6 files changed, 529 insertions, 1 deletions

diff --git a/src/mem/cache/compressors/Compressors.py b/src/mem/cache/compressors/Compressors.py
index 721b6a251..607491ad4 100644
--- a/src/mem/cache/compressors/Compressors.py
+++ b/src/mem/cache/compressors/Compressors.py
@@ -48,6 +48,36 @@ class BaseDictionaryCompressor(BaseCacheCompressor):
     dictionary_size = Param.Int(Parent.cache_line_size,
         "Number of dictionary entries")
 
+class Base64Delta8(BaseDictionaryCompressor):
+    type = 'Base64Delta8'
+    cxx_class = 'Base64Delta8'
+    cxx_header = "mem/cache/compressors/base_delta.hh"
+
+class Base64Delta16(BaseDictionaryCompressor):
+    type = 'Base64Delta16'
+    cxx_class = 'Base64Delta16'
+    cxx_header = "mem/cache/compressors/base_delta.hh"
+
+class Base64Delta32(BaseDictionaryCompressor):
+    type = 'Base64Delta32'
+    cxx_class = 'Base64Delta32'
+    cxx_header = "mem/cache/compressors/base_delta.hh"
+
+class Base32Delta8(BaseDictionaryCompressor):
+    type = 'Base32Delta8'
+    cxx_class = 'Base32Delta8'
+    cxx_header = "mem/cache/compressors/base_delta.hh"
+
+class Base32Delta16(BaseDictionaryCompressor):
+    type = 'Base32Delta16'
+    cxx_class = 'Base32Delta16'
+    cxx_header = "mem/cache/compressors/base_delta.hh"
+
+class Base16Delta8(BaseDictionaryCompressor):
+    type = 'Base16Delta8'
+    cxx_class = 'Base16Delta8'
+    cxx_header = "mem/cache/compressors/base_delta.hh"
+
 class BDI(BaseCacheCompressor):
     type = 'BDI'
     cxx_class = 'BDI'
diff --git a/src/mem/cache/compressors/SConscript b/src/mem/cache/compressors/SConscript
index 05c1edede..517ec522a 100644
--- a/src/mem/cache/compressors/SConscript
+++ b/src/mem/cache/compressors/SConscript
@@ -34,6 +34,7 @@ SimObject('Compressors.py')
 
