libguile/inline.h

   1 /* classes: h_files */
   2
   3 #ifndef SCM_INLINE_H
   4 #define SCM_INLINE_H
   5
   6 /* Copyright (C) 2001, 2002 Free Software Foundation, Inc.
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  21  */
  22
  23 /* This file is for inline functions.  On platforms that don't support
  24    inlining functions, they are turned into ordinary functions.  See
  25    "inline.c".
  26 */
  27
  28 #include "libguile/__scm.h"
  29
  30 #if (SCM_DEBUG_CELL_ACCESSES == 1)
  31 #include <stdio.h>
  32 #endif
  33
  34 #include "libguile/pairs.h"
  35 #include "libguile/gc.h"
  36 #include "libguile/threads.h"
  37
  38
  39 SCM_API SCM scm_cell (scm_t_bits car, scm_t_bits cdr);
  40 SCM_API SCM scm_double_cell (scm_t_bits car, scm_t_bits cbr,
  41                              scm_t_bits ccr, scm_t_bits cdr);
  42
  43
  44
  45 #if defined SCM_C_INLINE || defined SCM_INLINE_C_INCLUDING_INLINE_H
  46 /* either inlining, or being included from inline.c.  We use (and
  47    repeat) this long #if test here and below so that we don't have to
  48    introduce any extraneous symbols into the public namespace.  We
  49    only need SCM_C_INLINE to be seen publically . */
  50
  51 extern unsigned scm_newcell2_count;
  52 extern unsigned scm_newcell_count;
  53
  54 #if defined SCM_C_INLINE && ! defined SCM_INLINE_C_INCLUDING_INLINE_H
  55 /* definitely inlining */
  56 extern SCM_C_INLINE
  57 #endif
  58 SCM
  59 scm_cell (scm_t_bits car, scm_t_bits cdr)
  60 {
  61   SCM z;
  62   /* We retrieve the SCM pointer only once since the call to
  63      SCM_FREELIST_LOC will be slightly expensive when we support
  64      preemptive multithreading.  SCM_FREELIST_DOC will then retrieve
  65      the thread specific freelist.
  66
  67      Until then, SCM_FREELIST_DOC expands to (&scm_i_freelist) and the
  68      following code will compile to the same as if we had worked
  69      directly on the scm_i_freelist variable.
  70    */
  71   SCM *freelist = SCM_FREELIST_LOC (scm_i_freelist);
  72
  73   if (SCM_NULLP (*freelist))
  74     z = scm_gc_for_newcell (&scm_i_master_freelist, freelist);
  75   else
  76     {
  77       z = *freelist;
  78       *freelist = SCM_FREE_CELL_CDR (*freelist);
  79     }
  80
  81   /*
  82     We update scm_cells_allocated from this function. If we don't
  83     update this explicitly, we will have to walk a freelist somewhere
  84     later on, which seems a lot more expensive.
  85    */
  86   scm_cells_allocated += 1;
  87
  88 #if (SCM_DEBUG_CELL_ACCESSES == 1)
  89     if (scm_debug_cell_accesses_p)
  90       {
  91         if (SCM_GC_MARK_P (z))
  92           {
  93             fprintf(stderr, "scm_cell tried to allocate a marked cell.\n");
  94             abort();
  95           }
  96         else if (SCM_GC_CELL_TYPE(z) != scm_tc_free_cell)
  97           {
  98             fprintf(stderr, "cell from freelist is not a free cell.\n");
  99             abort();
 100           }
 101       }
 102
 103     /*
 104       Always set mark. Otherwise cells that are alloced before
 105       scm_debug_cell_accesses_p is toggled seem invalid.
 106     */
 107     SCM_SET_GC_MARK (z);
 108
 109     /*
 110       TODO: figure out if this use of mark bits is valid with
 111       threading. What if another thread is doing GC at this point
 112       ... ?
 113      */
 114
 115 #endif
 116
 117
 118   /* Initialize the type slot last so that the cell is ignored by the
 119      GC until it is completely initialized.  This is only relevant
 120      when the GC can actually run during this code, which it can't for
 121      cooperating threads, but it might be important when we get true
 122      preemptive threads.
