1  /* { dg-do compile } */
       2  /* { dg-options "-O2 -ftree-parallelize-loops=4 -fdump-tree-parloops2-details -fdump-tree-optimized" } */
       3  
       4  #include <stdlib.h>
       5  #include <stdio.h>
       6  
       7  int main() 
       8  {
       9    unsigned int x, y, idx, H = 1024, W = 1024;
      10    
      11    int * tmps = (int *)malloc(H*W*sizeof(int));
      12    
      13    /* This loop gets parallelized even though output dependences exist 
      14       between writes to 'tmps' that prevent parallelization. 
      15       For example: tmps[1] = 1, ..., tmps[1] = 17.  */
      16    
      17    for(x = 1; x < H; x++) 
      18      {
      19        for(y = 1; y < W; y++) 
      20  	{
      21  	  idx = x*W+y;
      22  	  tmps[idx % 4096] = idx;	  
      23  	}
      24      }
      25    
      26    for(x = 1; x < 8; x++)
      27      printf("tmps[%d]=%d\n", x, tmps[x]);
      28    
      29    return 0;
      30  }
      31  /* Check that no loop gets parallelized.  */
      32  
      33  /* { dg-final { scan-tree-dump-times "SUCCESS: may be parallelized" 0 "parloops2" } } */
      34  /* { dg-final { scan-tree-dump-times "loopfn" 0 "optimized" } } */