boehm-gc/obj_map.c

   1 /*
   2  * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
   3  * Copyright (c) 1991, 1992 by Xerox Corporation.  All rights reserved.
   4  *
   5  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   6  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   7  *
   8  * Permission is hereby granted to use or copy this program
   9  * for any purpose,  provided the above notices are retained on all copies.
  10  * Permission to modify the code and to distribute modified code is granted,
  11  * provided the above notices are retained, and a notice that the code was
  12  * modified is included with the above copyright notice.
  13  */
  14 /* Boehm, October 9, 1995 1:09 pm PDT */
  15
  16 /* Routines for maintaining maps describing heap block
  17  * layouts for various object sizes.  Allows fast pointer validity checks
  18  * and fast location of object start locations on machines (such as SPARC)
  19  * with slow division.
  20  */
  21
  22 # include "gc_priv.h"
  23
  24 char * GC_invalid_map = 0;
  25
  26 /* Invalidate the object map associated with a block.   Free blocks     */
  27 /* are identified by invalid maps.                                      */
  28 void GC_invalidate_map(hhdr)
  29 hdr *hhdr;
  30 {
  31     register int displ;
  32
  33     if (GC_invalid_map == 0) {
  34         GC_invalid_map = GC_scratch_alloc(MAP_SIZE);
  35         if (GC_invalid_map == 0) {
  36             GC_err_printf0(
  37                 "Cant initialize GC_invalid_map: insufficient memory\n");
  38             EXIT();
  39         }
  40         for (displ = 0; displ < HBLKSIZE; displ++) {
  41             MAP_ENTRY(GC_invalid_map, displ) = OBJ_INVALID;
  42         }
  43     }
  44     hhdr -> hb_map = GC_invalid_map;
  45 }
  46
  47 /* Consider pointers that are offset bytes displaced from the beginning */
  48 /* of an object to be valid.                                            */
  49
  50 # if defined(__STDC__) || defined(__cplusplus)
  51     void GC_register_displacement(GC_word offset)
  52 # else
  53     void GC_register_displacement(offset)
  54     GC_word offset;
  55 # endif
  56 {
  57 # ifndef ALL_INTERIOR_POINTERS
  58     DCL_LOCK_STATE;
  59
  60     DISABLE_SIGNALS();
  61     LOCK();
  62     GC_register_displacement_inner(offset);
  63     UNLOCK();
  64     ENABLE_SIGNALS();
  65 # endif
  66 }
  67
  68 void GC_register_displacement_inner(offset)
  69 word offset;
  70 {
  71 # ifndef ALL_INTERIOR_POINTERS
  72     register unsigned i;
  73
  74     if (offset > MAX_OFFSET) {
  75         ABORT("Bad argument to GC_register_displacement");
  76     }
  77     if (!GC_valid_offsets[offset]) {
  78       GC_valid_offsets[offset] = TRUE;
  79       GC_modws_valid_offsets[offset % sizeof(word)] = TRUE;
  80       for (i = 0; i <= MAXOBJSZ; i++) {
  81           if (GC_obj_map[i] != 0) {
  82              if (i == 0) {
  83                GC_obj_map[i][offset + HDR_BYTES] = (char)BYTES_TO_WORDS(offset);
  84              } else {
  85                register unsigned j;
  86                register unsigned lb = WORDS_TO_BYTES(i);
  87
  88                if (offset < lb) {
  89                  for (j = offset + HDR_BYTES; j < HBLKSIZE; j += lb) {
  90                    GC_obj_map[i][j] = (char)BYTES_TO_WORDS(offset);
  91                  }
  92                }
  93              }
  94           }
  95       }
  96     }
  97 # endif
  98 }
  99
 100
 101 /* Add a heap block map for objects of size sz to obj_map.      */
 102 /* Return FALSE on failure.                                     */
 103 GC_bool GC_add_map_entry(sz)
 104 word sz;
 105 {
 106     register unsigned obj_start;
 107     register unsigned displ;
 108     register char * new_map;
 109
 110     if (sz > MAXOBJSZ) sz = 0;
 111     if (GC_obj_map[sz] != 0) {
 112         return(TRUE);
 113     }
 114     new_map = GC_scratch_alloc(MAP_SIZE);
 115     if (new_map == 0) return(FALSE);
 116 #   ifdef PRINTSTATS
 117         GC_printf1("Adding block map for size %lu\n", (unsigned long)sz);
 118 #   endif
 119     for (displ = 0; displ < HBLKSIZE; displ++) {
 120         MAP_ENTRY(new_map,displ) = OBJ_INVALID;
 121     }
 122     if (sz == 0) {
 123         for(displ = 0; displ <= MAX_OFFSET; displ++) {
 124             if (OFFSET_VALID(displ)) {
 125                 MAP_ENTRY(new_map,displ+HDR_BYTES) = BYTES_TO_WORDS(displ);
 126             }
 127         }
 128     } else {
 129         for (obj_start = HDR_BYTES;
 130              obj_start + WORDS_TO_BYTES(sz) <= HBLKSIZE;
 131              obj_start += WORDS_TO_BYTES(sz)) {
 132              for (displ = 0; displ < WORDS_TO_BYTES(sz); displ++) {
 133                  if (OFFSET_VALID(displ)) {
 134                      MAP_ENTRY(new_map, obj_start + displ) =
 135                                                 BYTES_TO_WORDS(displ);
 136                  }
 137              }
 138         }
 139     }
 140     GC_obj_map[sz] = new_map;
 141     return(TRUE);
 142 }