forked from zhangxz18/TAGE-Predictor
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathTagePredictor8Com.cc
270 lines (231 loc) · 8.15 KB
/
TagePredictor8Com.cc
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
#include "predictor.h"
#include <math.h>
/////////////// STORAGE BUDGET JUSTIFICATION ////////////////
// Total storage budget: 32KB + 17 bits
// Total PHT counters: 2^17
// Total PHT size = 2^17 * 2 bits/counter = 2^18 bits = 32KB
// GHR size: 17 bits
// Total Size = PHT size + GHR size
/////////////////////////////////////////////////////////////
#define TAGE_TABLE_NUM 8
#define BASE_TABLE_INDEX_WIDTH 14
#define BASE_CTR_WIDTH 2
#define BASE_CTR_INIT 2
#define BASE_CTR_MAX 3
#define TAG_WIDTH 11
#define U_WIDTH 2
#define CTR_WIDTH 3
#define TAGGED_ENTRY_LEN 11// each tagged table has 2^10 entry
#define TAGGED_CTR_INIT 0
#define TAGGED_CTR_MAX 7
#define TAGGED_WEAK_CORRECT 4
#define L1 5
#define L2 8
#define L3 12
#define L4 18
#define L5 28
#define L6 42
#define L7 65
#define L8 100
#define USE_ALT_MAX 15
#define USE_ALT_INIT 7
/////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////
PREDICTOR::PREDICTOR(void){
historyLength = L4;
ghr = 0;
numBaseTableEntries = 1 << BASE_TABLE_INDEX_WIDTH;
base_table = new uint8_t[numBaseTableEntries];
for(UINT32 ii=0; ii < numBaseTableEntries; ii++){
base_table[ii] = BASE_CTR_INIT;
}
numTageTableEntries = 1 << TAGGED_ENTRY_LEN;
tage_table_len = new UINT32[TAGE_TABLE_NUM];
tage_table_len[0] = L1;
tage_table_len[1] = L2;
tage_table_len[2] = L3;
tage_table_len[3] = L4;
tage_table_len[4] = L5;
tage_table_len[5] = L6;
tage_table_len[6] = L7;
tage_table_len[7] = L8;
tag_table = new TageEntry*[TAGE_TABLE_NUM];
for (UINT32 j = 0; j < TAGE_TABLE_NUM; j++){
tag_table[j] = new TageEntry[numTageTableEntries];
for(UINT32 ii=0; ii< numTageTableEntries; ii++){
tag_table[j][ii].tag = 0;
tag_table[j][ii].u = 0;
tag_table[j][ii].ctr = TAGGED_CTR_INIT;
}
}
clock = 0;
tag = new UINT32[TAGE_TABLE_NUM];
tag_table_idx = new UINT32[TAGE_TABLE_NUM];
use_alt = USE_ALT_INIT;
pred_is_new_entry = false;
}
/////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////
bool PREDICTOR::GetPrediction(UINT32 PC){
UINT32 base_index = PC % numBaseTableEntries;
uint8_t base_counter = base_table[base_index];
pred = base_counter > BASE_CTR_MAX/2;
provider_component = -1;
altpred_component = -1;
altpred = pred;
for(int i = 0; i < TAGE_TABLE_NUM; i++){
tag[i] = get_tag(PC, i);
tag_table_idx[i] = get_tagged_idx(PC, i);
if(tag_table[i][tag_table_idx[i]].tag == tag[i]){
altpred_component = provider_component;
altpred = pred;
provider_component = i;
pred = tag_table[i][tag_table_idx[i]].ctr > TAGGED_CTR_MAX / 2;
}
}
if(provider_component != -1 && tag_table[provider_component][tag_table_idx[provider_component]].u == 0 &&
(tag_table[provider_component][tag_table_idx[provider_component]].ctr == TAGGED_CTR_MAX / 2 ||
tag_table[provider_component][tag_table_idx[provider_component]].ctr == TAGGED_CTR_MAX / 2 + 1)){
pred_is_new_entry = true;
}
else{
pred_is_new_entry = false;
}
if(pred_is_new_entry && use_alt > USE_ALT_MAX / 2 + 1){
return (int)altpred;
}else{
return (int)pred;
}
}
/////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////
void PREDICTOR::UpdatePredictor(UINT32 PC, bool resolveDir, bool predDir, UINT32 branchTarget){
UINT32 base_index = PC % numBaseTableEntries;
uint8_t base_counter = base_table[base_index];
// update counter of provider component
if(provider_component == -1){
if(resolveDir == TAKEN){
base_table[base_index] = SatIncrement(base_counter, BASE_CTR_MAX);
}else{
base_table[base_index] = SatDecrement(base_counter);
}
}
else{
uint8_t pred_ctr = tag_table[provider_component][tag_table_idx[provider_component]].ctr;
if(resolveDir == TAKEN){
tag_table[provider_component][tag_table_idx[provider_component]].ctr = SatIncrement(pred_ctr, TAGGED_CTR_MAX);
}
else{
tag_table[provider_component][tag_table_idx[provider_component]].ctr = SatDecrement(pred_ctr);
}
}
// if prediction is incorrect, allocate entry
// don't need to allocate entry when altpred is false and pred is right, the u tag will do it(otherwise, we will always get the new entry?)
