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/*
* Copyright (c) 2013 Advanced Micro Devices, Inc
* 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.
*
* Author: Derek Hower
*/
#include "mem/ruby/structures/PseudoLRUPolicy.hh"
PseudoLRUPolicy::PseudoLRUPolicy(const Params * p)
: AbstractReplacementPolicy(p)
{
// associativity cannot exceed capacity of tree representation
assert(m_num_sets > 0 &&
m_assoc > 1 &&
m_assoc <= (int64_t) sizeof(uint64_t)*4);
m_trees = NULL;
m_num_levels = 0;
m_effective_assoc = 1;
while (m_effective_assoc < m_assoc) {
// effective associativity is ceiling power of 2
m_effective_assoc <<= 1;
}
int tmp_assoc = m_effective_assoc;
while (true) {
tmp_assoc /= 2;
if (!tmp_assoc) break;
m_num_levels++;
}
assert(m_num_levels < sizeof(unsigned int)*4);
m_trees = new uint64_t[m_num_sets];
for (unsigned i = 0; i < m_num_sets; i++) {
m_trees[i] = 0;
}
}
PseudoLRUPolicy *
PseudoLRUReplacementPolicyParams::create()
{
return new PseudoLRUPolicy(this);
}
PseudoLRUPolicy::~PseudoLRUPolicy()
{
if (m_trees != NULL)
delete[] m_trees;
}
void
PseudoLRUPolicy::touch(int64_t set, int64_t index, Tick time)
{
assert(index >= 0 && index < m_assoc);
assert(set >= 0 && set < m_num_sets);
int tree_index = 0;
int node_val;
for (int i = m_num_levels - 1; i >= 0; i--) {
node_val = (index >> i)&1;
if (node_val)
m_trees[set] |= node_val << tree_index;
else
m_trees[set] &= ~(1 << tree_index);
tree_index = node_val ? (tree_index*2)+2 : (tree_index*2)+1;
}
m_last_ref_ptr[set][index] = time;
}
int64_t
PseudoLRUPolicy::getVictim(int64_t set) const
{
int64_t index = 0;
int tree_index = 0;
int node_val;
for (unsigned i = 0; i < m_num_levels; i++){
node_val = (m_trees[set] >> tree_index) & 1;
index += node_val ? 0 : (m_effective_assoc >> (i + 1));
tree_index = node_val ? (tree_index * 2) + 1 : (tree_index * 2) + 2;
}
assert(index >= 0 && index < m_effective_assoc);
/* return either the found index or the max possible index */
/* NOTE: this is not a fair replacement when assoc is not a power of 2 */
return (index > (m_assoc - 1)) ? m_assoc - 1 : index;
}
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