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.
41 #include "private/gc_pmark.h"
44 # define TYPD_EXTRA_BYTES (sizeof(word) - EXTRA_BYTES)
46 GC_bool GC_explicit_typing_initialized = FALSE;
48 int GC_explicit_kind; /* Object kind for objects with indirect */
49 /* (possibly extended) descriptors. */
51 int GC_array_kind; /* Object kind for objects with complex */
52 /* descriptors and GC_array_mark_proc. */
54 /* Extended descriptors. GC_typed_mark_proc understands these. */
55 /* These are used for simple objects that are larger than what */
56 /* can be described by a BITMAP_BITS sized bitmap. */
58 word ed_bitmap; /* lsb corresponds to first word. */
59 GC_bool ed_continued; /* next entry is continuation. */
62 /* Array descriptors. GC_array_mark_proc understands these. */
63 /* We may eventually need to add provisions for headers and */
64 /* trailers. Hence we provide for tree structured descriptors, */
65 /* though we don't really use them currently. */
66 typedef union ComplexDescriptor {
67 struct LeafDescriptor { /* Describes simple array */
70 size_t ld_size; /* bytes per element */
71 /* multiple of ALIGNMENT */
72 size_t ld_nelements; /* Number of elements. */
73 GC_descr ld_descriptor; /* A simple length, bitmap, */
74 /* or procedure descriptor. */
76 struct ComplexArrayDescriptor {
80 union ComplexDescriptor * ad_element_descr;
82 struct SequenceDescriptor {
84 # define SEQUENCE_TAG 3
85 union ComplexDescriptor * sd_first;
86 union ComplexDescriptor * sd_second;
91 ext_descr * GC_ext_descriptors; /* Points to array of extended */
94 size_t GC_ed_size = 0; /* Current size of above arrays. */
95 # define ED_INITIAL_SIZE 100;
97 size_t GC_avail_descr = 0; /* Next available slot. */
99 int GC_typed_mark_proc_index; /* Indices of my mark */
100 int GC_array_mark_proc_index; /* procedures. */
102 static void GC_push_typed_structures_proc (void)
104 GC_push_all((ptr_t)&GC_ext_descriptors, (ptr_t)&GC_ext_descriptors + sizeof(word));
107 /* Add a multiword bitmap to GC_ext_descriptors arrays. Return */
108 /* starting index. */
109 /* Returns -1 on failure. */
110 /* Caller does not hold allocation lock. */
111 signed_word GC_add_ext_descriptor(GC_bitmap bm, word nbits)
113 size_t nwords = divWORDSZ(nbits + WORDSZ-1);
121 while (GC_avail_descr + nwords >= GC_ed_size) {
124 word ed_size = GC_ed_size;
127 GC_push_typed_structures = GC_push_typed_structures_proc;
129 new_size = ED_INITIAL_SIZE;
132 new_size = 2 * ed_size;
133 if (new_size > MAX_ENV) return(-1);
135 new = (ext_descr *) GC_malloc_atomic(new_size * sizeof(ext_descr));
136 if (new == 0) return(-1);
138 if (ed_size == GC_ed_size) {
139 if (GC_avail_descr != 0) {
140 BCOPY(GC_ext_descriptors, new,
141 GC_avail_descr * sizeof(ext_descr));
143 GC_ed_size = new_size;
144 GC_ext_descriptors = new;
145 } /* else another thread already resized it in the meantime */
147 result = GC_avail_descr;
148 for (i = 0; i < nwords-1; i++) {
149 GC_ext_descriptors[result + i].ed_bitmap = bm[i];
150 GC_ext_descriptors[result + i].ed_continued = TRUE;
153 /* Clear irrelevant bits. */
154 extra_bits = nwords * WORDSZ - nbits;
155 last_part <<= extra_bits;
156 last_part >>= extra_bits;
157 GC_ext_descriptors[result + i].ed_bitmap = last_part;
158 GC_ext_descriptors[result + i].ed_continued = FALSE;
159 GC_avail_descr += nwords;
164 /* Table of bitmap descriptors for n word long all pointer objects. */
165 GC_descr GC_bm_table[WORDSZ/2];
167 /* Return a descriptor for the concatenation of 2 nwords long objects, */
168 /* each of which is described by descriptor. */
