2000-12-12 H.J. Lu <hjl@gnu.org>

[binutils.git] / gas / dwarf2dbg.c

/* dwarf2dbg.c - DWARF2 debug support
   Copyright (C) 1999, 2000 Free Software Foundation, Inc.
   Contributed by David Mosberger-Tang <davidm@hpl.hp.com>

   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 2, 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, 59 Temple Place - Suite 330, Boston, MA
   02111-1307, USA.  */

/* Logical line numbers can be controlled by the compiler via the
   following two directives:

        .file FILENO "file.c"
        .loc  FILENO LINENO [COLUMN]

   FILENO is the filenumber.  */

#include "ansidecl.h"
#include <limits.h>

#include "as.h"

#ifdef BFD_ASSEMBLER

#include "dwarf2dbg.h"
#include "subsegs.h"

#include "elf/dwarf2.h"

/* Since we can't generate the prolog until the body is complete, we
   use three different subsegments for .debug_line: one holding the
   prolog, one for the directory and filename info, and one for the
   body ("statement program").  */
#define DL_PROLOG       0
#define DL_FILES        1
#define DL_BODY         2

/* First special line opcde - leave room for the standard opcodes.
   Note: If you want to change this, you'll have to update the
   "standard_opcode_lengths" table that is emitted below in
   dwarf2_finish().  */
#define DWARF2_LINE_OPCODE_BASE         10

#ifndef DWARF2_LINE_BASE
  /* Minimum line offset in a special line info. opcode.  This value
     was chosen to give a reasonable range of values.  */
# define DWARF2_LINE_BASE               -5
#endif

/* Range of line offsets in a special line info. opcode.  */
#ifndef DWARF2_LINE_RANGE
# define DWARF2_LINE_RANGE              14
#endif

#ifndef DWARF2_LINE_MIN_INSN_LENGTH
  /* Define the architecture-dependent minimum instruction length (in
     bytes).  This value should be rather too small than too big.  */
# define DWARF2_LINE_MIN_INSN_LENGTH    1
#endif

/* Flag that indicates the initial value of the is_stmt_start flag.
   In the present implementation, we do not mark any lines as
   the beginning of a source statement, because that information
   is not made available by the GCC front-end.  */
#define DWARF2_LINE_DEFAULT_IS_STMT     1

/* Given a special op, return the line skip amount.  */
#define SPECIAL_LINE(op) \
        (((op) - DWARF2_LINE_OPCODE_BASE)%DWARF2_LINE_RANGE + DWARF2_LINE_BASE)

/* Given a special op, return the address skip amount (in units of
   DWARF2_LINE_MIN_INSN_LENGTH.  */
#define SPECIAL_ADDR(op) (((op) - DWARF2_LINE_OPCODE_BASE)/DWARF2_LINE_RANGE)

/* The maximum address skip amount that can be encoded with a special op.  */
#define MAX_SPECIAL_ADDR_DELTA          SPECIAL_ADDR(255)


struct line_entry
{
  struct line_entry *next;
  fragS *frag;
  addressT frag_ofs;
  struct dwarf2_line_info loc;
};

struct line_subseg
{
  struct line_subseg *next;
  subsegT subseg;
  struct line_entry *head;
  struct line_entry **ptail;
};

struct line_seg
{
  struct line_seg *next;
  segT seg;
  struct line_subseg *head;
  symbolS *text_start;
  symbolS *text_end;
};

/* Collects data for all line table entries during assembly.  */
static struct line_seg *all_segs;

struct file_entry
{
  char *filename;
  unsigned int dir;
};

/* Table of files used by .debug_line.  */
static struct file_entry *files;
static unsigned int files_in_use;
static unsigned int files_allocated;

/* Correlate file numbers as given by the user in .file/.loc directives
   with the file numbers used in the output debug info.  */
static unsigned int *user_filenum;
static unsigned int user_filenum_allocated;

/* True when we've seen a .loc directive recently.  Used to avoid
   doing work when there's nothing to do.  */
static boolean loc_directive_seen;

/* Current location as indicated by the most recent .loc directive.  */
static struct dwarf2_line_info current;

/* Fake label name.  */
static char const fake_label_name[] = ".L0\001";

