mem: Create a separate class for the cache write buffer

This patch breaks out the cache write buffer into a separate class,
without affecting any stats. The goal of the patch is to avoid
encumbering the much-simpler write queue with the complex MSHR
handling. In a follow on patch this simplification allows us to
implement write combining.

The WriteQueue gets its own class, but shares a common ancestor, the
generic Queue, with the MSHRQueue.

1 files changed, 109 insertions, 0 deletions

diff --git a/src/mem/cache/queue_entry.hh b/src/mem/cache/queue_entry.hh
new file mode 100644
index 000000000..02daee01a
--- /dev/null
+++ b/src/mem/cache/queue_entry.hh
@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2012-2013, 2015-2016 ARM Limited
+ * All rights reserved.
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Copyright (c) 2002-2005 The Regents of The University of Michigan
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Erik Hallnor
+ *          Andreas Hansson
+ */
+
+/**
+ * @file
+ * Generic queue entry
+ */
+
+#ifndef __MEM_CACHE_QUEUE_ENTRY_HH__
+#define __MEM_CACHE_QUEUE_ENTRY_HH__
+
+#include "mem/packet.hh"
+
+class Cache;
+
+/**
+ * A queue entry base class, to be used by both the MSHRs and
+ * write-queue entries.
+ */
+class QueueEntry : public Packet::SenderState
+{
+
+    /**
+     * Consider the Queue a friend to avoid making everything public
+     */
+    template <class Entry>
+    friend class Queue;
+
+  protected:
+
+    /** Tick when ready to issue */
+    Tick readyTime;
+
+    /** True if the entry is uncacheable */
+    bool _isUncacheable;
+
+  public:
+
+    /** True if the entry has been sent downstream. */
+    bool inService;
+
+    /** Order number assigned to disambiguate writes and misses. */
+    Counter order;
+
+    /** Block aligned address. */
+    Addr blkAddr;
+
+    /** Block size of the cache. */
+    unsigned blkSize;
+
+    /** True if the entry targets the secure memory space. */
+    bool isSecure;
+
+    QueueEntry() : readyTime(0), _isUncacheable(false),
+                   inService(false), order(0), blkAddr(0), blkSize(0),
+                   isSecure(false)
+    {}
+
+    bool isUncacheable() const { return _isUncacheable; }
+
+    /**
+     * Send this queue entry as a downstream packet, with the exact
+     * behaviour depending on the specific entry type.
+     */
+    virtual bool sendPacket(Cache &cache) = 0;
+
+};
+
+#endif // __MEM_CACHE_QUEUE_ENTRY_HH__