169 /* The result is known to be short enough to fit into a bitmap */
171 /* Descriptor is a GC_DS_LENGTH or GC_DS_BITMAP descriptor. */
172 GC_descr GC_double_descr(GC_descr descriptor, word nwords)
174 if ((descriptor & GC_DS_TAGS) == GC_DS_LENGTH) {
175 descriptor = GC_bm_table[BYTES_TO_WORDS((word)descriptor)];
177 descriptor |= (descriptor & ~GC_DS_TAGS) >> nwords;
181 complex_descriptor * GC_make_sequence_descriptor();
183 /* Build a descriptor for an array with nelements elements, */
184 /* each of which can be described by a simple descriptor. */
185 /* We try to optimize some common cases. */
186 /* If the result is COMPLEX, then a complex_descr* is returned */
188 /* If the result is LEAF, then we built a LeafDescriptor in */
189 /* the structure pointed to by leaf. */
190 /* The tag in the leaf structure is not set. */
191 /* If the result is SIMPLE, then a GC_descr */
192 /* is returned in *simple_d. */
193 /* If the result is NO_MEM, then */
194 /* we failed to allocate the descriptor. */
195 /* The implementation knows that GC_DS_LENGTH is 0. */
196 /* *leaf, *complex_d, and *simple_d may be used as temporaries */
197 /* during the construction. */
202 int GC_make_array_descriptor(size_t nelements, size_t size, GC_descr descriptor,
204 complex_descriptor **complex_d,
205 struct LeafDescriptor * leaf)
207 # define OPT_THRESHOLD 50
208 /* For larger arrays, we try to combine descriptors of adjacent */
209 /* descriptors to speed up marking, and to reduce the amount */
210 /* of space needed on the mark stack. */
211 if ((descriptor & GC_DS_TAGS) == GC_DS_LENGTH) {
212 if (descriptor == (GC_descr)size) {
213 *simple_d = nelements * descriptor;
215 } else if ((word)descriptor == 0) {
216 *simple_d = (GC_descr)0;
220 if (nelements <= OPT_THRESHOLD) {
221 if (nelements <= 1) {
222 if (nelements == 1) {
223 *simple_d = descriptor;
226 *simple_d = (GC_descr)0;
230 } else if (size <= BITMAP_BITS/2
231 && (descriptor & GC_DS_TAGS) != GC_DS_PROC
232 && (size & (sizeof(word)-1)) == 0) {
234 GC_make_array_descriptor(nelements/2, 2*size,
235 GC_double_descr(descriptor,
236 BYTES_TO_WORDS(size)),
237 simple_d, complex_d, leaf);
238 if ((nelements & 1) == 0) {
241 struct LeafDescriptor * one_element =
242 (struct LeafDescriptor *)
243 GC_malloc_atomic(sizeof(struct LeafDescriptor));
245 if (result == NO_MEM || one_element == 0) return(NO_MEM);
246 one_element -> ld_tag = LEAF_TAG;
247 one_element -> ld_size = size;
248 one_element -> ld_nelements = 1;
249 one_element -> ld_descriptor = descriptor;
253 struct LeafDescriptor * beginning =
254 (struct LeafDescriptor *)
255 GC_malloc_atomic(sizeof(struct LeafDescriptor));
256 if (beginning == 0) return(NO_MEM);
257 beginning -> ld_tag = LEAF_TAG;
258 beginning -> ld_size = size;
259 beginning -> ld_nelements = 1;
260 beginning -> ld_descriptor = *simple_d;
261 *complex_d = GC_make_sequence_descriptor(
262 (complex_descriptor *)beginning,
263 (complex_descriptor *)one_element);
268 struct LeafDescriptor * beginning =
269 (struct LeafDescriptor *)
270 GC_malloc_atomic(sizeof(struct LeafDescriptor));
271 if (beginning == 0) return(NO_MEM);
272 beginning -> ld_tag = LEAF_TAG;
273 beginning -> ld_size = leaf -> ld_size;
274 beginning -> ld_nelements = leaf -> ld_nelements;
275 beginning -> ld_descriptor = leaf -> ld_descriptor;
276 *complex_d = GC_make_sequence_descriptor(
277 (complex_descriptor *)beginning,
278 (complex_descriptor *)one_element);
282 *complex_d = GC_make_sequence_descriptor(
284 (complex_descriptor *)one_element);
291 leaf -> ld_size = size;
292 leaf -> ld_nelements = nelements;
