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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <stdint.h>
  4.  
  5. #define TLB_SETS 16
  6. #define TLB_WAYS 4
  7. #define POBITS 12
  8.  
  9. typedef struct {
  10.     size_t vpn;
  11.     size_t ppn;
  12.     int valid;
  13.     int lru_counter;
  14. } TLBEntry;
  15.  
  16. TLBEntry tlb[TLB_SETS][TLB_WAYS];
  17.  
  18. void tlb_clear() {
  19.     for (int i = 0; i < TLB_SETS; i++) {
  20.         for (int j = 0; j < TLB_WAYS; j++) {
  21.             tlb[i][j].valid = 0;
  22.             tlb[i][j].lru_counter = 0;
  23.         }
  24.     }
  25. }
  26.  
  27. int tlb_peek(size_t va) {
  28.     size_t vpn = va >> POBITS;
  29.     int set = vpn % TLB_SETS;
  30.  
  31.     for (int i = 0; i < TLB_WAYS; i++) {
  32.         if (tlb[set][i].valid && tlb[set][i].vpn == vpn) {
  33.             return tlb[set][i].lru_counter;
  34.         }
  35.     }
  36.     return 0;
  37. }
  38.  
  39. void update_lru(int set, int way) {
  40.     int used_counter = tlb[set][way].lru_counter;
  41.     for (int i = 0; i < TLB_WAYS; i++) {
  42.         if (tlb[set][i].lru_counter < used_counter) {
  43.             tlb[set][i].lru_counter++;
  44.         }
  45.     }
  46.     tlb[set][way].lru_counter = 1;
  47. }
  48.  
  49. size_t translate(size_t va) {
  50.     if (va >= 0x12345000 && va < 0x12346000) {
  51.         return 0x22345000 + (va - 0x12345000);
  52.     } else if (va >= 0x23456000 && va < 0x23457000) {
  53.         return 0x33456000 + (va - 0x23456000);
  54.     } else {
  55.         return (size_t)-1;
  56.     }
  57. }
  58.  
  59. size_t tlb_translate(size_t va) {
  60.     size_t vpn = va >> POBITS;
  61.     int set = vpn % TLB_SETS;
  62.  
  63.     for (int i = 0; i < TLB_WAYS; i++) {
  64.         if (tlb[set][i].valid && tlb[set][i].vpn == vpn) {
  65.             update_lru(set, i);
  66.             return (tlb[set][i].ppn << POBITS) | (va & ((1 << POBITS) - 1));
  67.         }
  68.     }
  69.  
  70.     size_t pa = translate(vpn << POBITS);
  71.     if (pa == (size_t)-1) return (size_t)-1;
  72.  
  73.     int lru_way = 0;
  74.     for (int i = 1; i < TLB_WAYS; i++) {
  75.         if (tlb[set][i].lru_counter > tlb[set][lru_way].lru_counter) {
  76.             lru_way = i;
  77.         }
  78.     }
  79.  
  80.     tlb[set][lru_way].vpn = vpn;
  81.     tlb[set][lru_way].ppn = pa >> POBITS;
  82.     tlb[set][lru_way].valid = 1;
  83.     update_lru(set, lru_way);
  84.  
  85.     return (tlb[set][lru_way].ppn << POBITS) | (va & ((1 << POBITS) - 1));
  86. }
  87.  
  88. int main() {
  89.     tlb_clear();
  90.  
  91.     printf("Translating VA: 0x12345678\n");
  92.     size_t pa = tlb_translate(0x12345678);
  93.     if (pa == (size_t)-1) {
  94.         printf("Translation failed for VA: 0x12345678\n");
  95.     } else {
  96.         printf("Translated PA: 0x%zx\n", pa);
  97.     }
  98.  
  99.     printf("Translating VA: 0x23456789\n");
  100.     pa = tlb_translate(0x23456789);
  101.     if (pa == (size_t)-1) {
  102.         printf("Translation failed for VA: 0x23456789\n");
  103.     } else {
  104.         printf("Translated PA: 0x%zx\n", pa);
  105.     }
  106.  
  107.     return 0;
  108. }
  109.  
Success #stdin #stdout 0s 5284KB
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Translating VA: 0x12345678
Translated PA: 0x22345678
Translating VA: 0x23456789
Translated PA: 0x33456789
https://ideone.com/VLbXlu
language:
C (gcc 8.3)
created:
5 days ago
visibility:
public

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