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
   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 = (segment_info_type *) xmalloc (sizeof (*seginfo));
  69       memset ((PTR) seginfo, 0, sizeof (*seginfo));
  70       seginfo->fix_root = NULL;
  71       seginfo->fix_tail = NULL;
  72       seginfo->bfd_section = seg;
  73       seginfo->sym = 0;
  74       bfd_set_section_userdata (stdoutput, seg, (PTR) seginfo);
  75     }
  76 }
  77 \f
  78 static void
  79 subseg_set_rest (segT seg, subsegT subseg)
  80 {
  81   frchainS *frcP;               /* crawl frchain chain */
  82   frchainS **lastPP;            /* address of last pointer */
  83   frchainS *newP;               /* address of new frchain */
  84   segment_info_type *seginfo;
  85
  86   mri_common_symbol = NULL;
  87
  88   if (frag_now && frchain_now)
  89     frchain_now->frch_frag_now = frag_now;
  90
  91   assert (frchain_now == 0
  92           || frchain_now->frch_last == frag_now);
  93
  94   subseg_change (seg, (int) subseg);
  95
  96   seginfo = seg_info (seg);
  97
  98   /* Attempt to find or make a frchain for that subsection.
  99      We keep the list sorted by subsection number.  */
 100   for (frcP = *(lastPP = &seginfo->frchainP);
 101        frcP != NULL;
 102        frcP = *(lastPP = &frcP->frch_next))
 103     if (frcP->frch_subseg >= subseg)
 104       break;
 105
 106   if (frcP == NULL || frcP->frch_subseg != subseg)
 107     {
 108       /* This should be the only code that creates a frchainS.  */
 109
 110       newP = (frchainS *) obstack_alloc (&frchains, sizeof (frchainS));
 111       newP->frch_subseg = subseg;
 112       newP->fix_root = NULL;
 113       newP->fix_tail = NULL;
 114       obstack_begin (&newP->frch_obstack, chunksize);
 115 #if __GNUC__ >= 2
 116       obstack_alignment_mask (&newP->frch_obstack) = __alignof__ (fragS) - 1;
 117 #endif
 118       newP->frch_frag_now = frag_alloc (&newP->frch_obstack);
 119       newP->frch_frag_now->fr_type = rs_fill;
 120
 121       newP->frch_root = newP->frch_last = newP->frch_frag_now;
 122
 123       *lastPP = newP;
 124       newP->frch_next = frcP;
 125       frcP = newP;
 126     }
 127
 128   frchain_now = frcP;
 129   frag_now = frcP->frch_frag_now;
 130
 131   assert (frchain_now->frch_last == frag_now);
 132 }
 133
 134 /*
 135  *                      subseg_set(segT, subsegT)
 136  *
 137  * If you attempt to change to the current subsegment, nothing happens.
 138  *
 139  * In:  segT, subsegT code for new subsegment.
 140  *      frag_now -> incomplete frag for current subsegment.
 141  *      If frag_now==NULL, then there is no old, incomplete frag, so
 142  *      the old frag is not closed off.
 143  *
 144  * Out: now_subseg, now_seg updated.
 145  *      Frchain_now points to the (possibly new) struct frchain for this
 146  *      sub-segment.
 147  */
 148
 149 segT
 150 subseg_get (const char *segname, int force_new)
 151 {
 152   segT secptr;
 153   segment_info_type *seginfo;
 154   const char *now_seg_name = (now_seg
 155                               ? bfd_get_section_name (stdoutput, now_seg)
 156                               : 0);
 157
 158   if (!force_new
 159       && now_seg_name
 160       && (now_seg_name == segname
 161           || !strcmp (now_seg_name, segname)))
 162     return now_seg;
 163
 164   if (!force_new)
 165     secptr = bfd_make_section_old_way (stdoutput, segname);
 166   else
 167     secptr = bfd_make_section_anyway (stdoutput, segname);
 168
 169   seginfo = seg_info (secptr);
 170   if (! seginfo)
 171     {
 172       secptr->output_section = secptr;
 173       seginfo = (segment_info_type *) xmalloc (sizeof (*seginfo));
 174       memset ((PTR) seginfo, 0, sizeof (*seginfo));
 175       seginfo->fix_root = NULL;
 176       seginfo->fix_tail = NULL;
 177       seginfo->bfd_section = secptr;
 178       bfd_set_section_userdata (stdoutput, secptr, (PTR) seginfo);
 179       seginfo->frchainP = NULL;
 180       seginfo->lineno_list_head = seginfo->lineno_list_tail = NULL;
 181       seginfo->sym = NULL;
 182       seginfo->dot = NULL;
 183     }
 184   return secptr;
 185 }
 186
 187 segT
 188 subseg_new (const char *segname, subsegT subseg)
 189 {
 190   segT secptr;
 191
 192   secptr = subseg_get (segname, 0);
