boehm-gc/gc_mark.h

   1 /*
   2  * Copyright (c) 1991-1994 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 ptr_t GC_find_start();
 121
 122 mse * GC_signal_mark_stack_overflow();
 123
 124 # ifdef GATHERSTATS
 125 #   define ADD_TO_ATOMIC(sz) GC_atomic_in_use += (sz)
 126 #   define ADD_TO_COMPOSITE(sz) GC_composite_in_use += (sz)
 127 # else
 128 #   define ADD_TO_ATOMIC(sz)
 129 #   define ADD_TO_COMPOSITE(sz)
 130 # endif
 131
 132 /* Push the object obj with corresponding heap block header hhdr onto   */
 133 /* the mark stack.                                                      */
 134 # define PUSH_OBJ(obj, hhdr, mark_stack_top, mark_stack_limit) \
 135 { \
 136     register word _descr = (hhdr) -> hb_descr; \
 137         \
 138     if (_descr == 0) { \
 139         ADD_TO_ATOMIC((hhdr) -> hb_sz); \
 140     } else { \
 141         ADD_TO_COMPOSITE((hhdr) -> hb_sz); \
 142         mark_stack_top++; \
 143         if (mark_stack_top >= mark_stack_limit) { \
 144           mark_stack_top = GC_signal_mark_stack_overflow(mark_stack_top); \
 145         } \
 146         mark_stack_top -> mse_start = (obj); \
 147         mark_stack_top -> mse_descr = _descr; \
 148     } \
 149 }
 150
 151 #ifdef PRINT_BLACK_LIST
 152 #   define GC_FIND_START(current, hhdr, source) \
 153         GC_find_start(current, hhdr, source)
 154 #else
 155 #   define GC_FIND_START(current, hhdr, source) \
 156         GC_find_start(current, hhdr)
 157 #endif
 158
 159 /* Push the contents of current onto the mark stack if it is a valid    */
 160 /* ptr to a currently unmarked object.  Mark it.                        */
 161 /* If we assumed a standard-conforming compiler, we could probably      */
 162 /* generate the exit_label transparently.                               */
 163 # define PUSH_CONTENTS(current, mark_stack_top, mark_stack_limit, \
 164                        source, exit_label) \
 165 { \
 166     hdr * my_hhdr; \
 167     ptr_t my_current = current; \
 168  \
 169     GET_HDR(my_current, my_hhdr); \
 170     if (IS_FORWARDING_ADDR_OR_NIL(my_hhdr)) { \
 171          my_current = GC_FIND_START(my_current, my_hhdr, (word)source); \
 172          if (my_current == 0) goto exit_label; \
 173          my_hhdr = GC_find_header(my_current); \
 174     } \
 175     PUSH_CONTENTS_HDR(my_current, mark_stack_top, mark_stack_limit, \
 176                   source, exit_label, my_hhdr); \
 177 exit_label: ; \
 178 }
 179
 180 /* As above, but use header cache for header lookup.    */
 181 # define HC_PUSH_CONTENTS(current, mark_stack_top, mark_stack_limit, \
 182                        source, exit_label) \
 183 { \
 184     hdr * my_hhdr; \
 185     ptr_t my_current = current; \
 186  \
 187     HC_GET_HDR(my_current, my_hhdr, source); \
 188     PUSH_CONTENTS_HDR(my_current, mark_stack_top, mark_stack_limit, \
 189                   source, exit_label, my_hhdr); \
 190 exit_label: ; \
 191 }
 192
 193 /* As above, but deal with two pointers in interleaved fashion. */
 194 # define HC_PUSH_CONTENTS2(current1, current2, mark_stack_top, \
 195                            mark_stack_limit, \
 196                            source1, source2, exit_label1, exit_label2) \
 197 { \
 198     hdr * hhdr1; \
 199     ptr_t my_current1 = current1; \
 200     hdr * hhdr2; \
 201     ptr_t my_current2 = current2; \
 202  \
 203     HC_GET_HDR2(my_current1, hhdr1, source1, my_current2, hhdr2, source2); \
 204     PUSH_CONTENTS_HDR(my_current1, mark_stack_top, mark_stack_limit, \
 205                   source1, exit_label1, hhdr1); \
 206 exit_label1: ; \
 207     if (0 != hhdr2) { \
 208       PUSH_CONTENTS_HDR(my_current2, mark_stack_top, mark_stack_limit, \
 209                   source2, exit_label2, hhdr2); \
 210     } \
 211 exit_label2: ; \
 212 }
 213
 214 # define PUSH_CONTENTS_HDR(current, mark_stack_top, mark_stack_limit, \
 215                            source, exit_label, hhdr) \
 216 { \
 217     int displ;  /* Displacement in block; first bytes, then words */ \
 218     map_entry_type map_entry; \
 219     \
 220     displ = HBLKDISPL(current); \
 221     map_entry = MAP_ENTRY((hhdr -> hb_map), displ); \
 222     if (map_entry == OBJ_INVALID) { \
 223         GC_ADD_TO_BLACK_LIST_NORMAL(current, source); goto exit_label; \
 224     } \
 225     displ = BYTES_TO_WORDS(displ); \
 226     displ -= map_entry; \
 227         \
 228     { \
 229         register word * mark_word_addr = hhdr -> hb_marks + divWORDSZ(displ); \
 230         register word mark_word = *mark_word_addr; \
 231         register word mark_bit = (word)1 << modWORDSZ(displ); \
 232           \
 233         if (mark_word & mark_bit) { \
 234               /* Mark bit is already set */ \
 235               goto exit_label; \
 236         } \
 237         GC_STORE_BACK_PTR((ptr_t)source, (ptr_t)HBLKPTR(current) \
 238                                       + WORDS_TO_BYTES(displ)); \
 239         *mark_word_addr = mark_word | mark_bit; \
 240     } \
 241     PUSH_OBJ(((word *)(HBLKPTR(current)) + displ), hhdr, \
 242              mark_stack_top, mark_stack_limit) \
 243 }
 244
 245 #if defined(PRINT_BLACK_LIST) || defined(KEEP_BACK_PTRS)
 246 #   define PUSH_ONE_CHECKED(p, ip, source) \
 247         GC_push_one_checked(p, ip, (ptr_t)(source))
 248 #else
 249 #   define PUSH_ONE_CHECKED(p, ip, source) \
 250         GC_push_one_checked(p, ip)
 251 #endif
 252
 253 /*
 254  * Push a single value onto mark stack. Mark from the object pointed to by p.