if(resolveDir != pred && provider_component != TAGE_TABLE_NUM - 1 /*&& !(pred == resolveDir && pred_is_new_entry)*/){
int unalloc_idx[TAGE_TABLE_NUM] = {-1, -1, -1, -1};
int count = 0;
for(int i = provider_component + 1; i < TAGE_TABLE_NUM; i++){
if(tag_table[i][tag_table_idx[i]].u == 0){
unalloc_idx[count] = i;
count ++;
}
}
// if uk > 0 for k in (i, M), then uk = uk-1 for all uk
if(count == 0){
for(int i = provider_component + 1; i < TAGE_TABLE_NUM; i++){
tag_table[i][tag_table_idx[i]].u = SatDecrement(tag_table[i][tag_table_idx[i]].u);
}
}
else{
srand(3407);
// allocate one entry each time
// if more than one T_i need allocate, for i < j, the probility of allocate entry in T_i = 2 * T_j
// example:count = 3, rand = {0} for unalloc[2], rand = {1, 2} for unalloc[1], rand = {3,4,5,6} for unalloc[0]
int total_pro = (1 << count) - 1;
int r = rand() % total_pro;
int choose_idx = -1;
for (int i = 0; i < count; i++){
if( r >= (1<<i) - 1 && r < ( 1 << (i + 1) ) - 1 ){
choose_idx = unalloc_idx[count - 1 - i];
}
}
UINT32 idx_in_tag_table_choose = tag_table_idx[choose_idx];
tag_table[choose_idx][idx_in_tag_table_choose].tag = tag[choose_idx];
tag_table[choose_idx][idx_in_tag_table_choose].u = 0;
if(resolveDir)
tag_table[choose_idx][idx_in_tag_table_choose].ctr = TAGGED_WEAK_CORRECT;
else
tag_table[choose_idx][idx_in_tag_table_choose].ctr = TAGGED_WEAK_CORRECT - 1;
}
}
// update use_alt
if(altpred != pred && provider_component != -1){
if(pred != resolveDir){
use_alt = SatIncrement(use_alt, USE_ALT_MAX);
}
else{
use_alt = SatDecrement(use_alt);
}
}
// update u
if(altpred != pred && provider_component != -1){
uint8_t u = tag_table[provider_component][tag_table_idx[provider_component]].u;
if(pred == resolveDir){
tag_table[provider_component][tag_table_idx[provider_component]].u = SatIncrement(u, 3);
}
else{
tag_table[provider_component][tag_table_idx[provider_component]].u = SatDecrement(u);
}
}
// After 256k branch, reset u
clock ++;
uint8_t mask = 0;
if(clock == 1 << 18){
mask = 1;
}
else if(clock == 1 << 19){
mask = 2;
clock = 0;
}
if(mask){
for(int i = 0; i < TAGE_TABLE_NUM; i++){
for (UINT32 j = 0; j < numTageTableEntries; j++){
tag_table[i][j].u = tag_table[i][j].u & mask;
}
}
}
// update ghr
ghr = ghr << 1;
if(resolveDir){
ghr++;
}
}
UINT32 PREDICTOR::get_tagged_idx(UINT32 PC, int bank_no){
__uint128_t temp_ghr = ghr;
int history_width = tage_table_len[bank_no];
UINT32 temp_pc = PC & ( (1 << TAGGED_ENTRY_LEN) - 1 );
// folder
while(history_width > 0){
int block_width = min(history_width, TAGGED_ENTRY_LEN);
temp_pc ^= temp_ghr & ( (1 << block_width) - 1 );
temp_ghr = temp_ghr >> block_width;
history_width -= block_width;
}
return temp_pc & ( (1 << TAGGED_ENTRY_LEN) - 1 ) ;
}
uint16_t PREDICTOR::get_tag(UINT32 PC, int bank_no){
__uint128_t temp_ghr = ghr & ((1 << tage_table_len[bank_no])-1);
// TODO
return (temp_ghr + PC * 1000000007) & ((1<<TAG_WIDTH) - 1);
}
/////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////
void PREDICTOR::TrackOtherInst(UINT32 PC, OpType opType, UINT32 branchTarget){
// This function is called for instructions which are not
// conditional branches, just in case someone decides to design
// a predictor that uses information from such instructions.
// We expect most contestants to leave this function untouched.
return;
}
/////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////