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 /* A client supplied mark procedure.  Returns new mark stack pointer.   */
  24 /* Primary effect should be to push new entries on the mark stack.      */
  25 /* Mark stack pointer values are passed and returned explicitly.        */
  26 /* Global variables decribing mark stack are not necessarily valid.     */
  27 /* (This usually saves a few cycles by keeping things in registers.)    */
  28 /* Assumed to scan about PROC_BYTES on average.  If it needs to do      */
  29 /* much more work than that, it should do it in smaller pieces by       */
  30 /* pushing itself back on the mark stack.                               */
  31 /* Note that it should always do some work (defined as marking some     */
  32 /* objects) before pushing more than one entry on the mark stack.       */
  33 /* This is required to ensure termination in the event of mark stack    */
  34 /* overflows.                                                           */
  35 /* This procedure is always called with at least one empty entry on the */
  36 /* mark stack.                                                          */
  37 /* Currently we require that mark procedures look for pointers in a     */
  38 /* subset of the places the conservative marker would.  It must be safe */
  39 /* to invoke the normal mark procedure instead.                         */
  40 # define PROC_BYTES 100
  41 /* The real declarations of the following are in gc_priv.h, so that     */
  42 /* we can avoid scanning the following table.                           */
  43 /*
  44 typedef struct ms_entry * (*mark_proc)(   word * addr, mark_stack_ptr,
  45                                           mark_stack_limit, env   );
  46
  47 # define LOG_MAX_MARK_PROCS 6
  48 # define MAX_MARK_PROCS (1 << LOG_MAX_MARK_PROCS)
  49 extern mark_proc GC_mark_procs[MAX_MARK_PROCS];
  50 */
  51
  52 extern word GC_n_mark_procs;
  53
  54 /* Object descriptors on mark stack or in objects.  Low order two       */
  55 /* bits are tags distinguishing among the following 4 possibilities     */
  56 /* for the high order 30 bits.                                          */
  57 #define DS_TAG_BITS 2
  58 #define DS_TAGS   ((1 << DS_TAG_BITS) - 1)
  59 #define DS_LENGTH 0     /* The entire word is a length in bytes that    */
  60                         /* must be a multiple of 4.                     */
  61 #define DS_BITMAP 1     /* 30 bits are a bitmap describing pointer      */
  62                         /* fields.  The msb is 1 iff the first word     */
  63                         /* is a pointer.                                */
  64                         /* (This unconventional ordering sometimes      */
  65                         /* makes the marker slightly faster.)           */
  66                         /* Zeroes indicate definite nonpointers.  Ones  */
  67                         /* indicate possible pointers.                  */
  68                         /* Only usable if pointers are word aligned.    */
  69 #   define BITMAP_BITS (WORDSZ - DS_TAG_BITS)
  70 #define DS_PROC   2
  71                         /* The objects referenced by this object can be */
  72                         /* pushed on the mark stack by invoking         */
  73                         /* PROC(descr).  ENV(descr) is passed as the    */
  74                         /* last argument.                               */
  75 #   define PROC(descr) \
  76                 (GC_mark_procs[((descr) >> DS_TAG_BITS) & (MAX_MARK_PROCS-1)])
  77 #   define ENV(descr) \
  78                 ((descr) >> (DS_TAG_BITS + LOG_MAX_MARK_PROCS))
  79 #   define MAX_ENV \
  80               (((word)1 << (WORDSZ - DS_TAG_BITS - LOG_MAX_MARK_PROCS)) - 1)
  81 #   define MAKE_PROC(proc_index, env) \
  82             (((((env) << LOG_MAX_MARK_PROCS) | (proc_index)) << DS_TAG_BITS) \
  83             | DS_PROC)
  84 #define DS_PER_OBJECT 3 /* The real descriptor is at the                */
  85                         /* byte displacement from the beginning of the  */
  86                         /* object given by descr & ~DS_TAGS             */
