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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"
#include "sim-config.h"
#include "spr_defs.h"
#include "sprs.h"
#include "sim-config.h"
 
extern struct dev_memarea *cur_area;
struct ic_set {
  struct {
    unsigned long line[MAX_IC_BLOCK_SIZE];
    unsigned long tagaddr;  /* tag address */
    int lru;    /* least recently used */
  } way[MAX_IC_WAYS];
} ic[MAX_IC_SETS];
 
void ic_info()
{
  if (!testsprbits(SPR_UPR, SPR_UPR_ICP)) {
    printf("ICache not implemented. Set UPR[ICP].\n");
    return;
  }
 
  printf("Instruction cache %dKB: ", config.ic.nsets * config.ic.blocksize * config.ic.nways / 1024);
  printf("%d ways, %d sets, block size %d bytes\n", config.ic.nways, config.ic.nsets, config.ic.blocksize);
}
 
/* First check if instruction is already in the cache and if it is:
    - increment IC read hit stats,
    - set 'lru' at this way to config.ic.ustates - 1 and
      decrement 'lru' of other ways unless they have reached 0,
    - read insn from the cache line
   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 config.ic.ustates - 1 and decrement 'lru' of other
      ways unless they have reached 0
    - refill cache line
*/
 
unsigned long ic_simulate_fetch(unsigned long fetchaddr)
{
  int set, way = -1;
  int i;
  unsigned long tagaddr;
 
  /* ICache simulation enabled/disabled. */
  if ((!testsprbits(SPR_UPR, SPR_UPR_ICP)) || (!testsprbits(SPR_SR, SPR_SR_ICE)) || insn_ci)
    return evalsim_mem32(fetchaddr);
 
  /* Which set to check out? */
  set = (fetchaddr / config.ic.blocksize) % config.ic.nsets;
  tagaddr = (fetchaddr / config.ic.blocksize) / config.ic.nsets;
 
  /* Scan all ways and try to find a matching way. */
  for (i = 0; i < config.ic.nways; 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 < config.ic.nways; i++)
      if (ic[set].way[i].lru > ic[set].way[way].lru)
        ic[set].way[i].lru--;
    ic[set].way[way].lru = config.ic.ustates - 1;
    runtime.sim.mem_cycles += config.ic.hitdelay;
    return (ic[set].way[way].line[(fetchaddr & (config.ic.blocksize - 1)) >> 2]);
  }
  else {  /* No, we didn't. */
    int minlru = config.ic.ustates - 1;
    int minway = 0;
 
    ic_stats.readmiss++;
 
    for (i = 0; i < config.ic.nways; i++)
      if (ic[set].way[i].lru < minlru)
        minway = i;
 
    for (i = 0; i < (config.ic.blocksize); i += 4) {
      ic[set].way[minway].line[((fetchaddr + i) & (config.ic.blocksize - 1)) >> 2] = 
        evalsim_mem32((fetchaddr & ~(config.ic.blocksize - 1)) + ((fetchaddr + i) & (config.ic.blocksize - 1)));
      if(!cur_area) {
        ic[set].way[minway].tagaddr = -1;
        ic[set].way[minway].lru = 0;
        return 0;
      }
    }
 
    ic[set].way[minway].tagaddr = tagaddr;
    for (i = 0; i < config.ic.nways; i++)
      if (ic[set].way[i].lru)
        ic[set].way[i].lru--;
    ic[set].way[minway].lru = config.ic.ustates - 1;
    runtime.sim.mem_cycles += config.ic.missdelay;
    return (ic[set].way[minway].line[(fetchaddr & (config.ic.blocksize - 1)) >> 2]);
  }
}
 
/* First check if data is already in the cache and if it is:
    - invalidate block if way isn't locked
   otherwise don't do anything.
*/
 
void ic_inv(unsigned long dataaddr)
{
  int set, way = -1;
  int i;
  unsigned long tagaddr;
 
  if (!testsprbits(SPR_UPR, SPR_UPR_ICP))
    return;
 
  /* Which set to check out? */
  set = (dataaddr / config.ic.blocksize) % config.ic.nsets;
  tagaddr = (dataaddr / config.ic.blocksize) / config.ic.nsets;
 
  if (!testsprbits(SPR_SR, SPR_SR_ICE)) {
    for (i = 0; i < config.ic.nways; i++) {
      ic[set].way[i].tagaddr = -1;
      ic[set].way[i].lru = 0;
    }
    return;
  }
 
  /* Scan all ways and try to find a matching way. */
  for (i = 0; i < config.ic.nways; i++)
    if (ic[set].way[i].tagaddr == tagaddr)
      way = i;
 
  /* Did we find our cached data? */
  if (way >= 0) { /* Yes, we did. */
    ic[set].way[way].tagaddr = -1;
    ic[set].way[way].lru = 0;
  }
}
 
inline void ic_clock()
{
  unsigned long addr;
 
  if (addr = mfspr(SPR_ICBPR)) {
    ic_simulate_fetch(addr);
    mtspr(SPR_ICBPR, 0);
  }
  if (addr = mfspr(SPR_ICBIR)) {
    ic_inv(addr);
    mtspr(SPR_ICBIR, 0);
  }
  if (addr = mfspr(SPR_ICBLR)) {
    mtspr(SPR_ICBLR, 0);
  }
}