inconsistent state.

Change-Id: I3f7a8e97bfd3e2e49bebad056d11bbfb087aad91
Reviewed-by: Andreas Hansson <andreas.hansson@arm.com>
Reviewed-by: Stephan Diestelhorst <stephan.diestelhorst@arm.com>

src/mem/cache/mshr.cc

@@ -74,9 +74,8 @@ MSHR::TargetList::TargetList()
 {}
 
 
-inline void
+void
-MSHR::TargetList::add(PacketPtr pkt, Tick readyTime,
+MSHR::TargetList::updateFlags(PacketPtr pkt, Target::Source source)
-                      Counter order, Target::Source source, bool markPending)
 {
     if (source != Target::FromSnoop) {
         if (pkt->needsWritable()) {
@@ -90,7 +89,22 @@ MSHR::TargetList::add(PacketPtr pkt, Tick readyTime,
             hasUpgrade = true;
         }
     }
+}
 
+void
+MSHR::TargetList::populateFlags()
+{
+    resetFlags();
+    for (auto& t: *this) {
+        updateFlags(t.pkt, t.source);
+    }
+}
+
+inline void
+MSHR::TargetList::add(PacketPtr pkt, Tick readyTime,
+                      Counter order, Target::Source source, bool markPending)
+{
+    updateFlags(pkt, source);
     if (markPending) {
         // Iterate over the SenderState stack and see if we find
         // an MSHR entry. If we do, set the downstreamPending

src/mem/cache/mshr.hh

@@ -143,7 +143,26 @@ class MSHR : public QueueEntry, public Printable
         bool hasUpgrade;
 
         TargetList();
+
+        /**
+         * Use the provided packet and the source to update the
+         * flags of this TargetList.
+         *
+         * @param pkt Packet considered for the flag update
+         * @param source Indicates the source of the packet
+         */
+        void updateFlags(PacketPtr pkt, Target::Source source);
+
         void resetFlags() { needsWritable = hasUpgrade = false; }
+
+        /**
+         * Goes through the list of targets and uses them to populate
+         * the flags of this TargetList. When the function returns the
+         * flags are consistent with the properties of packets in the
+         * list.
+         */
+        void populateFlags();
+
         bool isReset() const { return !needsWritable && !hasUpgrade; }
         void add(PacketPtr pkt, Tick readyTime, Counter order,
                  Target::Source source, bool markPending);