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/* icache_model.c -- instruction cache simulation

   Copyright (C) 1999 Damjan Lampret, lampret@opencores.org

This file is part of OpenRISC 1000 Architectural Simulator.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

GNU General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */

/* Cache functions.

   At the moment this functions only simulate functionality of instruction

   caches and do not influence on fetche/decode/execute stages and timings.

   They are here only to verify performance of various cache configurations.

 */

#include <stdio.h>

#include <string.h>

#include <errno.h>

#include <stdarg.h>

#include "icache_model.h"

#include "abstract.h"

#include "stats.h"

/* Instruction cache */

/* Number of IC sets (power of 2) */

#define IC_SETS 256

/* Block size in bytes (1, 2, 4, 8, 16, 32 etc.) */

#define IC_BLOCK_SIZE 4

/* Number of IC ways (1, 2, 3 etc.). */

#define IC_WAYS 1

/* Number of usage states (2, 3, 4 etc.). */

#define IC_USTATES 2

struct ic_set {

        struct {

                unsigned long tagaddr;  /* tag address */

                int lru;                /* least recently used */

        } way[IC_WAYS];

} ic[IC_SETS];

void ic_info()

{

        printf("Instruction cache %dKB: ", IC_SETS * IC_BLOCK_SIZE * IC_WAYS / 1024);

        printf("%d ways, %d sets, block size %d bytes\n", IC_WAYS, IC_SETS, IC_BLOCK_SIZE);

}

/* First check if instruction is already in the cache and if it is:

    - increment IC read hit stats,

    - set 'lru' at this way to IC_USTATES - 1 and

      decrement 'lru' of other ways unless they have reached 0,

   and if not:

    - increment IC read miss stats

    - find lru way and entry and replace old tag with tag of the 'fetchaddr'

    - set 'lru' with IC_USTATES - 1 and decrement 'lru' of other

      ways unless they have reached 0

*/

void ic_simulate(unsigned long fetchaddr)

{

        int set, way = -1;

        int i;

        unsigned long tagaddr;

        /* Which set to check out? */

        set = (fetchaddr / IC_BLOCK_SIZE) % IC_SETS;

        tagaddr = (fetchaddr / IC_BLOCK_SIZE) / IC_SETS;

        /* Scan all ways and try to find a matching way. */

        for (i = 0; i < IC_WAYS; i++)

                if (ic[set].way[i].tagaddr == tagaddr)

                        way = i;

        /* Did we find our cached instruction? */

        if (way >= 0) { /* Yes, we did. */

                ic_stats.readhit++;

                for (i = 0; i < IC_WAYS; i++)

                        if (ic[set].way[i].lru)

                                ic[set].way[i].lru--;

                ic[set].way[way].lru = IC_USTATES - 1;

        }

        else {  /* No, we didn't. */

                int minlru = IC_USTATES - 1;

                int minway = 0;

                ic_stats.readmiss++;

                for (i = 0; i < IC_WAYS; i++)

                        if (ic[set].way[i].lru < minlru)

                                minway = i;

                ic[set].way[minway].tagaddr = tagaddr;

                for (i = 0; i < IC_WAYS; i++)

                        if (ic[set].way[i].lru)

                                ic[set].way[i].lru--;

                ic[set].way[minway].lru = IC_USTATES - 1;

        }

}