/**
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* \file
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* GC descriptors describe object layout.
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*
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* Copyright 2001-2003 Ximian, Inc
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* Copyright 2003-2010 Novell, Inc.
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* Copyright 2011 Xamarin Inc (http://www.xamarin.com)
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* Copyright (C) 2012 Xamarin Inc
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*
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* Licensed under the MIT license. See LICENSE file in the project root for full license information.
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*/
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#include "config.h"
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#ifdef HAVE_SGEN_GC
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#ifdef HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#ifdef HAVE_PTHREAD_H
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#include <pthread.h>
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#endif
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#ifdef HAVE_SEMAPHORE_H
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#include <semaphore.h>
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#endif
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#include <stdio.h>
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#include <string.h>
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#include <errno.h>
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#include <assert.h>
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#ifdef __MACH__
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#undef _XOPEN_SOURCE
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#endif
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#ifdef __MACH__
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#define _XOPEN_SOURCE
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#endif
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#include "mono/sgen/sgen-gc.h"
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#include "mono/sgen/gc-internal-agnostic.h"
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#include "mono/sgen/sgen-array-list.h"
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#define MAX_USER_DESCRIPTORS 16
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#define MAKE_ROOT_DESC(type,val) ((type) | ((val) << ROOT_DESC_TYPE_SHIFT))
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#define ALIGN_TO(val,align) ((((guint64)val) + ((align) - 1)) & ~((align) - 1))
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static SgenArrayList complex_descriptors = SGEN_ARRAY_LIST_INIT (NULL, NULL, NULL, INTERNAL_MEM_COMPLEX_DESCRIPTORS);
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static SgenUserRootMarkFunc user_descriptors [MAX_USER_DESCRIPTORS];
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static int user_descriptors_next = 0;
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static SgenDescriptor all_ref_root_descrs [32];
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#ifdef HEAVY_STATISTICS
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static guint64 stat_scanned_count_per_descriptor [DESC_TYPE_MAX];
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static guint64 stat_copied_count_per_descriptor [DESC_TYPE_MAX];
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#endif
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static int
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alloc_complex_descriptor (gsize *bitmap, int numbits)
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{
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int nwords, res, i;
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volatile gpointer *slot;
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gsize *descriptor;
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SGEN_ASSERT (0, sizeof (gsize) == sizeof (mword), "We expect gsize and mword to have same size");
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numbits = ALIGN_TO (numbits, GC_BITS_PER_WORD);
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nwords = numbits / GC_BITS_PER_WORD + 1;
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sgen_gc_lock ();
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/* linear search, so we don't have duplicates with domain load/unload
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* this should not be performance critical or we'd have bigger issues
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* (the number and size of complex descriptors should be small).
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*/
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SGEN_ARRAY_LIST_FOREACH_SLOT (&complex_descriptors, slot) {
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gsize first_word = *(gsize*)slot;
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if (first_word == 0) {
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/* Unused slots should be 0 so we simply skip them */
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continue;
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} else if (first_word == nwords) {
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int j, found = TRUE;
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for (j = 0; j < nwords - 1; ++j) {
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if (((gsize*)slot) [j + 1] != bitmap [j]) {
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found = FALSE;
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break;
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}
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}
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if (found) {
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sgen_gc_unlock ();
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return __index;
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}
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}
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/* Skip the bitmap words */
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__index += (guint32)(first_word - 1);
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__offset += (guint32)(first_word - 1);
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} SGEN_ARRAY_LIST_END_FOREACH_SLOT;
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res = sgen_array_list_alloc_block (&complex_descriptors, nwords);
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SGEN_LOG (6, "Complex descriptor %d, size: %d (total desc memory: %d)", res, nwords, complex_descriptors.capacity);
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descriptor = (gsize*)sgen_array_list_get_slot (&complex_descriptors, res);
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descriptor [0] = nwords;
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for (i = 0; i < nwords - 1; ++i) {
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descriptor [1 + i] = bitmap [i];
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SGEN_LOG (6, "\tvalue: %p", (void*)descriptor [1 + i]);
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}
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sgen_gc_unlock ();
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return res;
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}
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gsize*
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sgen_get_complex_descriptor (SgenDescriptor desc)
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{
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return (gsize*) sgen_array_list_get_slot (&complex_descriptors, desc >> LOW_TYPE_BITS);
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}
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/*
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* Descriptor builders.
