Use the stock 3.2.1-prerelease file.

[FreeBSD/FreeBSD.git] / contrib / gcc / stor-layout.c

/* C-compiler utilities for types and variables storage layout
   Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1996, 1998,
   1999, 2000, 2001, 2002 Free Software Foundation, Inc.

This file is part of GCC.

GCC 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.

GCC 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 GCC; see the file COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */


#include "config.h"
#include "system.h"
#include "tree.h"
#include "rtl.h"
#include "tm_p.h"
#include "flags.h"
#include "function.h"
#include "expr.h"
#include "toplev.h"
#include "ggc.h"
#include "target.h"

/* Set to one when set_sizetype has been called.  */
static int sizetype_set;

/* List of types created before set_sizetype has been called.  We do not
   make this a GGC root since we want these nodes to be reclaimed.  */
static tree early_type_list;

/* Data type for the expressions representing sizes of data types.
   It is the first integer type laid out.  */
tree sizetype_tab[(int) TYPE_KIND_LAST];

/* If nonzero, this is an upper limit on alignment of structure fields.
   The value is measured in bits.  */
unsigned int maximum_field_alignment;

/* If non-zero, the alignment of a bitstring or (power-)set value, in bits.
   May be overridden by front-ends.  */
unsigned int set_alignment = 0;

/* Nonzero if all REFERENCE_TYPEs are internal and hence should be
   allocated in Pmode, not ptr_mode.   Set only by internal_reference_types
   called only by a front end.  */
static int reference_types_internal = 0;

static void finalize_record_size        PARAMS ((record_layout_info));
static void finalize_type_size          PARAMS ((tree));
static void place_union_field           PARAMS ((record_layout_info, tree));
extern void debug_rli                   PARAMS ((record_layout_info));
\f
/* SAVE_EXPRs for sizes of types and decls, waiting to be expanded.  */

static tree pending_sizes;

/* Nonzero means cannot safely call expand_expr now,
   so put variable sizes onto `pending_sizes' instead.  */

int immediate_size_expand;

/* Show that REFERENCE_TYPES are internal and should be Pmode.  Called only
   by front end.  */

void
internal_reference_types ()
{
  reference_types_internal = 1;
}

/* Get a list of all the objects put on the pending sizes list.  */

tree
get_pending_sizes ()
{
  tree chain = pending_sizes;
  tree t;

  /* Put each SAVE_EXPR into the current function.  */
  for (t = chain; t; t = TREE_CHAIN (t))
    SAVE_EXPR_CONTEXT (TREE_VALUE (t)) = current_function_decl;

  pending_sizes = 0;
  return chain;
}

/* Return non-zero if EXPR is present on the pending sizes list.  */

int
is_pending_size (expr)
     tree expr;
{
  tree t;

  for (t = pending_sizes; t; t = TREE_CHAIN (t))
    if (TREE_VALUE (t) == expr)
      return 1;
  return 0;
}

/* Add EXPR to the pending sizes list.  */

void
put_pending_size (expr)
     tree expr;
{
  /* Strip any simple arithmetic from EXPR to see if it has an underlying
     SAVE_EXPR.  */
  while (TREE_CODE_CLASS (TREE_CODE (expr)) == '1'
         || (TREE_CODE_CLASS (TREE_CODE (expr)) == '2'
            && TREE_CONSTANT (TREE_OPERAND (expr, 1))))
    expr = TREE_OPERAND (expr, 0);

  if (TREE_CODE (expr) == SAVE_EXPR)
    pending_sizes = tree_cons (NULL_TREE, expr, pending_sizes);
}

/* Put a chain of objects into the pending sizes list, which must be
   empty.  */

void
put_pending_sizes (chain)
     tree chain;
{
  if (pending_sizes)
    abort ();

  pending_sizes = chain;
}

/* Given a size SIZE that may not be a constant, return a SAVE_EXPR
   to serve as the actual size-expression for a type or decl.  */

tree
variable_size (size)
     tree size;
{
  /* If the language-processor is to take responsibility for variable-sized
     items (e.g., languages which have elaboration procedures like Ada),
     just return SIZE unchanged.  Likewise for self-referential sizes and
     constant sizes.  */
  if (TREE_CONSTANT (size)
      || global_bindings_p () < 0 || contains_placeholder_p (size))
    return size;

  size = save_expr (size);

  /* If an array with a variable number of elements is declared, and
     the elements require destruction, we will emit a cleanup for the
     array.  That cleanup is run both on normal exit from the block
     and in the exception-handler for the block.  Normally, when code
     is used in both ordinary code and in an exception handler it is
     `unsaved', i.e., all SAVE_EXPRs are recalculated.  However, we do
     not wish to do that here; the array-size is the same in both
     places.  */
  if (TREE_CODE (size) == SAVE_EXPR)
    SAVE_EXPR_PERSISTENT_P (size) = 1;

  if (global_bindings_p ())
    {
      if (TREE_CONSTANT (size))
        error ("type size can't be explicitly evaluated");
      else
        error ("variable-size type declared outside of any function");

      return size_one_node;
    }

  if (immediate_size_expand)
    /* NULL_RTX is not defined; neither is the rtx type. 
       Also, we would like to pass const0_rtx here, but don't have it.  */
    expand_expr (size, expand_expr (integer_zero_node, NULL_RTX, VOIDmode, 0),
                 VOIDmode, 0);
  else if (cfun != 0 && cfun->x_dont_save_pending_sizes_p)
    /* The front-end doesn't want us to keep a list of the expressions
       that determine sizes for variable size objects.  */
    ;
  else
    put_pending_size (size);

  return size;
}
\f
#ifndef MAX_FIXED_MODE_SIZE
#define MAX_FIXED_MODE_SIZE GET_MODE_BITSIZE (DImode)
#endif

/* Return the machine mode to use for a nonscalar of SIZE bits.
   The mode must be in class CLASS, and have exactly that many bits.
   If LIMIT is nonzero, modes of wider than MAX_FIXED_MODE_SIZE will not
   be used.  */

enum machine_mode
mode_for_size (size, class, limit)
     unsigned int size;
     enum mode_class class;
     int limit;
{
  enum machine_mode mode;

  if (limit && size > MAX_FIXED_MODE_SIZE)
    return BLKmode;

  /* Get the first mode which has this size, in the specified class.  */
  for (mode = GET_CLASS_NARROWEST_MODE (class); mode != VOIDmode;
       mode = GET_MODE_WIDER_MODE (mode))
    if (GET_MODE_BITSIZE (mode) == size)
      return mode;

  return BLKmode;
}

/* Similar, except passed a tree node.  */

enum machine_mode
mode_for_size_tree (size, class, limit)
     tree size;
     enum mode_class class;
     int limit;
{
  if (TREE_CODE (size) != INTEGER_CST
      /* What we really want to say here is that the size can fit in a
         host integer, but we know there's no way we'd find a mode for
         this many bits, so there's no point in doing the precise test.  */
      || compare_tree_int (size, 1000) > 0)
    return BLKmode;
  else
    return mode_for_size (TREE_INT_CST_LOW (size), class, limit);
}

/* Similar, but never return BLKmode; return the narrowest mode that
   contains at least the requested number of bits.  */

enum machine_mode
smallest_mode_for_size (size, class)
     unsigned int size;
     enum mode_class class;
{
  enum machine_mode mode;

  /* Get the first mode which has at least this size, in the
     specified class.  */
  for (mode = GET_CLASS_NARROWEST_MODE (class); mode != VOIDmode;
       mode = GET_MODE_WIDER_MODE (mode))
    if (GET_MODE_BITSIZE (mode) >= size)
      return mode;

  abort ();
}

/* Find an integer mode of the exact same size, or BLKmode on failure.  */

enum machine_mode
int_mode_for_mode (mode)
     enum machine_mode mode;
{
  switch (GET_MODE_CLASS (mode))
    {
    case MODE_INT:
    case MODE_PARTIAL_INT:
      break;

    case MODE_COMPLEX_INT:
    case MODE_COMPLEX_FLOAT:
    case MODE_FLOAT:
    case MODE_VECTOR_INT:
    case MODE_VECTOR_FLOAT:
      mode = mode_for_size (GET_MODE_BITSIZE (mode), MODE_INT, 0);
      break;

    case MODE_RANDOM:
      if (mode == BLKmode)
        break;

