runtime/gc/object.c

   1 /* Copyright (C) 2012,2016 Matthew Fluet.
   2  * Copyright (C) 1999-2006 Henry Cejtin, Matthew Fluet, Suresh
   3  *    Jagannathan, and Stephen Weeks.
   4  * Copyright (C) 1997-2000 NEC Research Institute.
   5  *
   6  * MLton is released under a BSD-style license.
   7  * See the file MLton-LICENSE for details.
   8  */
   9
  10 const char* objectTypeTagToString (GC_objectTypeTag tag) {
  11   switch (tag) {
  12   case ARRAY_TAG:
  13     return "ARRAY";
  14   case NORMAL_TAG:
  15     return "NORMAL";
  16   case STACK_TAG:
  17     return "STACK";
  18   case WEAK_TAG:
  19     return "WEAK";
  20   default:
  21     die ("bad GC_objectTypeTag %u", tag);
  22   }
  23 }
  24
  25 /* getHeaderp (p)
  26  *
  27  * Returns a pointer to the header for the object pointed to by p.
  28  */
  29 GC_header* getHeaderp (pointer p) {
  30   return (GC_header*)(p
  31                       - GC_HEADER_SIZE);
  32 }
  33
  34 /* getHeader (p)
  35  *
  36  * Returns the header for the object pointed to by p.
  37  */
  38 GC_header getHeader (pointer p) {
  39   return *(getHeaderp(p));
  40 }
  41
  42 /*
  43  * Build the header for an object, given the index to its type info.
  44  */
  45 GC_header buildHeaderFromTypeIndex (uint32_t t) {
  46   assert (t < TWOPOWER (TYPE_INDEX_BITS));
  47   return 1 | (t << 1);
  48 }
  49
  50 void splitHeader(GC_state s, GC_header header,
  51                  GC_objectTypeTag *tagRet, bool *hasIdentityRet,
  52                  uint16_t *bytesNonObjptrsRet, uint16_t *numObjptrsRet) {
  53   unsigned int objectTypeIndex;
  54   GC_objectType objectType;
  55   GC_objectTypeTag tag;
  56   bool hasIdentity;
  57   uint16_t bytesNonObjptrs, numObjptrs;
  58
  59   assert (1 == (header & GC_VALID_HEADER_MASK));
  60   objectTypeIndex = (header & TYPE_INDEX_MASK) >> TYPE_INDEX_SHIFT;
  61   assert (objectTypeIndex < s->objectTypesLength);
  62   objectType = &(s->objectTypes[objectTypeIndex]);
  63   tag = objectType->tag;
  64   hasIdentity = objectType->hasIdentity;
  65   bytesNonObjptrs = objectType->bytesNonObjptrs;
  66   numObjptrs = objectType->numObjptrs;
  67
  68   if (DEBUG_DETAILED)
  69     fprintf (stderr,
  70              "splitHeader ("FMTHDR")"
  71              "  objectTypeIndex = %u"
  72              "  tag = %s"
  73              "  hasIdentity = %s"
  74              "  bytesNonObjptrs = %"PRIu16
  75              "  numObjptrs = %"PRIu16"\n",
  76              header,
  77              objectTypeIndex,
  78              objectTypeTagToString(tag),
  79              boolToString(hasIdentity),
  80              bytesNonObjptrs, numObjptrs);
  81
  82   if (tagRet != NULL)
  83     *tagRet = tag;
  84   if (hasIdentityRet != NULL)
  85     *hasIdentityRet = hasIdentity;
  86   if (bytesNonObjptrsRet != NULL)
  87     *bytesNonObjptrsRet = bytesNonObjptrs;
  88   if (numObjptrsRet != NULL)
  89     *numObjptrsRet = numObjptrs;
  90 }
  91
  92 /* advanceToObjectData (s, p)
  93  *
  94  * If p points at the beginning of an object, then advanceToObjectData
  95  * returns a pointer to the start of the object data.
  96  */
  97 pointer advanceToObjectData (ARG_USED_FOR_ASSERT GC_state s, pointer p) {
  98   GC_header header;
  99   pointer res;
 100
 101   assert (isFrontierAligned (s, p));
 102   header = *(GC_header*)p;
 103   if (0 == header)
 104     /* Looking at the counter word in an array. */
 105     res = p + GC_ARRAY_METADATA_SIZE;
 106   else
 107     /* Looking at a header word. */
 108     res = p + GC_NORMAL_METADATA_SIZE;
 109   assert (isAligned ((uintptr_t)res, s->alignment));
 110   if (DEBUG_DETAILED)
 111     fprintf (stderr, FMTPTR" = advanceToObjectData ("FMTPTR")\n",
 112              (uintptr_t)res, (uintptr_t)p);
 113   return res;
 114 }