/* The size of an address on the target.  */
static unsigned int sizeof_address;
\f
static struct line_subseg *get_line_subseg PARAMS ((segT, subsegT));
static unsigned int get_filenum PARAMS ((const char *));
static struct frag *first_frag_for_seg PARAMS ((segT));
static struct frag *last_frag_for_seg PARAMS ((segT));
static void out_byte PARAMS ((int));
static void out_opcode PARAMS ((int));
static void out_two PARAMS ((int));
static void out_four PARAMS ((int));
static void out_abbrev PARAMS ((int, int));
static void out_uleb128 PARAMS ((addressT));
static symbolS *symbol_new_now PARAMS ((void));
static void set_symbol_value_now PARAMS ((symbolS *));
static offsetT get_frag_fix PARAMS ((fragS *));
static void out_set_addr PARAMS ((segT, fragS *, addressT));
static int size_inc_line_addr PARAMS ((int, addressT));
static void emit_inc_line_addr PARAMS ((int, addressT, char *, int));
static void out_inc_line_addr PARAMS ((int, addressT));
static void relax_inc_line_addr PARAMS ((int, segT, fragS *, addressT,
                                         fragS *, addressT));
static void process_entries PARAMS ((segT, struct line_entry *));
static void out_file_list PARAMS ((void));
static void out_debug_line PARAMS ((segT));
static void out_debug_aranges PARAMS ((segT, segT));
static void out_debug_abbrev PARAMS ((segT));
static void out_debug_info PARAMS ((segT, segT, segT));
\f
/* Find or create an entry for SEG+SUBSEG in ALL_SEGS.  */

static struct line_subseg *
get_line_subseg (seg, subseg)
     segT seg;
     subsegT subseg;
{
  static segT last_seg;
  static subsegT last_subseg;
  static struct line_subseg *last_line_subseg;

  struct line_seg *s;
  struct line_subseg **pss, *ss;

  if (seg == last_seg && subseg == last_subseg)
    return last_line_subseg;

  for (s = all_segs; s ; s = s->next)  
    if (s->seg == seg)
      goto found_seg;

  s = (struct line_seg *) xmalloc (sizeof (*s));
  s->next = all_segs;
  s->seg = seg;
  s->head = NULL;
  all_segs = s;

 found_seg:
  for (pss = &s->head; (ss = *pss) != NULL ; pss = &ss->next)
    {
      if (ss->subseg == subseg)
        goto found_subseg;
      if (ss->subseg > subseg)
        break;
    }

  ss = (struct line_subseg *) xmalloc (sizeof (*ss));
  ss->next = *pss;
  ss->subseg = subseg;
  ss->head = NULL;
  ss->ptail = &ss->head;
  *pss = ss;

 found_subseg:
  last_seg = seg;
  last_subseg = subseg;
  last_line_subseg = ss;

  return ss;
}

/* Record an entry for LOC ocurring at OFS within the current fragment.  */

void
dwarf2_gen_line_info (ofs, loc)
     addressT ofs;
     struct dwarf2_line_info *loc;
{
  struct line_subseg *ss;
  struct line_entry *e;

  /* Early out for as-yet incomplete location information.  */
  if (loc->filenum == 0 || loc->line == 0)
    return;

  e = (struct line_entry *) xmalloc (sizeof (*e));
  e->next = NULL;
  e->frag = frag_now;
  e->frag_ofs = ofs;
  e->loc = *loc;

  ss = get_line_subseg (now_seg, now_subseg);
  *ss->ptail = e;
  ss->ptail = &e->next;
}

void
dwarf2_where (line)
     struct dwarf2_line_info *line;
{
  if (debug_type == DEBUG_DWARF2)
    {
      char *filename;
      as_where (&filename, &line->line);
      line->filenum = get_filenum (filename);
      line->column = 0;
      line->flags = DWARF2_FLAG_BEGIN_STMT;
    }
  else
    *line = current;
}

/* Called for each machine instruction, or relatively atomic group of
   machine instructions (ie built-in macro).  The instruction or group
   is SIZE bytes in length.  If dwarf2 line number generation is called
   for, emit a line statement appropriately.  */

void
dwarf2_emit_insn (size)
     int size;
{
  struct dwarf2_line_info loc;

  if (debug_type != DEBUG_DWARF2 && ! loc_directive_seen)
    return;
  loc_directive_seen = false;
     
  dwarf2_where (&loc);
  dwarf2_gen_line_info (frag_now_fix () - size, &loc);
}

/* Get a .debug_line file number for FILENAME.  */

static unsigned int
get_filenum (filename)
     const char *filename;
{
  static unsigned int last_used;
  unsigned int i;

  if (last_used)
    if (strcmp (filename, files[last_used].filename) == 0)
      return last_used;

  for (i = 1; i < files_in_use; ++i)
    if (strcmp (filename, files[i].filename) == 0)
      return i;

  if (i >= files_allocated)
    {
      files_allocated = i + 32;
      files = (struct file_entry *)
        xrealloc (files, (i + 32) * sizeof(struct file_entry));
    }

  files[i].filename = xstrdup(filename);
  files[i].dir = 0;
  files_in_use = i + 1;
  last_used = i;

  return i;
}

/* Handle the .file directive.  */

void
dwarf2_directive_file (dummy)
     int dummy ATTRIBUTE_UNUSED;
{
  offsetT num;
  const char *filename;
  int filename_len;

