| /* |
| * 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 |
| * Declaration of a skewed associative tag store. |
| */ |
| |
| #ifndef __MEM_CACHE_TAGS_SKEWED_ASSOC_HH__ |
| #define __MEM_CACHE_TAGS_SKEWED_ASSOC_HH__ |
| |
| #include "mem/cache/blk.hh" |
| #include "mem/cache/tags/base_set_assoc.hh" |
| #include "params/SkewedAssoc.hh" |
| |
| /** |
| * A SkewedAssoc cache tag store. |
| * @sa \ref gem5MemorySystem "gem5 Memory System" |
| * |
| * The SkewedAssoc placement policy divides the cache into s sets of w |
| * cache lines (ways). A cache line has a different set mapping for each way, |
| * according to a skewing function. |
| * |
| * If provided with an associativity higher than the number of skewing |
| * functions, the skewing functions of the extra ways might be sub-optimal. |
| */ |
| class SkewedAssoc : public BaseSetAssoc |
| { |
| private: |
| /** |
| * The number of skewing functions implemented. Should be updated if more |
| * functions are added. If more than this number of skewing functions are |
| * needed (i.e., assoc > this value), we programatically generate new ones, |
| * which may be sub-optimal. |
| */ |
| const int NUM_SKEWING_FUNCTIONS = 8; |
| |
| /** |
| * The amount to shift a set index to get its MSB. |
| */ |
| const int msbShift; |
| |
| /** |
| * The hash function itself. Uses the hash function H, as described in |
| * "Skewed-Associative Caches", from Seznec et al. (section 3.3): It |
| * applies an XOR to the MSB and LSB, shifts all bits one bit to the right, |
| * and set the result of the XOR as the new MSB. |
| * |
| * This function is not bijective if the address has only 1 bit, as the MSB |
| * and LSB will be the same, and therefore the xor will always be 0. |
| * |
| * @param addr The address to be hashed. |
| * @param The hashed address. |
| */ |
| Addr hash(const Addr addr) const; |
| |
| /** |
| * Inverse of the hash function. |
| * @sa hash(). |
| * |
| * @param addr The address to be dehashed. |
| * @param The dehashed address. |
| */ |
| Addr dehash(const Addr addr) const; |
| |
| /** |
| * Address skewing function selection. It selects and applies one of the |
| * skewing functions functions based on the way provided. |
| * |
| * @param addr Address to be skewed. Should contain the set and tag bits. |
| * @param way The cache way, used to select a hash function. |
| * @return The skewed address. |
| */ |
| Addr skew(const Addr addr, const unsigned way) const; |
| |
| /** |
| * Address deskewing function (inverse of the skew function) of the given |
| * way. |
| * @sa skew() |
| * |
| * @param addr Address to be deskewed. Should contain the set and tag bits. |
| * @param way The cache way, used to select a hash function. |
| * @return The deskewed address. |
| */ |
| Addr deskew(const Addr addr, const unsigned way) const; |
| |
| /** |
| * Apply a skewing function to calculate address' set given a way. |
| * |
| * @param addr The address to calculate the set for. |
| * @param way The way to get the set from. |
| * @return The set index for given combination of address and way. |
| */ |
| unsigned extractSet(Addr addr, unsigned way) const; |
| |
| public: |
| /** Convenience typedef. */ |
| typedef SkewedAssocParams Params; |
| |
| /** |
| * Construct and initialize this tag store. |
| */ |
| SkewedAssoc(const Params *p); |
| |
| /** |
| * Destructor |
| */ |
| ~SkewedAssoc() {}; |
| |
| /** |
| * Find all possible block locations for insertion and replacement of |
| * an address. Should be called immediately before ReplacementPolicy's |
| * findVictim() not to break cache resizing. |
| * Returns blocks in all ways belonging to the set of the address. |
| * |
| * @param addr The addr to a find possible locations for. |
| * @return The possible locations. |
| */ |
| const std::vector<CacheBlk*> getPossibleLocations(Addr addr) const |
| override; |
| |
| /** |
| * Finds the given address in the cache, do not update replacement data. |
| * i.e. This is a no-side-effect find of a block. |
| * |
| * @param addr The address to find. |
| * @param is_secure True if the target memory space is secure. |
| * @return Pointer to the cache block if found. |
| */ |
| CacheBlk* findBlock(Addr addr, bool is_secure) const override; |
| |
| /** |
| * Regenerate the block address from the tag, set and way. Uses the |
| * inverse of the skewing function. |
| * |
| * @param block The block. |
| * @return the block address. |
| */ |
| Addr regenerateBlkAddr(const CacheBlk* blk) const override; |
| }; |
| |
| #endif //__MEM_CACHE_TAGS_SKEWED_ASSOC_HH__ |