[Bug tree-optimization/21591] New: not vectorizing a loop with access to structs

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

Take the following C code (reduced from Java code and what the Java front-end produces).
We cannot vectorize the second loop
struct a
{
  int length;
  int a1[256];
};

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

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];
    }
    free(a);
    free(b);
    free(c);
}


Here is what we get from the dump:
t.c:21: note: not vectorized: can't determine dependence between: b_5->a1[i_12] and a_3->a1[i_12]

-- 
           Summary: not vectorizing a loop with access to structs
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21591