      /* ... fall through ...  */

    case MODE_CC:
    default:
      abort ();
    }

  return mode;
}

/* Return the value of VALUE, rounded up to a multiple of DIVISOR.
   This can only be applied to objects of a sizetype.  */

tree
round_up (value, divisor)
     tree value;
     int divisor;
{
  tree arg = size_int_type (divisor, TREE_TYPE (value));

  return size_binop (MULT_EXPR, size_binop (CEIL_DIV_EXPR, value, arg), arg);
}

/* Likewise, but round down.  */

tree
round_down (value, divisor)
     tree value;
     int divisor;
{
  tree arg = size_int_type (divisor, TREE_TYPE (value));

  return size_binop (MULT_EXPR, size_binop (FLOOR_DIV_EXPR, value, arg), arg);
}
\f
/* Set the size, mode and alignment of a ..._DECL node.
   TYPE_DECL does need this for C++.
   Note that LABEL_DECL and CONST_DECL nodes do not need this,
   and FUNCTION_DECL nodes have them set up in a special (and simple) way.
   Don't call layout_decl for them.

   KNOWN_ALIGN is the amount of alignment we can assume this
   decl has with no special effort.  It is relevant only for FIELD_DECLs
   and depends on the previous fields.
   All that matters about KNOWN_ALIGN is which powers of 2 divide it.
   If KNOWN_ALIGN is 0, it means, "as much alignment as you like":
   the record will be aligned to suit.  */

void
layout_decl (decl, known_align)
     tree decl;
     unsigned int known_align;
{
  tree type = TREE_TYPE (decl);
  enum tree_code code = TREE_CODE (decl);

  if (code == CONST_DECL)
    return;
  else if (code != VAR_DECL && code != PARM_DECL && code != RESULT_DECL
           && code != TYPE_DECL && code != FIELD_DECL)
    abort ();

  if (type == error_mark_node)
    type = void_type_node;

  /* Usually the size and mode come from the data type without change,
     however, the front-end may set the explicit width of the field, so its
     size may not be the same as the size of its type.  This happens with
     bitfields, of course (an `int' bitfield may be only 2 bits, say), but it
     also happens with other fields.  For example, the C++ front-end creates
     zero-sized fields corresponding to empty base classes, and depends on
     layout_type setting DECL_FIELD_BITPOS correctly for the field.  Set the
     size in bytes from the size in bits.  If we have already set the mode,
     don't set it again since we can be called twice for FIELD_DECLs.  */

  TREE_UNSIGNED (decl) = TREE_UNSIGNED (type);
  if (DECL_MODE (decl) == VOIDmode)
    DECL_MODE (decl) = TYPE_MODE (type);

  if (DECL_SIZE (decl) == 0)
    {
      DECL_SIZE (decl) = TYPE_SIZE (type);
      DECL_SIZE_UNIT (decl) = TYPE_SIZE_UNIT (type);
    }
  else
    DECL_SIZE_UNIT (decl)
      = convert (sizetype, size_binop (CEIL_DIV_EXPR, DECL_SIZE (decl),
                                       bitsize_unit_node));

  /* Force alignment required for the data type.
     But if the decl itself wants greater alignment, don't override that.
     Likewise, if the decl is packed, don't override it.  */
  if (! (code == FIELD_DECL && DECL_BIT_FIELD (decl))
      && (DECL_ALIGN (decl) == 0
          || (! (code == FIELD_DECL && DECL_PACKED (decl))
              && TYPE_ALIGN (type) > DECL_ALIGN (decl))))
    {         
      DECL_ALIGN (decl) = TYPE_ALIGN (type);
      DECL_USER_ALIGN (decl) = 0;
    }

  /* For fields, set the bit field type and update the alignment.  */
  if (code == FIELD_DECL)
    {
      DECL_BIT_FIELD_TYPE (decl) = DECL_BIT_FIELD (decl) ? type : 0;
      if (maximum_field_alignment != 0)
        DECL_ALIGN (decl) = MIN (DECL_ALIGN (decl), maximum_field_alignment);

      /* If the field is of variable size, we can't misalign it since we
         have no way to make a temporary to align the result.  But this
         isn't an issue if the decl is not addressable.  Likewise if it
         is of unknown size.  */
      else if (DECL_PACKED (decl)
               && (DECL_NONADDRESSABLE_P (decl)
                   || DECL_SIZE_UNIT (decl) == 0
                   || TREE_CODE (DECL_SIZE_UNIT (decl)) == INTEGER_CST))
        {
          DECL_ALIGN (decl) = MIN (DECL_ALIGN (decl), BITS_PER_UNIT);
          DECL_USER_ALIGN (decl) = 0;
        }
    }

  /* See if we can use an ordinary integer mode for a bit-field. 
     Conditions are: a fixed size that is correct for another mode
     and occupying a complete byte or bytes on proper boundary.  */
  if (code == FIELD_DECL && DECL_BIT_FIELD (decl)
      && TYPE_SIZE (type) != 0
      && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST
      && GET_MODE_CLASS (TYPE_MODE (type)) == MODE_INT)
    {
      enum machine_mode xmode
        = mode_for_size_tree (DECL_SIZE (decl), MODE_INT, 1);

      if (xmode != BLKmode && known_align >= GET_MODE_ALIGNMENT (xmode))
        {
          DECL_ALIGN (decl) = MAX (GET_MODE_ALIGNMENT (xmode),
                                   DECL_ALIGN (decl));
          DECL_MODE (decl) = xmode;
          DECL_BIT_FIELD (decl) = 0;
        }
    }

  /* Turn off DECL_BIT_FIELD if we won't need it set.  */
  if (code == FIELD_DECL && DECL_BIT_FIELD (decl)
      && TYPE_MODE (type) == BLKmode && DECL_MODE (decl) == BLKmode
      && known_align >= TYPE_ALIGN (type)
      && DECL_ALIGN (decl) >= TYPE_ALIGN (type)
      && DECL_SIZE_UNIT (decl) != 0)
    DECL_BIT_FIELD (decl) = 0;

  /* Evaluate nonconstant size only once, either now or as soon as safe.  */
  if (DECL_SIZE (decl) != 0 && TREE_CODE (DECL_SIZE (decl)) != INTEGER_CST)
    DECL_SIZE (decl) = variable_size (DECL_SIZE (decl));
  if (DECL_SIZE_UNIT (decl) != 0
      && TREE_CODE (DECL_SIZE_UNIT (decl)) != INTEGER_CST)
    DECL_SIZE_UNIT (decl) = variable_size (DECL_SIZE_UNIT (decl));

  /* If requested, warn about definitions of large data objects.  */
  if (warn_larger_than
      && (code == VAR_DECL || code == PARM_DECL)
      && ! DECL_EXTERNAL (decl))
    {
      tree size = DECL_SIZE_UNIT (decl);

      if (size != 0 && TREE_CODE (size) == INTEGER_CST
          && compare_tree_int (size, larger_than_size) > 0)
        {
          unsigned int size_as_int = TREE_INT_CST_LOW (size);

          if (compare_tree_int (size, size_as_int) == 0)
            warning_with_decl (decl, "size of `%s' is %d bytes", size_as_int);
          else
            warning_with_decl (decl, "size of `%s' is larger than %d bytes",
                               larger_than_size);
        }
    }
}
\f
/* Hook for a front-end function that can modify the record layout as needed
   immediately before it is finalized.  */

void (*lang_adjust_rli) PARAMS ((record_layout_info)) = 0;

void
set_lang_adjust_rli (f)
     void (*f) PARAMS ((record_layout_info));
{
  lang_adjust_rli = f;
}

/* Begin laying out type T, which may be a RECORD_TYPE, UNION_TYPE, or
   QUAL_UNION_TYPE.  Return a pointer to a struct record_layout_info which
   is to be passed to all other layout functions for this record.  It is the
   responsibility of the caller to call `free' for the storage returned. 
   Note that garbage collection is not permitted until we finish laying
   out the record.  */

record_layout_info
start_record_layout (t)
     tree t;
{
  record_layout_info rli 
    = (record_layout_info) xmalloc (sizeof (struct record_layout_info_s));

  rli->t = t;