 193   subseg_set_rest (secptr, subseg);
 194   return secptr;
 195 }
 196
 197 /* Like subseg_new, except a new section is always created, even if
 198    a section with that name already exists.  */
 199 segT
 200 subseg_force_new (const char *segname, subsegT subseg)
 201 {
 202   segT secptr;
 203
 204   secptr = subseg_get (segname, 1);
 205   subseg_set_rest (secptr, subseg);
 206   return secptr;
 207 }
 208
 209 void
 210 subseg_set (segT secptr, subsegT subseg)
 211 {
 212   if (! (secptr == now_seg && subseg == now_subseg))
 213     subseg_set_rest (secptr, subseg);
 214   mri_common_symbol = NULL;
 215 }
 216
 217 #ifndef obj_sec_sym_ok_for_reloc
 218 #define obj_sec_sym_ok_for_reloc(SEC)   0
 219 #endif
 220
 221 symbolS *
 222 section_symbol (segT sec)
 223 {
 224   segment_info_type *seginfo = seg_info (sec);
 225   symbolS *s;
 226
 227   if (seginfo == 0)
 228     abort ();
 229   if (seginfo->sym)
 230     return seginfo->sym;
 231
 232 #ifndef EMIT_SECTION_SYMBOLS
 233 #define EMIT_SECTION_SYMBOLS 1
 234 #endif
 235
 236   if (! EMIT_SECTION_SYMBOLS || symbol_table_frozen)
 237     {
 238       /* Here we know it won't be going into the symbol table.  */
 239       s = symbol_create (sec->symbol->name, sec, 0, &zero_address_frag);
 240     }
 241   else
 242     {
 243       segT seg;
 244       s = symbol_find (sec->symbol->name);
 245       /* We have to make sure it is the right symbol when we
 246          have multiple sections with the same section name.  */
 247       if (s == NULL
 248           || ((seg = S_GET_SEGMENT (s)) != sec
 249               && seg != undefined_section))
 250         s = symbol_new (sec->symbol->name, sec, 0, &zero_address_frag);
 251       else if (seg == undefined_section)
 252         {
 253           S_SET_SEGMENT (s, sec);
 254           symbol_set_frag (s, &zero_address_frag);
 255         }
 256     }
 257
 258   S_CLEAR_EXTERNAL (s);
 259
 260   /* Use the BFD section symbol, if possible.  */
 261   if (obj_sec_sym_ok_for_reloc (sec))
 262     symbol_set_bfdsym (s, sec->symbol);
 263   else
 264     symbol_get_bfdsym (s)->flags |= BSF_SECTION_SYM;
 265
 266   seginfo->sym = s;
 267   return s;
 268 }
 269
 270 /* Return whether the specified segment is thought to hold text.  */
 271
 272 int
 273 subseg_text_p (segT sec)
 274 {
 275   return (bfd_get_section_flags (stdoutput, sec) & SEC_CODE) != 0;
 276 }
 277
 278 /* Return non zero if SEC has at least one byte of data.  It is
 279    possible that we'll return zero even on a non-empty section because
 280    we don't know all the fragment types, and it is possible that an
 281    fr_fix == 0 one still contributes data.  Think of this as
 282    seg_definitely_not_empty_p.  */
 283
 284 int
 285 seg_not_empty_p (segT sec ATTRIBUTE_UNUSED)
 286 {
 287   segment_info_type *seginfo = seg_info (sec);
 288   frchainS *chain;
 289   fragS *frag;
 290
 291   if (!seginfo)
 292     return 0;
 293
 294   for (chain = seginfo->frchainP; chain; chain = chain->frch_next)
 295     {
 296       for (frag = chain->frch_root; frag; frag = frag->fr_next)
 297         if (frag->fr_fix)
 298           return 1;
 299       if (obstack_next_free (&chain->frch_obstack)
 300           != chain->frch_last->fr_literal)
 301         return 1;
 302     }
 303   return 0;
 304 }
 305
 306 void
 307 subsegs_print_statistics (FILE *file)
 308 {
 309   frchainS *frchp;
 310   asection *s;
 311
 312   fprintf (file, "frag chains:\n");
 313   for (s = stdoutput->sections; s; s = s->next)
 314     {
 315       segment_info_type *seginfo;
 316
 317       /* Skip gas-internal sections.  */
 318       if (segment_name (s)[0] == '*')
 319         continue;
 320
 321       seginfo = seg_info (s);
 322       if (!seginfo)
 323         continue;
 324
 325       for (frchp = seginfo->frchainP; frchp; frchp = frchp->frch_next)
 326         {
 327           int count = 0;
 328           fragS *fragp;
 329
 330           for (fragp = frchp->frch_root; fragp; fragp = fragp->fr_next)
 331             count++;
 332
 333           fprintf (file, "\n");
 334           fprintf (file, "\t%p %-10s\t%10d frags\n", (void *) frchp,
 335                    segment_name (s), count);
 336         }
 337     }
 338 }
 339
 340 /* end of subsegs.c */