boehm-gc/gc_mark.h

   1 /*
   2  * Copyright (c) 1991-1994, 2000 by Xerox Corporation.  All rights reserved.
   3  *
   4  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   5  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   6  *
   7  * Permission is hereby granted to use or copy this program
   8  * for any purpose,  provided the above notices are retained on all copies.
   9  * Permission to modify the code and to distribute modified code is granted,
  10  * provided the above notices are retained, and a notice that the code was
  11  * modified is included with the above copyright notice.
  12  *
  13  */
  14 /* Boehm, November 7, 1994 4:56 pm PST */
  15
  16 /*
  17  * Declarations of mark stack.  Needed by marker and client supplied mark
  18  * routines.  To be included after gc_priv.h.
  19  */
  20 #ifndef GC_MARK_H
  21 # define GC_MARK_H
  22
  23 # ifdef KEEP_BACK_PTRS
  24 #   include "dbg_mlc.h"
  25 # endif
  26
  27 /* A client supplied mark procedure.  Returns new mark stack pointer.   */
  28 /* Primary effect should be to push new entries on the mark stack.      */
  29 /* Mark stack pointer values are passed and returned explicitly.        */
  30 /* Global variables decribing mark stack are not necessarily valid.     */
  31 /* (This usually saves a few cycles by keeping things in registers.)    */
  32 /* Assumed to scan about PROC_BYTES on average.  If it needs to do      */
  33 /* much more work than that, it should do it in smaller pieces by       */
  34 /* pushing itself back on the mark stack.                               */
  35 /* Note that it should always do some work (defined as marking some     */
  36 /* objects) before pushing more than one entry on the mark stack.       */
  37 /* This is required to ensure termination in the event of mark stack    */
  38 /* overflows.                                                           */
  39 /* This procedure is always called with at least one empty entry on the */
  40 /* mark stack.                                                          */
  41 /* Currently we require that mark procedures look for pointers in a     */
  42 /* subset of the places the conservative marker would.  It must be safe */
  43 /* to invoke the normal mark procedure instead.                         */
  44 # define PROC_BYTES 100
  45 /* The real declarations of the following are in gc_priv.h, so that     */
  46 /* we can avoid scanning the following table.                           */
  47 /*
  48 typedef struct ms_entry * (*mark_proc)(   word * addr,
  49                                           struct ms_entry *mark_stack_ptr,
  50                                           struct ms_entry *mark_stack_limit,
  51                                           word env   );
  52
  53 # define LOG_MAX_MARK_PROCS 6
  54 # define MAX_MARK_PROCS (1 << LOG_MAX_MARK_PROCS)
  55 extern mark_proc GC_mark_procs[MAX_MARK_PROCS];
  56 */
  57
  58 extern word GC_n_mark_procs;
  59
  60 /* In a few cases it's necessary to assign statically known indices to  */
  61 /* certain mark procs.  Thus we reserve a few for well known clients.   */
  62 /* (This is necessary if mark descriptors are compiler generated.)      */
  63 #define GC_RESERVED_MARK_PROCS 8
  64 #   define GCJ_RESERVED_MARK_PROC_INDEX 0
  65
  66 /* Object descriptors on mark stack or in objects.  Low order two       */
  67 /* bits are tags distinguishing among the following 4 possibilities     */
  68 /* for the high order 30 bits.                                          */
  69 #define DS_TAG_BITS 2
  70 #define DS_TAGS   ((1 << DS_TAG_BITS) - 1)
  71 #define DS_LENGTH 0     /* The entire word is a length in bytes that    */
  72                         /* must be a multiple of 4.                     */
  73 #define DS_BITMAP 1     /* 30 bits are a bitmap describing pointer      */
  74                         /* fields.  The msb is 1 iff the first word     */
  75                         /* is a pointer.                                */