  /* If the type has a minimum specified alignment (via an attribute
     declaration, for example) use it -- otherwise, start with a
     one-byte alignment.  */
  rli->record_align = MAX (BITS_PER_UNIT, TYPE_ALIGN (t));
  rli->unpacked_align = rli->unpadded_align = rli->record_align;
  rli->offset_align = MAX (rli->record_align, BIGGEST_ALIGNMENT);

#ifdef STRUCTURE_SIZE_BOUNDARY
  /* Packed structures don't need to have minimum size.  */
  if (! TYPE_PACKED (t))
    rli->record_align = MAX (rli->record_align, STRUCTURE_SIZE_BOUNDARY);
#endif

  rli->offset = size_zero_node;
  rli->bitpos = bitsize_zero_node;
  rli->prev_field = 0;
  rli->pending_statics = 0;
  rli->packed_maybe_necessary = 0;

  return rli;
}

/* These four routines perform computations that convert between
   the offset/bitpos forms and byte and bit offsets.  */

tree
bit_from_pos (offset, bitpos)
     tree offset, bitpos;
{
  return size_binop (PLUS_EXPR, bitpos,
                     size_binop (MULT_EXPR, convert (bitsizetype, offset),
                                 bitsize_unit_node));
}

tree
byte_from_pos (offset, bitpos)
     tree offset, bitpos;
{
  return size_binop (PLUS_EXPR, offset,
                     convert (sizetype,
                              size_binop (TRUNC_DIV_EXPR, bitpos,
                                          bitsize_unit_node)));
}

void
pos_from_byte (poffset, pbitpos, off_align, pos)
     tree *poffset, *pbitpos;
     unsigned int off_align;
     tree pos;
{
  *poffset
    = size_binop (MULT_EXPR,
                  convert (sizetype,
                           size_binop (FLOOR_DIV_EXPR, pos,
                                       bitsize_int (off_align
                                                    / BITS_PER_UNIT))),
                  size_int (off_align / BITS_PER_UNIT));
  *pbitpos = size_binop (MULT_EXPR,
                         size_binop (FLOOR_MOD_EXPR, pos,
                                     bitsize_int (off_align / BITS_PER_UNIT)),
                         bitsize_unit_node);
}

void
pos_from_bit (poffset, pbitpos, off_align, pos)
     tree *poffset, *pbitpos;
     unsigned int off_align;
     tree pos;
{
  *poffset = size_binop (MULT_EXPR,
                         convert (sizetype,
                                  size_binop (FLOOR_DIV_EXPR, pos,
                                              bitsize_int (off_align))),
                         size_int (off_align / BITS_PER_UNIT));
  *pbitpos = size_binop (FLOOR_MOD_EXPR, pos, bitsize_int (off_align));
}

/* Given a pointer to bit and byte offsets and an offset alignment,
   normalize the offsets so they are within the alignment.  */

void
normalize_offset (poffset, pbitpos, off_align)
     tree *poffset, *pbitpos;
     unsigned int off_align;
{
  /* If the bit position is now larger than it should be, adjust it
     downwards.  */
  if (compare_tree_int (*pbitpos, off_align) >= 0)
    {
      tree extra_aligns = size_binop (FLOOR_DIV_EXPR, *pbitpos,
                                      bitsize_int (off_align));

      *poffset
        = size_binop (PLUS_EXPR, *poffset,
                      size_binop (MULT_EXPR, convert (sizetype, extra_aligns),
                                  size_int (off_align / BITS_PER_UNIT)));
                                
      *pbitpos
        = size_binop (FLOOR_MOD_EXPR, *pbitpos, bitsize_int (off_align));
    }
}

/* Print debugging information about the information in RLI.  */

void
debug_rli (rli)
     record_layout_info rli;
{
  print_node_brief (stderr, "type", rli->t, 0);
  print_node_brief (stderr, "\noffset", rli->offset, 0);
  print_node_brief (stderr, " bitpos", rli->bitpos, 0);

  fprintf (stderr, "\naligns: rec = %u, unpack = %u, unpad = %u, off = %u\n",
           rli->record_align, rli->unpacked_align, rli->unpadded_align,
           rli->offset_align);
  if (rli->packed_maybe_necessary)
    fprintf (stderr, "packed may be necessary\n");

  if (rli->pending_statics)
    {
      fprintf (stderr, "pending statics:\n");
      debug_tree (rli->pending_statics);
    }
}

/* Given an RLI with a possibly-incremented BITPOS, adjust OFFSET and
   BITPOS if necessary to keep BITPOS below OFFSET_ALIGN.  */

void
normalize_rli (rli)
     record_layout_info rli;
{
  normalize_offset (&rli->offset, &rli->bitpos, rli->offset_align);
}

/* Returns the size in bytes allocated so far.  */

tree
rli_size_unit_so_far (rli)
     record_layout_info rli;
{
  return byte_from_pos (rli->offset, rli->bitpos);
}

/* Returns the size in bits allocated so far.  */

tree
rli_size_so_far (rli)
     record_layout_info rli;
{
  return bit_from_pos (rli->offset, rli->bitpos);
}

/* Called from place_field to handle unions.  */

static void
place_union_field (rli, field)
     record_layout_info rli;
     tree field;
{
  unsigned int desired_align;

  layout_decl (field, 0);
  
  DECL_FIELD_OFFSET (field) = size_zero_node;
  DECL_FIELD_BIT_OFFSET (field) = bitsize_zero_node;
  SET_DECL_OFFSET_ALIGN (field, BIGGEST_ALIGNMENT);

  desired_align = DECL_ALIGN (field);

#ifdef BIGGEST_FIELD_ALIGNMENT
  /* Some targets (i.e. i386) limit union field alignment
     to a lower boundary than alignment of variables unless
     it was overridden by attribute aligned.  */
  if (! DECL_USER_ALIGN (field))
    desired_align =
      MIN (desired_align, (unsigned) BIGGEST_FIELD_ALIGNMENT);
#endif

#ifdef ADJUST_FIELD_ALIGN
  if (! DECL_USER_ALIGN (field))
    desired_align = ADJUST_FIELD_ALIGN (field, desired_align);
#endif

  TYPE_USER_ALIGN (rli->t) |= DECL_USER_ALIGN (field);

  /* Union must be at least as aligned as any field requires.  */
  rli->record_align = MAX (rli->record_align, desired_align);
  rli->unpadded_align = MAX (rli->unpadded_align, desired_align);

#ifdef PCC_BITFIELD_TYPE_MATTERS
  /* On the m88000, a bit field of declare type `int' forces the
     entire union to have `int' alignment.  */
  if (PCC_BITFIELD_TYPE_MATTERS && DECL_BIT_FIELD_TYPE (field))
    {
      unsigned int type_align = TYPE_ALIGN (TREE_TYPE (field));

#ifdef ADJUST_FIELD_ALIGN
      if (! TYPE_USER_ALIGN (TREE_TYPE (field)))
        type_align = ADJUST_FIELD_ALIGN (field, type_align);
#endif
      rli->record_align = MAX (rli->record_align, type_align);
      rli->unpadded_align = MAX (rli->unpadded_align, type_align);
      TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (TREE_TYPE (field));
    }
#endif

  /* We assume the union's size will be a multiple of a byte so we don't
     bother with BITPOS.  */
  if (TREE_CODE (rli->t) == UNION_TYPE)
    rli->offset = size_binop (MAX_EXPR, rli->offset, DECL_SIZE_UNIT (field));
  else if (TREE_CODE (rli->t) == QUAL_UNION_TYPE)
    rli->offset = fold (build (COND_EXPR, sizetype, 
                               DECL_QUALIFIER (field),
                               DECL_SIZE_UNIT (field), rli->offset));
}