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*/
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SgenDescriptor
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mono_gc_make_descr_for_object (gsize *bitmap, int numbits, size_t obj_size)
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{
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int first_set = -1, num_set = 0, last_set = -1, i;
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SgenDescriptor desc = 0;
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size_t stored_size = SGEN_ALIGN_UP (obj_size);
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for (i = 0; i < numbits; ++i) {
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if (bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
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if (first_set < 0)
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first_set = i;
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last_set = i;
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num_set++;
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}
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}
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if (first_set < 0) {
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SGEN_LOG (6, "Ptrfree descriptor %p, size: %zd", (void*)desc, stored_size);
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if (stored_size <= MAX_RUNLEN_OBJECT_SIZE && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE)
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return DESC_TYPE_SMALL_PTRFREE | stored_size;
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return DESC_TYPE_COMPLEX_PTRFREE;
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}
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g_assert (!(stored_size & 0x7));
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SGEN_ASSERT (5, stored_size == SGEN_ALIGN_UP (stored_size), "Size is not aligned");
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/* we know the 2-word header is ptr-free */
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if (last_set < BITMAP_NUM_BITS + OBJECT_HEADER_WORDS && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE) {
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desc = DESC_TYPE_BITMAP | ((*bitmap >> OBJECT_HEADER_WORDS) << LOW_TYPE_BITS);
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SGEN_LOG (6, "Largebitmap descriptor %p, size: %zd, last set: %d", (void*)desc, stored_size, last_set);
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return desc;
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}
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if (stored_size <= MAX_RUNLEN_OBJECT_SIZE && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE) {
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/* check run-length encoding first: one byte offset, one byte number of pointers
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* on 64 bit archs, we can have 3 runs, just one on 32.
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* It may be better to use nibbles.
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*/
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if (first_set < 256 && num_set < 256 && (first_set + num_set == last_set + 1)) {
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desc = DESC_TYPE_RUN_LENGTH | stored_size | (first_set << 16) | (num_set << 24);
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SGEN_LOG (6, "Runlen descriptor %p, size: %zd, first set: %d, num set: %d", (void*)desc, stored_size, first_set, num_set);
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return desc;
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}
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}
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/* it's a complex object ... */
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desc = DESC_TYPE_COMPLEX | (alloc_complex_descriptor (bitmap, last_set + 1) << LOW_TYPE_BITS);
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return desc;
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}
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/* If the array holds references, numbits == 1 and the first bit is set in elem_bitmap */
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SgenDescriptor
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mono_gc_make_descr_for_array (int vector, gsize *elem_bitmap, int numbits, size_t elem_size)
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{
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int first_set = -1, num_set = 0, last_set = -1, i;
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SgenDescriptor desc = DESC_TYPE_VECTOR | (vector ? VECTOR_KIND_SZARRAY : VECTOR_KIND_ARRAY);
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for (i = 0; i < numbits; ++i) {
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if (elem_bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
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if (first_set < 0)
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first_set = i;
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last_set = i;
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num_set++;
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}
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}
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if (first_set < 0) {
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if (elem_size <= MAX_ELEMENT_SIZE)
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return desc | VECTOR_SUBTYPE_PTRFREE | (elem_size << VECTOR_ELSIZE_SHIFT);
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return DESC_TYPE_COMPLEX_PTRFREE;
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}
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if (elem_size <= MAX_ELEMENT_SIZE) {
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desc |= elem_size << VECTOR_ELSIZE_SHIFT;
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if (!num_set) {
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return desc | VECTOR_SUBTYPE_PTRFREE;
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}
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/* Note: we also handle structs with just ref fields */
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if (num_set * sizeof (gpointer) == elem_size) {
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return desc | VECTOR_SUBTYPE_REFS | ((gsize)(-1) << 16);
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}
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/* FIXME: try run-len first */
