2 * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
3 * opyright (c) 1999-2000 by Hewlett-Packard Company. All rights reserved.
5 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
6 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
8 * Permission is hereby granted to use or copy this program
9 * for any purpose, provided the above notices are retained on all copies.
10 * Permission to modify the code and to distribute modified code is granted,
11 * provided the above notices are retained, and a notice that the code was
12 * modified is included with the above copyright notice.
18 * Some simple primitives for allocation with explicit type information.
19 * Simple objects are allocated such that they contain a GC_descr at the
20 * end (in the last allocated word). This descriptor may be a procedure
21 * which then examines an extended descriptor passed as its environment.
23 * Arrays are treated as simple objects if they have sufficiently simple
24 * structure. Otherwise they are allocated from an array kind that supplies
25 * a special mark procedure. These arrays contain a pointer to a
26 * complex_descriptor as their last word.
27 * This is done because the environment field is too small, and the collector
28 * must trace the complex_descriptor.
30 * Note that descriptors inside objects may appear cleared, if we encounter a
31 * false refrence to an object on a free list. In the GC_descr case, this
32 * is OK, since a 0 descriptor corresponds to examining no fields.
33 * In the complex_descriptor case, we explicitly check for that case.
35 * MAJOR PARTS OF THIS CODE HAVE NOT BEEN TESTED AT ALL and are not testable,
36 * since they are not accessible through the current interface.
39 #include "private/gc_pmark.h"
42 # define TYPD_EXTRA_BYTES (sizeof(word) - EXTRA_BYTES)
44 GC_bool GC_explicit_typing_initialized = FALSE;
46 int GC_explicit_kind; /* Object kind for objects with indirect */
47 /* (possibly extended) descriptors. */
49 int GC_array_kind; /* Object kind for objects with complex */
50 /* descriptors and GC_array_mark_proc. */
52 /* Extended descriptors. GC_typed_mark_proc understands these. */
53 /* These are used for simple objects that are larger than what */
54 /* can be described by a BITMAP_BITS sized bitmap. */
56 word ed_bitmap; /* lsb corresponds to first word. */
57 GC_bool ed_continued; /* next entry is continuation. */
60 /* Array descriptors. GC_array_mark_proc understands these. */
61 /* We may eventually need to add provisions for headers and */
62 /* trailers. Hence we provide for tree structured descriptors, */
63 /* though we don't really use them currently. */
64 typedef union ComplexDescriptor {
65 struct LeafDescriptor { /* Describes simple array */
68 size_t ld_size; /* bytes per element */
69 /* multiple of ALIGNMENT */
70 size_t ld_nelements; /* Number of elements. */
71 GC_descr ld_descriptor; /* A simple length, bitmap, */
72 /* or procedure descriptor. */
74 struct ComplexArrayDescriptor {
78 union ComplexDescriptor * ad_element_descr;
80 struct SequenceDescriptor {
82 # define SEQUENCE_TAG 3
83 union ComplexDescriptor * sd_first;
84 union ComplexDescriptor * sd_second;
89 ext_descr * GC_ext_descriptors; /* Points to array of extended */
92 size_t GC_ed_size = 0; /* Current size of above arrays. */