/* RLI contains information about the layout of a RECORD_TYPE.  FIELD
   is a FIELD_DECL to be added after those fields already present in
   T.  (FIELD is not actually added to the TYPE_FIELDS list here;
   callers that desire that behavior must manually perform that step.)  */

void
place_field (rli, field)
     record_layout_info rli;
     tree field;
{
  /* The alignment required for FIELD.  */
  unsigned int desired_align;
  /* The alignment FIELD would have if we just dropped it into the
     record as it presently stands.  */
  unsigned int known_align;
  unsigned int actual_align;
  unsigned int user_align;
  /* The type of this field.  */
  tree type = TREE_TYPE (field);
 
  if (TREE_CODE (field) == ERROR_MARK || TREE_CODE (type) == ERROR_MARK)
      return;

  /* If FIELD is static, then treat it like a separate variable, not
     really like a structure field.  If it is a FUNCTION_DECL, it's a
     method.  In both cases, all we do is lay out the decl, and we do
     it *after* the record is laid out.  */
  if (TREE_CODE (field) == VAR_DECL)
    {
      rli->pending_statics = tree_cons (NULL_TREE, field,
                                        rli->pending_statics);
      return;
    }

  /* Enumerators and enum types which are local to this class need not
     be laid out.  Likewise for initialized constant fields.  */
  else if (TREE_CODE (field) != FIELD_DECL)
    return;

  /* Unions are laid out very differently than records, so split
     that code off to another function.  */
  else if (TREE_CODE (rli->t) != RECORD_TYPE)
    {
      place_union_field (rli, field);
      return;
    }

  /* Work out the known alignment so far.  Note that A & (-A) is the
     value of the least-significant bit in A that is one.  */
  if (! integer_zerop (rli->bitpos))
    known_align = (tree_low_cst (rli->bitpos, 1)
                   & - tree_low_cst (rli->bitpos, 1));
  else if (integer_zerop (rli->offset))
    known_align = BIGGEST_ALIGNMENT;
  else if (host_integerp (rli->offset, 1))
    known_align = (BITS_PER_UNIT
                   * (tree_low_cst (rli->offset, 1)
                      & - tree_low_cst (rli->offset, 1)));
  else
    known_align = rli->offset_align;

  /* Lay out the field so we know what alignment it needs.  For a
     packed field, use the alignment as specified, disregarding what
     the type would want.  */
  desired_align = DECL_ALIGN (field);
  user_align = DECL_USER_ALIGN (field);
  layout_decl (field, known_align);
  if (! DECL_PACKED (field))
    {
      desired_align = DECL_ALIGN (field);
      user_align = DECL_USER_ALIGN (field);
    }

  /* Some targets (i.e. i386, VMS) limit struct field alignment
     to a lower boundary than alignment of variables unless
     it was overridden by attribute aligned.  */
#ifdef BIGGEST_FIELD_ALIGNMENT
  if (! user_align)
    desired_align
      = MIN (desired_align, (unsigned) BIGGEST_FIELD_ALIGNMENT);
#endif

#ifdef ADJUST_FIELD_ALIGN
  if (! user_align)
    desired_align = ADJUST_FIELD_ALIGN (field, desired_align);
#endif

  /* Record must have at least as much alignment as any field.
     Otherwise, the alignment of the field within the record is
     meaningless.  */
  if ((* targetm.ms_bitfield_layout_p) (rli->t)
      && type != error_mark_node
      && DECL_BIT_FIELD_TYPE (field)
      && ! integer_zerop (TYPE_SIZE (type))
      && integer_zerop (DECL_SIZE (field)))
    {
      if (rli->prev_field
          && DECL_BIT_FIELD_TYPE (rli->prev_field)
          && ! integer_zerop (DECL_SIZE (rli->prev_field)))
        {
          rli->record_align = MAX (rli->record_align, desired_align);
          rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
        }
      else
        desired_align = 1;
    }   
  else
#ifdef PCC_BITFIELD_TYPE_MATTERS
  if (PCC_BITFIELD_TYPE_MATTERS && type != error_mark_node
      && ! (* targetm.ms_bitfield_layout_p) (rli->t)
      && DECL_BIT_FIELD_TYPE (field)
      && ! integer_zerop (TYPE_SIZE (type)))
    {
      /* For these machines, a zero-length field does not
         affect the alignment of the structure as a whole.
         It does, however, affect the alignment of the next field
         within the structure.  */
      if (! integer_zerop (DECL_SIZE (field)))
        rli->record_align = MAX (rli->record_align, desired_align);
      else if (! DECL_PACKED (field))
        desired_align = TYPE_ALIGN (type);

      /* A named bit field of declared type `int'
         forces the entire structure to have `int' alignment.  */
      if (DECL_NAME (field) != 0)
        {
          unsigned int type_align = TYPE_ALIGN (type);

#ifdef ADJUST_FIELD_ALIGN
          if (! TYPE_USER_ALIGN (type))
            type_align = ADJUST_FIELD_ALIGN (field, type_align);
#endif

          if (maximum_field_alignment != 0)
            type_align = MIN (type_align, maximum_field_alignment);
          else if (DECL_PACKED (field))
            type_align = MIN (type_align, BITS_PER_UNIT);

          rli->record_align = MAX (rli->record_align, type_align);
          rli->unpadded_align = MAX (rli->unpadded_align, DECL_ALIGN (field));
          if (warn_packed)
            rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
          user_align |= TYPE_USER_ALIGN (type);
        }
    }
  else
#endif
    {
      rli->record_align = MAX (rli->record_align, desired_align);
      rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
      rli->unpadded_align = MAX (rli->unpadded_align, DECL_ALIGN (field));
    }

  if (warn_packed && DECL_PACKED (field))
    {
      if (known_align > TYPE_ALIGN (type))
        {
          if (TYPE_ALIGN (type) > desired_align)
            {
              if (STRICT_ALIGNMENT)
                warning_with_decl (field, "packed attribute causes inefficient alignment for `%s'");
              else
                warning_with_decl (field, "packed attribute is unnecessary for `%s'");
            }
        }
      else
        rli->packed_maybe_necessary = 1;
    }

  /* Does this field automatically have alignment it needs by virtue
     of the fields that precede it and the record's own alignment?  */
  if (known_align < desired_align)
    {
      /* No, we need to skip space before this field.
         Bump the cumulative size to multiple of field alignment.  */

      if (warn_padded)
        warning_with_decl (field, "padding struct to align `%s'");

      /* If the alignment is still within offset_align, just align
         the bit position.  */
      if (desired_align < rli->offset_align)
        rli->bitpos = round_up (rli->bitpos, desired_align);
      else
        {
          /* First adjust OFFSET by the partial bits, then align.  */
          rli->offset
            = size_binop (PLUS_EXPR, rli->offset,
                          convert (sizetype,
                                   size_binop (CEIL_DIV_EXPR, rli->bitpos,
                                               bitsize_unit_node)));
          rli->bitpos = bitsize_zero_node;

          rli->offset = round_up (rli->offset, desired_align / BITS_PER_UNIT);
        }

      if (! TREE_CONSTANT (rli->offset))
        rli->offset_align = desired_align;

    }

  /* Handle compatibility with PCC.  Note that if the record has any
     variable-sized fields, we need not worry about compatibility.  */
#ifdef PCC_BITFIELD_TYPE_MATTERS
  if (PCC_BITFIELD_TYPE_MATTERS
      && ! (* targetm.ms_bitfield_layout_p) (rli->t)
      && TREE_CODE (field) == FIELD_DECL
      && type != error_mark_node
      && DECL_BIT_FIELD (field)
      && ! DECL_PACKED (field)
      && maximum_field_alignment == 0
      && ! integer_zerop (DECL_SIZE (field))
      && host_integerp (DECL_SIZE (field), 1)
      && host_integerp (rli->offset, 1)
      && host_integerp (TYPE_SIZE (type), 1))
    {
      unsigned int type_align = TYPE_ALIGN (type);
      tree dsize = DECL_SIZE (field);
      HOST_WIDE_INT field_size = tree_low_cst (dsize, 1);
      HOST_WIDE_INT offset = tree_low_cst (rli->offset, 0);
      HOST_WIDE_INT bit_offset = tree_low_cst (rli->bitpos, 0);

#ifdef ADJUST_FIELD_ALIGN
      if (! TYPE_USER_ALIGN (type))
        type_align = ADJUST_FIELD_ALIGN (field, type_align);
#endif

