static void invert_pointer_at (word *p)
{
word q = *p;
Assert (Ecolor ((intnat) p) == 0);
/* Use Ecolor (q) == 0 instead of Is_block (q) because q could be an
inverted pointer for an infix header (with Ecolor == 2). */
if (Ecolor (q) == 0 && (Classify_addr (q) & In_heap)) {
switch (Ecolor (Hd_val (q))) {
case 0:
case 3: /* Pointer or header: insert in inverted list. */
*p = Hd_val (q);
Hd_val (q) = (header_t) p;
break;
case 1: /* Infix header: make inverted infix list. */
/* Double inversion: the last of the inverted infix list points to
the next infix header in this block. The last of the last list
contains the original block header. */
{
/* This block as a value. */
value val = (value) q - Infix_offset_val (q);
/* Get the block header. */
word *hp = (word *) Hp_val (val);
while (Ecolor (*hp) == 0) hp = (word *) *hp;
Assert (Ecolor (*hp) == 3);
if (Tag_ehd (*hp) == Closure_tag) {
/* This is the first infix found in this block. */
/* Save original header. */
*p = *hp;
/* Link inverted infix list. */
Hd_val (q) = (header_t) ((word) p | 2);
/* Change block header's tag to Infix_tag, and change its size
to point to the infix list. */
*hp = Make_ehd (Wosize_bhsize (q - val), Infix_tag, 3);
} else {
Assert (Tag_ehd (*hp) == Infix_tag);
/* Point the last of this infix list to the current first infix
list of the block. */
*p = (word) &Field (val, Wosize_ehd (*hp)) | 1;
/* Point the head of this infix list to the above. */
Hd_val (q) = (header_t) ((word) p | 2);
/* Change block header's size to point to this infix list. */
*hp = Make_ehd (Wosize_bhsize (q - val), Infix_tag, 3);
}
}
break;
case 2: /* Inverted infix list: insert. */
*p = Hd_val (q);
Hd_val (q) = (header_t) ((word) p | 2);
break;
}
}
}
static void do_compaction_r (CAML_R)
{
char *ch, *chend;
Assert (caml_gc_phase == Phase_idle);
caml_gc_message (0x10, "Compacting heap...\n", 0);
#ifdef DEBUG
caml_heap_check_r (ctx);
#endif
/* First pass: encode all noninfix headers. */
{
ch = caml_heap_start;
while (ch != NULL){
header_t *p = (header_t *) ch;
chend = ch + Chunk_size (ch);
while ((char *) p < chend){
header_t hd = Hd_hp (p);
mlsize_t sz = Wosize_hd (hd);
if (Is_blue_hd (hd)){
/* Free object. Give it a string tag. */
Hd_hp (p) = Make_ehd (sz, String_tag, 3);
}else{ Assert (Is_white_hd (hd));
/* Live object. Keep its tag. */
Hd_hp (p) = Make_ehd (sz, Tag_hd (hd), 3);
}
p += Whsize_wosize (sz);
}
ch = Chunk_next (ch);
}
}
/* Second pass: invert pointers.
Link infix headers in each block in an inverted list of inverted lists.
Don't forget roots and weak pointers. */
{
/* Invert roots first because the threads library needs some heap
data structures to find its roots. Fortunately, it doesn't need
the headers (see above). */
caml_do_roots_r (ctx, invert_root_r);
caml_final_do_weak_roots_r (ctx, invert_root_r);
ch = caml_heap_start;
while (ch != NULL){
word *p = (word *) ch;
chend = ch + Chunk_size (ch);
while ((char *) p < chend){
word q = *p;
size_t sz, i;
tag_t t;
word *infixes;
while (Ecolor (q) == 0) q = * (word *) q;
sz = Whsize_ehd (q);
t = Tag_ehd (q);
if (t == Infix_tag){
/* Get the original header of this block. */
infixes = p + sz;
q = *infixes;
while (Ecolor (q) != 3) q = * (word *) (q & ~(uintnat)3);
sz = Whsize_ehd (q);
t = Tag_ehd (q);
}
if (t < No_scan_tag){
for (i = 1; i < sz; i++) invert_pointer_at_r (ctx, &(p[i]));
}
p += sz;
}
ch = Chunk_next (ch);
}
/* Invert weak pointers. */
{
value *pp = &caml_weak_list_head;
value p;
word q;
size_t sz, i;
while (1){
p = *pp;
if (p == (value) NULL) break;
q = Hd_val (p);
while (Ecolor (q) == 0) q = * (word *) q;
sz = Wosize_ehd (q);
for (i = 1; i < sz; i++){
if (Field (p,i) != caml_weak_none){
invert_pointer_at_r (ctx, (word *) &(Field (p,i)));
}
}
invert_pointer_at_r (ctx, (word *) pp);
pp = &Field (p, 0);
}
}
}
/* Third pass: reallocate virtually; revert pointers; decode headers.