93 # define ED_INITIAL_SIZE 100;
95 size_t GC_avail_descr = 0; /* Next available slot. */
97 int GC_typed_mark_proc_index; /* Indices of my mark */
98 int GC_array_mark_proc_index; /* procedures. */
100 static void GC_push_typed_structures_proc (void)
102 GC_push_all((ptr_t)&GC_ext_descriptors, (ptr_t)&GC_ext_descriptors + sizeof(word));
105 /* Add a multiword bitmap to GC_ext_descriptors arrays. Return */
106 /* starting index. */
107 /* Returns -1 on failure. */
108 /* Caller does not hold allocation lock. */
109 signed_word GC_add_ext_descriptor(GC_bitmap bm, word nbits)
111 size_t nwords = divWORDSZ(nbits + WORDSZ-1);
119 while (GC_avail_descr + nwords >= GC_ed_size) {
122 word ed_size = GC_ed_size;
125 GC_push_typed_structures = GC_push_typed_structures_proc;
127 new_size = ED_INITIAL_SIZE;
130 new_size = 2 * ed_size;
131 if (new_size > MAX_ENV) return(-1);
133 new = (ext_descr *) GC_malloc_atomic(new_size * sizeof(ext_descr));
134 if (new == 0) return(-1);
136 if (ed_size == GC_ed_size) {
137 if (GC_avail_descr != 0) {
138 BCOPY(GC_ext_descriptors, new,
139 GC_avail_descr * sizeof(ext_descr));
141 GC_ed_size = new_size;
142 GC_ext_descriptors = new;
143 } /* else another thread already resized it in the meantime */
145 result = GC_avail_descr;
146 for (i = 0; i < nwords-1; i++) {
147 GC_ext_descriptors[result + i].ed_bitmap = bm[i];
148 GC_ext_descriptors[result + i].ed_continued = TRUE;
151 /* Clear irrelevant bits. */
152 extra_bits = nwords * WORDSZ - nbits;
153 last_part <<= extra_bits;
154 last_part >>= extra_bits;
155 GC_ext_descriptors[result + i].ed_bitmap = last_part;
156 GC_ext_descriptors[result + i].ed_continued = FALSE;
157 GC_avail_descr += nwords;
162 /* Table of bitmap descriptors for n word long all pointer objects. */
163 GC_descr GC_bm_table[WORDSZ/2];
165 /* Return a descriptor for the concatenation of 2 nwords long objects, */
166 /* each of which is described by descriptor. */
167 /* The result is known to be short enough to fit into a bitmap */
169 /* Descriptor is a GC_DS_LENGTH or GC_DS_BITMAP descriptor. */
170 GC_descr GC_double_descr(GC_descr descriptor, word nwords)
172 if ((descriptor & GC_DS_TAGS) == GC_DS_LENGTH) {
173 descriptor = GC_bm_table[BYTES_TO_WORDS((word)descriptor)];
175 descriptor |= (descriptor & ~GC_DS_TAGS) >> nwords;
179 complex_descriptor * GC_make_sequence_descriptor();
181 /* Build a descriptor for an array with nelements elements, */
182 /* each of which can be described by a simple descriptor. */
183 /* We try to optimize some common cases. */
184 /* If the result is COMPLEX, then a complex_descr* is returned */
186 /* If the result is LEAF, then we built a LeafDescriptor in */
187 /* the structure pointed to by leaf. */
188 /* The tag in the leaf structure is not set. */
189 /* If the result is SIMPLE, then a GC_descr */
190 /* is returned in *simple_d. */
191 /* If the result is NO_MEM, then */
192 /* we failed to allocate the descriptor. */
193 /* The implementation knows that GC_DS_LENGTH is 0. */
194 /* *leaf, *complex_d, and *simple_d may be used as temporaries */
195 /* during the construction. */
200 int GC_make_array_descriptor(size_t nelements, size_t size, GC_descr descriptor,
202 complex_descriptor **complex_d,
