mem-cache: Create cache compressor

Create basic template for cache compressors. A basic compressor
must implement a compression and a decompression method.

Change-Id: I83dc4d2b8d2bc5ed9f760c938edfa4ebdd6b8583
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/11100
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>

4 files changed, 396 insertions, 0 deletions

diff --git a/src/mem/cache/compressors/Compressors.py b/src/mem/cache/compressors/Compressors.py
new file mode 100644
index 000000000..1b0d9980e
--- /dev/null
+++ b/src/mem/cache/compressors/Compressors.py
@@ -0,0 +1,38 @@
+# Copyright (c) 2018 Inria
+# 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: Daniel Carvalho
+
+from m5.params import *
+from m5.proxy import *
+from m5.SimObject import SimObject
+
+class BaseCacheCompressor(SimObject):
+    type = 'BaseCacheCompressor'
+    abstract = True
+    cxx_header = "mem/cache/compressors/base.hh"
+
+    block_size = Param.Int(Parent.cache_line_size, "Block size in bytes")
diff --git a/src/mem/cache/compressors/SConscript b/src/mem/cache/compressors/SConscript
new file mode 100644
index 000000000..44cf4a570
--- /dev/null
+++ b/src/mem/cache/compressors/SConscript
@@ -0,0 +1,35 @@
+# -*- mode:python -*-
+
+# Copyright (c) 2018 Inria
+# 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: Daniel Carvalho
+
+Import('*')
+
+SimObject('Compressors.py')
+
+Source('base.cc')
diff --git a/src/mem/cache/compressors/base.cc b/src/mem/cache/compressors/base.cc
new file mode 100644
index 000000000..2991dfeda
--- /dev/null
+++ b/src/mem/cache/compressors/base.cc
@@ -0,0 +1,142 @@
+/*
+ * Copyright (c) 2018 Inria
+ * 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: Daniel Carvalho
+ */
+
+/** @file
+ * Definition of a basic cache compressor.
+ */
+
+#include "mem/cache/compressors/base.hh"
+
+#include <algorithm>
+#include <cstdint>
+
+#include "debug/CacheComp.hh"
+#include "mem/cache/tags/super_blk.hh"
+#include "params/BaseCacheCompressor.hh"
+
+// Uncomment this line if debugging compression
+//#define DEBUG_COMPRESSION
+
+BaseCacheCompressor::CompressionData::CompressionData()
+    : _size(0)
+{
+}
+
+BaseCacheCompressor::CompressionData::~CompressionData()
+{
+}
+
+void
+BaseCacheCompressor::CompressionData::setSizeBits(std::size_t size)
+{
+    _size = size;
+}
+
+std::size_t
+BaseCacheCompressor::CompressionData::getSizeBits() const
+{
+    return _size;
+}
+
+std::size_t
+BaseCacheCompressor::CompressionData::getSize() const
+{
+    return std::ceil(_size/8);
+}
+
+BaseCacheCompressor::BaseCacheCompressor(const Params *p)
+    : SimObject(p), blkSize(p->block_size)
+{
+}
+
+void
+BaseCacheCompressor::compress(const uint64_t* data, Cycles& comp_lat,
+                              Cycles& decomp_lat, std::size_t& comp_size_bits)
+{
+    // Apply compression
+    std::unique_ptr<CompressionData> comp_data =
+        compress(data, comp_lat, decomp_lat);
+
+    // If we are in debug mode apply decompression just after the compression.
+    // If the results do not match, we've got an error
+    #ifdef DEBUG_COMPRESSION
+    uint64_t decomp_data[blkSize/8];
+
+    // Apply decompression
+    decompress(comp_data.get(), decomp_data);
+
+    // Check if decompressed line matches original cache line
+    fatal_if(std::memcmp(data, decomp_data, blkSize),
+             "Decompressed line does not match original line.");
+    #endif
+
+    // Get compression size
+    comp_size_bits = comp_data->getSizeBits();
+
+    // Print debug information
+    DPRINTF(CacheComp, "Compressed cache line from %d to %d bits. " \
+            "Compression latency: %llu, decompression latency: %llu\n",
+            blkSize*8, comp_size_bits, comp_lat, decomp_lat);
+}
+
+Cycles
+BaseCacheCompressor::getDecompressionLatency(const CacheBlk* blk)
+{
+    const CompressionBlk* comp_blk = static_cast<const CompressionBlk*>(blk);
+
+    // If block is compressed, return its decompression latency
+    if (comp_blk && comp_blk->isCompressed()){
+        return comp_blk->getDecompressionLatency();
+    }
+
+    // Block is not compressed, so there is no decompression latency
+    return Cycles(0);
+}
+
+void
+BaseCacheCompressor::setDecompressionLatency(CacheBlk* blk, const Cycles lat)
+{
+    // Sanity check
+    assert(blk != nullptr);
+
+    // Assign latency
+    static_cast<CompressionBlk*>(blk)->setDecompressionLatency(lat);
+}
+
+void
+BaseCacheCompressor::setSizeBits(CacheBlk* blk, const std::size_t size_bits)
+{
+    // Sanity check
+    assert(blk != nullptr);
+
+    // Assign size
+    static_cast<CompressionBlk*>(blk)->setSizeBits(size_bits);
+}
