1 /* Functions related to the Boehm garbage collector.
2 Copyright (C) 2000 Free Software Foundation, Inc.
4 This file is part of GNU CC.
6 GNU CC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 GNU CC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU CC; see the file COPYING. If not, write to
18 the Free Software Foundation, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA.
21 Java and all Java-based marks are trademarks or registered trademarks
22 of Sun Microsystems, Inc. in the United States and other countries.
23 The Free Software Foundation is independent of Sun Microsystems, Inc. */
25 /* Written by Tom Tromey <tromey@cygnus.com>. */
31 #include "java-tree.h"
34 static unsigned int mark_reference_fields PARAMS ((tree,
35 unsigned HOST_WIDE_INT *,
36 unsigned HOST_WIDE_INT *,
38 int *, int *, int *));
39 static void set_bit PARAMS ((unsigned HOST_WIDE_INT *,
40 unsigned HOST_WIDE_INT *,
43 /* Compute a procedure-based object descriptor. We know that our
44 `kind' is 0, and `env' is likewise 0, so we have a simple
45 computation. From the GC sources:
46 (((((env) << LOG_MAX_MARK_PROCS) | (proc_index)) << DS_TAG_BITS) \
49 #define PROCEDURE_OBJECT_DESCRIPTOR integer_two_node
51 /* Treat two HOST_WIDE_INT's as a contiguous bitmap, with bit 0 being
52 the least significant. This function sets bit N in the bitmap. */
54 set_bit (low, high, n)
55 unsigned HOST_WIDE_INT *low, *high;
60 if (n >= HOST_BITS_PER_WIDE_INT)
62 n -= HOST_BITS_PER_WIDE_INT;
68 *which |= (HOST_WIDE_INT) 1 << n;
71 /* Recursively mark reference fields. */
73 mark_reference_fields (field, low, high, ubit,
74 pointer_after_end, all_bits_set, last_set_index)
76 unsigned HOST_WIDE_INT *low, *high;
78 int *pointer_after_end, *all_bits_set, *last_set_index;
80 unsigned int count = 0;
82 /* See if we have fields from our superclass. */
83 if (DECL_NAME (field) == NULL_TREE)
85 count += mark_reference_fields (TYPE_FIELDS (TREE_TYPE (field)),
87 pointer_after_end, all_bits_set,
89 field = TREE_CHAIN (field);
92 for (; field != NULL_TREE; field = TREE_CHAIN (field))
94 if (FIELD_STATIC (field))
97 if (JREFERENCE_TYPE_P (TREE_TYPE (field)))
99 *last_set_index = count;
100 /* First word in object corresponds to most significant byte
102 set_bit (low, high, ubit - count - 1);
103 if (count > ubit - 2)
104 *pointer_after_end = 1;
115 /* Return the marking bitmap for the class TYPE. For now this is a
116 single word describing the type. */
118 get_boehm_type_descriptor (tree type)
120 unsigned int count, log2_size, ubit;
122 int all_bits_set = 1;
123 int last_set_index = 0;
124 int pointer_after_end = 0;
125 unsigned HOST_WIDE_INT low = 0, high = 0;
128 /* If the GC wasn't requested, just use a null pointer. */
129 if (! flag_use_boehm_gc)
130 return null_pointer_node;
132 /* If we have a type of unknown size, use a proc. */
133 if (int_size_in_bytes (type) == -1)
134 return PROCEDURE_OBJECT_DESCRIPTOR;
136 bit = POINTER_SIZE / BITS_PER_UNIT;
137 /* The size of this node has to be known. And, we only support 32
138 and 64 bit targets, so we need to know that the log2 is one of
140 log2_size = exact_log2 (bit);
141 if (bit == -1 || (log2_size != 2 && log2_size != 3))
143 /* This means the GC isn't supported. We should probably
144 abort or give an error. Instead, for now, we just silently
146 return null_pointer_node;
148 bit *= BITS_PER_UNIT;
150 /* Warning avoidance. */
151 ubit = (unsigned int) bit;
153 field = TYPE_FIELDS (type);
154 count = mark_reference_fields (field, &low, &high, ubit,
155 &pointer_after_end, &all_bits_set,
158 /* If the object is all pointers, or if the part with pointers fits
159 in our bitmap, then we are ok. Otherwise we have to allocate it
163 /* In the GC the computation looks something like this:
164 value = DS_LENGTH | WORDS_TO_BYTES (last_set_index + 1);
166 WORDS_TO_BYTES shifts by log2(bytes-per-pointer). */
171 while (last_set_index)
173 if ((last_set_index & 1))
174 set_bit (&low, &high, log2_size + count);
175 last_set_index >>= 1;
178 value = build_int_2 (low, high);
180 else if (! pointer_after_end)
182 /* Bottom two bits for bitmap mark type are 01. */
183 set_bit (&low, &high, 0);
184 value = build_int_2 (low, high);
187 value = PROCEDURE_OBJECT_DESCRIPTOR;