[Bug c/68462] New: -fno-strict-aliasing not respected

["manjeetdahiya at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68462

            Bug ID: 68462
           Summary: -fno-strict-aliasing not respected
           Product: gcc
           Version: 4.8.4
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: manjeetdahiya at gmail dot com
  Target Milestone: ---

For the following code -fno-strict-aliasing is not respected in function
add_link_to_domain. The variable N_domains is cached before executing:

  domain_array[N_domains].lol = lol;
  domain_array[N_domains].size++;

However, it should have been read again from the memory for the second
statement. 

* I checked on clang-3.6 and it works as desired.
* Another thing I noticed is that when I make the variable N_domains non-static
-fno-strict-aliasing is respected.

code listing:
-------------
struct List_o_links{
    struct List_o_links * next;
};

struct Domain{
    int size;
    struct List_o_links * lol;
};

static int N_domains;
int Size;
static struct Domain domain_array[500];

void* mymalloc(int size);

void add_link_to_domain(int link) {
    struct List_o_links *lol;
    lol = (struct List_o_links *) mymalloc(sizeof(struct List_o_links));
    lol->next = domain_array[N_domains].lol;
    domain_array[N_domains].lol = lol;
    domain_array[N_domains].size++;
}

void build_dom()
{
  int i;
  for(i = 0; i < Size; ++i)
    N_domains++;
}

Relevent assembly:
------------------
N_global static:
  call  mymalloc
  movl  N_domains, %edx
  movl  domain_array+4(,%edx,8), %ecx
  addl  $1, domain_array(,%edx,8)
  movl  %eax, domain_array+4(,%edx,8)

N_global non-static:
  call  mymalloc
  movl  N_domains, %edx
  movl  domain_array+4(,%edx,8), %edx
  movl  %edx, (%eax)
  movl  N_domains, %edx
  movl  %eax, domain_array+4(,%edx,8)