  76                         /* (This unconventional ordering sometimes      */
  77                         /* makes the marker slightly faster.)           */
  78                         /* Zeroes indicate definite nonpointers.  Ones  */
  79                         /* indicate possible pointers.                  */
  80                         /* Only usable if pointers are word aligned.    */
  81 #   define BITMAP_BITS (WORDSZ - DS_TAG_BITS)
  82 #define DS_PROC   2
  83                         /* The objects referenced by this object can be */
  84                         /* pushed on the mark stack by invoking         */
  85                         /* PROC(descr).  ENV(descr) is passed as the    */
  86                         /* last argument.                               */
  87 #   define PROC(descr) \
  88                 (GC_mark_procs[((descr) >> DS_TAG_BITS) & (MAX_MARK_PROCS-1)])
  89 #   define ENV(descr) \
  90                 ((descr) >> (DS_TAG_BITS + LOG_MAX_MARK_PROCS))
  91 #   define MAX_ENV \
  92               (((word)1 << (WORDSZ - DS_TAG_BITS - LOG_MAX_MARK_PROCS)) - 1)
  93 #   define MAKE_PROC(proc_index, env) \
  94             (((((env) << LOG_MAX_MARK_PROCS) | (proc_index)) << DS_TAG_BITS) \
  95             | DS_PROC)
  96 #define DS_PER_OBJECT 3 /* The real descriptor is at the                */
  97                         /* byte displacement from the beginning of the  */
  98                         /* object given by descr & ~DS_TAGS             */
  99                         /* If the descriptor is negative, the real      */
 100                         /* descriptor is at (*<object_start>) -         */
 101                         /* (descr & ~DS_TAGS) - INDIR_PER_OBJ_BIAS      */
 102                         /* The latter alternative can be used if each   */
 103                         /* object contains a type descriptor in the     */
 104                         /* first word.                                  */
 105 #define INDIR_PER_OBJ_BIAS 0x10
 106
 107 typedef struct ms_entry {
 108     word * mse_start;   /* First word of object */
 109     word mse_descr;     /* Descriptor; low order two bits are tags,     */
 110                         /* identifying the upper 30 bits as one of the  */
 111                         /* following:                                   */
 112 } mse;
 113
 114 extern word GC_mark_stack_size;
 115
 116 extern mse * GC_mark_stack_top;
 117
 118 extern mse * GC_mark_stack;
 119
 120 #ifdef PRINT_BLACK_LIST
 121 ptr_t GC_find_start(ptr_t, hdr*, word);
 122 #else
 123 ptr_t GC_find_start(ptr_t, hdr*);
 124 #endif
 125
 126 mse * GC_signal_mark_stack_overflow(mse *);
 127
 128 # ifdef GATHERSTATS
 129 #   define ADD_TO_ATOMIC(sz) GC_atomic_in_use += (sz)
 130 #   define ADD_TO_COMPOSITE(sz) GC_composite_in_use += (sz)
 131 # else
 132 #   define ADD_TO_ATOMIC(sz)
 133 #   define ADD_TO_COMPOSITE(sz)
 134 # endif
 135
 136 /* Push the object obj with corresponding heap block header hhdr onto   */
 137 /* the mark stack.                                                      */
 138 # define PUSH_OBJ(obj, hhdr, mark_stack_top, mark_stack_limit) \
 139 { \
 140     register word _descr = (hhdr) -> hb_descr; \
 141         \
 142     if (_descr == 0) { \
 143         ADD_TO_ATOMIC((hhdr) -> hb_sz); \
 144     } else { \
 145         ADD_TO_COMPOSITE((hhdr) -> hb_sz); \
 146         mark_stack_top++; \
 147         if (mark_stack_top >= mark_stack_limit) { \
 148           mark_stack_top = GC_signal_mark_stack_overflow(mark_stack_top); \
 149         } \
 150         mark_stack_top -> mse_start = (obj); \
 151         mark_stack_top -> mse_descr = _descr; \
 152     } \
 153 }
 154
 155 #ifdef PRINT_BLACK_LIST
 156 #   define GC_FIND_START(current, hhdr, source) \
 157         GC_find_start(current, hhdr, source)
 158 #else
 159 #   define GC_FIND_START(current, hhdr, source) \
 160         GC_find_start(current, hhdr)
 161 #endif
 162