      /* A bit field may not span more units of alignment of its type
         than its type itself.  Advance to next boundary if necessary.  */
      if ((((offset * BITS_PER_UNIT + bit_offset + field_size +
             type_align - 1)
            / type_align)
           - (offset * BITS_PER_UNIT + bit_offset) / type_align)
          > tree_low_cst (TYPE_SIZE (type), 1) / type_align)
        rli->bitpos = round_up (rli->bitpos, type_align);

      user_align |= TYPE_USER_ALIGN (type);
    }
#endif

#ifdef BITFIELD_NBYTES_LIMITED
  if (BITFIELD_NBYTES_LIMITED
      && ! (* targetm.ms_bitfield_layout_p) (rli->t)
      && TREE_CODE (field) == FIELD_DECL
      && type != error_mark_node
      && DECL_BIT_FIELD_TYPE (field)
      && ! DECL_PACKED (field)
      && ! integer_zerop (DECL_SIZE (field))
      && host_integerp (DECL_SIZE (field), 1)
      && host_integerp (rli->offset, 1)
      && host_integerp (TYPE_SIZE (type), 1))
    {
      unsigned int type_align = TYPE_ALIGN (type);
      tree dsize = DECL_SIZE (field);
      HOST_WIDE_INT field_size = tree_low_cst (dsize, 1);
      HOST_WIDE_INT offset = tree_low_cst (rli->offset, 0);
      HOST_WIDE_INT bit_offset = tree_low_cst (rli->bitpos, 0);

#ifdef ADJUST_FIELD_ALIGN
      if (! TYPE_USER_ALIGN (type))
        type_align = ADJUST_FIELD_ALIGN (field, type_align);
#endif

      if (maximum_field_alignment != 0)
        type_align = MIN (type_align, maximum_field_alignment);
      /* ??? This test is opposite the test in the containing if
         statement, so this code is unreachable currently.  */
      else if (DECL_PACKED (field))
        type_align = MIN (type_align, BITS_PER_UNIT);

      /* A bit field may not span the unit of alignment of its type.
         Advance to next boundary if necessary.  */
      /* ??? This code should match the code above for the
         PCC_BITFIELD_TYPE_MATTERS case.  */
      if ((offset * BITS_PER_UNIT + bit_offset) / type_align
          != ((offset * BITS_PER_UNIT + bit_offset + field_size - 1)
              / type_align))
        rli->bitpos = round_up (rli->bitpos, type_align);

      user_align |= TYPE_USER_ALIGN (type);
    }
#endif

  /* See the docs for TARGET_MS_BITFIELD_LAYOUT_P for details.  */
  if ((* targetm.ms_bitfield_layout_p) (rli->t)
      && TREE_CODE (field) == FIELD_DECL
      && type != error_mark_node
      && ! DECL_PACKED (field)
      && rli->prev_field
      && DECL_SIZE (field)
      && host_integerp (DECL_SIZE (field), 1)
      && DECL_SIZE (rli->prev_field)
      && host_integerp (DECL_SIZE (rli->prev_field), 1)
      && host_integerp (rli->offset, 1)
      && host_integerp (TYPE_SIZE (type), 1)
      && host_integerp (TYPE_SIZE (TREE_TYPE (rli->prev_field)), 1)
      && ((DECL_BIT_FIELD_TYPE (rli->prev_field)
           && ! integer_zerop (DECL_SIZE (rli->prev_field)))
          || (DECL_BIT_FIELD_TYPE (field)
              && ! integer_zerop (DECL_SIZE (field))))
      && (! simple_cst_equal (TYPE_SIZE (type),
                              TYPE_SIZE (TREE_TYPE (rli->prev_field)))
          /* If the previous field was a zero-sized bit-field, either
             it was ignored, in which case we must ensure the proper
             alignment of this field here, or it already forced the
             alignment of this field, in which case forcing the
             alignment again is harmless.  So, do it in both cases.  */
          || (DECL_BIT_FIELD_TYPE (rli->prev_field)
              && integer_zerop (DECL_SIZE (rli->prev_field)))))
    {
      unsigned int type_align = TYPE_ALIGN (type);

      if (rli->prev_field
          && DECL_BIT_FIELD_TYPE (rli->prev_field)
          /* If the previous bit-field is zero-sized, we've already
             accounted for its alignment needs (or ignored it, if
             appropriate) while placing it.  */
          && ! integer_zerop (DECL_SIZE (rli->prev_field)))
        type_align = MAX (type_align,
                          TYPE_ALIGN (TREE_TYPE (rli->prev_field)));

      if (maximum_field_alignment != 0)
        type_align = MIN (type_align, maximum_field_alignment);

      rli->bitpos = round_up (rli->bitpos, type_align);
    }

  /* Offset so far becomes the position of this field after normalizing.  */
  normalize_rli (rli);
  DECL_FIELD_OFFSET (field) = rli->offset;
  DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
  SET_DECL_OFFSET_ALIGN (field, rli->offset_align);

  TYPE_USER_ALIGN (rli->t) |= user_align;

  /* If this field ended up more aligned than we thought it would be (we
     approximate this by seeing if its position changed), lay out the field
     again; perhaps we can use an integral mode for it now.  */
  if (! integer_zerop (DECL_FIELD_BIT_OFFSET (field)))
    actual_align = (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
                    & - tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1));
  else if (integer_zerop (DECL_FIELD_OFFSET (field)))
    actual_align = BIGGEST_ALIGNMENT;
  else if (host_integerp (DECL_FIELD_OFFSET (field), 1))
    actual_align = (BITS_PER_UNIT
                   * (tree_low_cst (DECL_FIELD_OFFSET (field), 1)
                      & - tree_low_cst (DECL_FIELD_OFFSET (field), 1)));
  else
    actual_align = DECL_OFFSET_ALIGN (field);

  if (known_align != actual_align)
    layout_decl (field, actual_align);

  rli->prev_field = field;

  /* Now add size of this field to the size of the record.  If the size is
     not constant, treat the field as being a multiple of bytes and just
     adjust the offset, resetting the bit position.  Otherwise, apportion the
     size amongst the bit position and offset.  First handle the case of an
     unspecified size, which can happen when we have an invalid nested struct
     definition, such as struct j { struct j { int i; } }.  The error message
     is printed in finish_struct.  */
  if (DECL_SIZE (field) == 0)
    /* Do nothing.  */;
  else if (TREE_CODE (DECL_SIZE_UNIT (field)) != INTEGER_CST
           || TREE_CONSTANT_OVERFLOW (DECL_SIZE_UNIT (field)))
    {
      rli->offset
        = size_binop (PLUS_EXPR, rli->offset,
                      convert (sizetype,
                               size_binop (CEIL_DIV_EXPR, rli->bitpos,
                                           bitsize_unit_node)));
      rli->offset
        = size_binop (PLUS_EXPR, rli->offset, DECL_SIZE_UNIT (field));
      rli->bitpos = bitsize_zero_node;
      rli->offset_align = MIN (rli->offset_align, DECL_ALIGN (field));
    }
  else
    {
      rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field));
      normalize_rli (rli);
    }
}

/* Assuming that all the fields have been laid out, this function uses
   RLI to compute the final TYPE_SIZE, TYPE_ALIGN, etc. for the type
   inidicated by RLI.  */

static void
finalize_record_size (rli)
     record_layout_info rli;
{
  tree unpadded_size, unpadded_size_unit;

  /* Now we want just byte and bit offsets, so set the offset alignment
     to be a byte and then normalize.  */
  rli->offset_align = BITS_PER_UNIT;
  normalize_rli (rli);

  /* Determine the desired alignment.  */
#ifdef ROUND_TYPE_ALIGN
  TYPE_ALIGN (rli->t) = ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t),
                                          rli->record_align);
#else
  TYPE_ALIGN (rli->t) = MAX (TYPE_ALIGN (rli->t), rli->record_align);
#endif

  /* Compute the size so far.  Be sure to allow for extra bits in the
     size in bytes.  We have guaranteed above that it will be no more
     than a single byte.  */
  unpadded_size = rli_size_so_far (rli);
  unpadded_size_unit = rli_size_unit_so_far (rli);
  if (! integer_zerop (rli->bitpos))
    unpadded_size_unit
      = size_binop (PLUS_EXPR, unpadded_size_unit, size_one_node);

