static void reset_back_edge(ptr_t p, size_t n_bytes GC_ATTR_UNUSED,
word gc_descr GC_ATTR_UNUSED)
{
/* Skip any free list links, or dropped blocks */
if (GC_HAS_DEBUG_INFO(p)) {
ptr_t old_back_ptr = GET_OH_BG_PTR(p);
if ((word)old_back_ptr & FLAG_MANY) {
back_edges *be = (back_edges *)((word)old_back_ptr & ~FLAG_MANY);
if (!(be -> flags & RETAIN)) {
deallocate_back_edges(be);
SET_OH_BG_PTR(p, 0);
} else {
GC_ASSERT(GC_is_marked(p));
/* Back edges may point to objects that will not be retained. */
/* Delete them for now, but remember the height. */
/* Some will be added back at next GC. */
be -> n_edges = 0;
if (0 != be -> cont) {
deallocate_back_edges(be -> cont);
be -> cont = 0;
}
GC_ASSERT(GC_is_marked(p));
/* We only retain things for one GC cycle at a time. */
be -> flags &= ~RETAIN;
}
} else /* Simple back pointer */ {
/* Clear to avoid dangling pointer. */
SET_OH_BG_PTR(p, 0);
}
}
}
/* q are pointers to the object base, i.e. pointers to an oh. */
static void add_edge(ptr_t p, ptr_t q)
{
ptr_t old_back_ptr = GET_OH_BG_PTR(q);
back_edges * be, *be_cont;
word i;
static unsigned random_number = 13;
# define GOT_LUCKY_NUMBER (((++random_number) & 0x7f) == 0)
/* A not very random number we use to occasionally allocate a */
/* back_edges structure even for a single backward edge. This */
/* prevents us from repeatedly tracing back through very long */
/* chains, since we will have some place to store height and */
/* in_progress flags along the way. */
GC_ASSERT(p == GC_base(p) && q == GC_base(q));
if (!GC_HAS_DEBUG_INFO(q) || !GC_HAS_DEBUG_INFO(p)) {
/* This is really a misinterpreted free list link, since we saw */
/* a pointer to a free list. Dont overwrite it! */
return;
}
if (0 == old_back_ptr) {
SET_OH_BG_PTR(q, p);
if (GOT_LUCKY_NUMBER) ensure_struct(q);
return;
}
/* Check whether it was already in the list of predecessors. */
FOR_EACH_PRED(pred, q, { if (p == pred) return; });
/* Ensure that p has a back_edges structure associated with it. */
static void ensure_struct(ptr_t p)
{
ptr_t old_back_ptr = GET_OH_BG_PTR(p);
if (!((word)old_back_ptr & FLAG_MANY)) {
back_edges *be = new_back_edges();
be -> flags = 0;
if (0 == old_back_ptr) {
be -> n_edges = 0;
} else {
be -> n_edges = 1;
be -> edges[0] = old_back_ptr;
}
be -> height = HEIGHT_UNKNOWN;
be -> height_gc_no = (unsigned short)(GC_gc_no - 1);
GC_ASSERT(be >= back_edge_space);
SET_OH_BG_PTR(p, (word)be | FLAG_MANY);
}
}
GC_ASSERT(p == GC_base(p) && q == GC_base(q));
if (!GC_HAS_DEBUG_INFO(q) || !GC_HAS_DEBUG_INFO(p)) {
/* This is really a misinterpreted free list link, since we saw */
/* a pointer to a free list. Dont overwrite it! */
return;
}
if (0 == old_back_ptr) {
SET_OH_BG_PTR(q, p);
if (GOT_LUCKY_NUMBER) ensure_struct(q);
return;
}
/* Check whether it was already in the list of predecessors. */
FOR_EACH_PRED(pred, q, { if (p == pred) return; });
ensure_struct(q);
old_back_ptr = GET_OH_BG_PTR(q);
be = (back_edges *)((word)old_back_ptr & ~FLAG_MANY);
for (i = be -> n_edges, be_cont = be; i > MAX_IN;
be_cont = be_cont -> cont, i -= MAX_IN) {}
if (i == MAX_IN) {
be_cont -> cont = new_back_edges();
be_cont = be_cont -> cont;
i = 0;
}
be_cont -> edges[i] = p;
be -> n_edges++;
if (be -> n_edges == 100) {
# if 0
if (GC_print_stats) {
GC_err_printf("The following object has in-degree >= 100:\n");
GC_print_heap_obj(q);
/* GC_deepest_obj to be the corresponding object. */
static void update_max_height(ptr_t p, size_t n_bytes GC_ATTR_UNUSED,
word gc_descr GC_ATTR_UNUSED)
{
if (GC_is_marked(p) && GC_HAS_DEBUG_INFO(p)) {
word p_height = 0;
ptr_t p_deepest_obj = 0;
ptr_t back_ptr;
back_edges *be = 0;
/* If we remembered a height last time, use it as a minimum. */
/* It may have increased due to newly unreachable chains pointing */
/* to p, but it can't have decreased. */
back_ptr = GET_OH_BG_PTR(p);
if (0 != back_ptr && ((word)back_ptr & FLAG_MANY)) {
be = (back_edges *)((word)back_ptr & ~FLAG_MANY);
if (be -> height != HEIGHT_UNKNOWN) p_height = be -> height;
}
{
ptr_t pred = GET_OH_BG_PTR(p);
back_edges *e = (back_edges *)((word)pred & ~FLAG_MANY);
word n_edges;
word total;
int local = 0;
if (((word)pred & FLAG_MANY) != 0) {
n_edges = e -> n_edges;
} else if (pred != NULL && ((word)pred & 1) == 0) {
/* A misinterpreted freelist link. */
n_edges = 1;
local = -1;
} else {
n_edges = 0;
}
for (total = 0; total < n_edges; ++total) {