  87
  88 typedef struct ms_entry {
  89     word * mse_start;   /* First word of object */
  90     word mse_descr;     /* Descriptor; low order two bits are tags,     */
  91                         /* identifying the upper 30 bits as one of the  */
  92                         /* following:                                   */
  93 } mse;
  94
  95 extern word GC_mark_stack_size;
  96
  97 extern mse * GC_mark_stack_top;
  98
  99 extern mse * GC_mark_stack;
 100
 101 word GC_find_start();
 102
 103 mse * GC_signal_mark_stack_overflow();
 104
 105 # ifdef GATHERSTATS
 106 #   define ADD_TO_ATOMIC(sz) GC_atomic_in_use += (sz)
 107 #   define ADD_TO_COMPOSITE(sz) GC_composite_in_use += (sz)
 108 # else
 109 #   define ADD_TO_ATOMIC(sz)
 110 #   define ADD_TO_COMPOSITE(sz)
 111 # endif
 112
 113 /* Push the object obj with corresponding heap block header hhdr onto   */
 114 /* the mark stack.                                                      */
 115 # define PUSH_OBJ(obj, hhdr, mark_stack_top, mark_stack_limit) \
 116 { \
 117     register word _descr = (hhdr) -> hb_descr; \
 118         \
 119     if (_descr == 0) { \
 120         ADD_TO_ATOMIC((hhdr) -> hb_sz); \
 121     } else { \
 122         ADD_TO_COMPOSITE((hhdr) -> hb_sz); \
 123         mark_stack_top++; \
 124         if (mark_stack_top >= mark_stack_limit) { \
 125           mark_stack_top = GC_signal_mark_stack_overflow(mark_stack_top); \
 126         } \
 127         mark_stack_top -> mse_start = (obj); \
 128         mark_stack_top -> mse_descr = _descr; \
 129     } \
 130 }
 131
 132 #ifdef PRINT_BLACK_LIST
 133 #   define GC_FIND_START(current, hhdr, source) \
 134         GC_find_start(current, hhdr, source)
 135 #else
 136 #   define GC_FIND_START(current, hhdr, source) \
 137         GC_find_start(current, hhdr)
 138 #endif
 139
 140 /* Push the contents of current onto the mark stack if it is a valid    */
 141 /* ptr to a currently unmarked object.  Mark it.                        */
 142 /* If we assumed a standard-conforming compiler, we could probably      */
 143 /* generate the exit_label transparently.                               */
 144 # define PUSH_CONTENTS(current, mark_stack_top, mark_stack_limit, \
 145                        source, exit_label) \
 146 { \
 147     register int displ;  /* Displacement in block; first bytes, then words */ \
 148     register hdr * hhdr; \
 149     register map_entry_type map_entry; \
 150     \
 151     GET_HDR(current,hhdr); \
 152     if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) { \
 153          current = GC_FIND_START(current, hhdr, (word)source); \
 154          if (current == 0) goto exit_label; \
 155          hhdr = HDR(current); \
 156     } \
 157     displ = HBLKDISPL(current); \
 158     map_entry = MAP_ENTRY((hhdr -> hb_map), displ); \
 159     if (map_entry == OBJ_INVALID) { \
 160         GC_ADD_TO_BLACK_LIST_NORMAL(current, source); goto exit_label; \
 161     } \
 162     displ = BYTES_TO_WORDS(displ); \
 163     displ -= map_entry; \
 164         \
 165     { \
 166         register word * mark_word_addr = hhdr -> hb_marks + divWORDSZ(displ); \
 167         register word mark_word = *mark_word_addr; \
 168         register word mark_bit = (word)1 << modWORDSZ(displ); \
 169           \
 170         if (mark_word & mark_bit) { \
 171               /* Mark bit is already set */ \
 172               goto exit_label; \
 173         } \
 174         GC_STORE_BACK_PTR((ptr_t)source, (ptr_t)HBLKPTR(current) \
 175                                       + WORDS_TO_BYTES(displ)); \
 176         *mark_word_addr = mark_word | mark_bit; \
 177     } \
 178     PUSH_OBJ(((word *)(HBLKPTR(current)) + displ), hhdr, \
 179              mark_stack_top, mark_stack_limit) \
 180   exit_label: ; \
 181 }
 182
 183 #ifdef PRINT_BLACK_LIST
 184 #   define PUSH_ONE_CHECKED(p, ip, source) \
 185         GC_push_one_checked(p, ip, (ptr_t)(source))
 186 #else
 187 #   define PUSH_ONE_CHECKED(p, ip, source) \
 188         GC_push_one_checked(p, ip)
 189 #endif
 190
 191 /*
 192  * Push a single value onto mark stack. Mark from the object pointed to by p.