 255  * P is considered valid even if it is an interior pointer.
 256  * Previously marked objects are not pushed.  Hence we make progress even
 257  * if the mark stack overflows.
 258  */
 259 # define GC_PUSH_ONE_STACK(p, source) \
 260     if ((ptr_t)(p) >= GC_least_plausible_heap_addr      \
 261          && (ptr_t)(p) < GC_greatest_plausible_heap_addr) {     \
 262          PUSH_ONE_CHECKED(p, TRUE, source);     \
 263     }
 264
 265 /*
 266  * As above, but interior pointer recognition as for
 267  * normal for heap pointers.
 268  */
 269 # ifdef ALL_INTERIOR_POINTERS
 270 #   define AIP TRUE
 271 # else
 272 #   define AIP FALSE
 273 # endif
 274 # define GC_PUSH_ONE_HEAP(p,source) \
 275     if ((ptr_t)(p) >= GC_least_plausible_heap_addr      \
 276          && (ptr_t)(p) < GC_greatest_plausible_heap_addr) {     \
 277          PUSH_ONE_CHECKED(p,AIP,source);        \
 278     }
 279
 280 /*
 281  * Mark from one finalizable object using the specified
 282  * mark proc. May not mark the object pointed to by
 283  * real_ptr. That is the job of the caller, if appropriate
 284  */
 285 # define GC_MARK_FO(real_ptr, mark_proc) \
 286 { \
 287     (*(mark_proc))(real_ptr); \
 288     while (!GC_mark_stack_empty()) GC_mark_from_mark_stack(); \
 289     if (GC_mark_state != MS_NONE) { \
 290         GC_set_mark_bit(real_ptr); \
 291         while (!GC_mark_some((ptr_t)0)); \
 292     } \
 293 }
 294
 295 extern GC_bool GC_mark_stack_too_small;
 296                                 /* We need a larger mark stack.  May be */
 297                                 /* set by client supplied mark routines.*/
 298
 299 typedef int mark_state_t;       /* Current state of marking, as follows:*/
 300                                 /* Used to remember where we are during */
 301                                 /* concurrent marking.                  */
 302
 303                                 /* We say something is dirty if it was  */
 304                                 /* written since the last time we       */
 305                                 /* retrieved dirty bits.  We say it's   */
 306                                 /* grungy if it was marked dirty in the */
 307                                 /* last set of bits we retrieved.       */
 308
 309                                 /* Invariant I: all roots and marked    */
 310                                 /* objects p are either dirty, or point */
 311                                 /* to objects q that are either marked  */
 312                                 /* or a pointer to q appears in a range */
 313                                 /* on the mark stack.                   */
 314
 315 # define MS_NONE 0              /* No marking in progress. I holds.     */
 316                                 /* Mark stack is empty.                 */
 317
 318 # define MS_PUSH_RESCUERS 1     /* Rescuing objects are currently       */
 319                                 /* being pushed.  I holds, except       */
 320                                 /* that grungy roots may point to       */
 321                                 /* unmarked objects, as may marked      */
 322                                 /* grungy objects above scan_ptr.       */
 323
 324 # define MS_PUSH_UNCOLLECTABLE 2
 325                                 /* I holds, except that marked          */
 326                                 /* uncollectable objects above scan_ptr */
 327                                 /* may point to unmarked objects.       */
 328                                 /* Roots may point to unmarked objects  */
 329
 330 # define MS_ROOTS_PUSHED 3      /* I holds, mark stack may be nonempty  */
 331
 332 # define MS_PARTIALLY_INVALID 4 /* I may not hold, e.g. because of M.S. */
 333                                 /* overflow.  However marked heap       */
 334                                 /* objects below scan_ptr point to      */
 335                                 /* marked or stacked objects.           */
 336
 337 # define MS_INVALID 5           /* I may not hold.                      */
 338
 339 extern mark_state_t GC_mark_state;
 340
 341 #endif  /* GC_MARK_H */
 342