293 leaf -> ld_descriptor = descriptor;
298 complex_descriptor * GC_make_sequence_descriptor(complex_descriptor *first,
299 complex_descriptor *second)
301 struct SequenceDescriptor * result =
302 (struct SequenceDescriptor *)
303 GC_malloc(sizeof(struct SequenceDescriptor));
304 /* Can't result in overly conservative marking, since tags are */
305 /* very small integers. Probably faster than maintaining type */
308 result -> sd_tag = SEQUENCE_TAG;
309 result -> sd_first = first;
310 result -> sd_second = second;
312 return((complex_descriptor *)result);
316 complex_descriptor * GC_make_complex_array_descriptor(word nelements,
317 complex_descriptor *descr)
319 struct ComplexArrayDescriptor * result =
320 (struct ComplexArrayDescriptor *)
321 GC_malloc(sizeof(struct ComplexArrayDescriptor));
324 result -> ad_tag = ARRAY_TAG;
325 result -> ad_nelements = nelements;
326 result -> ad_element_descr = descr;
328 return((complex_descriptor *)result);
332 ptr_t * GC_eobjfreelist;
334 ptr_t * GC_arobjfreelist;
336 mse * GC_typed_mark_proc(word * addr, mse * mark_stack_ptr,
337 mse * mark_stack_limit, word env);
339 mse * GC_array_mark_proc(word * addr, mse * mark_stack_ptr,
340 mse * mark_stack_limit, word env);
342 /* Caller does not hold allocation lock. */
343 void GC_init_explicit_typing(void)
349 /* Ignore gcc "no effect" warning. */
350 GC_STATIC_ASSERT(sizeof(struct LeafDescriptor) % sizeof(word) == 0);
352 if (GC_explicit_typing_initialized) {
356 GC_explicit_typing_initialized = TRUE;
357 /* Set up object kind with simple indirect descriptor. */
358 GC_eobjfreelist = (ptr_t *)GC_new_free_list_inner();
359 GC_explicit_kind = GC_new_kind_inner(
360 (void **)GC_eobjfreelist,
361 (((word)WORDS_TO_BYTES(-1)) | GC_DS_PER_OBJECT),
363 /* Descriptors are in the last word of the object. */
364 GC_typed_mark_proc_index = GC_new_proc_inner(GC_typed_mark_proc);
365 /* Set up object kind with array descriptor. */
366 GC_arobjfreelist = (ptr_t *)GC_new_free_list_inner();
367 GC_array_mark_proc_index = GC_new_proc_inner(GC_array_mark_proc);
368 GC_array_kind = GC_new_kind_inner(
369 (void **)GC_arobjfreelist,
370 GC_MAKE_PROC(GC_array_mark_proc_index, 0),
372 for (i = 0; i < WORDSZ/2; i++) {
373 GC_descr d = (((word)(-1)) >> (WORDSZ - i)) << (WORDSZ - i);
380 mse * GC_typed_mark_proc(word * addr, mse * mark_stack_ptr,
381 mse * mark_stack_limit, word env)
383 word bm = GC_ext_descriptors[env].ed_bitmap;
384 word * current_p = addr;
386 ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
387 ptr_t least_ha = GC_least_plausible_heap_addr;
391 for (; bm != 0; bm >>= 1, current_p++) {
393 current = *current_p;
394 FIXUP_POINTER(current);
395 if ((ptr_t)current >= least_ha && (ptr_t)current <= greatest_ha) {
396 PUSH_CONTENTS((ptr_t)current, mark_stack_ptr,
397 mark_stack_limit, current_p, exit1);
401 if (GC_ext_descriptors[env].ed_continued) {
402 /* Push an entry with the rest of the descriptor back onto the */
403 /* stack. Thus we never do too much work at once. Note that */
404 /* we also can't overflow the mark stack unless we actually */
405 /* mark something. */
407 if (mark_stack_ptr >= mark_stack_limit) {
408 mark_stack_ptr = GC_signal_mark_stack_overflow(mark_stack_ptr);
410 mark_stack_ptr -> mse_start = (ptr_t)(addr + WORDSZ);
411 mark_stack_ptr -> mse_descr =
412 GC_MAKE_PROC(GC_typed_mark_proc_index, env+1);
414 return(mark_stack_ptr);
417 /* Return the size of the object described by d. It would be faster to */
418 /* store this directly, or to compute it as part of */
419 /* GC_push_complex_descriptor, but hopefully it doesn't matter. */