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/* Note: we can't skip the object header here, because it's not present */
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if (last_set < VECTOR_BITMAP_SIZE) {
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return desc | VECTOR_SUBTYPE_BITMAP | (*elem_bitmap << 16);
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}
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}
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/* it's am array of complex structs ... */
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desc = DESC_TYPE_COMPLEX_ARR;
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desc |= alloc_complex_descriptor (elem_bitmap, last_set + 1) << LOW_TYPE_BITS;
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return desc;
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}
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/* Return the bitmap encoded by a descriptor */
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gsize*
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mono_gc_get_bitmap_for_descr (SgenDescriptor descr, int *numbits)
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{
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SgenDescriptor d = (SgenDescriptor)descr;
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gsize *bitmap;
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switch (d & DESC_TYPE_MASK) {
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case DESC_TYPE_RUN_LENGTH: {
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int first_set = (d >> 16) & 0xff;
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int num_set = (d >> 24) & 0xff;
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int i;
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bitmap = g_new0 (gsize, (first_set + num_set + 7) / 8);
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for (i = first_set; i < first_set + num_set; ++i)
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bitmap [i / GC_BITS_PER_WORD] |= ((gsize)1 << (i % GC_BITS_PER_WORD));
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*numbits = first_set + num_set;
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return bitmap;
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}
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case DESC_TYPE_BITMAP: {
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gsize bmap = (d >> LOW_TYPE_BITS) << OBJECT_HEADER_WORDS;
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bitmap = g_new0 (gsize, 1);
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bitmap [0] = bmap;
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*numbits = 0;
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while (bmap) {
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(*numbits) ++;
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bmap >>= 1;
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}
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return bitmap;
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}
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case DESC_TYPE_COMPLEX: {
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gsize *bitmap_data = sgen_get_complex_descriptor (d);
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int bwords = (int)(*bitmap_data) - 1;//Max scalar object size is 1Mb, which means up to 32k descriptor words
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int i;
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bitmap = g_new0 (gsize, bwords);
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*numbits = bwords * GC_BITS_PER_WORD;
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for (i = 0; i < bwords; ++i) {
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bitmap [i] = bitmap_data [i + 1];
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}
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return bitmap;
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}
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default:
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g_assert_not_reached ();
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}
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}
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/**
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* mono_gc_make_descr_from_bitmap:
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*/
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SgenDescriptor
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mono_gc_make_descr_from_bitmap (gsize *bitmap, int numbits)
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{
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if (numbits == 0) {
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return MAKE_ROOT_DESC (ROOT_DESC_BITMAP, 0);
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} else if (numbits < ((sizeof (*bitmap) * 8) - ROOT_DESC_TYPE_SHIFT)) {
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return MAKE_ROOT_DESC (ROOT_DESC_BITMAP, bitmap [0]);
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} else {
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SgenDescriptor complex = alloc_complex_descriptor (bitmap, numbits);
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return MAKE_ROOT_DESC (ROOT_DESC_COMPLEX, complex);
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}
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}
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SgenDescriptor
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mono_gc_make_vector_descr (void)
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{
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return MAKE_ROOT_DESC (ROOT_DESC_VECTOR, 0);
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}
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SgenDescriptor
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mono_gc_make_root_descr_all_refs (int numbits)
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{
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gsize *gc_bitmap;
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SgenDescriptor descr;
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int num_bytes = numbits / 8;
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if (numbits < 32 && all_ref_root_descrs [numbits])
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return all_ref_root_descrs [numbits];
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gc_bitmap = (gsize *)g_malloc0 (ALIGN_TO (ALIGN_TO (numbits, 8) + 1, sizeof (gsize)));
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memset (gc_bitmap, 0xff, num_bytes);