  /* Record the un-rounded size in the binfo node.  But first we check
     the size of TYPE_BINFO to make sure that BINFO_SIZE is available.  */
  if (TYPE_BINFO (rli->t) && TREE_VEC_LENGTH (TYPE_BINFO (rli->t)) > 6)
    {
      TYPE_BINFO_SIZE (rli->t) = unpadded_size;
      TYPE_BINFO_SIZE_UNIT (rli->t) = unpadded_size_unit;
    }

    /* Round the size up to be a multiple of the required alignment */
#ifdef ROUND_TYPE_SIZE
  TYPE_SIZE (rli->t) = ROUND_TYPE_SIZE (rli->t, unpadded_size,
                                        TYPE_ALIGN (rli->t));
  TYPE_SIZE_UNIT (rli->t)
    = ROUND_TYPE_SIZE_UNIT (rli->t, unpadded_size_unit,
                            TYPE_ALIGN (rli->t) / BITS_PER_UNIT);
#else
  TYPE_SIZE (rli->t) = round_up (unpadded_size, TYPE_ALIGN (rli->t));
  TYPE_SIZE_UNIT (rli->t) = round_up (unpadded_size_unit,
                                      TYPE_ALIGN (rli->t) / BITS_PER_UNIT);
#endif

  if (warn_padded && TREE_CONSTANT (unpadded_size)
      && simple_cst_equal (unpadded_size, TYPE_SIZE (rli->t)) == 0)
    warning ("padding struct size to alignment boundary");
  
  if (warn_packed && TREE_CODE (rli->t) == RECORD_TYPE
      && TYPE_PACKED (rli->t) && ! rli->packed_maybe_necessary
      && TREE_CONSTANT (unpadded_size))
    {
      tree unpacked_size;

#ifdef ROUND_TYPE_ALIGN
      rli->unpacked_align
        = ROUND_TYPE_ALIGN (rli->t, TYPE_ALIGN (rli->t), rli->unpacked_align);
#else
      rli->unpacked_align = MAX (TYPE_ALIGN (rli->t), rli->unpacked_align);
#endif

#ifdef ROUND_TYPE_SIZE
      unpacked_size = ROUND_TYPE_SIZE (rli->t, TYPE_SIZE (rli->t),
                                       rli->unpacked_align);
#else
      unpacked_size = round_up (TYPE_SIZE (rli->t), rli->unpacked_align);
#endif

      if (simple_cst_equal (unpacked_size, TYPE_SIZE (rli->t)))
        {
          TYPE_PACKED (rli->t) = 0;

          if (TYPE_NAME (rli->t))
            {
              const char *name;

              if (TREE_CODE (TYPE_NAME (rli->t)) == IDENTIFIER_NODE)
                name = IDENTIFIER_POINTER (TYPE_NAME (rli->t));
              else
                name = IDENTIFIER_POINTER (DECL_NAME (TYPE_NAME (rli->t)));

              if (STRICT_ALIGNMENT)
                warning ("packed attribute causes inefficient alignment for `%s'", name);
              else
                warning ("packed attribute is unnecessary for `%s'", name);
            }
          else
            {
              if (STRICT_ALIGNMENT)
                warning ("packed attribute causes inefficient alignment");
              else
                warning ("packed attribute is unnecessary");
            }
        }
    }
}

/* Compute the TYPE_MODE for the TYPE (which is a RECORD_TYPE).  */

void
compute_record_mode (type)
     tree type;
{
  tree field;
  enum machine_mode mode = VOIDmode;

  /* Most RECORD_TYPEs have BLKmode, so we start off assuming that.
     However, if possible, we use a mode that fits in a register
     instead, in order to allow for better optimization down the
     line.  */
  TYPE_MODE (type) = BLKmode;

  if (! host_integerp (TYPE_SIZE (type), 1))
    return;

  /* A record which has any BLKmode members must itself be
     BLKmode; it can't go in a register.  Unless the member is
     BLKmode only because it isn't aligned.  */
  for (field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field))
    {
      unsigned HOST_WIDE_INT bitpos;

      if (TREE_CODE (field) != FIELD_DECL)
        continue;

      if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK
          || (TYPE_MODE (TREE_TYPE (field)) == BLKmode
              && ! TYPE_NO_FORCE_BLK (TREE_TYPE (field)))
          || ! host_integerp (bit_position (field), 1)
          || DECL_SIZE (field) == 0
          || ! host_integerp (DECL_SIZE (field), 1))
        return;

      bitpos = int_bit_position (field);
          
      /* Must be BLKmode if any field crosses a word boundary,
         since extract_bit_field can't handle that in registers.  */
      if (bitpos / BITS_PER_WORD
          != ((tree_low_cst (DECL_SIZE (field), 1) + bitpos - 1)
              / BITS_PER_WORD)
          /* But there is no problem if the field is entire words.  */
          && tree_low_cst (DECL_SIZE (field), 1) % BITS_PER_WORD != 0)
        return;

      /* If this field is the whole struct, remember its mode so
         that, say, we can put a double in a class into a DF
         register instead of forcing it to live in the stack.  */
      if (simple_cst_equal (TYPE_SIZE (type), DECL_SIZE (field)))
        mode = DECL_MODE (field);

#ifdef MEMBER_TYPE_FORCES_BLK
      /* With some targets, eg. c4x, it is sub-optimal
         to access an aligned BLKmode structure as a scalar.  */

      /* On ia64-*-hpux we need to ensure that we don't change the
         mode of a structure containing a single field or else we
         will pass it incorrectly.  Since a structure with a single
         field causes mode to get set above we can't allow the
         check for mode == VOIDmode in this case.  Perhaps
         MEMBER_TYPE_FORCES_BLK should be extended to include mode
         as an argument and the check could be put in there for c4x.  */

      if ((mode == VOIDmode || FUNCTION_ARG_REG_LITTLE_ENDIAN)
          && MEMBER_TYPE_FORCES_BLK (field))
        return;
#endif /* MEMBER_TYPE_FORCES_BLK  */
    }

  /* If we only have one real field; use its mode.  This only applies to
     RECORD_TYPE.  This does not apply to unions.  */
  if (TREE_CODE (type) == RECORD_TYPE && mode != VOIDmode)
    TYPE_MODE (type) = mode;
  else
    TYPE_MODE (type) = mode_for_size_tree (TYPE_SIZE (type), MODE_INT, 1);

  /* If structure's known alignment is less than what the scalar
     mode would need, and it matters, then stick with BLKmode.  */
  if (TYPE_MODE (type) != BLKmode
      && STRICT_ALIGNMENT
      && ! (TYPE_ALIGN (type) >= BIGGEST_ALIGNMENT
            || TYPE_ALIGN (type) >= GET_MODE_ALIGNMENT (TYPE_MODE (type))))
    {
      /* If this is the only reason this type is BLKmode, then
         don't force containing types to be BLKmode.  */
      TYPE_NO_FORCE_BLK (type) = 1;
      TYPE_MODE (type) = BLKmode;
    }
}

/* Compute TYPE_SIZE and TYPE_ALIGN for TYPE, once it has been laid
   out.  */

static void
finalize_type_size (type)
     tree type;
{
  /* Normally, use the alignment corresponding to the mode chosen.
     However, where strict alignment is not required, avoid
     over-aligning structures, since most compilers do not do this
     alignment.  */

  if (TYPE_MODE (type) != BLKmode && TYPE_MODE (type) != VOIDmode
      && (STRICT_ALIGNMENT
          || (TREE_CODE (type) != RECORD_TYPE && TREE_CODE (type) != UNION_TYPE
              && TREE_CODE (type) != QUAL_UNION_TYPE
              && TREE_CODE (type) != ARRAY_TYPE)))
    {
      TYPE_ALIGN (type) = GET_MODE_ALIGNMENT (TYPE_MODE (type));
      TYPE_USER_ALIGN (type) = 0;
    }

