new_hblk.c

/*
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
 * Copyright (c) 2000 by Hewlett-Packard Company.  All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program
 * for any purpose, provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 */

#include "private/gc_priv.h"

/*
 * This file contains the functions:
 *      ptr_t GC_build_flXXX(h, old_fl)
 *      void GC_new_hblk(size, kind)
 */

#ifndef SMALL_CONFIG
  /* Build a free list for size 2 (words) cleared objects inside        */
  /* hblk h.  Set the last link to be ofl.  Return a pointer to the     */
  /* first free list entry.                                             */
  STATIC ptr_t GC_build_fl_clear2(struct hblk *h, ptr_t ofl)
  {
    word * p = (word *)(h -> hb_body);
    word * lim = (word *)(h + 1);

    p[0] = (word)ofl;
    p[1] = 0;
    p[2] = (word)p;
    p[3] = 0;
    p += 4;
    for (; ADDR_LT((ptr_t)p, (ptr_t)lim); p += 4) {
        p[0] = (word)(p-2);
        p[1] = 0;
        p[2] = (word)p;
        p[3] = 0;
    }
    return (ptr_t)(p-2);
  }

  /* The same for size 4 cleared objects.       */
  STATIC ptr_t GC_build_fl_clear4(struct hblk *h, ptr_t ofl)
  {
    word * p = (word *)(h -> hb_body);
    word * lim = (word *)(h + 1);

    p[0] = (word)ofl;
    p[1] = 0;
    p[2] = 0;
    p[3] = 0;
    p += 4;
    for (; ADDR_LT((ptr_t)p, (ptr_t)lim); p += 4) {
        GC_PREFETCH_FOR_WRITE((ptr_t)(p + 64));
        p[0] = (word)(p-4);
        p[1] = 0;
        CLEAR_DOUBLE(p+2);
    }
    return (ptr_t)(p-4);
  }

  /* The same for size 2 uncleared objects.     */
  STATIC ptr_t GC_build_fl2(struct hblk *h, ptr_t ofl)
  {
    word * p = (word *)(h -> hb_body);
    word * lim = (word *)(h + 1);

    p[0] = (word)ofl;
    p[2] = (word)p;
    p += 4;
    for (; ADDR_LT((ptr_t)p, (ptr_t)lim); p += 4) {
        p[0] = (word)(p-2);
        p[2] = (word)p;
    }
    return (ptr_t)(p-2);
  }

  /* The same for size 4 uncleared objects.     */
  STATIC ptr_t GC_build_fl4(struct hblk *h, ptr_t ofl)
  {
    word * p = (word *)(h -> hb_body);
    word * lim = (word *)(h + 1);

    p[0] = (word)ofl;
    p[4] = (word)p;
    p += 8;
    for (; ADDR_LT((ptr_t)p, (ptr_t)lim); p += 8) {
        GC_PREFETCH_FOR_WRITE((ptr_t)(p + 64));
        p[0] = (word)(p-4);
        p[4] = (word)p;
    }
    return (ptr_t)(p-4);
  }
#endif /* !SMALL_CONFIG */

GC_INNER ptr_t GC_build_fl(struct hblk *h, size_t lw, GC_bool clear,
                           ptr_t list)
{
  word *p, *prev;
  word *last_object;            /* points to last object in new hblk    */

  /* Do a few prefetches here, just because it's cheap.         */
  /* If we were more serious about it, these should go inside   */
  /* the loops.  But write prefetches usually don't seem to     */
  /* matter much.                                               */
    GC_PREFETCH_FOR_WRITE((ptr_t)h);
    GC_PREFETCH_FOR_WRITE((ptr_t)h + 128);
    GC_PREFETCH_FOR_WRITE((ptr_t)h + 256);
    GC_PREFETCH_FOR_WRITE((ptr_t)h + 378);
# ifndef SMALL_CONFIG
    /* Handle small objects sizes more efficiently.  For larger objects */
    /* the difference is less significant.                              */
    switch (lw) {
        case 2: if (clear) {
                    return GC_build_fl_clear2(h, list);
                } else {
                    return GC_build_fl2(h, list);
                }
        case 4: if (clear) {
                    return GC_build_fl_clear4(h, list);
                } else {
                    return GC_build_fl4(h, list);
                }
        default:
                break;
    }
# endif /* !SMALL_CONFIG */

  /* Clear the page if necessary. */
    if (clear) BZERO(h, HBLKSIZE);

  /* Add objects to free list */
    prev = (word *)(h -> hb_body);              /* One object behind p  */
    last_object = (word *)((char *)h + HBLKSIZE) - lw;
                            /* Last place for last object to start */

  /* Make a list of all objects in *h with head as last object. */
    for (p = prev + lw; ADDR_GE((ptr_t)last_object, (ptr_t)p); p += lw) {
      /* current object's link points to last object */
        obj_link(p) = (ptr_t)prev;
        prev = p;
    }
    p -= lw;    /* p now points to last object */

  /* Put p (which is now head of list of objects in *h) as first    */
  /* pointer in the appropriate free list for this size.            */
    *(ptr_t *)h = list;
    return (ptr_t)p;
}

GC_INNER void GC_new_hblk(size_t lg, int k)
{
  struct hblk *h;       /* the new heap block */
  size_t lb_adjusted = GRANULES_TO_BYTES(lg);

  GC_STATIC_ASSERT(sizeof(struct hblk) == HBLKSIZE);
  GC_ASSERT(I_HOLD_LOCK());
  /* Allocate a new heap block. */
  h = GC_allochblk(lb_adjusted, k, 0 /* flags */, 0 /* align_m1 */);
  if (EXPECT(NULL == h, FALSE)) return; /* out of memory */

  /* Mark all objects if appropriate. */
  if (IS_UNCOLLECTABLE(k)) GC_set_hdr_marks(HDR(h));

  /* Build the free list.       */
  GC_obj_kinds[k].ok_freelist[lg] =
        GC_build_fl(h, GRANULES_TO_WORDS(lg),
                    GC_debugging_started || GC_obj_kinds[k].ok_init,
                    (ptr_t)GC_obj_kinds[k].ok_freelist[lg]);
}