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if (numbits < ((sizeof (*gc_bitmap) * 8) - ROOT_DESC_TYPE_SHIFT))
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gc_bitmap[0] = GUINT64_TO_LE(gc_bitmap[0]);
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else if (numbits && num_bytes % (sizeof (*gc_bitmap)))
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gc_bitmap[num_bytes / 8] = GUINT64_TO_LE(gc_bitmap [num_bytes / 8]);
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if (numbits % 8)
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gc_bitmap [numbits / 8] = (1 << (numbits % 8)) - 1;
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descr = mono_gc_make_descr_from_bitmap (gc_bitmap, numbits);
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g_free (gc_bitmap);
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if (numbits < 32)
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all_ref_root_descrs [numbits] = descr;
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return descr;
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}
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SgenDescriptor
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sgen_make_user_root_descriptor (SgenUserRootMarkFunc marker)
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{
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SgenDescriptor descr;
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g_assert (user_descriptors_next < MAX_USER_DESCRIPTORS);
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descr = MAKE_ROOT_DESC (ROOT_DESC_USER, (SgenDescriptor)user_descriptors_next);
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user_descriptors [user_descriptors_next ++] = marker;
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return descr;
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}
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void*
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sgen_get_complex_descriptor_bitmap (SgenDescriptor desc)
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{
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return (void*) sgen_array_list_get_slot (&complex_descriptors, desc >> ROOT_DESC_TYPE_SHIFT);
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}
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SgenUserRootMarkFunc
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sgen_get_user_descriptor_func (SgenDescriptor desc)
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{
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return user_descriptors [desc >> ROOT_DESC_TYPE_SHIFT];
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}
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#ifdef HEAVY_STATISTICS
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void
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sgen_descriptor_count_scanned_object (SgenDescriptor desc)
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{
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int type = desc & DESC_TYPE_MASK;
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SGEN_ASSERT (0, type, "Descriptor type can't be zero");
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++stat_scanned_count_per_descriptor [type - 1];
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}
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void
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sgen_descriptor_count_copied_object (SgenDescriptor desc)
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{
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int type = desc & DESC_TYPE_MASK;
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SGEN_ASSERT (0, type, "Descriptor type can't be zero");
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++stat_copied_count_per_descriptor [type - 1];
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}
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#endif
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void
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sgen_init_descriptors (void)
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{
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#ifdef HEAVY_STATISTICS
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mono_counters_register ("# scanned RUN_LENGTH", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_RUN_LENGTH - 1]);
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mono_counters_register ("# scanned SMALL_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_SMALL_PTRFREE - 1]);
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mono_counters_register ("# scanned COMPLEX", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX - 1]);
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mono_counters_register ("# scanned VECTOR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_VECTOR - 1]);
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mono_counters_register ("# scanned BITMAP", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_BITMAP - 1]);
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mono_counters_register ("# scanned COMPLEX_ARR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_ARR - 1]);
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mono_counters_register ("# scanned COMPLEX_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_PTRFREE - 1]);
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mono_counters_register ("# copied RUN_LENGTH", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_RUN_LENGTH - 1]);
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mono_counters_register ("# copied SMALL_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_SMALL_PTRFREE - 1]);
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mono_counters_register ("# copied COMPLEX", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX - 1]);
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mono_counters_register ("# copied VECTOR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_VECTOR - 1]);
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mono_counters_register ("# copied BITMAP", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_BITMAP - 1]);
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mono_counters_register ("# copied COMPLEX_ARR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX_ARR - 1]);
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mono_counters_register ("# copied COMPLEX_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX_PTRFREE - 1]);
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#endif
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}
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#endif
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