203 struct LeafDescriptor * leaf)
205 # define OPT_THRESHOLD 50
206 /* For larger arrays, we try to combine descriptors of adjacent */
207 /* descriptors to speed up marking, and to reduce the amount */
208 /* of space needed on the mark stack. */
209 if ((descriptor & GC_DS_TAGS) == GC_DS_LENGTH) {
210 if (descriptor == (GC_descr)size) {
211 *simple_d = nelements * descriptor;
213 } else if ((word)descriptor == 0) {
214 *simple_d = (GC_descr)0;
218 if (nelements <= OPT_THRESHOLD) {
219 if (nelements <= 1) {
220 if (nelements == 1) {
221 *simple_d = descriptor;
224 *simple_d = (GC_descr)0;
228 } else if (size <= BITMAP_BITS/2
229 && (descriptor & GC_DS_TAGS) != GC_DS_PROC
230 && (size & (sizeof(word)-1)) == 0) {
232 GC_make_array_descriptor(nelements/2, 2*size,
233 GC_double_descr(descriptor,
234 BYTES_TO_WORDS(size)),
235 simple_d, complex_d, leaf);
236 if ((nelements & 1) == 0) {
239 struct LeafDescriptor * one_element =
240 (struct LeafDescriptor *)
241 GC_malloc_atomic(sizeof(struct LeafDescriptor));
243 if (result == NO_MEM || one_element == 0) return(NO_MEM);
244 one_element -> ld_tag = LEAF_TAG;
245 one_element -> ld_size = size;
246 one_element -> ld_nelements = 1;
247 one_element -> ld_descriptor = descriptor;
251 struct LeafDescriptor * beginning =
252 (struct LeafDescriptor *)
253 GC_malloc_atomic(sizeof(struct LeafDescriptor));
254 if (beginning == 0) return(NO_MEM);
255 beginning -> ld_tag = LEAF_TAG;
256 beginning -> ld_size = size;
257 beginning -> ld_nelements = 1;
258 beginning -> ld_descriptor = *simple_d;
259 *complex_d = GC_make_sequence_descriptor(
260 (complex_descriptor *)beginning,
261 (complex_descriptor *)one_element);
266 struct LeafDescriptor * beginning =
267 (struct LeafDescriptor *)
268 GC_malloc_atomic(sizeof(struct LeafDescriptor));
269 if (beginning == 0) return(NO_MEM);
270 beginning -> ld_tag = LEAF_TAG;
271 beginning -> ld_size = leaf -> ld_size;
272 beginning -> ld_nelements = leaf -> ld_nelements;
273 beginning -> ld_descriptor = leaf -> ld_descriptor;
274 *complex_d = GC_make_sequence_descriptor(
275 (complex_descriptor *)beginning,
276 (complex_descriptor *)one_element);
280 *complex_d = GC_make_sequence_descriptor(
282 (complex_descriptor *)one_element);
289 leaf -> ld_size = size;
290 leaf -> ld_nelements = nelements;
291 leaf -> ld_descriptor = descriptor;
296 complex_descriptor * GC_make_sequence_descriptor(complex_descriptor *first,
297 complex_descriptor *second)
299 struct SequenceDescriptor * result =
300 (struct SequenceDescriptor *)
301 GC_malloc(sizeof(struct SequenceDescriptor));
302 /* Can't result in overly conservative marking, since tags are */
303 /* very small integers. Probably faster than maintaining type */
306 result -> sd_tag = SEQUENCE_TAG;
307 result -> sd_first = first;
308 result -> sd_second = second;
310 return((complex_descriptor *)result);
314 complex_descriptor * GC_make_complex_array_descriptor(word nelements,
315 complex_descriptor *descr)
317 struct ComplexArrayDescriptor * result =
318 (struct ComplexArrayDescriptor *)
319 GC_malloc(sizeof(struct ComplexArrayDescriptor));
322 result -> ad_tag = ARRAY_TAG;
323 result -> ad_nelements = nelements;
324 result -> ad_element_descr = descr;
326 return((complex_descriptor *)result);
330 ptr_t * GC_eobjfreelist;