  /* Do machine-dependent extra alignment.  */
#ifdef ROUND_TYPE_ALIGN
  TYPE_ALIGN (type)
    = ROUND_TYPE_ALIGN (type, TYPE_ALIGN (type), BITS_PER_UNIT);
#endif

  /* If we failed to find a simple way to calculate the unit size
     of the type, find it by division.  */
  if (TYPE_SIZE_UNIT (type) == 0 && TYPE_SIZE (type) != 0)
    /* TYPE_SIZE (type) is computed in bitsizetype.  After the division, the
       result will fit in sizetype.  We will get more efficient code using
       sizetype, so we force a conversion.  */
    TYPE_SIZE_UNIT (type)
      = convert (sizetype,
                 size_binop (FLOOR_DIV_EXPR, TYPE_SIZE (type),
                             bitsize_unit_node));

  if (TYPE_SIZE (type) != 0)
    {
#ifdef ROUND_TYPE_SIZE
      TYPE_SIZE (type)
        = ROUND_TYPE_SIZE (type, TYPE_SIZE (type), TYPE_ALIGN (type));
      TYPE_SIZE_UNIT (type)
        = ROUND_TYPE_SIZE_UNIT (type, TYPE_SIZE_UNIT (type),
                                TYPE_ALIGN (type) / BITS_PER_UNIT);
#else
      TYPE_SIZE (type) = round_up (TYPE_SIZE (type), TYPE_ALIGN (type));
      TYPE_SIZE_UNIT (type)
        = round_up (TYPE_SIZE_UNIT (type), TYPE_ALIGN (type) / BITS_PER_UNIT);
#endif
    }

  /* Evaluate nonconstant sizes only once, either now or as soon as safe.  */
  if (TYPE_SIZE (type) != 0 && TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST)
    TYPE_SIZE (type) = variable_size (TYPE_SIZE (type));
  if (TYPE_SIZE_UNIT (type) != 0
      && TREE_CODE (TYPE_SIZE_UNIT (type)) != INTEGER_CST)
    TYPE_SIZE_UNIT (type) = variable_size (TYPE_SIZE_UNIT (type));

  /* Also layout any other variants of the type.  */
  if (TYPE_NEXT_VARIANT (type)
      || type != TYPE_MAIN_VARIANT (type))
    {
      tree variant;
      /* Record layout info of this variant.  */
      tree size = TYPE_SIZE (type);
      tree size_unit = TYPE_SIZE_UNIT (type);
      unsigned int align = TYPE_ALIGN (type);
      unsigned int user_align = TYPE_USER_ALIGN (type);
      enum machine_mode mode = TYPE_MODE (type);

      /* Copy it into all variants.  */
      for (variant = TYPE_MAIN_VARIANT (type);
           variant != 0;
           variant = TYPE_NEXT_VARIANT (variant))
        {
          TYPE_SIZE (variant) = size;
          TYPE_SIZE_UNIT (variant) = size_unit;
          TYPE_ALIGN (variant) = align;
          TYPE_USER_ALIGN (variant) = user_align;
          TYPE_MODE (variant) = mode;
        }
    }
}

/* Do all of the work required to layout the type indicated by RLI,
   once the fields have been laid out.  This function will call `free'
   for RLI.  */

void
finish_record_layout (rli)
     record_layout_info rli;
{
  /* Compute the final size.  */
  finalize_record_size (rli);

  /* Compute the TYPE_MODE for the record.  */
  compute_record_mode (rli->t);

  /* Perform any last tweaks to the TYPE_SIZE, etc.  */
  finalize_type_size (rli->t);

  /* Lay out any static members.  This is done now because their type
     may use the record's type.  */
  while (rli->pending_statics)
    {
      layout_decl (TREE_VALUE (rli->pending_statics), 0);
      rli->pending_statics = TREE_CHAIN (rli->pending_statics);
    }

  /* Clean up.  */
  free (rli);
}
\f
/* Calculate the mode, size, and alignment for TYPE.
   For an array type, calculate the element separation as well.
   Record TYPE on the chain of permanent or temporary types
   so that dbxout will find out about it.

   TYPE_SIZE of a type is nonzero if the type has been laid out already.
   layout_type does nothing on such a type.

   If the type is incomplete, its TYPE_SIZE remains zero.  */

void
layout_type (type)
     tree type;
{
  if (type == 0)
    abort ();

  /* Do nothing if type has been laid out before.  */
  if (TYPE_SIZE (type))
    return;

  switch (TREE_CODE (type))
    {
    case LANG_TYPE:
      /* This kind of type is the responsibility
         of the language-specific code.  */
      abort ();

    case BOOLEAN_TYPE:  /* Used for Java, Pascal, and Chill.  */
      if (TYPE_PRECISION (type) == 0)
        TYPE_PRECISION (type) = 1; /* default to one byte/boolean.  */

      /* ... fall through ...  */

    case INTEGER_TYPE:
    case ENUMERAL_TYPE:
    case CHAR_TYPE:
      if (TREE_CODE (TYPE_MIN_VALUE (type)) == INTEGER_CST
          && tree_int_cst_sgn (TYPE_MIN_VALUE (type)) >= 0)
        TREE_UNSIGNED (type) = 1;

      TYPE_MODE (type) = smallest_mode_for_size (TYPE_PRECISION (type),
                                                 MODE_INT);
      TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
      TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
      break;

    case REAL_TYPE:
      TYPE_MODE (type) = mode_for_size (TYPE_PRECISION (type), MODE_FLOAT, 0);
      TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
      TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
      break;

    case COMPLEX_TYPE:
      TREE_UNSIGNED (type) = TREE_UNSIGNED (TREE_TYPE (type));
      TYPE_MODE (type)
        = mode_for_size (2 * TYPE_PRECISION (TREE_TYPE (type)),
                         (TREE_CODE (TREE_TYPE (type)) == INTEGER_TYPE
                          ? MODE_COMPLEX_INT : MODE_COMPLEX_FLOAT),
                         0);
      TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
      TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
      break;

    case VECTOR_TYPE:
      {
        tree subtype;

        subtype = TREE_TYPE (type);
        TREE_UNSIGNED (type) = TREE_UNSIGNED (subtype);
        TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
        TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
      }
      break;

    case VOID_TYPE:
      /* This is an incomplete type and so doesn't have a size.  */
      TYPE_ALIGN (type) = 1;
      TYPE_USER_ALIGN (type) = 0;
      TYPE_MODE (type) = VOIDmode;
      break;

    case OFFSET_TYPE:
      TYPE_SIZE (type) = bitsize_int (POINTER_SIZE);
      TYPE_SIZE_UNIT (type) = size_int (POINTER_SIZE / BITS_PER_UNIT);
      /* A pointer might be MODE_PARTIAL_INT,
         but ptrdiff_t must be integral.  */
      TYPE_MODE (type) = mode_for_size (POINTER_SIZE, MODE_INT, 0);
      break;

    case FUNCTION_TYPE:
    case METHOD_TYPE:
      TYPE_MODE (type) = mode_for_size (2 * POINTER_SIZE, MODE_INT, 0);
      TYPE_SIZE (type) = bitsize_int (2 * POINTER_SIZE);
      TYPE_SIZE_UNIT (type) = size_int ((2 * POINTER_SIZE) / BITS_PER_UNIT);
      break;

    case POINTER_TYPE:
    case REFERENCE_TYPE:
      {
        int nbits = ((TREE_CODE (type) == REFERENCE_TYPE
                      && reference_types_internal)
                     ? GET_MODE_BITSIZE (Pmode) : POINTER_SIZE);

        TYPE_MODE (type) = nbits == POINTER_SIZE ? ptr_mode : Pmode;
        TYPE_SIZE (type) = bitsize_int (nbits);
        TYPE_SIZE_UNIT (type) = size_int (nbits / BITS_PER_UNIT);
        TREE_UNSIGNED (type) = 1;
        TYPE_PRECISION (type) = nbits;
      }
      break;

    case ARRAY_TYPE:
      {
        tree index = TYPE_DOMAIN (type);
        tree element = TREE_TYPE (type);

        build_pointer_type (element);