 Source('base.cc')
 Source('base_dictionary_compressor.cc')
+Source('base_delta.cc')
 Source('bdi.cc')
 Source('cpack.cc')
 Source('fpcd.cc')
diff --git a/src/mem/cache/compressors/base_delta.cc b/src/mem/cache/compressors/base_delta.cc
new file mode 100644
index 000000000..66349282f
--- /dev/null
+++ b/src/mem/cache/compressors/base_delta.cc
@@ -0,0 +1,107 @@
+/*
+ * Copyright (c) 2019 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
+ * Implementation of the specialized sub-compressors used by BDI. @see BDI
+ */
+
+#include "mem/cache/compressors/base_delta_impl.hh"
+#include "params/Base16Delta8.hh"
+#include "params/Base32Delta16.hh"
+#include "params/Base32Delta8.hh"
+#include "params/Base64Delta16.hh"
+#include "params/Base64Delta32.hh"
+#include "params/Base64Delta8.hh"
+
+Base64Delta8::Base64Delta8(const Params *p)
+    : BaseDelta<uint64_t, 8>(p)
+{
+}
+
+Base64Delta16::Base64Delta16(const Params *p)
+    : BaseDelta<uint64_t, 16>(p)
+{
+}
+
+Base64Delta32::Base64Delta32(const Params *p)
+    : BaseDelta<uint64_t, 32>(p)
+{
+}
+
+Base32Delta8::Base32Delta8(const Params *p)
+    : BaseDelta<uint32_t, 8>(p)
+{
+}
+
+Base32Delta16::Base32Delta16(const Params *p)
+    : BaseDelta<uint32_t, 16>(p)
+{
+}
+
+Base16Delta8::Base16Delta8(const Params *p)
+    : BaseDelta<uint16_t, 8>(p)
+{
+}
+
+Base64Delta8*
+Base64Delta8Params::create()
+{
+    return new Base64Delta8(this);
+}
+
+Base64Delta16*
+Base64Delta16Params::create()
+{
+    return new Base64Delta16(this);
+}
+
+Base64Delta32*
+Base64Delta32Params::create()
+{
+    return new Base64Delta32(this);
+}
+
+Base32Delta8*
+Base32Delta8Params::create()
+{
+    return new Base32Delta8(this);
+}
+
+Base32Delta16*
+Base32Delta16Params::create()
+{
+    return new Base32Delta16(this);
+}
+
+Base16Delta8*
+Base16Delta8Params::create()
+{
+    return new Base16Delta8(this);
+}
diff --git a/src/mem/cache/compressors/base_delta.hh b/src/mem/cache/compressors/base_delta.hh
new file mode 100644
index 000000000..b20814441
--- /dev/null
+++ b/src/mem/cache/compressors/base_delta.hh
@@ -0,0 +1,206 @@
+/*
+ * Copyright (c) 2019 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 base delta immediate compressor. @see BDI
+ */
+
+#ifndef __MEM_CACHE_COMPRESSORS_BASE_DELTA_HH__
+#define __MEM_CACHE_COMPRESSORS_BASE_DELTA_HH__
+
+#include <array>
+#include <cstdint>
+#include <map>
+#include <memory>
+
+#include "base/bitfield.hh"
+#include "mem/cache/compressors/dictionary_compressor.hh"
+
+struct BaseDictionaryCompressorParams;
+struct Base64Delta8Params;
+struct Base64Delta16Params;
+struct Base64Delta32Params;
+struct Base32Delta8Params;
+struct Base32Delta16Params;
+struct Base16Delta8Params;
+
+/**
+ * Base class for all base-delta-immediate compressors. Although not proposed
+ * like this in the original paper, the sub-compressors of BDI are dictionary
+ * based with 2 possible patterns: no match, where a dictionary entry must be
+ * allocated, and masked delta match with a dictionary entry, where the delta
+ * must be stored instead. The maximum number of dictionary entries is 2, and
+ * one of them is reserved for a zero base if using immediate compression.
+ *
+ * @tparam BaseType Type of a base (dictionary) entry.
+ */
+template <class BaseType, std::size_t DeltaSizeBits>
+class BaseDelta : public DictionaryCompressor<BaseType>
+{
+  protected:
+    static constexpr int DEFAULT_MAX_NUM_BASES = 2;
+
+    using DictionaryEntry =
+        typename DictionaryCompressor<BaseType>::DictionaryEntry;
+
+    // Forward declaration of all possible patterns
+    class PatternX;
+    class PatternM;
+
+    /**
+     * The patterns proposed in the paper. Each letter represents a byte:
+     * Z is a null byte, M is a dictionary match, X is a new value.
+     * These are used as indexes to reference the pattern data. If a new
+     * pattern is added, it must be done before NUM_PATTERNS.
+     */
+    typedef enum {
+        X, M, NUM_PATTERNS
+    } PatternNumber;
+
+    uint64_t getNumPatterns() const override { return NUM_PATTERNS; }
+
+    /**
+     * Convenience factory declaration. The templates must be organized by
+     * size, with the smallest first, and "no-match" last.
+     */
+    using PatternFactory = typename DictionaryCompressor<BaseType>::template
+        Factory<PatternM, PatternX>;
+
+    std::unique_ptr<typename DictionaryCompressor<BaseType>::Pattern>
+    getPattern(const DictionaryEntry& bytes,
+        const DictionaryEntry& dict_bytes,
+        const int match_location) const override
+    {
+        return PatternFactory::getPattern(bytes, dict_bytes, match_location);
+    }
+
+    std::string
+    getName(int number) const override
+    {
+        static std::map<int, std::string> pattern_names = {
+            {X, "X"}, {M, "M"}
+        };
+
+        return pattern_names[number];
+    }
+
+    void resetDictionary() override;
+
+    void addToDictionary(DictionaryEntry data) override;
+
+    std::unique_ptr<BaseCacheCompressor::CompressionData>
+    compress(const uint64_t* data, Cycles& comp_lat,
+        Cycles& decomp_lat) override;
+
+  public:
+    typedef BaseDictionaryCompressorParams Params;
+    BaseDelta(const Params *p);
+    ~BaseDelta() = default;
+};
+
+template <class BaseType, std::size_t DeltaSizeBits>
+class BaseDelta<BaseType, DeltaSizeBits>::PatternX
+    : public DictionaryCompressor<BaseType>::UncompressedPattern
+{
+  public:
+    // A delta entry containing the value 0 is added even if it is an entirely
+    // new base
+    PatternX(const DictionaryEntry bytes, const int match_location)
+        : DictionaryCompressor<BaseType>::UncompressedPattern(X, 0,
+          std::ceil(std::log2(DEFAULT_MAX_NUM_BASES)) + DeltaSizeBits,
+          match_location, bytes)
+    {
+    }
+};
+
+template <class BaseType, std::size_t DeltaSizeBits>
+class BaseDelta<BaseType, DeltaSizeBits>::PatternM : public
+    DictionaryCompressor<BaseType>::template DeltaPattern<DeltaSizeBits>
+{
+  public:
+    // The number of bits reserved for the bitmask entry is proportional to
+    // the maximum number of bases
+    PatternM(const DictionaryEntry bytes, const int match_location)
+        : DictionaryCompressor<BaseType>::template DeltaPattern<DeltaSizeBits>(
+          M, 1, std::ceil(std::log2(DEFAULT_MAX_NUM_BASES)), match_location,
+          bytes)
+    {
+    }
+};
+
+class Base64Delta8 : public BaseDelta<uint64_t, 8>
+{
+  public:
+    typedef Base64Delta8Params Params;
+    Base64Delta8(const Params *p);
+    ~Base64Delta8() = default;
+};
+
+class Base64Delta16 : public BaseDelta<uint64_t, 16>
+{
+  public:
+    typedef Base64Delta16Params Params;
+    Base64Delta16(const Params *p);
+    ~Base64Delta16() = default;
+};
+
+class Base64Delta32 : public BaseDelta<uint64_t, 32>
+{
+  public:
+    typedef Base64Delta32Params Params;
+    Base64Delta32(const Params *p);
+    ~Base64Delta32() = default;
+};
+
+class Base32Delta8 : public BaseDelta<uint32_t, 8>
+{
+  public:
+    typedef Base32Delta8Params Params;
+    Base32Delta8(const Params *p);
+    ~Base32Delta8() = default;
+};
+
+class Base32Delta16 : public BaseDelta<uint32_t, 16>
+{
+  public:
+    typedef Base32Delta16Params Params;
+    Base32Delta16(const Params *p);
+    ~Base32Delta16() = default;
+};
+
+class Base16Delta8 : public BaseDelta<uint16_t, 8>
+{
+  public:
+    typedef Base16Delta8Params Params;
+    Base16Delta8(const Params *p);
+    ~Base16Delta8() = default;
+};
+
+#endif //__MEM_CACHE_COMPRESSORS_BASE_DELTA_HH__
diff --git a/src/mem/cache/compressors/base_delta_impl.hh b/src/mem/cache/compressors/base_delta_impl.hh
new file mode 100644
index 000000000..7685a3d80
--- /dev/null
+++ b/src/mem/cache/compressors/base_delta_impl.hh
@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2019 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
+ * Implementation of a base delta immediate compressor. @see BDI
+ */
+
+#ifndef __MEM_CACHE_COMPRESSORS_BASE_DELTA_IMPL_HH__
+#define __MEM_CACHE_COMPRESSORS_BASE_DELTA_IMPL_HH__
+
+#include "debug/CacheComp.hh"
+#include "mem/cache/compressors/base_delta.hh"
+#include "mem/cache/compressors/dictionary_compressor_impl.hh"
+
+template <class BaseType, std::size_t DeltaSizeBits>
+BaseDelta<BaseType, DeltaSizeBits>::BaseDelta(const Params *p)
+    : DictionaryCompressor<BaseType>(p)
+{
+}
+
+template <class BaseType, std::size_t DeltaSizeBits>
+void
+BaseDelta<BaseType, DeltaSizeBits>::resetDictionary()
+{
+    DictionaryCompressor<BaseType>::resetDictionary();
+
+    // Add zero base for the immediate values
+    addToDictionary(DictionaryCompressor<BaseType>::toDictionaryEntry(0));
+}
+
+template <class BaseType, std::size_t DeltaSizeBits>
+void
+BaseDelta<BaseType, DeltaSizeBits>::addToDictionary(DictionaryEntry data)
+{
+    assert(DictionaryCompressor<BaseType>::numEntries <
+        DictionaryCompressor<BaseType>::dictionarySize);
+    DictionaryCompressor<BaseType>::dictionary[
+        DictionaryCompressor<BaseType>::numEntries++] = data;
+}
+
+template <class BaseType, std::size_t DeltaSizeBits>
+std::unique_ptr<BaseCacheCompressor::CompressionData>
+BaseDelta<BaseType, DeltaSizeBits>::compress(const uint64_t* data,
+    Cycles& comp_lat, Cycles& decomp_lat)
+{
+    std::unique_ptr<BaseCacheCompressor::CompressionData> comp_data =
+        DictionaryCompressor<BaseType>::compress(data);
+
+    // If there are more bases than the maximum, the compressor failed.
+    // Otherwise, we have to take into account all bases that have not
+    // been used, considering that there is an implicit zero base that
+    // does not need to be added to the final size.
+    const int diff = DEFAULT_MAX_NUM_BASES -
+        DictionaryCompressor<BaseType>::numEntries;
+    if (diff < 0) {
+        comp_data->setSizeBits(DictionaryCompressor<BaseType>::blkSize * 8);
+        DPRINTF(CacheComp, "Base%dDelta%d compression failed\n",
+            8 * sizeof(BaseType), DeltaSizeBits);
+    } else if (diff > 0) {
+        comp_data->setSizeBits(comp_data->getSizeBits() +
+            8 * sizeof(BaseType) * diff);
+    }
+
+    // Set compression latency (Assumes 1 cycle per entry and 1 cycle for
+    // packing)
+    comp_lat = Cycles(1 + (DictionaryCompressor<BaseType>::blkSize /
+        sizeof(BaseType)));
+
+    // Set decompression latency
+    decomp_lat = Cycles(1);
+
+    // Return compressed line
+    return comp_data;
+}
+
+#endif //__MEM_CACHE_COMPRESSORS_BASE_DELTA_IMPL_HH__
diff --git a/src/mem/cache/compressors/dictionary_compressor.hh b/src/mem/cache/compressors/dictionary_compressor.hh
index 8a7df4dc6..1615990b4 100644
--- a/src/mem/cache/compressors/dictionary_compressor.hh
+++ b/src/mem/cache/compressors/dictionary_compressor.hh
@@ -50,6 +50,7 @@
 #include <map>
 #include <memory>
 #include <string>
+#include <type_traits>
 #include <vector>
 