 163 /* Push the contents of current onto the mark stack if it is a valid    */
 164 /* ptr to a currently unmarked object.  Mark it.                        */
 165 /* If we assumed a standard-conforming compiler, we could probably      */
 166 /* generate the exit_label transparently.                               */
 167 # define PUSH_CONTENTS(current, mark_stack_top, mark_stack_limit, \
 168                        source, exit_label) \
 169 { \
 170     hdr * my_hhdr; \
 171     ptr_t my_current = current; \
 172  \
 173     GET_HDR(my_current, my_hhdr); \
 174     if (IS_FORWARDING_ADDR_OR_NIL(my_hhdr)) { \
 175          my_current = GC_FIND_START(my_current, my_hhdr, (word)source); \
 176          if (my_current == 0) goto exit_label; \
 177          my_hhdr = GC_find_header(my_current); \
 178     } \
 179     PUSH_CONTENTS_HDR(my_current, mark_stack_top, mark_stack_limit, \
 180                   source, exit_label, my_hhdr); \
 181 exit_label: ; \
 182 }
 183
 184 /* As above, but use header cache for header lookup.    */
 185 # define HC_PUSH_CONTENTS(current, mark_stack_top, mark_stack_limit, \
 186                        source, exit_label) \
 187 { \
 188     hdr * my_hhdr; \
 189     ptr_t my_current = current; \
 190  \
 191     HC_GET_HDR(my_current, my_hhdr, source); \
 192     PUSH_CONTENTS_HDR(my_current, mark_stack_top, mark_stack_limit, \
 193                   source, exit_label, my_hhdr); \
 194 exit_label: ; \
 195 }
 196
 197 /* As above, but deal with two pointers in interleaved fashion. */
 198 # define HC_PUSH_CONTENTS2(current1, current2, mark_stack_top, \
 199                            mark_stack_limit, \
 200                            source1, source2, exit_label1, exit_label2) \
 201 { \
 202     hdr * hhdr1; \
 203     ptr_t my_current1 = current1; \
 204     hdr * hhdr2; \
 205     ptr_t my_current2 = current2; \
 206  \
 207     HC_GET_HDR2(my_current1, hhdr1, source1, my_current2, hhdr2, source2); \
 208     PUSH_CONTENTS_HDR(my_current1, mark_stack_top, mark_stack_limit, \
 209                   source1, exit_label1, hhdr1); \
 210 exit_label1: ; \
 211     if (0 != hhdr2) { \
 212       PUSH_CONTENTS_HDR(my_current2, mark_stack_top, mark_stack_limit, \
 213                   source2, exit_label2, hhdr2); \
 214     } \
 215 exit_label2: ; \
 216 }
 217
 218 # define PUSH_CONTENTS_HDR(current, mark_stack_top, mark_stack_limit, \
 219                            source, exit_label, hhdr) \
 220 { \
 221     int displ;  /* Displacement in block; first bytes, then words */ \
 222     map_entry_type map_entry; \
 223     \
 224     displ = HBLKDISPL(current); \
 225     map_entry = MAP_ENTRY((hhdr -> hb_map), displ); \
 226     if (map_entry == OBJ_INVALID) { \
 227         GC_ADD_TO_BLACK_LIST_NORMAL(current, source); goto exit_label; \
 228     } \
 229     displ = BYTES_TO_WORDS(displ); \
 230     displ -= map_entry; \
 231         \
 232     { \
 233         register word * mark_word_addr = hhdr -> hb_marks + divWORDSZ(displ); \
 234         register word mark_word = *mark_word_addr; \
 235         register word mark_bit = (word)1 << modWORDSZ(displ); \
 236           \
 237         if (mark_word & mark_bit) { \
 238               /* Mark bit is already set */ \
 239               goto exit_label; \
 240         } \
 241         GC_STORE_BACK_PTR((ptr_t)source, (ptr_t)HBLKPTR(current) \
 242                                       + WORDS_TO_BYTES(displ)); \
 243         *mark_word_addr = mark_word | mark_bit; \
 244     } \
 245     PUSH_OBJ(((word *)(HBLKPTR(current)) + displ), hhdr, \
 246              mark_stack_top, mark_stack_limit) \
 247 }
 248
 249 #if defined(PRINT_BLACK_LIST) || defined(KEEP_BACK_PTRS)
 250 #   define PUSH_ONE_CHECKED(p, ip, source) \
 251         GC_push_one_checked(p, ip, (ptr_t)(source))
 252 #else
 253 #   define PUSH_ONE_CHECKED(p, ip, source) \
 254         GC_push_one_checked(p, ip)
 255 #endif
 256
 257 /*
 258  * Push a single value onto mark stack. Mark from the object pointed to by p.
