gas/subsegs.c

   1 /* subsegs.c - subsegments -
   2    Copyright 1987, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   3    1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GAS, the GNU Assembler.
   7
   8    GAS is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2, or (at your option)
  11    any later version.
  12
  13    GAS 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
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with GAS; see the file COPYING.  If not, write to the Free
  20    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
  21    02110-1301, USA.  */
  22
  23 /* Segments & sub-segments.  */
  24
  25 #include "as.h"
  26
  27 #include "subsegs.h"
  28 #include "obstack.h"
  29
  30 frchainS *frchain_now;
  31
  32 static struct obstack frchains;
  33
  34 static fragS dummy_frag;
  35
  36 \f
  37 void
  38 subsegs_begin (void)
  39 {
  40   obstack_begin (&frchains, chunksize);
  41 #if __GNUC__ >= 2
  42   obstack_alignment_mask (&frchains) = __alignof__ (frchainS) - 1;
  43 #endif
  44
  45   frchain_now = NULL;           /* Warn new_subseg() that we are booting.  */
  46   frag_now = &dummy_frag;
  47 }
  48 \f
  49 /*
  50  *                      subseg_change()
  51  *
  52  * Change the subsegment we are in, BUT DO NOT MAKE A NEW FRAG for the
  53  * subsegment. If we are already in the correct subsegment, change nothing.
  54  * This is used eg as a worker for subseg_set [which does make a new frag_now]
  55  * and for changing segments after we have read the source. We construct eg
  56  * fixSs even after the source file is read, so we do have to keep the
  57  * segment context correct.
  58  */
  59 void
  60 subseg_change (register segT seg, register int subseg)
  61 {
  62   segment_info_type *seginfo = seg_info (seg);
  63   now_seg = seg;
  64   now_subseg = subseg;
  65
  66   if (! seginfo)
  67     {
  68       seginfo = xcalloc (1, sizeof (*seginfo));
  69       seginfo->bfd_section = seg;
  70       bfd_set_section_userdata (stdoutput, seg, seginfo);
  71     }
  72 }
  73 \f
  74 static void
  75 subseg_set_rest (segT seg, subsegT subseg)
  76 {
  77   frchainS *frcP;               /* crawl frchain chain */
  78   frchainS **lastPP;            /* address of last pointer */
  79   frchainS *newP;               /* address of new frchain */
  80   segment_info_type *seginfo;
  81
  82   mri_common_symbol = NULL;
  83
  84   if (frag_now && frchain_now)
  85     frchain_now->frch_frag_now = frag_now;
  86
  87   assert (frchain_now == 0
  88           || frchain_now->frch_last == frag_now);
  89
  90   subseg_change (seg, (int) subseg);
  91
  92   seginfo = seg_info (seg);
  93
  94   /* Attempt to find or make a frchain for that subsection.
  95      We keep the list sorted by subsection number.  */
  96   for (frcP = *(lastPP = &seginfo->frchainP);
  97        frcP != NULL;
  98        frcP = *(lastPP = &frcP->frch_next))
  99     if (frcP->frch_subseg >= subseg)
 100       break;
 101
 102   if (frcP == NULL || frcP->frch_subseg != subseg)
 103     {
 104       /* This should be the only code that creates a frchainS.  */
 105
 106       newP = obstack_alloc (&frchains, sizeof (frchainS));
 107       newP->frch_subseg = subseg;
 108       newP->fix_root = NULL;
 109       newP->fix_tail = NULL;
 110       obstack_begin (&newP->frch_obstack, chunksize);
 111 #if __GNUC__ >= 2
 112       obstack_alignment_mask (&newP->frch_obstack) = __alignof__ (fragS) - 1;
 113 #endif
 114       newP->frch_frag_now = frag_alloc (&newP->frch_obstack);
 115       newP->frch_frag_now->fr_type = rs_fill;
 116       newP->frch_cfi_data = NULL;
 117
 118       newP->frch_root = newP->frch_last = newP->frch_frag_now;
 119
 120       *lastPP = newP;
 121       newP->frch_next = frcP;
 122       frcP = newP;
 123     }
 124
 125   frchain_now = frcP;
 126   frag_now = frcP->frch_frag_now;
 127
 128   assert (frchain_now->frch_last == frag_now);
 129 }
 130
 131 /*
 132  *                      subseg_set(segT, subsegT)
 133  *
 134  * If you attempt to change to the current subsegment, nothing happens.
 135  *
 136  * In:  segT, subsegT code for new subsegment.
 137  *      frag_now -> incomplete frag for current subsegment.
 138  *      If frag_now==NULL, then there is no old, incomplete frag, so
 139  *      the old frag is not closed off.
 140  *
 141  * Out: now_subseg, now_seg updated.
 142  *      Frchain_now points to the (possibly new) struct frchain for this
 143  *      sub-segment.