 #include "base/types.hh"
@@ -131,6 +132,8 @@ class DictionaryCompressor : public BaseDictionaryCompressor
     class LocatedMaskedPattern;
     template <class RepT>
     class RepeatedValuePattern;
+    template <std::size_t DeltaSizeBits>
+    class DeltaPattern;
 
     /**
      * Create a factory to determine if input matches a pattern. The if else
@@ -209,7 +212,7 @@ class DictionaryCompressor : public BaseDictionaryCompressor
     T decompressValue(const Pattern* pattern);
 
     /** Clear all dictionary entries. */
-    void resetDictionary();
+    virtual void resetDictionary();
 
     /**
      * Add an entry to the dictionary.
@@ -644,4 +647,82 @@ class DictionaryCompressor<T>::RepeatedValuePattern
     }
 };
 
+/**
+ * A pattern that checks whether the difference of the value and the dictionary
+ * entries' is below a certain threshold. If so, the pattern is successful,
+ * and only the delta bits need to be stored.
+ *
+ * For example, if the delta can only contain up to 4 bits, and the dictionary
+ * contains the entry 0xA231, the value 0xA232 would be compressible, and
+ * the delta 0x1 would be stored. The value 0xA249, on the other hand, would
+ * not be compressible, since its delta (0x18) needs 5 bits to be stored.
+ *
+ * @tparam DeltaSizeBits Size of a delta entry, in number of bits, which
+ *                       determines the threshold. Must always be smaller
+ *                       than the dictionary entry type's size.
+ */
+template <class T>
+template <std::size_t DeltaSizeBits>
+class DictionaryCompressor<T>::DeltaPattern
+    : public DictionaryCompressor<T>::Pattern
+{
+  private:
+    static_assert(DeltaSizeBits < (sizeof(T) * 8),
+        "Delta size must be smaller than base size");
+
+    /**
+     * The original value. In theory we should keep only the deltas, but
+     * the dictionary entry is not inserted in the dictionary before the
+     * call to the constructor, so the delta cannot be calculated then.
+     */
+    const DictionaryEntry bytes;
+
+  public:
+    DeltaPattern(const int number,
+        const uint64_t code,
+        const uint64_t metadata_length,
+        const int match_location,
+        const DictionaryEntry bytes)
+      : DictionaryCompressor<T>::Pattern(number, code, metadata_length,
+            DeltaSizeBits, match_location, false),
+        bytes(bytes)
+    {
+    }
+
+    /**
+     * Compares a given value against a base to calculate their delta, and
+     * then determines whether it fits a limited sized container.
+     *
+     * @param bytes Value to be compared against base.
+     * @param base_bytes Base value.
+     * @return Whether the value fits in the container.
+     */
+    static bool
+    isValidDelta(const DictionaryEntry& bytes,
+        const DictionaryEntry& base_bytes)
+    {
+        const typename std::make_signed<T>::type limit = DeltaSizeBits ?
+            mask(DeltaSizeBits - 1) : 0;
+        const T value =
+            DictionaryCompressor<T>::fromDictionaryEntry(bytes);
+        const T base =
+            DictionaryCompressor<T>::fromDictionaryEntry(base_bytes);
+        const typename std::make_signed<T>::type delta = value - base;
+        return (delta >= -limit) && (delta <= limit);
+    }
+
+    static bool
+    isPattern(const DictionaryEntry& bytes,
+        const DictionaryEntry& dict_bytes, const int match_location)
+    {
+        return (match_location >= 0) && isValidDelta(bytes, dict_bytes);
+    }
+
+    DictionaryEntry
+    decompress(const DictionaryEntry dict_bytes) const override
+    {
+        return bytes;
+    }
+};
+
 #endif //__MEM_CACHE_COMPRESSORS_DICTIONARY_COMPRESSOR_HH__