gas/subsegs.c

/* subsegs.c - subsegments -
   Copyright (C) 1987-2016 Free Software Foundation, Inc.

   This file is part of GAS, the GNU Assembler.

   GAS is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3, or (at your option)
   any later version.

   GAS is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GAS; see the file COPYING.  If not, write to the Free
   Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
   02110-1301, USA.  */

/* Segments & sub-segments.  */

#include "as.h"

#include "subsegs.h"
#include "obstack.h"

frchainS *frchain_now;

static struct obstack frchains;

static fragS dummy_frag;


void
subsegs_begin (void)
{
  obstack_begin (&frchains, chunksize);
#if __GNUC__ >= 2
  obstack_alignment_mask (&frchains) = __alignof__ (frchainS) - 1;
#endif

  frchain_now = NULL;		/* Warn new_subseg() that we are booting.  */
  frag_now = &dummy_frag;
}

/*
 *			subseg_change()
 *
 * Change the subsegment we are in, BUT DO NOT MAKE A NEW FRAG for the
 * subsegment. If we are already in the correct subsegment, change nothing.
 * This is used eg as a worker for subseg_set [which does make a new frag_now]
 * and for changing segments after we have read the source. We construct eg
 * fixSs even after the source file is read, so we do have to keep the
 * segment context correct.
 */
void
subseg_change (segT seg, int subseg)
{
  segment_info_type *seginfo = seg_info (seg);
  now_seg = seg;
  now_subseg = subseg;

  if (! seginfo)
    {
      seginfo = XCNEW (segment_info_type);
      seginfo->bfd_section = seg;
      bfd_set_section_userdata (stdoutput, seg, seginfo);
    }
}

static void
subseg_set_rest (segT seg, subsegT subseg)
{
  frchainS *frcP;		/* crawl frchain chain */
  frchainS **lastPP;		/* address of last pointer */
  frchainS *newP;		/* address of new frchain */
  segment_info_type *seginfo;

  mri_common_symbol = NULL;

  if (frag_now && frchain_now)
    frchain_now->frch_frag_now = frag_now;

  gas_assert (frchain_now == 0
	  || frchain_now->frch_last == frag_now);

  subseg_change (seg, (int) subseg);

  seginfo = seg_info (seg);

  /* Attempt to find or make a frchain for that subsection.
     We keep the list sorted by subsection number.  */
  for (frcP = *(lastPP = &seginfo->frchainP);
       frcP != NULL;
       frcP = *(lastPP = &frcP->frch_next))
    if (frcP->frch_subseg >= subseg)
      break;

  if (frcP == NULL || frcP->frch_subseg != subseg)
    {
      /* This should be the only code that creates a frchainS.  */

      newP = (frchainS *) obstack_alloc (&frchains, sizeof (frchainS));
      newP->frch_subseg = subseg;
      newP->fix_root = NULL;
      newP->fix_tail = NULL;
      obstack_begin (&newP->frch_obstack, chunksize);
#if __GNUC__ >= 2
      obstack_alignment_mask (&newP->frch_obstack) = __alignof__ (fragS) - 1;
#endif
      newP->frch_frag_now = frag_alloc (&newP->frch_obstack);
      newP->frch_frag_now->fr_type = rs_fill;
      newP->frch_cfi_data = NULL;

      newP->frch_root = newP->frch_last = newP->frch_frag_now;

      *lastPP = newP;
      newP->frch_next = frcP;
      frcP = newP;
    }

  frchain_now = frcP;
  frag_now = frcP->frch_frag_now;

  gas_assert (frchain_now->frch_last == frag_now);
}

/*
 *			subseg_set(segT, subsegT)
 *
 * If you attempt to change to the current subsegment, nothing happens.
 *
 * In:	segT, subsegT code for new subsegment.
 *	frag_now -> incomplete frag for current subsegment.
 *	If frag_now==NULL, then there is no old, incomplete frag, so
 *	the old frag is not closed off.
 *
 * Out:	now_subseg, now_seg updated.
 *	Frchain_now points to the (possibly new) struct frchain for this
 *	sub-segment.
 */

segT
subseg_get (const char *segname, int force_new)
{
  segT secptr;
  segment_info_type *seginfo;
  const char *now_seg_name = (now_seg
			      ? bfd_get_section_name (stdoutput, now_seg)
			      : 0);

  if (!force_new
      && now_seg_name
      && (now_seg_name == segname
	  || !strcmp (now_seg_name, segname)))
    return now_seg;

  if (!force_new)
    secptr = bfd_make_section_old_way (stdoutput, segname);
  else
    secptr = bfd_make_section_anyway (stdoutput, segname);

  seginfo = seg_info (secptr);
  if (! seginfo)
    {
      secptr->output_section = secptr;
      seginfo = XCNEW (segment_info_type);
      seginfo->bfd_section = secptr;
      bfd_set_section_userdata (stdoutput, secptr, seginfo);
    }
  return secptr;
}

segT
subseg_new (const char *segname, subsegT subseg)
{
  segT secptr;

  secptr = subseg_get (segname, 0);
  subseg_set_rest (secptr, subseg);
  return secptr;
}

