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111
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1 /* { dg-do compile } */
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2 /* { dg-options "-O2 -ftree-loop-distribution -fdump-tree-ldist-all" } */
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3
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4 int loop1 (int k)
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5 {
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6 unsigned int i;
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7 int a[1000], b[1000], c[1000], d[1000];
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8
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9 for (i = 2; i < (1000-1); i ++) {
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10 a[i] = k * i; /* S1 */
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11 b[i] = a[i-2] + k; /* S2 */
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12 c[i] = b[i-1] + a[i+1]; /* S3 */
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13 d[i] = c[i-1] + k + i; /* S4 */
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14 }
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15 /* Dependences:
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16 S1->S2 (flow, level 1)
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17 S2->S3 (flow, level 1)
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18 S3->S1 (anti, level 1)
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19 S3->S4 (flow, level 1)
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20
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21 There are two partitions: {S1, S2, S3} and {S4}.
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22
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23 {S1, S2, S3} have to be in the same partition because:
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24 - S1 (i) has to be executed before S2 (i+2), as S1 produces a[i] that is then consumed 2 iterations later by S2.
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25 - S2 (i) has to be executed before S3 (i+1), as S2 produces b[i] that is then consumed one iteration later by S3,
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26 - S3 (i) has to be executed before S1 (i+1), as a[i+1] has to execute before the update to a[i],
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27
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28 {S4} is the consumer partition: it consumes the values from array "c" produced in S3.
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29
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30 The cost model should fuse all the tasks together as the cost of
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31 fetching data from caches is too high.
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32 */
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33
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34 return a[1000-2] + b[1000-1] + c[1000-2] + d[1000-2];
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35 }
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36
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37 /* { dg-final { scan-tree-dump-times "distributed: split to 2 loops" 0 "ldist" { xfail *-*-* } } } */
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