mem-cache: Split array indexing and replacement policies.

Replacement policies (LRU, Random) are currently considered as array
indexing methods, but have completely different functionalities:

- Array indexers determine the possible locations for block allocation.
  This information is used to generate replacement candidates when
  conflicts happen.
- Replacement policies determine which of the replacement candidates
  should be evicted to make room for new allocations.

For this reason, they were split into different classes. Advantages:

- Easier and more straightforward to implement other replacement
  policies (RRIP, LFU, ARC, ...)
- Allow easier future implementation of cache organization schemes

As now we can't assure the use of sets, the previous way to create a
true LRU is not viable. Now a timestamp_bits parameter controls how
many bits are dedicated for the timestamp, and a true LRU can be
achieved through an infinite number of bits (although a few bits suffice
in practice).

Change-Id: I23750db121f1474d17831137e6ff618beb2b3eda
Reviewed-on: https://gem5-review.googlesource.com/8501
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

1 files changed, 0 insertions, 120 deletions

diff --git a/src/mem/cache/tags/lru.cc b/src/mem/cache/tags/lru.cc
deleted file mode 100644
index 4302a8de6..000000000
--- a/src/mem/cache/tags/lru.cc
+++ /dev/null
@@ -1,120 +0,0 @@
-/*
- * Copyright (c) 2012-2013 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.
- *
- * Copyright (c) 2003-2005,2014 The Regents of The University of Michigan
- * 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: Erik Hallnor
- */
-
-/**
- * @file
- * Definitions of a LRU tag store.
- */
-
-#include "mem/cache/tags/lru.hh"
-
-#include "debug/CacheRepl.hh"
-#include "mem/cache/base.hh"
-
-LRU::LRU(const Params *p)
-    : BaseSetAssoc(p)
-{
-}
-
-CacheBlk*
-LRU::accessBlock(Addr addr, bool is_secure, Cycles &lat)
-{
-    CacheBlk *blk = BaseSetAssoc::accessBlock(addr, is_secure, lat);
-
-    if (blk != nullptr) {
-        // move this block to head of the MRU list
-        sets[blk->set].moveToHead(blk);
-        DPRINTF(CacheRepl, "set %x: moving blk %x (%s) to MRU\n",
-                blk->set, regenerateBlkAddr(blk),
-                is_secure ? "s" : "ns");
-    }
-
-    return blk;
-}
-
-CacheBlk*
-LRU::findVictim(Addr addr)
-{
-    int set = extractSet(addr);
-    // grab a replacement candidate
-    BlkType *blk = nullptr;
-    for (int i = assoc - 1; i >= 0; i--) {
-        BlkType *b = sets[set].blks[i];
-        if (b->way < allocAssoc) {
-            blk = b;
-            break;
-        }
-    }
-    assert(!blk || blk->way < allocAssoc);
-
-    if (blk && blk->isValid()) {
-        DPRINTF(CacheRepl, "set %x: selecting blk %x for replacement\n",
-                set, regenerateBlkAddr(blk));
-    }
-
-    return blk;
-}
-
-void
-LRU::insertBlock(PacketPtr pkt, BlkType *blk)
-{
-    BaseSetAssoc::insertBlock(pkt, blk);
-
-    int set = extractSet(pkt->getAddr());
-    sets[set].moveToHead(blk);
-}
-
-void
-LRU::invalidate(CacheBlk *blk)
-{
-    BaseSetAssoc::invalidate(blk);
-
-    // should be evicted before valid blocks
-    int set = blk->set;
-    sets[set].moveToTail(blk);
-}
-
-LRU*
-LRUParams::create()
-{
-    return new LRU(this);
-}