+
diff --git a/src/mem/cache/compressors/base.hh b/src/mem/cache/compressors/base.hh
new file mode 100644
index 000000000..1a8c82c9b
--- /dev/null
+++ b/src/mem/cache/compressors/base.hh
@@ -0,0 +1,181 @@
+/*
+ * Copyright (c) 2018 Inria
+ * 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: Daniel Carvalho
+ */
+
+/** @file
+ * Definition of a basic cache compressor.
+ * A cache compressor must consist of a compression and a decompression
+ * methods. It must also be aware of the size of an uncompressed cache
+ * line.
+ */
+
+#ifndef __MEM_CACHE_COMPRESSORS_BASE_HH__
+#define __MEM_CACHE_COMPRESSORS_BASE_HH__
+
+#include <cstdint>
+
+#include "base/types.hh"
+#include "sim/sim_object.hh"
+
+class CacheBlk;
+struct BaseCacheCompressorParams;
+
+/**
+ * Base cache compressor interface. Every cache compressor must implement a
+ * compression and a decompression method.
+ */
+class BaseCacheCompressor : public SimObject {
+  protected:
+    /**
+     * Forward declaration of compression data. Every new compressor must
+     * create a new compression data based on it.
+     */
+    class CompressionData;
+
+    /**
+     * Uncompressed cache line size (in bytes).
+     */
+    const std::size_t blkSize;
+
+    /**
+     * Apply the compression process to the cache line.
+     * Returns the number of cycles used by the compressor, however it is
+     * usually covered by a good pipelined execution, and is currently ignored.
+     * The decompression latency is also returned, in order to avoid
+     * increasing simulation time and memory consumption.
+     *
+     * @param cache_line The cache line to be compressed.
+     * @param comp_lat Compression latency in number of cycles.
+     * @param decomp_lat Decompression latency in number of cycles.
+     * @return Cache line after compression.
+     */
+    virtual std::unique_ptr<CompressionData> compress(
+        const uint64_t* cache_line, Cycles& comp_lat, Cycles& decomp_lat) = 0;
+
+    /**
+     * Apply the decompression process to the compressed data.
+     *
+     * @param comp_data Compressed cache line.
+     * @param cache_line The cache line to be decompressed.
+     */
+    virtual void decompress(const CompressionData* comp_data,
+                              uint64_t* cache_line) = 0;
+
+  public:
+    /** Convenience typedef. */
+     typedef BaseCacheCompressorParams Params;
+
+    /**
+     * Default constructor.
+     */
+    BaseCacheCompressor(const Params *p);
+
+    /**
+     * Default destructor.
+     */
+    virtual ~BaseCacheCompressor() {};
+
+    /**
+     * Apply the compression process to the cache line. Ignores compression
+     * cycles.
+     *
+     * @param data The cache line to be compressed.
+     * @param comp_lat Compression latency in number of cycles.
+     * @param decomp_lat Decompression latency in number of cycles.
+     * @param comp_size_bits Compressed data size (in bits).
+     */
+    void compress(const uint64_t* data, Cycles& comp_lat,
+                  Cycles& decomp_lat, std::size_t& comp_size_bits);
+
+    /**
+     * Get the decompression latency if the block is compressed. Latency is 0
+     * otherwise.
+     *
+     * @param blk The compressed block.
+     */
+    static Cycles getDecompressionLatency(const CacheBlk* blk);
+
+    /**
+     * Set the decompression latency of compressed block.
+     *
+     * @param blk The compressed block.
+     * @param lat The decompression latency.
+     */
+    static void setDecompressionLatency(CacheBlk* blk, const Cycles lat);
+
+    /**
+     * Set the size of the compressed block, in bits.
+     *
+     * @param blk The compressed block.
+     * @param size_bits The block size.
+     */
+    static void setSizeBits(CacheBlk* blk, const std::size_t size_bits);
+};
+
+class BaseCacheCompressor::CompressionData {
+  private:
+    /**
+     * Compressed cache line size (in bits).
+     */
+    std::size_t _size;
+
+  public:
+    /**
+     * Default constructor.
+     */
+    CompressionData();
+
+    /**
+     * Virtual destructor. Without it unique_ptr will cause mem leak.
+     */
+    virtual ~CompressionData();
+
+    /**
+     * Set compression size (in bits).
+     *
+     * @param size Compressed data size.
+     */
+    void setSizeBits(std::size_t size);
+
+    /**
+     * Get compression size (in bits).
+     *
+     * @return Compressed data size.
+     */
+    std::size_t getSizeBits() const;
+
+    /**
+     * Get compression size (in bytes).
+     *
+     * @return Compressed data size.
+     */
+    std::size_t getSize() const;
+};
+
+#endif //__MEM_CACHE_COMPRESSORS_BASE_HH__