  /* Continue to accept a bare string and pass it off.  */
  SKIP_WHITESPACE ();
  if (*input_line_pointer == '"')
    {
      s_app_file (0);
      return;
    }

  num = get_absolute_expression ();
  filename = demand_copy_C_string (&filename_len);
  demand_empty_rest_of_line ();

  if (num < 0)
    {
      as_bad (_("File number less than zero"));
      return;
    }

  if (num >= (int) user_filenum_allocated)
    {
      unsigned int old = user_filenum_allocated;

      user_filenum_allocated = num + 16;
      user_filenum = (unsigned int *)
        xrealloc (user_filenum, (num + 16) * sizeof (unsigned int));

      /* Zero the new memory.  */
      memset (user_filenum + old, 0, (num + 16 - old) * sizeof(unsigned int));
    }

  user_filenum[num] = get_filenum (filename);
}

void
dwarf2_directive_loc (dummy)
     int dummy ATTRIBUTE_UNUSED;
{
  offsetT filenum, line, column;

  filenum = get_absolute_expression ();
  SKIP_WHITESPACE ();
  line = get_absolute_expression ();
  SKIP_WHITESPACE ();
  column = get_absolute_expression ();
  demand_empty_rest_of_line ();

  if (filenum < 0)
    {
      as_bad (_("File number less than zero"));
      return;
    }
  if (filenum >= (int) user_filenum_allocated
      || user_filenum[filenum] == 0)
    {
      as_bad (_("Unassigned file number %ld"), (long) filenum);
      return;
    }

  current.filenum = user_filenum[filenum];
  current.line = line;
  current.column = column;
  current.flags = DWARF2_FLAG_BEGIN_STMT;

  loc_directive_seen = true;

#ifndef NO_LISTING
  if (listing)
    listing_source_line (line);
#endif
}

\f
static struct frag *
first_frag_for_seg (seg)
     segT seg;
{
  frchainS *f, *first = NULL;

  for (f = frchain_root; f ; f = f->frch_next)
    if (f->frch_seg == seg
        && (! first || first->frch_subseg > f->frch_subseg))
      first = f;

  return first ? first->frch_root : NULL;
}

static struct frag *
last_frag_for_seg (seg)
     segT seg;
{
  frchainS *f, *last = NULL;

  for (f = frchain_root; f ; f = f->frch_next)
    if (f->frch_seg == seg
        && (! last || last->frch_subseg < f->frch_subseg))
      last= f;

  return last ? last->frch_last : NULL;
}
\f
/* Emit a single byte into the current segment.  */

static inline void
out_byte (byte)
     int byte;
{
  FRAG_APPEND_1_CHAR (byte);
}

/* Emit a statement program opcode into the current segment.  */

static inline void
out_opcode (opc)
     int opc;
{
  out_byte (opc);
}

/* Emit a two-byte word into the current segment.  */

static inline void
out_two (data)
     int data;
{
  md_number_to_chars (frag_more (2), data, 2);
}

/* Emit a four byte word into the current segment.  */

static inline void
out_four (data)
     int data;
{
  md_number_to_chars (frag_more (4), data, 4);
}

/* Emit an unsigned "little-endian base 128" number.  */

static void
out_uleb128 (value)
     addressT value;
{
  output_leb128 (frag_more (sizeof_leb128 (value, 0)), value, 0);
}

/* Emit a tuple for .debug_abbrev.  */

static inline void
out_abbrev (name, form)
     int name, form;
{
  out_uleb128 (name);
  out_uleb128 (form);
}

/* Create a new fake symbol whose value is the current position.  */

static symbolS *
symbol_new_now ()
{
  return symbol_new (fake_label_name, now_seg, frag_now_fix (), frag_now);
}

/* Set the value of SYM to the current position in the current segment.  */

static void
set_symbol_value_now (sym)
     symbolS *sym;
{
  S_SET_SEGMENT (sym, now_seg);
  S_SET_VALUE (sym, frag_now_fix ());
  symbol_set_frag (sym, frag_now);
}

/* Get the size of a fragment.  */

static offsetT
get_frag_fix (frag)
     fragS *frag;
{
  frchainS *fr;

  if (frag->fr_next)
    return frag->fr_fix;

  /* If a fragment is the last in the chain, special measures must be
     taken to find its size before relaxation, since it may be pending
     on some subsegment chain.  */
  for (fr = frchain_root; fr ; fr = fr->frch_next)
    if (fr->frch_last == frag)
      {
        return ((char *) obstack_next_free (&fr->frch_obstack)
                - frag->fr_literal);
      }

  abort ();
}

/* Set an absolute address (may result in a relocation entry).  */

static void
out_set_addr (seg, frag, ofs)
     segT seg;
     fragS *frag;
     addressT ofs;
{
  expressionS expr;
  symbolS *sym;

  sym = symbol_new (fake_label_name, seg, ofs, frag);

  out_opcode (DW_LNS_extended_op);
  out_uleb128 (sizeof_address + 1);

  out_opcode (DW_LNE_set_address);
  expr.X_op = O_symbol;
  expr.X_add_symbol = sym;
  expr.X_add_number = 0;
  emit_expr (&expr, sizeof_address);
}

/* Encode a pair of line and address skips as efficiently as possible.
   Note that the line skip is signed, whereas the address skip is unsigned.

