mem, cpu: Add assertions to snoop invalidation logic

This patch adds assertions that enforce that only invalidating snoops
will ever reach into the logic that tracks in-order load completion and
also invalidation of LL/SC (and MONITOR / MWAIT) monitors. Also adds
some comments to MSHR::replaceUpgrades().

1 files changed, 6 insertions, 0 deletions

diff --git a/src/mem/cache/mshr.hh b/src/mem/cache/mshr.hh
index 82a674672..ea3719343 100644
--- a/src/mem/cache/mshr.hh
+++ b/src/mem/cache/mshr.hh
@@ -149,7 +149,13 @@ class MSHR : public Packet::SenderState, public Printable
         bool isReset() const { return !needsWritable && !hasUpgrade; }
         void add(PacketPtr pkt, Tick readyTime, Counter order,
                  Target::Source source, bool markPending);
+
+        /**
+         * Convert upgrades to the equivalent request if the cache line they
+         * refer to would have been invalid (Upgrade -> ReadEx, SC* -> Fail).
+         * Used to rejig ordering between targets waiting on an MSHR. */
         void replaceUpgrades();
+
         void clearDownstreamPending();
         bool checkFunctional(PacketPtr pkt);
         void print(std::ostream &os, int verbosity,