 193  * P is considered valid even if it is an interior pointer.
 194  * Previously marked objects are not pushed.  Hence we make progress even
 195  * if the mark stack overflows.
 196  */
 197 # define GC_PUSH_ONE_STACK(p, source) \
 198     if ((ptr_t)(p) >= GC_least_plausible_heap_addr      \
 199          && (ptr_t)(p) < GC_greatest_plausible_heap_addr) {     \
 200          PUSH_ONE_CHECKED(p, TRUE, source);     \
 201     }
 202
 203 /*
 204  * As above, but interior pointer recognition as for
 205  * normal for heap pointers.
 206  */
 207 # ifdef ALL_INTERIOR_POINTERS
 208 #   define AIP TRUE
 209 # else
 210 #   define AIP FALSE
 211 # endif
 212 # define GC_PUSH_ONE_HEAP(p,source) \
 213     if ((ptr_t)(p) >= GC_least_plausible_heap_addr      \
 214          && (ptr_t)(p) < GC_greatest_plausible_heap_addr) {     \
 215          PUSH_ONE_CHECKED(p,AIP,source);        \
 216     }
 217
 218 /*
 219  * Mark from one finalizable object using the specified
 220  * mark proc. May not mark the object pointed to by
 221  * real_ptr. That is the job of the caller, if appropriate
 222  */
 223 # define GC_MARK_FO(real_ptr, mark_proc) \
 224 { \
 225     (*(mark_proc))(real_ptr); \
 226     while (!GC_mark_stack_empty()) GC_mark_from_mark_stack(); \
 227     if (GC_mark_state != MS_NONE) { \
 228         GC_set_mark_bit(real_ptr); \
 229         while (!GC_mark_some((ptr_t)0)); \
 230     } \
 231 }
 232
 233 extern GC_bool GC_mark_stack_too_small;
 234                                 /* We need a larger mark stack.  May be */
 235                                 /* set by client supplied mark routines.*/
 236
 237 typedef int mark_state_t;       /* Current state of marking, as follows:*/
 238                                 /* Used to remember where we are during */
 239                                 /* concurrent marking.                  */
 240
 241                                 /* We say something is dirty if it was  */
 242                                 /* written since the last time we       */
 243                                 /* retrieved dirty bits.  We say it's   */
 244                                 /* grungy if it was marked dirty in the */
 245                                 /* last set of bits we retrieved.       */
 246
 247                                 /* Invariant I: all roots and marked    */
 248                                 /* objects p are either dirty, or point */
 249                                 /* to objects q that are either marked  */
 250                                 /* or a pointer to q appears in a range */
 251                                 /* on the mark stack.                   */
 252
 253 # define MS_NONE 0              /* No marking in progress. I holds.     */
 254                                 /* Mark stack is empty.                 */
 255
 256 # define MS_PUSH_RESCUERS 1     /* Rescuing objects are currently       */
 257                                 /* being pushed.  I holds, except       */
 258                                 /* that grungy roots may point to       */
 259                                 /* unmarked objects, as may marked      */
 260                                 /* grungy objects above scan_ptr.       */
 261
 262 # define MS_PUSH_UNCOLLECTABLE 2
 263                                 /* I holds, except that marked          */
 264                                 /* uncollectable objects above scan_ptr */
 265                                 /* may point to unmarked objects.       */
 266                                 /* Roots may point to unmarked objects  */
 267
 268 # define MS_ROOTS_PUSHED 3      /* I holds, mark stack may be nonempty  */
 269
 270 # define MS_PARTIALLY_INVALID 4 /* I may not hold, e.g. because of M.S. */
 271                                 /* overflow.  However marked heap       */
 272                                 /* objects below scan_ptr point to      */
 273                                 /* marked or stacked objects.           */
 274
 275 # define MS_INVALID 5           /* I may not hold.                      */
 276
 277 extern mark_state_t GC_mark_state;
 278
 279 #endif  /* GC_MARK_H */
 280