   The following two routines *must* be kept in sync.  This is
   enforced by making emit_inc_line_addr abort if we do not emit
   exactly the expected number of bytes.  */

static int
size_inc_line_addr (line_delta, addr_delta)
     int line_delta;
     addressT addr_delta;
{
  unsigned int tmp, opcode;
  int len = 0;

  /* Scale the address delta by the minimum instruction length.  */
#if DWARF2_LINE_MIN_INSN_LENGTH > 1  
  assert (addr_delta % DWARF2_LINE_MIN_INSN_LENGTH == 0);
  addr_delta /= DWARF2_LINE_MIN_INSN_LENGTH;
#endif

  /* INT_MAX is a signal that this is actually a DW_LNE_end_sequence.
     We cannot use special opcodes here, since we want the end_sequence
     to emit the matrix entry.  */
  if (line_delta == INT_MAX)
    {
      if (addr_delta == MAX_SPECIAL_ADDR_DELTA)
        len = 1;
      else
        len = 1 + sizeof_leb128 (addr_delta, 0);
      return len + 3;
    }

  /* Bias the line delta by the base.  */
  tmp = line_delta - DWARF2_LINE_BASE;

  /* If the line increment is out of range of a special opcode, we
     must encode it with DW_LNS_advance_line.  */
  if (tmp >= DWARF2_LINE_RANGE)
    {
      len = 1 + sizeof_leb128 (line_delta, 1);
      line_delta = 0;
      tmp = 0 - DWARF2_LINE_BASE;
    }

  /* Bias the opcode by the special opcode base.  */
  tmp += DWARF2_LINE_OPCODE_BASE;

  /* Avoid overflow when addr_delta is large.  */
  if (addr_delta < 256 + MAX_SPECIAL_ADDR_DELTA)
    {
      /* Try using a special opcode.  */
      opcode = tmp + addr_delta * DWARF2_LINE_RANGE;
      if (opcode <= 255)
        return len + 1;

      /* Try using DW_LNS_const_add_pc followed by special op.  */
      opcode = tmp + (addr_delta - MAX_SPECIAL_ADDR_DELTA) * DWARF2_LINE_RANGE;
      if (opcode <= 255)
        return len + 2;
    }

  /* Otherwise use DW_LNS_advance_pc.  */
  len += 1 + sizeof_leb128 (addr_delta, 0);

  /* DW_LNS_copy or special opcode.  */
  len += 1;

  return len;
}

static void
emit_inc_line_addr (line_delta, addr_delta, p, len)
     int line_delta;
     addressT addr_delta;
     char *p;
     int len;
{
  unsigned int tmp, opcode;
  int need_copy = 0;
  char *end = p + len;

#if DWARF2_LINE_MIN_INSN_LENGTH > 1  
  /* Scale the address delta by the minimum instruction length.  */
  assert (addr_delta % DWARF2_LINE_MIN_INSN_LENGTH == 0);
  addr_delta /= DWARF2_LINE_MIN_INSN_LENGTH;
#endif
  /* INT_MAX is a signal that this is actually a DW_LNE_end_sequence.
     We cannot use special opcodes here, since we want the end_sequence
     to emit the matrix entry.  */
  if (line_delta == INT_MAX)
    {
      if (addr_delta == MAX_SPECIAL_ADDR_DELTA)
        *p++ = DW_LNS_const_add_pc;
      else
        {
          *p++ = DW_LNS_advance_pc;
          p += output_leb128 (p, addr_delta, 0);
        }

      *p++ = DW_LNS_extended_op;
      *p++ = 1;
      *p++ = DW_LNE_end_sequence;
      goto done;
    }

  /* Bias the line delta by the base.  */
  tmp = line_delta - DWARF2_LINE_BASE;

  /* If the line increment is out of range of a special opcode, we
     must encode it with DW_LNS_advance_line.  */
  if (tmp >= DWARF2_LINE_RANGE)
    {
      *p++ = DW_LNS_advance_line;
      p += output_leb128 (p, line_delta, 1);