 123   */
 124   SCM_GC_SET_CELL_WORD (z, 1, cdr);
 125   SCM_GC_SET_CELL_WORD (z, 0, car);
 126
 127 #if 0 /*fixme* Hmm... let's consider this later. */
 128 #if !defined(SCM_USE_COOP_THREADS) && !defined(SCM_USE_NULL_THREADS) && !defined(SCM_USE_COPT_THREADS)
 129   /* When we are using preemtive threads, we might need to make
 130      sure that the initial values for the slots are protected until
 131      the cell is completely initialized.
 132   */
 133 #error review me
 134   scm_remember_upto_here_1 (SCM_PACK (cdr));
 135 #endif
 136 #endif
 137
 138 #if (SCM_DEBUG_CELL_ACCESSES == 1)
 139   if (scm_expensive_debug_cell_accesses_p )
 140     scm_i_expensive_validation_check (z);
 141 #endif
 142
 143   return z;
 144 }
 145
 146 #if defined SCM_C_INLINE && ! defined SCM_INLINE_C_INCLUDING_INLINE_H
 147 /* definitely inlining */
 148 extern SCM_C_INLINE
 149 #endif
 150 SCM
 151 scm_double_cell (scm_t_bits car, scm_t_bits cbr,
 152                  scm_t_bits ccr, scm_t_bits cdr)
 153 {
 154   SCM z;
 155   SCM *freelist = SCM_FREELIST_LOC (scm_i_freelist2);
 156
 157   if (SCM_NULLP (*freelist))
 158     z = scm_gc_for_newcell (&scm_i_master_freelist2, freelist);
 159   else
 160     {
 161       z = *freelist;
 162       *freelist = SCM_FREE_CELL_CDR (*freelist);
 163     }
 164
 165   scm_cells_allocated += 2;
 166
 167   /* Initialize the type slot last so that the cell is ignored by the
 168      GC until it is completely initialized.  This is only relevant
 169      when the GC can actually run during this code, which it can't for
 170      cooperating threads, but it might be important when we get true
 171      preemptive threads.
 172   */
 173   SCM_GC_SET_CELL_WORD (z, 1, cbr);
 174   SCM_GC_SET_CELL_WORD (z, 2, ccr);
 175   SCM_GC_SET_CELL_WORD (z, 3, cdr);
 176   SCM_GC_SET_CELL_WORD (z, 0, car);
 177
 178 #if 0 /*fixme* Hmm... let's consider this later. */
 179 #if !defined(SCM_USE_COOP_THREADS) && !defined(SCM_USE_NULL_THREADS) && !defined(SCM_USE_COPT_THREADS)
 180   /* When we are using non-cooperating threads, we might need to make
 181      sure that the initial values for the slots are protected until
 182      the cell is completely initialized.
 183   */
 184 #error review me
 185   scm_remember_upto_here_3 (SCM_PACK (cbr), SCM_PACK (ccr), SCM_PACK (cdr));
 186 #endif
 187 #endif
 188
 189
 190 #if (SCM_DEBUG_CELL_ACCESSES == 1)
 191   if (scm_debug_cell_accesses_p)
 192     {
 193       if (SCM_GC_MARK_P (z))
 194         {
 195           fprintf(stderr,
 196                   "scm_double_cell tried to allocate a marked cell.\n");
 197           abort();
 198         }
 199     }
 200
 201   /* see above. */
 202   SCM_SET_GC_MARK (z);
 203
 204 #endif
 205
 206   /* When this function is inlined, it's possible that the last
 207      SCM_GC_SET_CELL_WORD above will be adjacent to a following
 208      initialization of z.  E.g., it occurred in scm_make_real.  GCC
 209      from around version 3 (e.g., certainly 3.2) began taking
 210      advantage of strict C aliasing rules which say that it's OK to
 211      interchange the initialization above and the one below when the
 212      pointer types appear to differ sufficiently.  We don't want that,
 213      of course.  GCC allows this behaviour to be disabled with the
 214      -fno-strict-aliasing option, but would also need to be supplied
 215      by Guile users.  Instead, the following statements prevent the
 216      reordering.
 217    */
 218 #ifdef __GNUC__
 219   asm volatile ("" : : : "memory");
 220 #else
 221   /* portable version, just in case any other compiler does the same
 222      thing.  */
 223   scm_remember_upto_here_1 (z);
 224 #endif
 225
 226   return z;
 227 }
 228
 229
 230
 231 #endif
 232 #endif