420 word GC_descr_obj_size(complex_descriptor *d)
424 return(d -> ld.ld_nelements * d -> ld.ld_size);
426 return(d -> ad.ad_nelements
427 * GC_descr_obj_size(d -> ad.ad_element_descr));
429 return(GC_descr_obj_size(d -> sd.sd_first)
430 + GC_descr_obj_size(d -> sd.sd_second));
432 ABORT("Bad complex descriptor");
433 /*NOTREACHED*/ return 0; /*NOTREACHED*/
437 /* Push descriptors for the object at addr with complex descriptor d */
438 /* onto the mark stack. Return 0 if the mark stack overflowed. */
439 mse * GC_push_complex_descriptor(word *addr, complex_descriptor *d,
442 register ptr_t current = (ptr_t) addr;
443 register word nelements;
450 register GC_descr descr = d -> ld.ld_descriptor;
452 nelements = d -> ld.ld_nelements;
453 if (msl - msp <= (ptrdiff_t)nelements) return(0);
454 sz = d -> ld.ld_size;
455 for (i = 0; i < nelements; i++) {
457 msp -> mse_start = current;
458 msp -> mse_descr = descr;
465 register complex_descriptor *descr = d -> ad.ad_element_descr;
467 nelements = d -> ad.ad_nelements;
468 sz = GC_descr_obj_size(descr);
469 for (i = 0; i < nelements; i++) {
470 msp = GC_push_complex_descriptor((word *)current, descr,
472 if (msp == 0) return(0);
479 sz = GC_descr_obj_size(d -> sd.sd_first);
480 msp = GC_push_complex_descriptor((word *)current, d -> sd.sd_first,
482 if (msp == 0) return(0);
484 msp = GC_push_complex_descriptor((word *)current, d -> sd.sd_second,
489 ABORT("Bad complex descriptor");
490 /*NOTREACHED*/ return 0; /*NOTREACHED*/
495 mse * GC_array_mark_proc(word * addr, mse * mark_stack_ptr,
496 mse * mark_stack_limit, word env)
498 hdr * hhdr = HDR(addr);
499 size_t sz = hhdr -> hb_sz;
500 size_t nwords = BYTES_TO_WORDS(sz);
501 complex_descriptor * descr = (complex_descriptor *)(addr[nwords-1]);
502 mse * orig_mark_stack_ptr = mark_stack_ptr;
503 mse * new_mark_stack_ptr;
506 /* Found a reference to a free list entry. Ignore it. */
507 return(orig_mark_stack_ptr);
509 /* In use counts were already updated when array descriptor was */
510 /* pushed. Here we only replace it by subobject descriptors, so */
511 /* no update is necessary. */
512 new_mark_stack_ptr = GC_push_complex_descriptor(addr, descr,
515 if (new_mark_stack_ptr == 0) {
516 /* Doesn't fit. Conservatively push the whole array as a unit */
517 /* and request a mark stack expansion. */
518 /* This cannot cause a mark stack overflow, since it replaces */
519 /* the original array entry. */
520 GC_mark_stack_too_small = TRUE;
521 new_mark_stack_ptr = orig_mark_stack_ptr + 1;
522 new_mark_stack_ptr -> mse_start = (ptr_t)addr;
523 new_mark_stack_ptr -> mse_descr = sz | GC_DS_LENGTH;
525 /* Push descriptor itself */
526 new_mark_stack_ptr++;
527 new_mark_stack_ptr -> mse_start = (ptr_t)(addr + nwords - 1);
528 new_mark_stack_ptr -> mse_descr = sizeof(word) | GC_DS_LENGTH;
530 return new_mark_stack_ptr;
533 GC_descr GC_make_descriptor(GC_bitmap bm, size_t len)
535 signed_word last_set_bit = len - 1;
538 # define HIGH_BIT (((word)1) << (WORDSZ - 1))
540 if (!GC_explicit_typing_initialized) GC_init_explicit_typing();
541 while (last_set_bit >= 0 && !GC_get_bit(bm, last_set_bit)) last_set_bit --;
542 if (last_set_bit < 0) return(0 /* no pointers */);
543 # if ALIGNMENT == CPP_WORDSZ/8
545 register GC_bool all_bits_set = TRUE;
546 for (i = 0; i < last_set_bit; i++) {
547 if (!GC_get_bit(bm, i)) {
548 all_bits_set = FALSE;
553 /* An initial section contains all pointers. Use length descriptor. */
554 return (WORDS_TO_BYTES(last_set_bit+1) | GC_DS_LENGTH);
558 if (last_set_bit < BITMAP_BITS) {
559 /* Hopefully the common case. */
560 /* Build bitmap descriptor (with bits reversed) */
