gcc/testsuite/gcc.dg/vect/pr21591.c

/* { dg-do compile } */
/* { dg-require-effective-target vect_int } */

struct a
{
  int length;
  int a1[256];
};

struct a *malloc1(__SIZE_TYPE__) __attribute__((malloc));
void free(void*);

struct a *p, *q, *r;

void f(void)
{
   struct a *a = malloc1(sizeof(struct a));
   struct a *b = malloc1(sizeof(struct a));
   struct a *c = malloc1(sizeof(struct a));
   int i;

   for (i = 0; i < 256; i++) 
   {
      b->a1[i] = i;
      c->a1[i] = i;
   }
   for (i = 0; i < 256; i++) 
   {
      a->a1[i] = b->a1[i] + c->a1[i];
   }
   p = a;
   q = b;
   r = c;
}

/* { dg-final { scan-tree-dump-times "vectorized 2 loops" 1 "vect" } } */