332 ptr_t * GC_arobjfreelist;
334 mse * GC_typed_mark_proc(word * addr, mse * mark_stack_ptr,
335 mse * mark_stack_limit, word env);
337 mse * GC_array_mark_proc(word * addr, mse * mark_stack_ptr,
338 mse * mark_stack_limit, word env);
340 /* Caller does not hold allocation lock. */
341 void GC_init_explicit_typing(void)
347 /* Ignore gcc "no effect" warning. */
348 GC_STATIC_ASSERT(sizeof(struct LeafDescriptor) % sizeof(word) == 0);
350 if (GC_explicit_typing_initialized) {
354 GC_explicit_typing_initialized = TRUE;
355 /* Set up object kind with simple indirect descriptor. */
356 GC_eobjfreelist = (ptr_t *)GC_new_free_list_inner();
357 GC_explicit_kind = GC_new_kind_inner(
358 (void **)GC_eobjfreelist,
359 (((word)WORDS_TO_BYTES(-1)) | GC_DS_PER_OBJECT),
361 /* Descriptors are in the last word of the object. */
362 GC_typed_mark_proc_index = GC_new_proc_inner(GC_typed_mark_proc);
363 /* Set up object kind with array descriptor. */
364 GC_arobjfreelist = (ptr_t *)GC_new_free_list_inner();
365 GC_array_mark_proc_index = GC_new_proc_inner(GC_array_mark_proc);
366 GC_array_kind = GC_new_kind_inner(
367 (void **)GC_arobjfreelist,
368 GC_MAKE_PROC(GC_array_mark_proc_index, 0),
370 for (i = 0; i < WORDSZ/2; i++) {
371 GC_descr d = (((word)(-1)) >> (WORDSZ - i)) << (WORDSZ - i);
378 mse * GC_typed_mark_proc(word * addr, mse * mark_stack_ptr,
379 mse * mark_stack_limit, word env)
381 word bm = GC_ext_descriptors[env].ed_bitmap;
382 word * current_p = addr;
384 ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
385 ptr_t least_ha = GC_least_plausible_heap_addr;
389 for (; bm != 0; bm >>= 1, current_p++) {
391 current = *current_p;
392 FIXUP_POINTER(current);
393 if ((ptr_t)current >= least_ha && (ptr_t)current <= greatest_ha) {
394 PUSH_CONTENTS((ptr_t)current, mark_stack_ptr,
395 mark_stack_limit, current_p, exit1);
399 if (GC_ext_descriptors[env].ed_continued) {
400 /* Push an entry with the rest of the descriptor back onto the */
401 /* stack. Thus we never do too much work at once. Note that */
402 /* we also can't overflow the mark stack unless we actually */
403 /* mark something. */
405 if (mark_stack_ptr >= mark_stack_limit) {
406 mark_stack_ptr = GC_signal_mark_stack_overflow(mark_stack_ptr);
408 mark_stack_ptr -> mse_start = (ptr_t)(addr + WORDSZ);
409 mark_stack_ptr -> mse_descr =
410 GC_MAKE_PROC(GC_typed_mark_proc_index, env+1);
412 return(mark_stack_ptr);
415 /* Return the size of the object described by d. It would be faster to */
416 /* store this directly, or to compute it as part of */
417 /* GC_push_complex_descriptor, but hopefully it doesn't matter. */
418 word GC_descr_obj_size(complex_descriptor *d)
422 return(d -> ld.ld_nelements * d -> ld.ld_size);
424 return(d -> ad.ad_nelements
425 * GC_descr_obj_size(d -> ad.ad_element_descr));
427 return(GC_descr_obj_size(d -> sd.sd_first)
428 + GC_descr_obj_size(d -> sd.sd_second));
430 ABORT("Bad complex descriptor");
431 /*NOTREACHED*/ return 0; /*NOTREACHED*/
435 /* Push descriptors for the object at addr with complex descriptor d */
436 /* onto the mark stack. Return 0 if the mark stack overflowed. */
437 mse * GC_push_complex_descriptor(word *addr, complex_descriptor *d,
440 register ptr_t current = (ptr_t) addr;
441 register word nelements;