      /* Prettier, I think, to use DW_LNS_copy instead of a
         "line +0, addr +0" special opcode.  */
      if (addr_delta == 0)
        {
          *p++ = DW_LNS_copy;
          goto done;
        }

      line_delta = 0;
      tmp = 0 - DWARF2_LINE_BASE;
      need_copy = 1;
    }

  /* Bias the opcode by the special opcode base.  */
  tmp += DWARF2_LINE_OPCODE_BASE;

  /* Avoid overflow when addr_delta is large.  */
  if (addr_delta < 256 + MAX_SPECIAL_ADDR_DELTA)
    {
      /* Try using a special opcode.  */
      opcode = tmp + addr_delta * DWARF2_LINE_RANGE;
      if (opcode <= 255)
        {
          *p++ = opcode;
          goto done;
        }

      /* Try using DW_LNS_const_add_pc followed by special op.  */
      opcode = tmp + (addr_delta - MAX_SPECIAL_ADDR_DELTA) * DWARF2_LINE_RANGE;
      if (opcode <= 255)
        {
          *p++ = DW_LNS_const_add_pc;
          *p++ = opcode;
          goto done;
        }
    }

  /* Otherwise use DW_LNS_advance_pc.  */
  *p++ = DW_LNS_advance_pc;
  p += output_leb128 (p, addr_delta, 0);

  if (need_copy)
    *p++ = DW_LNS_copy;
  else
    *p++ = tmp;

 done:
  assert (p == end);
}

/* Handy routine to combine calls to the above two routines.  */

static void
out_inc_line_addr (line_delta, addr_delta)
     int line_delta;
     addressT addr_delta;
{
  int len = size_inc_line_addr (line_delta, addr_delta);
  emit_inc_line_addr (line_delta, addr_delta, frag_more (len), len);
}

/* Generate a variant frag that we can use to relax address/line
   increments between fragments of the target segment.  */

static void
relax_inc_line_addr (line_delta, seg, to_frag, to_ofs, from_frag, from_ofs)
     int line_delta;
     segT seg;
     fragS *to_frag, *from_frag;
     addressT to_ofs, from_ofs;
{
  symbolS *to_sym, *from_sym;
  expressionS expr;
  int max_chars;

  to_sym = symbol_new (fake_label_name, seg, to_ofs, to_frag);
  from_sym = symbol_new (fake_label_name, seg, from_ofs, from_frag);

  expr.X_op = O_subtract;
  expr.X_add_symbol = to_sym;
  expr.X_op_symbol = from_sym;
  expr.X_add_number = 0;

  /* The maximum size of the frag is the line delta with a maximum
     sized address delta.  */
  max_chars = size_inc_line_addr (line_delta, -DWARF2_LINE_MIN_INSN_LENGTH);

  frag_var (rs_dwarf2dbg, max_chars, max_chars, 1,
            make_expr_symbol (&expr), line_delta, NULL);
}

/* The function estimates the size of a rs_dwarf2dbg variant frag
   based on the current values of the symbols.  It is called before
   the relaxation loop.  We set fr_subtype to the expected length.  */

int
dwarf2dbg_estimate_size_before_relax (frag)
     fragS *frag;
{
  offsetT addr_delta;
  int size;

  addr_delta = resolve_symbol_value (frag->fr_symbol, 0);
  size = size_inc_line_addr (frag->fr_offset, addr_delta);

  frag->fr_subtype = size;

  return size;
}

/* This function relaxes a rs_dwarf2dbg variant frag based on the
   current values of the symbols.  fr_subtype is the current length
   of the frag.  This returns the change in frag length.  */

int
dwarf2dbg_relax_frag (frag)
     fragS *frag;
{
  int old_size, new_size;

  old_size = frag->fr_subtype;
  new_size = dwarf2dbg_estimate_size_before_relax (frag);
  
  return new_size - old_size;
}

/* This function converts a rs_dwarf2dbg variant frag into a normal
   fill frag.  This is called after all relaxation has been done.
   fr_subtype will be the desired length of the frag.  */

void
dwarf2dbg_convert_frag (frag)
     fragS *frag;
{
  offsetT addr_diff;

  addr_diff = resolve_symbol_value (frag->fr_symbol, 1);

  /* fr_var carries the max_chars that we created the fragment with.
     fr_subtype carries the current expected length.  We must, of
     course, have allocated enough memory earlier.  */
  assert (frag->fr_var >= (int) frag->fr_subtype);

  emit_inc_line_addr (frag->fr_offset, addr_diff, 
                      frag->fr_literal + frag->fr_fix, frag->fr_subtype);

  frag->fr_fix += frag->fr_subtype;
  frag->fr_type = rs_fill;
  frag->fr_var = 0;
  frag->fr_offset = 0;
}

