1 /* Functions related to the Boehm garbage collector.
2 Copyright (C) 2000, 2003, 2004, 2006 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC 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 GCC 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 GCC; see the file COPYING. If not, write to
18 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
19 Boston, MA 02110-1301, 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>. */
30 #include "coretypes.h"
33 #include "java-tree.h"
37 static void mark_reference_fields (tree
, unsigned HOST_WIDE_INT
*,
38 unsigned HOST_WIDE_INT
*, unsigned int,
39 int *, int *, int *, HOST_WIDE_INT
*);
40 static void set_bit (unsigned HOST_WIDE_INT
*, unsigned HOST_WIDE_INT
*,
43 /* Treat two HOST_WIDE_INT's as a contiguous bitmap, with bit 0 being
44 the least significant. This function sets bit N in the bitmap. */
46 set_bit (unsigned HOST_WIDE_INT
*low
, unsigned HOST_WIDE_INT
*high
,
49 unsigned HOST_WIDE_INT
*which
;
51 if (n
>= HOST_BITS_PER_WIDE_INT
)
53 n
-= HOST_BITS_PER_WIDE_INT
;
59 *which
|= (unsigned HOST_WIDE_INT
) 1 << n
;
62 /* Recursively mark reference fields. */
64 mark_reference_fields (tree field
,
65 unsigned HOST_WIDE_INT
*low
,
66 unsigned HOST_WIDE_INT
*high
,
68 int *pointer_after_end
,
71 HOST_WIDE_INT
*last_view_index
)
73 /* See if we have fields from our superclass. */
74 if (DECL_NAME (field
) == NULL_TREE
)
76 mark_reference_fields (TYPE_FIELDS (TREE_TYPE (field
)),
78 pointer_after_end
, all_bits_set
,
79 last_set_index
, last_view_index
);
80 field
= TREE_CHAIN (field
);
83 for (; field
!= NULL_TREE
; field
= TREE_CHAIN (field
))
86 HOST_WIDE_INT size_bytes
;
88 if (FIELD_STATIC (field
))
91 offset
= int_byte_position (field
);
92 size_bytes
= int_size_in_bytes (TREE_TYPE (field
));
93 if (JREFERENCE_TYPE_P (TREE_TYPE (field
))
94 /* An `object' of type gnu.gcj.RawData is actually non-Java
96 && TREE_TYPE (field
) != rawdata_ptr_type_node
)
99 unsigned int size_words
;
102 /* If this reference slot appears to overlay a slot we think
103 we already covered, then we are doomed. */
104 gcc_assert (offset
> *last_view_index
);
106 count
= offset
* BITS_PER_UNIT
/ POINTER_SIZE
;
107 size_words
= size_bytes
* BITS_PER_UNIT
/ POINTER_SIZE
;
109 *last_set_index
= count
;
111 /* First word in object corresponds to most significant byte of
114 In the case of a multiple-word record, we set pointer
115 bits for all words in the record. This is conservative, but the
116 size_words != 1 case is impossible in regular java code. */
117 for (i
= 0; i
< size_words
; ++i
)
118 set_bit (low
, high
, ubit
- count
- i
- 1);
120 if (count
>= ubit
- 2)
121 *pointer_after_end
= 1;
123 /* If we saw a non-reference field earlier, then we can't
124 use the count representation. We keep track of that in
129 else if (*all_bits_set
> 0)
132 *last_view_index
= offset
;
136 /* Return the marking bitmap for the class TYPE. For now this is a
137 single word describing the type. */
139 get_boehm_type_descriptor (tree type
)
141 unsigned int count
, log2_size
, ubit
;
143 int all_bits_set
= 1;
144 int last_set_index
= 0;
145 HOST_WIDE_INT last_view_index
= -1;
146 int pointer_after_end
= 0;
147 unsigned HOST_WIDE_INT low
= 0, high
= 0;
148 tree field
, value
, value_type
;
150 /* If the GC wasn't requested, just use a null pointer. */
151 if (! flag_use_boehm_gc
)
152 return null_pointer_node
;
154 value_type
= java_type_for_mode (ptr_mode
, 1);
155 /* If we have a type of unknown size, use a proc. */
156 if (int_size_in_bytes (type
) == -1)
157 goto procedure_object_descriptor
;
159 bit
= POINTER_SIZE
/ BITS_PER_UNIT
;
160 /* The size of this node has to be known. And, we only support 32
161 and 64 bit targets, so we need to know that the log2 is one of
163 log2_size
= exact_log2 (bit
);
164 if (bit
== -1 || (log2_size
!= 2 && log2_size
!= 3))
166 /* This means the GC isn't supported. We should probably
167 abort or give an error. Instead, for now, we just silently
169 return null_pointer_node
;
171 bit
*= BITS_PER_UNIT
;
173 /* Warning avoidance. */
174 ubit
= (unsigned int) bit
;
176 if (type
== class_type_node
)
177 goto procedure_object_descriptor
;
179 field
= TYPE_FIELDS (type
);
180 mark_reference_fields (field
, &low
, &high
, ubit
,
181 &pointer_after_end
, &all_bits_set
,
182 &last_set_index
, &last_view_index
);
184 /* If the object is all pointers, or if the part with pointers fits
185 in our bitmap, then we are ok. Otherwise we have to allocate it
187 if (all_bits_set
!= -1 || (pointer_after_end
&& flag_reduced_reflection
))
189 /* In this case the initial part of the object is all reference
190 fields, and the end of the object is all non-reference
191 fields. We represent the mark as a count of the fields,
192 shifted. In the GC the computation looks something like
194 value = DS_LENGTH | WORDS_TO_BYTES (last_set_index + 1);
196 WORDS_TO_BYTES shifts by log2(bytes-per-pointer).
198 In the case of flag_reduced_reflection and the bitmap would
199 overflow, we tell the gc that the object is all pointers so
200 that we don't have to emit reflection data for run time
206 while (last_set_index
)
208 if ((last_set_index
& 1))
209 set_bit (&low
, &high
, log2_size
+ count
);
210 last_set_index
>>= 1;
213 value
= build_int_cst_wide (value_type
, low
, high
);
215 else if (! pointer_after_end
)
217 /* Bottom two bits for bitmap mark type are 01. */
218 set_bit (&low
, &high
, 0);
219 value
= build_int_cst_wide (value_type
, low
, high
);
223 /* Compute a procedure-based object descriptor. We know that our
224 `kind' is 0, and `env' is likewise 0, so we have a simple
225 computation. From the GC sources:
226 (((((env) << LOG_MAX_MARK_PROCS) | (proc_index)) << DS_TAG_BITS) \
228 Here DS_PROC == 2. */
229 procedure_object_descriptor
:
230 value
= build_int_cst (value_type
, 2);