mem-cache: Add multi-prefetcher adaptor

This patch adds a meta-prefetcher that enables gem5's cache models to
connect to multiple prefetchers. Sub-prefetchers still use the
probes-based interface and training can be controlled
independently. However, when the cache requests a prefetch packet, the
adaptor traverses the priority list of prefetchers and uses the first
prefetcher that is able to generate a prefetch.

Kudos to Mitch Hayenga for the original version of this patch.

Change-Id: I25569a834997e5404c7183ec995d212912c5dcdf
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18868
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

1 files changed, 72 insertions, 0 deletions

diff --git a/src/mem/cache/prefetch/multi.hh b/src/mem/cache/prefetch/multi.hh
new file mode 100644
index 000000000..88760f585
--- /dev/null
+++ b/src/mem/cache/prefetch/multi.hh
@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2014, 2019 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.
+ *
+ * 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: Mitch Hayenga
+ *          Andreas Sandberg
+ */
+
+#ifndef __MEM_CACHE_PREFETCH_MULTI_HH__
+#define __MEM_CACHE_PREFETCH_MULTI_HH__
+
+#include "mem/cache/prefetch/base.hh"
+
+struct MultiPrefetcherParams;
+
+class MultiPrefetcher : public BasePrefetcher
+{
+  public: // SimObject
+    MultiPrefetcher(const MultiPrefetcherParams *p);
+
+  public:  // BasePrefetcher
+    void setCache(BaseCache *_cache) override;
+    PacketPtr getPacket() override;
+    Tick nextPrefetchReadyTime() const override;
+
+    /** @{ */
+    /**
+     * Ignore notifications since each sub-prefetcher already gets a
+     * notification through their probes-based interface.
+     */
+    void notify(const PacketPtr &pkt, const PrefetchInfo &pfi) override {};
+    void notifyFill(const PacketPtr &pkt) override {};
+    /** @} */
+
+  protected:
+    /** List of sub-prefetchers ordered by priority. */
+    std::list<BasePrefetcher *> prefetchers;
+};
+
+#endif //__MEM_CACHE_PREFETCH_MULTI_HH__