/* Generate .debug_line content for the chain of line number entries
   beginning at E, for segment SEG.  */

static void
process_entries (seg, e)
     segT seg;
     struct line_entry *e;
{
  unsigned filenum = 1;
  unsigned line = 1;
  unsigned column = 0;
  unsigned flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_BEGIN_STMT : 0;
  fragS *frag = NULL;
  fragS *last_frag;
  addressT frag_ofs = 0;
  addressT last_frag_ofs;
  struct line_entry *next;

  while (e)
    {
      int changed = 0;

      if (filenum != e->loc.filenum)
        {
          filenum = e->loc.filenum;
          out_opcode (DW_LNS_set_file);
          out_uleb128 (filenum);
          changed = 1;
        }

      if (column != e->loc.column)
        {
          column = e->loc.column;
          out_opcode (DW_LNS_set_column);
          out_uleb128 (column);
          changed = 1;
        }

      if ((e->loc.flags ^ flags) & DWARF2_FLAG_BEGIN_STMT)
        {
          flags = e->loc.flags;
          out_opcode (DW_LNS_negate_stmt);
          changed = 1;
        }

      if (e->loc.flags & DWARF2_FLAG_BEGIN_BLOCK)
        {
          out_opcode (DW_LNS_set_basic_block);
          changed = 1;
        }

      if (line != e->loc.line || changed)
        {
          int line_delta = e->loc.line - line;
          if (frag == NULL)
            {
              out_set_addr (seg, e->frag, e->frag_ofs);
              out_inc_line_addr (line_delta, 0);
            }
          else if (frag == e->frag)
            out_inc_line_addr (line_delta, e->frag_ofs - frag_ofs);
          else
            relax_inc_line_addr (line_delta, seg, e->frag, e->frag_ofs,
                                 frag, frag_ofs);

          frag = e->frag;
          frag_ofs = e->frag_ofs;
          line = e->loc.line;
        }
      else if (frag == NULL)
        {
          out_set_addr (seg, e->frag, e->frag_ofs);
          frag = e->frag;
          frag_ofs = e->frag_ofs;
        }

      next = e->next;
      free (e);
      e = next;
    }

  /* Emit a DW_LNE_end_sequence for the end of the section.  */
  last_frag = last_frag_for_seg (seg);
  last_frag_ofs = get_frag_fix (last_frag);
  if (frag == last_frag)
    out_inc_line_addr (INT_MAX, last_frag_ofs - frag_ofs);
  else
    relax_inc_line_addr (INT_MAX, seg, last_frag, last_frag_ofs, 
                         frag, frag_ofs);
}

/* Emit the directory and file tables for .debug_line.  */

static void
out_file_list ()
{
  size_t size;
  char *cp;
  unsigned int i;

  /* Terminate directory list.  */
  out_byte ('\0');

  for (i = 1; i < files_in_use; ++i)
    {
      size = strlen (files[i].filename) + 1;
      cp = frag_more (size);
      memcpy (cp, files[i].filename, size);

      out_uleb128 (files[i].dir);       /* directory number */
      out_uleb128 (0);                  /* last modification timestamp */
      out_uleb128 (0);                  /* filesize */
    }

  /* Terminate filename list.  */
  out_byte (0);
}

/* Emit the collected .debug_line data.  */

static void
out_debug_line (line_seg)
     segT line_seg;
{
  expressionS expr;
  symbolS *line_start;
  symbolS *prologue_end;
  symbolS *line_end;
  struct line_seg *s;

  subseg_set (line_seg, 0);

  line_start = symbol_new_now ();
  prologue_end = symbol_make (fake_label_name);
  line_end = symbol_make (fake_label_name);

  /* Total length of the information for this compilation unit.  */
  expr.X_op = O_subtract;
  expr.X_add_symbol = line_end;
  expr.X_op_symbol = line_start;
  expr.X_add_number = -4;
  emit_expr (&expr, 4);

  /* Version.  */
  out_two (2);

  /* Length of the prologue following this length.  */
  expr.X_op = O_subtract;
  expr.X_add_symbol = prologue_end;
  expr.X_op_symbol = line_start;
  expr.X_add_number = - (4 + 2 + 4);
  emit_expr (&expr, 4);

  /* Parameters of the state machine.  */
  out_byte (DWARF2_LINE_MIN_INSN_LENGTH);
  out_byte (DWARF2_LINE_DEFAULT_IS_STMT);
  out_byte (DWARF2_LINE_BASE);
  out_byte (DWARF2_LINE_RANGE);
  out_byte (DWARF2_LINE_OPCODE_BASE);