if (local == MAX_IN) {
e = e -> cont;
local = 0;
}
if (local >= 0)
pred = e -> edges[local++];
/* Execute the following once for each predecessor pred of p */
/* in the points-to graph. */
if (!GC_is_marked(pred) && GC_HAS_DEBUG_INFO(pred)) {
word this_height = backwards_height(pred);
if (this_height > p_height) {
p_height = this_height;
p_deepest_obj = pred;
}
}
}
}
if (p_height > 0) {
/* Remember the height for next time. */
if (be == 0) {
ensure_struct(p);
back_ptr = GET_OH_BG_PTR(p);
be = (back_edges *)((word)back_ptr & ~FLAG_MANY);
}
be -> flags |= RETAIN;
be -> height = p_height;
be -> height_gc_no = (unsigned short)GC_gc_no;
}
if (p_height > GC_max_height) {
GC_max_height = p_height;
GC_deepest_obj = p_deepest_obj;
}
}
}
/* of p. */
static word backwards_height(ptr_t p)
{
word result;
ptr_t pred = GET_OH_BG_PTR(p);
back_edges *be;
if (NULL == pred)
return 1;
if (((word)pred & FLAG_MANY) == 0) {
if (is_in_progress(p)) return 0; /* DFS back edge, i.e. we followed */
/* an edge to an object already */
/* on our stack: ignore */
push_in_progress(p);
result = backwards_height(pred) + 1;
pop_in_progress(p);
return result;
}
be = (back_edges *)((word)pred & ~FLAG_MANY);
if (be -> height >= 0 && be -> height_gc_no == (unsigned short)GC_gc_no)
return be -> height;
/* Ignore back edges in DFS */
if (be -> height == HEIGHT_IN_PROGRESS) return 0;
result = (be -> height > 0? be -> height : 1);
be -> height = HEIGHT_IN_PROGRESS;
{
back_edges *e = be;
word n_edges;
word total;
int local = 0;
if (((word)pred & FLAG_MANY) != 0) {
n_edges = e -> n_edges;
} else if (pred != NULL && ((word)pred & 1) == 0) {
/* A misinterpreted freelist link. */
n_edges = 1;
local = -1;
} else {
n_edges = 0;
}
for (total = 0; total < n_edges; ++total) {
word this_height;
if (local == MAX_IN) {
e = e -> cont;
local = 0;
}
if (local >= 0)
pred = e -> edges[local++];
/* Execute the following once for each predecessor pred of p */
/* in the points-to graph. */
if (GC_is_marked(pred) && ((word)GET_OH_BG_PTR(p) & FLAG_MANY) == 0) {
GC_COND_LOG_PRINTF("Found bogus pointer from %p to %p\n",
(void *)pred, (void *)p);
/* Reachable object "points to" unreachable one. */
/* Could be caused by our lax treatment of GC descriptors. */
this_height = 1;
} else {
this_height = backwards_height(pred);
}
if (this_height >= result)
result = this_height + 1;
}
}
be -> height = result;
be -> height_gc_no = (unsigned short)GC_gc_no;
return result;
}
/* q are pointers to the object base, i.e. pointers to an oh. */
static void add_edge(ptr_t p, ptr_t q)
{
ptr_t pred = GET_OH_BG_PTR(q);
back_edges * be, *be_cont;
word i;
GC_ASSERT(p == GC_base(p) && q == GC_base(q));
if (!GC_HAS_DEBUG_INFO(q) || !GC_HAS_DEBUG_INFO(p)) {
/* This is really a misinterpreted free list link, since we saw */
/* a pointer to a free list. Don't overwrite it! */
return;
}
if (NULL == pred) {
static unsigned random_number = 13;
# define GOT_LUCKY_NUMBER (((++random_number) & 0x7f) == 0)
/* A not very random number we use to occasionally allocate a */
/* back_edges structure even for a single backward edge. This */
/* prevents us from repeatedly tracing back through very long */
/* chains, since we will have some place to store height and */
/* in_progress flags along the way. */
SET_OH_BG_PTR(q, p);
if (GOT_LUCKY_NUMBER) ensure_struct(q);
return;
}
/* Check whether it was already in the list of predecessors. */
{
back_edges *e = (back_edges *)((word)pred & ~FLAG_MANY);
word n_edges;
word total;
int local = 0;
if (((word)pred & FLAG_MANY) != 0) {
n_edges = e -> n_edges;
} else if (pred != NULL && ((word)pred & 1) == 0) {
/* A misinterpreted freelist link. */
n_edges = 1;
local = -1;
} else {
n_edges = 0;
}
for (total = 0; total < n_edges; ++total) {
if (local == MAX_IN) {
e = e -> cont;
local = 0;
}
if (local >= 0)
pred = e -> edges[local++];
if (pred == p)
return;
}
}
ensure_struct(q);
be = (back_edges *)((word)GET_OH_BG_PTR(q) & ~FLAG_MANY);
for (i = be -> n_edges, be_cont = be; i > MAX_IN; i -= MAX_IN)
be_cont = be_cont -> cont;
if (i == MAX_IN) {
be_cont -> cont = new_back_edges();
be_cont = be_cont -> cont;
i = 0;
}
be_cont -> edges[i] = p;
be -> n_edges++;
# ifdef DEBUG_PRINT_BIG_N_EDGES
if (GC_print_stats == VERBOSE && be -> n_edges == 100) {
GC_err_printf("The following object has big in-degree:\n");
GC_print_heap_obj(q);
}
# endif
}