448 register GC_descr descr = d -> ld.ld_descriptor;
450 nelements = d -> ld.ld_nelements;
451 if (msl - msp <= (ptrdiff_t)nelements) return(0);
452 sz = d -> ld.ld_size;
453 for (i = 0; i < nelements; i++) {
455 msp -> mse_start = current;
456 msp -> mse_descr = descr;
463 register complex_descriptor *descr = d -> ad.ad_element_descr;
465 nelements = d -> ad.ad_nelements;
466 sz = GC_descr_obj_size(descr);
467 for (i = 0; i < nelements; i++) {
468 msp = GC_push_complex_descriptor((word *)current, descr,
470 if (msp == 0) return(0);
477 sz = GC_descr_obj_size(d -> sd.sd_first);
478 msp = GC_push_complex_descriptor((word *)current, d -> sd.sd_first,
480 if (msp == 0) return(0);
482 msp = GC_push_complex_descriptor((word *)current, d -> sd.sd_second,
487 ABORT("Bad complex descriptor");
488 /*NOTREACHED*/ return 0; /*NOTREACHED*/
493 mse * GC_array_mark_proc(word * addr, mse * mark_stack_ptr,
494 mse * mark_stack_limit, word env)
496 hdr * hhdr = HDR(addr);
497 size_t sz = hhdr -> hb_sz;
498 size_t nwords = BYTES_TO_WORDS(sz);
499 complex_descriptor * descr = (complex_descriptor *)(addr[nwords-1]);
500 mse * orig_mark_stack_ptr = mark_stack_ptr;
501 mse * new_mark_stack_ptr;
504 /* Found a reference to a free list entry. Ignore it. */
505 return(orig_mark_stack_ptr);
507 /* In use counts were already updated when array descriptor was */
508 /* pushed. Here we only replace it by subobject descriptors, so */
509 /* no update is necessary. */
510 new_mark_stack_ptr = GC_push_complex_descriptor(addr, descr,
513 if (new_mark_stack_ptr == 0) {
514 /* Doesn't fit. Conservatively push the whole array as a unit */
515 /* and request a mark stack expansion. */
516 /* This cannot cause a mark stack overflow, since it replaces */
517 /* the original array entry. */
518 GC_mark_stack_too_small = TRUE;
519 new_mark_stack_ptr = orig_mark_stack_ptr + 1;
520 new_mark_stack_ptr -> mse_start = (ptr_t)addr;
521 new_mark_stack_ptr -> mse_descr = sz | GC_DS_LENGTH;
523 /* Push descriptor itself */
524 new_mark_stack_ptr++;
525 new_mark_stack_ptr -> mse_start = (ptr_t)(addr + nwords - 1);
526 new_mark_stack_ptr -> mse_descr = sizeof(word) | GC_DS_LENGTH;
528 return new_mark_stack_ptr;
531 GC_descr GC_make_descriptor(GC_bitmap bm, size_t len)
533 signed_word last_set_bit = len - 1;
536 # define HIGH_BIT (((word)1) << (WORDSZ - 1))
538 if (!GC_explicit_typing_initialized) GC_init_explicit_typing();
539 while (last_set_bit >= 0 && !GC_get_bit(bm, last_set_bit)) last_set_bit --;
540 if (last_set_bit < 0) return(0 /* no pointers */);
541 # if ALIGNMENT == CPP_WORDSZ/8
543 register GC_bool all_bits_set = TRUE;
544 for (i = 0; i < last_set_bit; i++) {
545 if (!GC_get_bit(bm, i)) {
546 all_bits_set = FALSE;
551 /* An initial section contains all pointers. Use length descriptor. */
552 return (WORDS_TO_BYTES(last_set_bit+1) | GC_DS_LENGTH);
556 if (last_set_bit < BITMAP_BITS) {
557 /* Hopefully the common case. */
558 /* Build bitmap descriptor (with bits reversed) */
560 for (i = last_set_bit - 1; i >= 0; i--) {
562 if (GC_get_bit(bm, i)) result |= HIGH_BIT;
564 result |= GC_DS_BITMAP;
569 index = GC_add_ext_descriptor(bm, (word)last_set_bit+1);
570 if (index == -1) return(WORDS_TO_BYTES(last_set_bit+1) | GC_DS_LENGTH);
571 /* Out of memory: use conservative */