  /* Standard opcode lengths.  */
  out_byte (0);                 /* DW_LNS_copy */
  out_byte (1);                 /* DW_LNS_advance_pc */
  out_byte (1);                 /* DW_LNS_advance_line */
  out_byte (1);                 /* DW_LNS_set_file */
  out_byte (1);                 /* DW_LNS_set_column */
  out_byte (0);                 /* DW_LNS_negate_stmt */
  out_byte (0);                 /* DW_LNS_set_basic_block */
  out_byte (0);                 /* DW_LNS_const_add_pc */
  out_byte (1);                 /* DW_LNS_fixed_advance_pc */

  out_file_list ();

  set_symbol_value_now (prologue_end);

  /* For each section, emit a statement program.  */
  for (s = all_segs; s ; s = s->next)
    process_entries (s->seg, s->head->head);

  set_symbol_value_now (line_end);
}

/* Emit data for .debug_aranges.  */

static void
out_debug_aranges (aranges_seg, info_seg)
     segT aranges_seg;
     segT info_seg;
{
  unsigned int addr_size = sizeof_address;
  addressT size, skip;
  struct line_seg *s;
  expressionS expr;
  char *p;

  size = 4 + 2 + 4 + 1 + 1;

  skip = 2*addr_size - (size & (2*addr_size - 1));
  if (skip == 2*addr_size)
    skip = 0;
  size += skip;

  for (s = all_segs; s ; s = s->next)
    size += 2*addr_size;

  size += 2*addr_size;

  subseg_set (aranges_seg, 0);

  /* Length of the compilation unit.  */
  out_four (size - 4);

  /* Version.  */
  out_two (2);

  /* Offset to .debug_info.  */
  expr.X_op = O_symbol;
  expr.X_add_symbol = section_symbol (info_seg);
  expr.X_add_number = 0;
  emit_expr (&expr, 4);

  /* Size of an address (offset portion).  */
  out_byte (addr_size);

  /* Size of a segment descriptor.  */
  out_byte (0);

  /* Align the header.  */
  if (skip)
    frag_align (ffs (2*addr_size) - 1, 0, 0);

  for (s = all_segs; s ; s = s->next)
    {
      fragS *frag;
      symbolS *beg, *end;

      frag = first_frag_for_seg (s->seg);
      beg = symbol_new (fake_label_name, s->seg, 0, frag);
      s->text_start = beg;

      frag = last_frag_for_seg (s->seg);
      end = symbol_new (fake_label_name, s->seg, get_frag_fix (frag), frag);
      s->text_end = end;

      expr.X_op = O_symbol;
      expr.X_add_symbol = beg;
      expr.X_add_number = 0;
      emit_expr (&expr, addr_size);

      expr.X_op = O_subtract;
      expr.X_add_symbol = end;
      expr.X_op_symbol = beg;
      expr.X_add_number = 0;
      emit_expr (&expr, addr_size);
    }

  p = frag_more (2 * addr_size);
  md_number_to_chars (p, 0, addr_size);
  md_number_to_chars (p + addr_size, 0, addr_size);
}

/* Emit data for .debug_abbrev.  Note that this must be kept in
   sync with out_debug_info below.  */

static void
out_debug_abbrev (abbrev_seg)
     segT abbrev_seg;
{
  subseg_set (abbrev_seg, 0);

  out_uleb128 (1);
  out_uleb128 (DW_TAG_compile_unit);
  out_byte (DW_CHILDREN_no);
  out_abbrev (DW_AT_stmt_list, DW_FORM_data4);
  if (all_segs->next == NULL)
    {
      out_abbrev (DW_AT_low_pc, DW_FORM_addr);
      out_abbrev (DW_AT_high_pc, DW_FORM_addr);
    }
  out_abbrev (DW_AT_comp_dir, DW_FORM_string);
  out_abbrev (DW_AT_producer, DW_FORM_string);
  out_abbrev (DW_AT_language, DW_FORM_data2);
  out_abbrev (0, 0);
}

/* Emit a description of this compilation unit for .debug_info.  */

static void
out_debug_info (info_seg, abbrev_seg, line_seg)
     segT info_seg;
     segT abbrev_seg;
     segT line_seg;
{
  char producer[128];
  char *comp_dir;
  expressionS expr;
  symbolS *info_start;
  symbolS *info_end;
  char *p;
  int len;

  subseg_set (info_seg, 0);

  info_start = symbol_new_now();
  info_end = symbol_make (fake_label_name);

  /* Compilation Unit length.  */
  expr.X_op = O_subtract;
  expr.X_add_symbol = info_end;
  expr.X_op_symbol = info_start;
  expr.X_add_number = -4;
  emit_expr (&expr, 4);

  /* DWARF version.  */
  out_two (2);

  /* .debug_abbrev offset */
  expr.X_op = O_symbol;
  expr.X_add_symbol = section_symbol (abbrev_seg);
  expr.X_add_number = 0;
  emit_expr (&expr, 4);

  /* Target address size.  */
  out_byte (sizeof_address);