Rebuild infix headers. */
{
init_compact_allocate_r (ctx);
ch = caml_heap_start;
while (ch != NULL){
word *p = (word *) ch;
chend = ch + Chunk_size (ch);
while ((char *) p < chend){
word q = *p;
if (Ecolor (q) == 0 || Tag_ehd (q) == Infix_tag){
/* There were (normal or infix) pointers to this block. */
size_t sz;
tag_t t;
char *newadr;
word *infixes = NULL;
while (Ecolor (q) == 0) q = * (word *) q;
sz = Whsize_ehd (q);
t = Tag_ehd (q);
if (t == Infix_tag){
/* Get the original header of this block. */
infixes = p + sz;
q = *infixes; Assert (Ecolor (q) == 2);
while (Ecolor (q) != 3) q = * (word *) (q & ~(uintnat)3);
sz = Whsize_ehd (q);
t = Tag_ehd (q);
}
newadr = compact_allocate_r (ctx, Bsize_wsize (sz));
q = *p;
while (Ecolor (q) == 0){
word next = * (word *) q;
* (word *) q = (word) Val_hp (newadr);
q = next;
}
*p = Make_header (Wosize_whsize (sz), t, Caml_white);
if (infixes != NULL){
/* Rebuild the infix headers and revert the infix pointers. */
while (Ecolor ((word) infixes) != 3){
infixes = (word *) ((word) infixes & ~(uintnat) 3);
q = *infixes;
while (Ecolor (q) == 2){
word next;
q = (word) q & ~(uintnat) 3;
next = * (word *) q;
* (word *) q = (word) Val_hp ((word *) newadr + (infixes - p));
q = next;
} Assert (Ecolor (q) == 1 || Ecolor (q) == 3);
*infixes = Make_header (infixes - p, Infix_tag, Caml_white);
infixes = (word *) q;
}
}
p += sz;
}else{ Assert (Ecolor (q) == 3);
/* This is guaranteed only if caml_compact_heap was called after a
nonincremental major GC: Assert (Tag_ehd (q) == String_tag);
*/
/* No pointers to the header and no infix header:
the object was free. */
*p = Make_header (Wosize_ehd (q), Tag_ehd (q), Caml_blue);
p += Whsize_ehd (q);
}
}
ch = Chunk_next (ch);
}
}
/* Fourth pass: reallocate and move objects.
Use the exact same allocation algorithm as pass 3. */
{
init_compact_allocate_r (ctx);
ch = caml_heap_start;
while (ch != NULL){
word *p = (word *) ch;
chend = ch + Chunk_size (ch);
while ((char *) p < chend){
word q = *p;
if (Color_hd (q) == Caml_white){
size_t sz = Bhsize_hd (q);
char *newadr = compact_allocate_r (ctx, sz);
memmove (newadr, p, sz);
p += Wsize_bsize (sz);
}else{
Assert (Color_hd (q) == Caml_blue);
p += Whsize_hd (q);
}
}
ch = Chunk_next (ch);
}
}
/* Shrink the heap if needed. */
{
/* Find the amount of live data and the unshrinkable free space. */
asize_t live = 0;
asize_t free = 0;
asize_t wanted;
ch = caml_heap_start;
while (ch != NULL){
if (Chunk_alloc (ch) != 0){
live += Wsize_bsize (Chunk_alloc (ch));
free += Wsize_bsize (Chunk_size (ch) - Chunk_alloc (ch));
}
ch = Chunk_next (ch);
}
/* Add up the empty chunks until there are enough, then remove the
other empty chunks. */
wanted = caml_percent_free * (live / 100 + 1);
ch = caml_heap_start;
while (ch != NULL){
char *next_chunk = Chunk_next (ch); /* Chunk_next (ch) will be erased */
if (Chunk_alloc (ch) == 0){
if (free < wanted){
free += Wsize_bsize (Chunk_size (ch));
}else{
caml_shrink_heap_r (ctx, ch);
}
}
ch = next_chunk;
}
}
/* Rebuild the free list. */
{
ch = caml_heap_start;
caml_fl_reset_r (ctx);
while (ch != NULL){
if (Chunk_size (ch) > Chunk_alloc (ch)){
caml_make_free_blocks_r (ctx, (value *) (ch + Chunk_alloc (ch)),
Wsize_bsize (Chunk_size(ch)-Chunk_alloc(ch)), 1,
Caml_white);
}
ch = Chunk_next (ch);
}
}
++ caml_stat_compactions;
caml_gc_message (0x10, "done.\n", 0);
}