573 result = GC_MAKE_PROC(GC_typed_mark_proc_index, (word)index);
578 ptr_t GC_clear_stack();
580 #define GENERAL_MALLOC(lb,k) \
581 (void *)GC_clear_stack(GC_generic_malloc((word)lb, k))
583 #define GENERAL_MALLOC_IOP(lb,k) \
584 (void *)GC_clear_stack(GC_generic_malloc_ignore_off_page(lb, k))
586 void * GC_malloc_explicitly_typed(size_t lb, GC_descr d)
593 lb += TYPD_EXTRA_BYTES;
595 lg = GC_size_map[lb];
596 opp = &(GC_eobjfreelist[lg]);
598 if( (op = *opp) == 0 ) {
600 op = (ptr_t)GENERAL_MALLOC((word)lb, GC_explicit_kind);
601 if (0 == op) return 0;
602 lg = GC_size_map[lb]; /* May have been uninitialized. */
606 GC_bytes_allocd += GRANULES_TO_BYTES(lg);
610 op = (ptr_t)GENERAL_MALLOC((word)lb, GC_explicit_kind);
612 lg = BYTES_TO_GRANULES(GC_size(op));
615 ((word *)op)[GRANULES_TO_WORDS(lg) - 1] = d;
619 void * GC_malloc_explicitly_typed_ignore_off_page(size_t lb, GC_descr d)
626 lb += TYPD_EXTRA_BYTES;
627 if( SMALL_OBJ(lb) ) {
628 lg = GC_size_map[lb];
629 opp = &(GC_eobjfreelist[lg]);
631 if( (op = *opp) == 0 ) {
633 op = (ptr_t)GENERAL_MALLOC_IOP(lb, GC_explicit_kind);
634 lg = GC_size_map[lb]; /* May have been uninitialized. */
638 GC_bytes_allocd += GRANULES_TO_BYTES(lg);
642 op = (ptr_t)GENERAL_MALLOC_IOP(lb, GC_explicit_kind);
644 lg = BYTES_TO_WORDS(GC_size(op));
647 ((word *)op)[GRANULES_TO_WORDS(lg) - 1] = d;
651 void * GC_calloc_explicitly_typed(size_t n, size_t lb, GC_descr d)
656 GC_descr simple_descr;
657 complex_descriptor *complex_descr;
658 register int descr_type;
659 struct LeafDescriptor leaf;
662 descr_type = GC_make_array_descriptor((word)n, (word)lb, d,
663 &simple_descr, &complex_descr, &leaf);
665 case NO_MEM: return(0);
666 case SIMPLE: return(GC_malloc_explicitly_typed(n*lb, simple_descr));
669 lb += sizeof(struct LeafDescriptor) + TYPD_EXTRA_BYTES;
673 lb += TYPD_EXTRA_BYTES;
676 if( SMALL_OBJ(lb) ) {
677 lg = GC_size_map[lb];
678 opp = &(GC_arobjfreelist[lg]);
680 if( (op = *opp) == 0 ) {
682 op = (ptr_t)GENERAL_MALLOC((word)lb, GC_array_kind);
683 if (0 == op) return(0);
684 lg = GC_size_map[lb]; /* May have been uninitialized. */
688 GC_bytes_allocd += GRANULES_TO_BYTES(lg);
692 op = (ptr_t)GENERAL_MALLOC((word)lb, GC_array_kind);
693 if (0 == op) return(0);
694 lg = BYTES_TO_GRANULES(GC_size(op));
696 if (descr_type == LEAF) {
697 /* Set up the descriptor inside the object itself. */
698 volatile struct LeafDescriptor * lp =
699 (struct LeafDescriptor *)
701 + GRANULES_TO_WORDS(lg)
702 - (BYTES_TO_WORDS(sizeof(struct LeafDescriptor)) + 1));
704 lp -> ld_tag = LEAF_TAG;
705 lp -> ld_size = leaf.ld_size;
706 lp -> ld_nelements = leaf.ld_nelements;
707 lp -> ld_descriptor = leaf.ld_descriptor;
708 ((volatile word *)op)[GRANULES_TO_WORDS(lg) - 1] = (word)lp;
710 extern unsigned GC_finalization_failures;
711 unsigned ff = GC_finalization_failures;
712 size_t lw = GRANULES_TO_WORDS(lg);
714 ((word *)op)[lw - 1] = (word)complex_descr;
715 /* Make sure the descriptor is cleared once there is any danger */
716 /* it may have been collected. */
718 GC_general_register_disappearing_link((void * *)
721 if (ff != GC_finalization_failures) {
722 /* Couldn't register it due to lack of memory. Punt. */
723 /* This will probably fail too, but gives the recovery code */
725 return(GC_malloc(n*lb));