[Bug middle-end/29272] [4.2 Regression] memcpy optimization causes wrong-code

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2006-09-29 09:14 -------
Here's an executable testcase which is miscompiled at the tree-level.

extern void abort(void);
struct Foo {
  int a;
  int b;
};
struct Node;
struct Node {
  struct Node *next;
};
struct Node *pool;
void grow (void)
{
  char *mem = __builtin_malloc (4096);
  struct Node *node = (struct Node *)mem;
  struct Foo *foo;
  __builtin_memcpy (&node->next, &pool, sizeof(struct Node*));
  pool = node;
}
static inline void *alloc_one (void)
{
  struct Node *node = pool;
  __builtin_memcpy (&pool, &node->next, sizeof(struct Node*));
  return node;
}
static inline void dealloc_one (void *p)
{
  struct Node *node = p;
  __builtin_memcpy (&node->next, &pool, sizeof(struct Node*));
  pool = node;
}
int main()
{
  grow();
  struct Foo* foo = alloc_one();
  foo->a = 0;
  foo->b = -1;
  dealloc_one (foo);
  if (foo->b == -1)
    abort ();
  return 0;
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29272