2 * sgen-descriptor.c: GC descriptors describe object layout.
4 * Copyright 2001-2003 Ximian, Inc
5 * Copyright 2003-2010 Novell, Inc.
6 * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
7 * Copyright (C) 2012 Xamarin Inc
9 * This library is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Library General Public
11 * License 2.0 as published by the Free Software Foundation;
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Library General Public License for more details.
18 * You should have received a copy of the GNU Library General Public
19 * License 2.0 along with this library; if not, write to the Free
20 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
31 #ifdef HAVE_SEMAPHORE_H
32 #include <semaphore.h>
46 #include "metadata/sgen-gc.h"
48 #define MAX_USER_DESCRIPTORS 16
50 #define MAKE_ROOT_DESC(type,val) ((type) | ((val) << ROOT_DESC_TYPE_SHIFT))
51 #define ALIGN_TO(val,align) ((((guint64)val) + ((align) - 1)) & ~((align) - 1))
54 static gsize* complex_descriptors = NULL;
55 static int complex_descriptors_size = 0;
56 static int complex_descriptors_next = 0;
57 static MonoGCRootMarkFunc user_descriptors [MAX_USER_DESCRIPTORS];
58 static int user_descriptors_next = 0;
59 static void *all_ref_root_descrs [32];
63 alloc_complex_descriptor (gsize *bitmap, int numbits)
67 numbits = ALIGN_TO (numbits, GC_BITS_PER_WORD);
68 nwords = numbits / GC_BITS_PER_WORD + 1;
71 res = complex_descriptors_next;
72 /* linear search, so we don't have duplicates with domain load/unload
73 * this should not be performance critical or we'd have bigger issues
74 * (the number and size of complex descriptors should be small).
76 for (i = 0; i < complex_descriptors_next; ) {
77 if (complex_descriptors [i] == nwords) {
79 for (j = 0; j < nwords - 1; ++j) {
80 if (complex_descriptors [i + 1 + j] != bitmap [j]) {
90 i += complex_descriptors [i];
92 if (complex_descriptors_next + nwords > complex_descriptors_size) {
93 int new_size = complex_descriptors_size * 2 + nwords;
94 complex_descriptors = g_realloc (complex_descriptors, new_size * sizeof (gsize));
95 complex_descriptors_size = new_size;
97 SGEN_LOG (6, "Complex descriptor %d, size: %d (total desc memory: %d)", res, nwords, complex_descriptors_size);
98 complex_descriptors_next += nwords;
99 complex_descriptors [res] = nwords;
100 for (i = 0; i < nwords - 1; ++i) {
101 complex_descriptors [res + 1 + i] = bitmap [i];
102 SGEN_LOG (6, "\tvalue: %p", (void*)complex_descriptors [res + 1 + i]);
109 sgen_get_complex_descriptor (mword desc)
111 return complex_descriptors + (desc >> LOW_TYPE_BITS);
115 * Descriptor builders.
118 mono_gc_make_descr_for_string (gsize *bitmap, int numbits)
120 return (void*) DESC_TYPE_RUN_LENGTH;
124 mono_gc_make_descr_for_object (gsize *bitmap, int numbits, size_t obj_size)
126 int first_set = -1, num_set = 0, last_set = -1, i;
128 size_t stored_size = obj_size;
130 stored_size += SGEN_ALLOC_ALIGN - 1;
131 stored_size &= ~(SGEN_ALLOC_ALIGN - 1);
133 for (i = 0; i < numbits; ++i) {
134 if (bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
143 SGEN_LOG (6, "Ptrfree descriptor %p, size: %zd", (void*)desc, stored_size);
144 if (stored_size <= MAX_RUNLEN_OBJECT_SIZE)
145 return (void*)(DESC_TYPE_RUN_LENGTH | stored_size);
146 return (void*)DESC_TYPE_COMPLEX_PTRFREE;
149 g_assert (!(stored_size & 0x7));
151 if (stored_size <= MAX_RUNLEN_OBJECT_SIZE) {
152 /* check run-length encoding first: one byte offset, one byte number of pointers
153 * on 64 bit archs, we can have 3 runs, just one on 32.
154 * It may be better to use nibbles.