 259  * P is considered valid even if it is an interior pointer.
 260  * Previously marked objects are not pushed.  Hence we make progress even
 261  * if the mark stack overflows.
 262  */
 263 # define GC_PUSH_ONE_STACK(p, source) \
 264     if ((ptr_t)(p) >= GC_least_plausible_heap_addr      \
 265          && (ptr_t)(p) < GC_greatest_plausible_heap_addr) {     \
 266          PUSH_ONE_CHECKED(p, TRUE, source);     \
 267     }
 268
 269 /*
 270  * As above, but interior pointer recognition as for
 271  * normal for heap pointers.
 272  */
 273 # ifdef ALL_INTERIOR_POINTERS
 274 #   define AIP TRUE
 275 # else
 276 #   define AIP FALSE
 277 # endif
 278 # define GC_PUSH_ONE_HEAP(p,source) \
 279     if ((ptr_t)(p) >= GC_least_plausible_heap_addr      \
 280          && (ptr_t)(p) < GC_greatest_plausible_heap_addr) {     \
 281          PUSH_ONE_CHECKED(p,AIP,source);        \
 282     }
 283
 284 /*
 285  * Mark from one finalizable object using the specified
 286  * mark proc. May not mark the object pointed to by
 287  * real_ptr. That is the job of the caller, if appropriate
 288  */
 289 # define GC_MARK_FO(real_ptr, mark_proc) \
 290 { \
 291     (*(mark_proc))(real_ptr); \
 292     while (!GC_mark_stack_empty()) GC_mark_from_mark_stack(); \
 293     if (GC_mark_state != MS_NONE) { \
 294         GC_set_mark_bit(real_ptr); \
 295         while (!GC_mark_some((ptr_t)0)); \
 296     } \
 297 }
 298
 299 extern GC_bool GC_mark_stack_too_small;
 300                                 /* We need a larger mark stack.  May be */
 301                                 /* set by client supplied mark routines.*/
 302
 303 typedef int mark_state_t;       /* Current state of marking, as follows:*/
 304                                 /* Used to remember where we are during */
 305                                 /* concurrent marking.                  */
 306
 307                                 /* We say something is dirty if it was  */
 308                                 /* written since the last time we       */
 309                                 /* retrieved dirty bits.  We say it's   */
 310                                 /* grungy if it was marked dirty in the */
 311                                 /* last set of bits we retrieved.       */
 312
 313                                 /* Invariant I: all roots and marked    */
 314                                 /* objects p are either dirty, or point */
 315                                 /* to objects q that are either marked  */
 316                                 /* or a pointer to q appears in a range */
 317                                 /* on the mark stack.                   */
 318
 319 # define MS_NONE 0              /* No marking in progress. I holds.     */
 320                                 /* Mark stack is empty.                 */
 321
 322 # define MS_PUSH_RESCUERS 1     /* Rescuing objects are currently       */
 323                                 /* being pushed.  I holds, except       */
 324                                 /* that grungy roots may point to       */
 325                                 /* unmarked objects, as may marked      */
 326                                 /* grungy objects above scan_ptr.       */
 327
 328 # define MS_PUSH_UNCOLLECTABLE 2
 329                                 /* I holds, except that marked          */
 330                                 /* uncollectable objects above scan_ptr */
 331                                 /* may point to unmarked objects.       */
 332                                 /* Roots may point to unmarked objects  */
 333
 334 # define MS_ROOTS_PUSHED 3      /* I holds, mark stack may be nonempty  */
 335
 336 # define MS_PARTIALLY_INVALID 4 /* I may not hold, e.g. because of M.S. */
 337                                 /* overflow.  However marked heap       */
 338                                 /* objects below scan_ptr point to      */
 339                                 /* marked or stacked objects.           */
 340
 341 # define MS_INVALID 5           /* I may not hold.                      */
 342
 343 extern mark_state_t GC_mark_state;
 344
 345 #endif  /* GC_MARK_H */
 346