xref: /gem5/src/mem/cache/tags/indexing_policies/base.hh

/*
 * Copyright (c) 2018 Inria
 * Copyright (c) 2012-2014,2017 ARM Limited
 * All rights reserved.
 *
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 * 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
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 * modified or unmodified, in source code or in binary form.
 *
 * Copyright (c) 2003-2005,2014 The Regents of The University of Michigan
 * All rights reserved.
 *
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 * 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
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 * 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
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 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 *
 * Authors: Daniel Carvalho
 *          Erik Hallnor
 */

/**
 * @file
 * Declaration of a common framework for indexing policies.
 */

#ifndef __MEM_CACHE_INDEXING_POLICIES_BASE_HH__
#define __MEM_CACHE_INDEXING_POLICIES_BASE_HH__

#include <vector>

#include "params/BaseIndexingPolicy.hh"
#include "sim/sim_object.hh"

class ReplaceableEntry;

/**
 * A common base class for indexing table locations. Classes that inherit
 * from it determine hash functions that should be applied based on the set
 * and way. These functions are then applied to re-map the original values.
 * @sa  \ref gem5MemorySystem "gem5 Memory System"
 */
class BaseIndexingPolicy : public SimObject
{
  protected:
    /**
     * The associativity.
     */
    const unsigned assoc;

    /**
     * The number of sets in the cache.
     */
    const uint32_t numSets;

    /**
     * The amount to shift the address to get the set.
     */
    const int setShift;

    /**
     * Mask out all bits that aren't part of the set index.
     */
    const unsigned setMask;

    /**
     * The cache sets.
     */
    std::vector<std::vector<ReplaceableEntry*>> sets;

    /**
     * The amount to shift the address to get the tag.
     */
    const int tagShift;

  public:
    /**
     * Convenience typedef.
     */
    typedef BaseIndexingPolicyParams Params;

    /**
     * Construct and initialize this policy.
     */
    BaseIndexingPolicy(const Params *p);

    /**
     * Destructor.
     */
    ~BaseIndexingPolicy() {};

    /**
     * Associate a pointer to an entry to its physical counterpart.
     *
     * @param entry The entry pointer.
     * @param index An unique index for the entry.
     */
    void setEntry(ReplaceableEntry* entry, const uint64_t index);

    /**
     * Get an entry based on its set and way. All entries must have been set
     * already before calling this function.
     *
     * @param set The set of the desired entry.
     * @param way The way of the desired entry.
     * @return entry The entry pointer.
     */
    ReplaceableEntry* getEntry(const uint32_t set, const uint32_t way) const;

    /**
     * Generate the tag from the given address.
     *
     * @param addr The address to get the tag from.
     * @return The tag of the address.
     */
    Addr extractTag(const Addr addr) const;

    /**
     * Find all possible entries for insertion and replacement of an address.
     * Should be called immediately before ReplacementPolicy's findVictim()
     * not to break cache resizing.
     *
     * @param addr The addr to a find possible entries for.
     * @return The possible entries.
     */
    virtual std::vector<ReplaceableEntry*> getPossibleEntries(const Addr addr)
                                                                    const = 0;

    /**
     * Regenerate an entry's address from its tag and assigned indexing bits.
     *
     * @param tag The tag bits.
     * @param entry The entry.
     * @return the entry's original address.
     */
    virtual Addr regenerateAddr(const Addr tag, const ReplaceableEntry* entry)
                                                                    const = 0;
};

#endif //__MEM_CACHE_INDEXING_POLICIES_BASE_HH__