  /* DW_TAG_compile_unit DIE abbrev */
  out_uleb128 (1);

  /* DW_AT_stmt_list */
  expr.X_op = O_symbol;
  expr.X_add_symbol = section_symbol (line_seg);
  expr.X_add_number = 0;
  emit_expr (&expr, 4);

  /* These two attributes may only be emitted if all of the code is
     contiguous.  Multiple sections are not that.  */
  if (all_segs->next == NULL)
    {
      /* DW_AT_low_pc */
      expr.X_op = O_symbol;
      expr.X_add_symbol = all_segs->text_start;
      expr.X_add_number = 0;
      emit_expr (&expr, sizeof_address);

      /* DW_AT_high_pc */
      expr.X_op = O_symbol;
      expr.X_add_symbol = all_segs->text_end;
      expr.X_add_number = 0;
      emit_expr (&expr, sizeof_address);
    }

  /* DW_AT_comp_dir */
  comp_dir = getpwd ();
  len = strlen (comp_dir) + 1;
  p = frag_more (len);
  memcpy (p, comp_dir, len);

  /* DW_AT_producer */
  sprintf (producer, "GNU AS %s", VERSION);
  len = strlen (producer) + 1;
  p = frag_more (len);
  memcpy (p, producer, len);

  /* DW_AT_language.  Yes, this is probably not really MIPS, but the
     dwarf2 draft has no standard code for assembler.  */
  out_two (DW_LANG_Mips_Assembler);

  set_symbol_value_now (info_end);
}

void
dwarf2_finish ()
{
  segT line_seg;
  struct line_seg *s;

  /* If no debug information was recorded, nothing to do.  */
  if (all_segs == NULL)
    return;

  /* Calculate the size of an address for the target machine.  */
#ifdef BFD_ASSEMBLER
  sizeof_address = bfd_arch_bits_per_address (stdoutput) / 8;
#else
  /* FIXME.  */
  sizeof_address = 4;
#endif

  /* Create and switch to the line number section.  */
  line_seg = subseg_new (".debug_line", 0);
#ifdef BFD_ASSEMBLER
  bfd_set_section_flags (stdoutput, line_seg, SEC_READONLY);
#endif

  /* For each subsection, chain the debug entries together.  */
  for (s = all_segs; s ; s = s->next)
    {
      struct line_subseg *ss = s->head;
      struct line_entry **ptail = ss->ptail;

      while ((ss = ss->next) != NULL)
        {
          *ptail = ss->head;
          ptail = ss->ptail;
        }
    }

  out_debug_line (line_seg);

  /* If this is assembler generated line info, we need .debug_info
     and .debug_abbrev sections as well.  */
  if (debug_type == DEBUG_DWARF2)
    {
      segT abbrev_seg;
      segT info_seg;
      segT aranges_seg;

      info_seg = subseg_new (".debug_info", 0);
      abbrev_seg = subseg_new (".debug_abbrev", 0);
      aranges_seg = subseg_new (".debug_aranges", 0);

#ifdef BFD_ASSEMBLER
      bfd_set_section_flags (stdoutput, info_seg, SEC_READONLY);
      bfd_set_section_flags (stdoutput, abbrev_seg, SEC_READONLY);
      bfd_set_section_flags (stdoutput, aranges_seg, SEC_READONLY);
#endif

      record_alignment (aranges_seg, ffs (2*sizeof_address) - 1);

      out_debug_aranges (aranges_seg, info_seg);
      out_debug_abbrev (abbrev_seg);
      out_debug_info (info_seg, abbrev_seg, line_seg);
    }
}

#else
void
dwarf2_finish ()
{
}

int
dwarf2dbg_estimate_size_before_relax (frag)
     fragS *frag ATTRIBUTE_UNUSED;
{
  as_fatal (_("dwarf2 is not supported for this object file format"));
  return 0;
}

int
dwarf2dbg_relax_frag (frag)
     fragS *frag ATTRIBUTE_UNUSED;
{
  as_fatal (_("dwarf2 is not supported for this object file format"));
  return 0;
}

void
dwarf2dbg_convert_frag (frag)
     fragS *frag ATTRIBUTE_UNUSED;
{
  as_fatal (_("dwarf2 is not supported for this object file format"));
}

void
dwarf2_emit_insn (size)
     int size ATTRIBUTE_UNUSED;
{
}

void
dwarf2_directive_file (dummy)
     int dummy ATTRIBUTE_UNUSED;
{
  as_fatal (_("dwarf2 is not supported for this object file format"));
}

void
dwarf2_directive_loc (dummy)
     int dummy ATTRIBUTE_UNUSED;
{
  as_fatal (_("dwarf2 is not supported for this object file format"));
}
#endif /* BFD_ASSEMBLER */