562 for (i = last_set_bit - 1; i >= 0; i--) {
564 if (GC_get_bit(bm, i)) result |= HIGH_BIT;
566 result |= GC_DS_BITMAP;
571 index = GC_add_ext_descriptor(bm, (word)last_set_bit+1);
572 if (index == -1) return(WORDS_TO_BYTES(last_set_bit+1) | GC_DS_LENGTH);
573 /* Out of memory: use conservative */
575 result = GC_MAKE_PROC(GC_typed_mark_proc_index, (word)index);
580 ptr_t GC_clear_stack();
582 #define GENERAL_MALLOC(lb,k) \
583 (void *)GC_clear_stack(GC_generic_malloc((word)lb, k))
585 #define GENERAL_MALLOC_IOP(lb,k) \
586 (void *)GC_clear_stack(GC_generic_malloc_ignore_off_page(lb, k))
588 void * GC_malloc_explicitly_typed(size_t lb, GC_descr d)
595 lb += TYPD_EXTRA_BYTES;
597 lg = GC_size_map[lb];
598 opp = &(GC_eobjfreelist[lg]);
600 if( (op = *opp) == 0 ) {
602 op = (ptr_t)GENERAL_MALLOC((word)lb, GC_explicit_kind);
603 if (0 == op) return 0;
604 lg = GC_size_map[lb]; /* May have been uninitialized. */
608 GC_bytes_allocd += GRANULES_TO_BYTES(lg);
612 op = (ptr_t)GENERAL_MALLOC((word)lb, GC_explicit_kind);
614 lg = BYTES_TO_GRANULES(GC_size(op));
617 ((word *)op)[GRANULES_TO_WORDS(lg) - 1] = d;
621 void * GC_malloc_explicitly_typed_ignore_off_page(size_t lb, GC_descr d)
628 lb += TYPD_EXTRA_BYTES;
629 if( SMALL_OBJ(lb) ) {
630 lg = GC_size_map[lb];
631 opp = &(GC_eobjfreelist[lg]);
633 if( (op = *opp) == 0 ) {
635 op = (ptr_t)GENERAL_MALLOC_IOP(lb, GC_explicit_kind);
636 lg = GC_size_map[lb]; /* May have been uninitialized. */
640 GC_bytes_allocd += GRANULES_TO_BYTES(lg);
644 op = (ptr_t)GENERAL_MALLOC_IOP(lb, GC_explicit_kind);
646 lg = BYTES_TO_WORDS(GC_size(op));
649 ((word *)op)[GRANULES_TO_WORDS(lg) - 1] = d;
653 void * GC_calloc_explicitly_typed(size_t n, size_t lb, GC_descr d)
658 GC_descr simple_descr;
659 complex_descriptor *complex_descr;
660 register int descr_type;
661 struct LeafDescriptor leaf;
664 descr_type = GC_make_array_descriptor((word)n, (word)lb, d,
665 &simple_descr, &complex_descr, &leaf);
667 case NO_MEM: return(0);
668 case SIMPLE: return(GC_malloc_explicitly_typed(n*lb, simple_descr));
671 lb += sizeof(struct LeafDescriptor) + TYPD_EXTRA_BYTES;
675 lb += TYPD_EXTRA_BYTES;
678 if( SMALL_OBJ(lb) ) {
679 lg = GC_size_map[lb];
680 opp = &(GC_arobjfreelist[lg]);
682 if( (op = *opp) == 0 ) {
684 op = (ptr_t)GENERAL_MALLOC((word)lb, GC_array_kind);
685 if (0 == op) return(0);
686 lg = GC_size_map[lb]; /* May have been uninitialized. */
690 GC_bytes_allocd += GRANULES_TO_BYTES(lg);
694 op = (ptr_t)GENERAL_MALLOC((word)lb, GC_array_kind);
695 if (0 == op) return(0);
696 lg = BYTES_TO_GRANULES(GC_size(op));
698 if (descr_type == LEAF) {
699 /* Set up the descriptor inside the object itself. */
700 volatile struct LeafDescriptor * lp =
701 (struct LeafDescriptor *)
703 + GRANULES_TO_WORDS(lg)
704 - (BYTES_TO_WORDS(sizeof(struct LeafDescriptor)) + 1));
706 lp -> ld_tag = LEAF_TAG;
707 lp -> ld_size = leaf.ld_size;
708 lp -> ld_nelements = leaf.ld_nelements;
709 lp -> ld_descriptor = leaf.ld_descriptor;
710 ((volatile word *)op)[GRANULES_TO_WORDS(lg) - 1] = (word)lp;
712 extern unsigned GC_finalization_failures;
713 unsigned ff = GC_finalization_failures;
714 size_t lw = GRANULES_TO_WORDS(lg);
716 ((word *)op)[lw - 1] = (word)complex_descr;
717 /* Make sure the descriptor is cleared once there is any danger */
718 /* it may have been collected. */
720 GC_general_register_disappearing_link((void * *)
723 if (ff != GC_finalization_failures) {
724 /* Couldn't register it due to lack of memory. Punt. */
725 /* This will probably fail too, but gives the recovery code */
727 return(GC_malloc(n*lb));