 144  */
 145
 146 segT
 147 subseg_get (const char *segname, int force_new)
 148 {
 149   segT secptr;
 150   segment_info_type *seginfo;
 151   const char *now_seg_name = (now_seg
 152                               ? bfd_get_section_name (stdoutput, now_seg)
 153                               : 0);
 154
 155   if (!force_new
 156       && now_seg_name
 157       && (now_seg_name == segname
 158           || !strcmp (now_seg_name, segname)))
 159     return now_seg;
 160
 161   if (!force_new)
 162     secptr = bfd_make_section_old_way (stdoutput, segname);
 163   else
 164     secptr = bfd_make_section_anyway (stdoutput, segname);
 165
 166   seginfo = seg_info (secptr);
 167   if (! seginfo)
 168     {
 169       secptr->output_section = secptr;
 170       seginfo = xcalloc (1, sizeof (*seginfo));
 171       seginfo->bfd_section = secptr;
 172       bfd_set_section_userdata (stdoutput, secptr, seginfo);
 173     }
 174   return secptr;
 175 }
 176
 177 segT
 178 subseg_new (const char *segname, subsegT subseg)
 179 {
 180   segT secptr;
 181
 182   secptr = subseg_get (segname, 0);
 183   subseg_set_rest (secptr, subseg);
 184   return secptr;
 185 }
 186
 187 /* Like subseg_new, except a new section is always created, even if
 188    a section with that name already exists.  */
 189 segT
 190 subseg_force_new (const char *segname, subsegT subseg)
 191 {
 192   segT secptr;
 193
 194   secptr = subseg_get (segname, 1);
 195   subseg_set_rest (secptr, subseg);
 196   return secptr;
 197 }
 198
 199 void
 200 subseg_set (segT secptr, subsegT subseg)
 201 {
 202   if (! (secptr == now_seg && subseg == now_subseg))
 203     subseg_set_rest (secptr, subseg);
 204   mri_common_symbol = NULL;
 205 }
 206
 207 #ifndef obj_sec_sym_ok_for_reloc
 208 #define obj_sec_sym_ok_for_reloc(SEC)   0
 209 #endif
 210
 211 symbolS *
 212 section_symbol (segT sec)
 213 {
 214   segment_info_type *seginfo = seg_info (sec);
 215   symbolS *s;
 216
 217   if (seginfo == 0)
 218     abort ();
 219   if (seginfo->sym)
 220     return seginfo->sym;
 221
 222 #ifndef EMIT_SECTION_SYMBOLS
 223 #define EMIT_SECTION_SYMBOLS 1
 224 #endif
 225
 226   if (! EMIT_SECTION_SYMBOLS || symbol_table_frozen)
 227     {
 228       /* Here we know it won't be going into the symbol table.  */
 229       s = symbol_create (sec->symbol->name, sec, 0, &zero_address_frag);
 230     }
 231   else
 232     {
 233       segT seg;
 234       s = symbol_find (sec->symbol->name);
 235       /* We have to make sure it is the right symbol when we
 236          have multiple sections with the same section name.  */
 237       if (s == NULL
 238           || ((seg = S_GET_SEGMENT (s)) != sec
 239               && seg != undefined_section))
 240         s = symbol_new (sec->symbol->name, sec, 0, &zero_address_frag);
 241       else if (seg == undefined_section)
 242         {
 243           S_SET_SEGMENT (s, sec);
 244           symbol_set_frag (s, &zero_address_frag);
 245         }
 246     }
 247
 248   S_CLEAR_EXTERNAL (s);
 249
 250   /* Use the BFD section symbol, if possible.  */
 251   if (obj_sec_sym_ok_for_reloc (sec))
 252     symbol_set_bfdsym (s, sec->symbol);
 253   else
 254     symbol_get_bfdsym (s)->flags |= BSF_SECTION_SYM;
 255
 256   seginfo->sym = s;
 257   return s;
 258 }
 259
 260 /* Return whether the specified segment is thought to hold text.  */
 261
 262 int
 263 subseg_text_p (segT sec)
 264 {
 265   return (bfd_get_section_flags (stdoutput, sec) & SEC_CODE) != 0;
 266 }
 267
 268 /* Return non zero if SEC has at least one byte of data.  It is
 269    possible that we'll return zero even on a non-empty section because
 270    we don't know all the fragment types, and it is possible that an
 271    fr_fix == 0 one still contributes data.  Think of this as
 272    seg_definitely_not_empty_p.  */
 273
 274 int
 275 seg_not_empty_p (segT sec ATTRIBUTE_UNUSED)
 276 {
 277   segment_info_type *seginfo = seg_info (sec);
 278   frchainS *chain;
 279   fragS *frag;
 280
 281   if (!seginfo)
 282     return 0;
 283
 284   for (chain = seginfo->frchainP; chain; chain = chain->frch_next)
 285     {
 286       for (frag = chain->frch_root; frag; frag = frag->fr_next)
 287         if (frag->fr_fix)
 288           return 1;
 289       if (obstack_next_free (&chain->frch_obstack)
 290           != chain->frch_last->fr_literal)
 291         return 1;
 292     }
 293   return 0;
 294 }
 295
 296 void
 297 subsegs_print_statistics (FILE *file)
 298 {
 299   frchainS *frchp;
 300   asection *s;
 301
 302   fprintf (file, "frag chains:\n");
 303   for (s = stdoutput->sections; s; s = s->next)
 304     {
 305       segment_info_type *seginfo;
 306
 307       /* Skip gas-internal sections.  */
 308       if (segment_name (s)[0] == '*')
 309         continue;
 310
 311       seginfo = seg_info (s);
 312       if (!seginfo)
 313         continue;
 314
 315       for (frchp = seginfo->frchainP; frchp; frchp = frchp->frch_next)
 316         {
 317           int count = 0;
 318           fragS *fragp;
 319
 320           for (fragp = frchp->frch_root; fragp; fragp = fragp->fr_next)
 321             count++;
 322
 323           fprintf (file, "\n");
 324           fprintf (file, "\t%p %-10s\t%10d frags\n", (void *) frchp,
 325                    segment_name (s), count);
 326         }
 327     }
 328 }
 329
 330 /* end of subsegs.c */