libguile/inline.h

   1 /* classes: h_files */
   2
   3 #ifndef SCM_INLINE_H
   4 #define SCM_INLINE_H
   5
   6 /* Copyright (C) 2001, 2002, 2003 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 #ifdef __GNUC__
  57 extern
  58 #else
  59 static
  60 #endif
  61 SCM_C_INLINE
  62 #endif
  63 SCM
  64 scm_cell (scm_t_bits car, scm_t_bits cdr)
  65 {
  66   SCM z;
  67   /* We retrieve the SCM pointer only once since the call to
  68      SCM_FREELIST_LOC will be slightly expensive when we support
  69      preemptive multithreading.  SCM_FREELIST_LOC will then retrieve
  70      the thread specific freelist.
  71
  72      Until then, SCM_FREELIST_DOC expands to (&scm_i_freelist) and the
  73      following code will compile to the same as if we had worked
  74      directly on the scm_i_freelist variable.
  75    */
  76   SCM *freelist = SCM_FREELIST_LOC (scm_i_freelist);
  77
  78   if (SCM_NULLP (*freelist))
  79     z = scm_gc_for_newcell (&scm_i_master_freelist, freelist);
  80   else
  81     {
  82       z = *freelist;
  83       *freelist = SCM_FREE_CELL_CDR (*freelist);
  84     }
  85
  86   /*
  87     We update scm_cells_allocated from this function. If we don't
  88     update this explicitly, we will have to walk a freelist somewhere
  89     later on, which seems a lot more expensive.
  90    */
  91   scm_cells_allocated += 1;
  92
  93 #if (SCM_DEBUG_CELL_ACCESSES == 1)
  94     if (scm_debug_cell_accesses_p)
  95       {
  96         if (SCM_GC_MARK_P (z))
  97           {
  98             fprintf(stderr, "scm_cell tried to allocate a marked cell.\n");
  99             abort();
 100           }
 101         else if (SCM_GC_CELL_WORD(z, 0) != scm_tc_free_cell)
 102           {
 103             fprintf(stderr, "cell from freelist is not a free cell.\n");
 104             abort();
 105           }
 106       }
 107
 108     /*
 109       Always set mark. Otherwise cells that are alloced before
 110       scm_debug_cell_accesses_p is toggled seem invalid.
 111     */
 112     SCM_SET_GC_MARK (z);
 113
 114     /*
 115       TODO: figure out if this use of mark bits is valid with
 116       threading. What if another thread is doing GC at this point
 117       ... ?
 118      */
 119
 120 #endif
 121
 122
 123   /* Initialize the type slot last so that the cell is ignored by the
 124      GC until it is completely initialized.  This is only relevant
 125      when the GC can actually run during this code, which it can't for
 126      cooperating threads, but it might be important when we get true
 127      preemptive threads.
 128   */
 129   SCM_GC_SET_CELL_WORD (z, 1, cdr);
 130   SCM_GC_SET_CELL_WORD (z, 0, car);
 131
 132 #if 0 /*fixme* Hmm... let's consider this later. */
 133 #if !defined(SCM_USE_COOP_THREADS) && !defined(SCM_USE_NULL_THREADS) && !defined(SCM_USE_COPT_THREADS)
 134   /* When we are using preemtive threads, we might need to make
 135      sure that the initial values for the slots are protected until
 136      the cell is completely initialized.
 137   */
 138 #error review me
 139   scm_remember_upto_here_1 (SCM_PACK (cdr));
 140 #endif
 141 #endif
 142
 143 #if (SCM_DEBUG_CELL_ACCESSES == 1)
 144   if (scm_expensive_debug_cell_accesses_p )
 145     scm_i_expensive_validation_check (z);
 146 #endif
 147
 148   return z;
 149 }
 150
 151 #if defined SCM_C_INLINE && ! defined SCM_INLINE_C_INCLUDING_INLINE_H
 152 /* definitely inlining */
 153 #ifdef __GNUC__
 154 extern
 155 #else
 156 static
 157 #endif
 158 SCM_C_INLINE
 159 #endif
 160 SCM
 161 scm_double_cell (scm_t_bits car, scm_t_bits cbr,
 162                  scm_t_bits ccr, scm_t_bits cdr)
 163 {
 164   SCM z;
 165   SCM *freelist = SCM_FREELIST_LOC (scm_i_freelist2);
 166
 167   if (SCM_NULLP (*freelist))
 168     z = scm_gc_for_newcell (&scm_i_master_freelist2, freelist);
 169   else
 170     {
 171       z = *freelist;
 172       *freelist = SCM_FREE_CELL_CDR (*freelist);
 173     }
 174
 175   scm_cells_allocated += 2;
 176
 177   /* Initialize the type slot last so that the cell is ignored by the
 178      GC until it is completely initialized.  This is only relevant
 179      when the GC can actually run during this code, which it can't for
 180      cooperating threads, but it might be important when we get true
 181      preemptive threads.
 182   */
 183   SCM_GC_SET_CELL_WORD (z, 1, cbr);
 184   SCM_GC_SET_CELL_WORD (z, 2, ccr);
 185   SCM_GC_SET_CELL_WORD (z, 3, cdr);
 186   SCM_GC_SET_CELL_WORD (z, 0, car);
 187
 188 #if 0 /*fixme* Hmm... let's consider this later. */
 189 #if !defined(SCM_USE_COOP_THREADS) && !defined(SCM_USE_NULL_THREADS) && !defined(SCM_USE_COPT_THREADS)
 190   /* When we are using non-cooperating threads, we might need to make
 191      sure that the initial values for the slots are protected until
 192      the cell is completely initialized.
 193   */
 194 #error review me
 195   scm_remember_upto_here_3 (SCM_PACK (cbr), SCM_PACK (ccr), SCM_PACK (cdr));
 196 #endif
 197 #endif
 198
 199
 200 #if (SCM_DEBUG_CELL_ACCESSES == 1)
 201   if (scm_debug_cell_accesses_p)
 202     {
 203       if (SCM_GC_MARK_P (z))
 204         {
 205           fprintf(stderr,
 206                   "scm_double_cell tried to allocate a marked cell.\n");
 207           abort();
 208         }
 209     }
 210
 211   /* see above. */
 212   SCM_SET_GC_MARK (z);
 213
 214 #endif
 215
 216   /* When this function is inlined, it's possible that the last
 217      SCM_GC_SET_CELL_WORD above will be adjacent to a following
 218      initialization of z.  E.g., it occurred in scm_make_real.  GCC
 219      from around version 3 (e.g., certainly 3.2) began taking
 220      advantage of strict C aliasing rules which say that it's OK to
 221      interchange the initialization above and the one below when the
 222      pointer types appear to differ sufficiently.  We don't want that,
 223      of course.  GCC allows this behaviour to be disabled with the
 224      -fno-strict-aliasing option, but would also need to be supplied
 225      by Guile users.  Instead, the following statements prevent the
 226      reordering.
 227    */
 228 #ifdef __GNUC__
 229   asm volatile ("" : : : "memory");
 230 #else
 231   /* portable version, just in case any other compiler does the same
 232      thing.  */
 233   scm_remember_upto_here_1 (z);
 234 #endif
 235
 236   return z;
 237 }
 238
 239
 240
 241 #endif
 242 #endif