/* Like subseg_new, except a new section is always created, even if
   a section with that name already exists.  */
segT
subseg_force_new (const char *segname, subsegT subseg)
{
  segT secptr;

  secptr = subseg_get (segname, 1);
  subseg_set_rest (secptr, subseg);
  return secptr;
}

void
subseg_set (segT secptr, subsegT subseg)
{
  if (! (secptr == now_seg && subseg == now_subseg))
    subseg_set_rest (secptr, subseg);
  mri_common_symbol = NULL;
}

#ifndef obj_sec_sym_ok_for_reloc
#define obj_sec_sym_ok_for_reloc(SEC)	0
#endif

symbolS *
section_symbol (segT sec)
{
  segment_info_type *seginfo = seg_info (sec);
  symbolS *s;

  if (seginfo == 0)
    abort ();
  if (seginfo->sym)
    return seginfo->sym;

#ifndef EMIT_SECTION_SYMBOLS
#define EMIT_SECTION_SYMBOLS 1
#endif

  if (! EMIT_SECTION_SYMBOLS || symbol_table_frozen)
    {
      /* Here we know it won't be going into the symbol table.  */
      s = symbol_create (sec->symbol->name, sec, 0, &zero_address_frag);
    }
  else
    {
      segT seg;
      s = symbol_find (sec->symbol->name);
      /* We have to make sure it is the right symbol when we
	 have multiple sections with the same section name.  */
      if (s == NULL
	  || ((seg = S_GET_SEGMENT (s)) != sec
	      && seg != undefined_section))
	s = symbol_new (sec->symbol->name, sec, 0, &zero_address_frag);
      else if (seg == undefined_section)
	{
	  S_SET_SEGMENT (s, sec);
	  symbol_set_frag (s, &zero_address_frag);
	}
    }

  S_CLEAR_EXTERNAL (s);

  /* Use the BFD section symbol, if possible.  */
  if (obj_sec_sym_ok_for_reloc (sec))
    symbol_set_bfdsym (s, sec->symbol);
  else
    symbol_get_bfdsym (s)->flags |= BSF_SECTION_SYM;

  seginfo->sym = s;
  return s;
}

/* Return whether the specified segment is thought to hold text.  */

int
subseg_text_p (segT sec)
{
  return (bfd_get_section_flags (stdoutput, sec) & SEC_CODE) != 0;
}

/* Return non zero if SEC has at least one byte of data.  It is
   possible that we'll return zero even on a non-empty section because
   we don't know all the fragment types, and it is possible that an
   fr_fix == 0 one still contributes data.  Think of this as
   seg_definitely_not_empty_p.  */

int
seg_not_empty_p (segT sec ATTRIBUTE_UNUSED)
{
  segment_info_type *seginfo = seg_info (sec);
  frchainS *chain;
  fragS *frag;

  if (!seginfo)
    return 0;

  for (chain = seginfo->frchainP; chain; chain = chain->frch_next)
    {
      for (frag = chain->frch_root; frag; frag = frag->fr_next)
	if (frag->fr_fix)
	  return 1;
      if (obstack_next_free (&chain->frch_obstack)
	  != chain->frch_last->fr_literal)
	return 1;
    }
  return 0;
}

void
subsegs_print_statistics (FILE *file)
{
  frchainS *frchp;
  asection *s;

  fprintf (file, "frag chains:\n");
  for (s = stdoutput->sections; s; s = s->next)
    {
      segment_info_type *seginfo;

      /* Skip gas-internal sections.  */
      if (segment_name (s)[0] == '*')
	continue;

      seginfo = seg_info (s);
      if (!seginfo)
	continue;

      for (frchp = seginfo->frchainP; frchp; frchp = frchp->frch_next)
	{
	  int count = 0;
	  fragS *fragp;

	  for (fragp = frchp->frch_root; fragp; fragp = fragp->fr_next)
	    count++;

	  fprintf (file, "\n");
	  fprintf (file, "\t%p %-10s\t%10d frags\n", (void *) frchp,
		   segment_name (s), count);
	}
    }
}

/* end of subsegs.c */