[Bug testsuite/65594] libgomp.graphite/force-parallel-6.c timeout

["vries at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65594

--- Comment #1 from vries at gcc dot gnu.org ---
The testcase contains one loop nest with 3 loops with iteration counts 500, so
the inner loop body is executed 125.000.000 times:
...
#define N 500

int X[2*N], Y[2*N], B[2*N];
int A[2*N][2*N], C[2*N][2*N];

int foo(void)
{
  int i, j, k;

  for (i = 0; i < N; i++)
    {
      X[i] = Y[i] + 10;
      for (j = 0; j < N; j++)
        {
          B[j] = A[j][N];
          for (k = 0; k < N; k++)
            {
              A[j+1][k] = B[j] + C[j][k];
            }
          Y[i+j] = A[j+1][N];
    }
    }

  return A[1][5]*B[6];
}
...

The testcase uses -ftree-parallelize-loops=4 -floop-parallelize-all, and we
parallelize the inner loop, which means we call __builtin_GOMP_parallel 250.000
times, to create 1.000.000 threads, which each handle 125 iterations.