156 if (first_set < 256 && num_set < 256 && (first_set + num_set == last_set + 1)) {
157 desc = DESC_TYPE_RUN_LENGTH | stored_size | (first_set << 16) | (num_set << 24);
158 SGEN_LOG (6, "Runlen descriptor %p, size: %zd, first set: %d, num set: %d", (void*)desc, stored_size, first_set, num_set);
163 /* we know the 2-word header is ptr-free */
164 if (last_set < SMALL_BITMAP_SIZE + OBJECT_HEADER_WORDS) {
165 desc = DESC_TYPE_SMALL_BITMAP | stored_size | ((*bitmap >> OBJECT_HEADER_WORDS) << SMALL_BITMAP_SHIFT);
166 SGEN_LOG (6, "Smallbitmap descriptor %p, size: %zd, last set: %d", (void*)desc, stored_size, last_set);
170 /* we know the 2-word header is ptr-free */
171 if (last_set < LARGE_BITMAP_SIZE + OBJECT_HEADER_WORDS) {
172 desc = DESC_TYPE_LARGE_BITMAP | ((*bitmap >> OBJECT_HEADER_WORDS) << LOW_TYPE_BITS);
173 SGEN_LOG (6, "Largebitmap descriptor %p, size: %zd, last set: %d", (void*)desc, stored_size, last_set);
176 /* it's a complex object ... */
177 desc = DESC_TYPE_COMPLEX | (alloc_complex_descriptor (bitmap, last_set + 1) << LOW_TYPE_BITS);
181 /* If the array holds references, numbits == 1 and the first bit is set in elem_bitmap */
183 mono_gc_make_descr_for_array (int vector, gsize *elem_bitmap, int numbits, size_t elem_size)
185 int first_set = -1, num_set = 0, last_set = -1, i;
186 mword desc = DESC_TYPE_VECTOR | (vector ? VECTOR_KIND_SZARRAY : VECTOR_KIND_ARRAY);
187 for (i = 0; i < numbits; ++i) {
188 if (elem_bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
197 if (elem_size <= MAX_ELEMENT_SIZE)
198 return (void*)(desc | VECTOR_SUBTYPE_PTRFREE | (elem_size << VECTOR_ELSIZE_SHIFT));
199 return (void*)DESC_TYPE_COMPLEX_PTRFREE;
202 if (elem_size <= MAX_ELEMENT_SIZE) {
203 desc |= elem_size << VECTOR_ELSIZE_SHIFT;
205 return (void*)(desc | VECTOR_SUBTYPE_PTRFREE);
207 /* Note: we also handle structs with just ref fields */
208 if (num_set * sizeof (gpointer) == elem_size) {
209 return (void*)(desc | VECTOR_SUBTYPE_REFS | ((gssize)(-1) << 16));
211 /* FIXME: try run-len first */
212 /* Note: we can't skip the object header here, because it's not present */
213 if (last_set <= SMALL_BITMAP_SIZE) {
214 return (void*)(desc | VECTOR_SUBTYPE_BITMAP | (*elem_bitmap << 16));
217 /* it's am array of complex structs ... */
218 desc = DESC_TYPE_COMPLEX_ARR;
219 desc |= alloc_complex_descriptor (elem_bitmap, last_set + 1) << LOW_TYPE_BITS;
223 /* Return the bitmap encoded by a descriptor */
225 mono_gc_get_bitmap_for_descr (void *descr, int *numbits)
227 mword d = (mword)descr;
231 case DESC_TYPE_RUN_LENGTH: {
232 int first_set = (d >> 16) & 0xff;
233 int num_set = (d >> 24) & 0xff;
236 bitmap = g_new0 (gsize, (first_set + num_set + 7) / 8);
238 for (i = first_set; i < first_set + num_set; ++i)
239 bitmap [i / GC_BITS_PER_WORD] |= ((gsize)1 << (i % GC_BITS_PER_WORD));
241 *numbits = first_set + num_set;
246 case DESC_TYPE_SMALL_BITMAP:
247 bitmap = g_new0 (gsize, 1);
249 bitmap [0] = (d >> SMALL_BITMAP_SHIFT) << OBJECT_HEADER_WORDS;
251 *numbits = GC_BITS_PER_WORD;
254 case DESC_TYPE_LARGE_BITMAP: {
255 gsize bmap = (d >> LOW_TYPE_BITS) << OBJECT_HEADER_WORDS;
257 bitmap = g_new0 (gsize, 1);
267 case DESC_TYPE_COMPLEX: {
268 gsize *bitmap_data = sgen_get_complex_descriptor (d);
269 int bwords = (*bitmap_data) - 1;
272 bitmap = g_new0 (gsize, bwords);
273 *numbits = bwords * GC_BITS_PER_WORD;
275 for (i = 0; i < bwords; ++i) {
276 bitmap [i] = bitmap_data [i + 1];
283 g_assert_not_reached ();
288 mono_gc_make_descr_from_bitmap (gsize *bitmap, int numbits)
291 return (void*)MAKE_ROOT_DESC (ROOT_DESC_BITMAP, 0);
292 } else if (numbits < ((sizeof (*bitmap) * 8) - ROOT_DESC_TYPE_SHIFT)) {
293 return (void*)MAKE_ROOT_DESC (ROOT_DESC_BITMAP, bitmap [0]);
295 mword complex = alloc_complex_descriptor (bitmap, numbits);
296 return (void*)MAKE_ROOT_DESC (ROOT_DESC_COMPLEX, complex);
301 mono_gc_make_root_descr_all_refs (int numbits)
305 int num_bytes = numbits / 8;
307 if (numbits < 32 && all_ref_root_descrs [numbits])
308 return all_ref_root_descrs [numbits];
310 gc_bitmap = g_malloc0 (ALIGN_TO (ALIGN_TO (numbits, 8) + 1, sizeof (gsize)));
311 memset (gc_bitmap, 0xff, num_bytes);
312 if (numbits < ((sizeof (*gc_bitmap) * 8) - ROOT_DESC_TYPE_SHIFT))
313 gc_bitmap[0] = GUINT64_TO_LE(gc_bitmap[0]);
314 else if (numbits && num_bytes % (sizeof (*gc_bitmap)))
315 gc_bitmap[num_bytes / 8] = GUINT64_TO_LE(gc_bitmap [num_bytes / 8]);
317 gc_bitmap [numbits / 8] = (1 << (numbits % 8)) - 1;
318 descr = mono_gc_make_descr_from_bitmap (gc_bitmap, numbits);
322 all_ref_root_descrs [numbits] = descr;
328 mono_gc_make_root_descr_user (MonoGCRootMarkFunc marker)
332 g_assert (user_descriptors_next < MAX_USER_DESCRIPTORS);
333 descr = (void*)MAKE_ROOT_DESC (ROOT_DESC_USER, (mword)user_descriptors_next);
334 user_descriptors [user_descriptors_next ++] = marker;
340 sgen_get_complex_descriptor_bitmap (mword desc)
342 return complex_descriptors + (desc >> ROOT_DESC_TYPE_SHIFT);
346 sgen_get_user_descriptor_func (mword desc)
348 return user_descriptors [desc >> ROOT_DESC_TYPE_SHIFT];