        /* We need to know both bounds in order to compute the size.  */
        if (index && TYPE_MAX_VALUE (index) && TYPE_MIN_VALUE (index)
            && TYPE_SIZE (element))
          {
            tree ub = TYPE_MAX_VALUE (index);
            tree lb = TYPE_MIN_VALUE (index);
            tree length;
            tree element_size;

            /* The initial subtraction should happen in the original type so
               that (possible) negative values are handled appropriately.  */
            length = size_binop (PLUS_EXPR, size_one_node,
                                 convert (sizetype,
                                          fold (build (MINUS_EXPR,
                                                       TREE_TYPE (lb),
                                                       ub, lb))));

            /* Special handling for arrays of bits (for Chill).  */
            element_size = TYPE_SIZE (element);
            if (TYPE_PACKED (type) && INTEGRAL_TYPE_P (element)
                && (integer_zerop (TYPE_MAX_VALUE (element))
                    || integer_onep (TYPE_MAX_VALUE (element)))
                && host_integerp (TYPE_MIN_VALUE (element), 1))
              {
                HOST_WIDE_INT maxvalue
                  = tree_low_cst (TYPE_MAX_VALUE (element), 1);
                HOST_WIDE_INT minvalue
                  = tree_low_cst (TYPE_MIN_VALUE (element), 1);

                if (maxvalue - minvalue == 1
                    && (maxvalue == 1 || maxvalue == 0))
                  element_size = integer_one_node;
              }

            TYPE_SIZE (type) = size_binop (MULT_EXPR, element_size,
                                           convert (bitsizetype, length));

            /* If we know the size of the element, calculate the total
               size directly, rather than do some division thing below.
               This optimization helps Fortran assumed-size arrays
               (where the size of the array is determined at runtime)
               substantially.
               Note that we can't do this in the case where the size of
               the elements is one bit since TYPE_SIZE_UNIT cannot be
               set correctly in that case.  */
            if (TYPE_SIZE_UNIT (element) != 0 && ! integer_onep (element_size))
              TYPE_SIZE_UNIT (type)
                = size_binop (MULT_EXPR, TYPE_SIZE_UNIT (element), length);
          }

        /* Now round the alignment and size,
           using machine-dependent criteria if any.  */

#ifdef ROUND_TYPE_ALIGN
        TYPE_ALIGN (type)
          = ROUND_TYPE_ALIGN (type, TYPE_ALIGN (element), BITS_PER_UNIT);
#else
        TYPE_ALIGN (type) = MAX (TYPE_ALIGN (element), BITS_PER_UNIT);
#endif
        TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (element);

#ifdef ROUND_TYPE_SIZE
        if (TYPE_SIZE (type) != 0)
          {
            tree tmp
              = ROUND_TYPE_SIZE (type, TYPE_SIZE (type), TYPE_ALIGN (type));

            /* If the rounding changed the size of the type, remove any
               pre-calculated TYPE_SIZE_UNIT.  */
            if (simple_cst_equal (TYPE_SIZE (type), tmp) != 1)
              TYPE_SIZE_UNIT (type) = NULL;

            TYPE_SIZE (type) = tmp;
          }
#endif

        TYPE_MODE (type) = BLKmode;
        if (TYPE_SIZE (type) != 0
#ifdef MEMBER_TYPE_FORCES_BLK
            && ! MEMBER_TYPE_FORCES_BLK (type)
#endif
            /* BLKmode elements force BLKmode aggregate;
               else extract/store fields may lose.  */
            && (TYPE_MODE (TREE_TYPE (type)) != BLKmode
                || TYPE_NO_FORCE_BLK (TREE_TYPE (type))))
          {
            /* One-element arrays get the component type's mode.  */
            if (simple_cst_equal (TYPE_SIZE (type),
                                  TYPE_SIZE (TREE_TYPE (type))))
              TYPE_MODE (type) = TYPE_MODE (TREE_TYPE (type));
            else
              TYPE_MODE (type)
                = mode_for_size_tree (TYPE_SIZE (type), MODE_INT, 1);

            if (TYPE_MODE (type) != BLKmode
                && STRICT_ALIGNMENT && TYPE_ALIGN (type) < BIGGEST_ALIGNMENT
                && TYPE_ALIGN (type) < GET_MODE_ALIGNMENT (TYPE_MODE (type))
                && TYPE_MODE (type) != BLKmode)
              {
                TYPE_NO_FORCE_BLK (type) = 1;
                TYPE_MODE (type) = BLKmode;
              }
          }
        break;
      }

    case RECORD_TYPE:
    case UNION_TYPE:
    case QUAL_UNION_TYPE:
      {
        tree field;
        record_layout_info rli;

        /* Initialize the layout information.  */
        rli = start_record_layout (type);

        /* If this is a QUAL_UNION_TYPE, we want to process the fields
           in the reverse order in building the COND_EXPR that denotes
           its size.  We reverse them again later.  */
        if (TREE_CODE (type) == QUAL_UNION_TYPE)
          TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type));

        /* Place all the fields.  */
        for (field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field))
          place_field (rli, field);

        if (TREE_CODE (type) == QUAL_UNION_TYPE)
          TYPE_FIELDS (type) = nreverse (TYPE_FIELDS (type));

        if (lang_adjust_rli)
          (*lang_adjust_rli) (rli);

        /* Finish laying out the record.  */
        finish_record_layout (rli);
      }
      break;

    case SET_TYPE:  /* Used by Chill and Pascal.  */
      if (TREE_CODE (TYPE_MAX_VALUE (TYPE_DOMAIN (type))) != INTEGER_CST
          || TREE_CODE (TYPE_MIN_VALUE (TYPE_DOMAIN (type))) != INTEGER_CST)
        abort ();
      else
        {
#ifndef SET_WORD_SIZE
#define SET_WORD_SIZE BITS_PER_WORD
#endif
          unsigned int alignment
            = set_alignment ? set_alignment : SET_WORD_SIZE;
          int size_in_bits
            = (TREE_INT_CST_LOW (TYPE_MAX_VALUE (TYPE_DOMAIN (type)))
               - TREE_INT_CST_LOW (TYPE_MIN_VALUE (TYPE_DOMAIN (type))) + 1);
          int rounded_size
            = ((size_in_bits + alignment - 1) / alignment) * alignment;

          if (rounded_size > (int) alignment)
            TYPE_MODE (type) = BLKmode;
          else
            TYPE_MODE (type) = mode_for_size (alignment, MODE_INT, 1);

          TYPE_SIZE (type) = bitsize_int (rounded_size);
          TYPE_SIZE_UNIT (type) = size_int (rounded_size / BITS_PER_UNIT);
          TYPE_ALIGN (type) = alignment;
          TYPE_USER_ALIGN (type) = 0;
          TYPE_PRECISION (type) = size_in_bits;
        }
      break;

    case FILE_TYPE:
      /* The size may vary in different languages, so the language front end
         should fill in the size.  */
      TYPE_ALIGN (type) = BIGGEST_ALIGNMENT;
      TYPE_USER_ALIGN (type) = 0;
      TYPE_MODE  (type) = BLKmode;
      break;

    default:
      abort ();
    }

  /* Compute the final TYPE_SIZE, TYPE_ALIGN, etc. for TYPE.  For
     records and unions, finish_record_layout already called this
     function.  */
  if (TREE_CODE (type) != RECORD_TYPE 
      && TREE_CODE (type) != UNION_TYPE
      && TREE_CODE (type) != QUAL_UNION_TYPE)
    finalize_type_size (type);

  /* If this type is created before sizetype has been permanently set,
     record it so set_sizetype can fix it up.  */
  if (! sizetype_set)
    early_type_list = tree_cons (NULL_TREE, type, early_type_list);

  /* If an alias set has been set for this aggregate when it was incomplete,
     force it into alias set 0.
     This is too conservative, but we cannot call record_component_aliases
     here because some frontends still change the aggregates after
     layout_type.  */
  if (AGGREGATE_TYPE_P (type) && TYPE_ALIAS_SET_KNOWN_P (type))
    TYPE_ALIAS_SET (type) = 0;
}
\f
/* Create and return a type for signed integers of PRECISION bits.  */

tree
make_signed_type (precision)
     int precision;
{
  tree type = make_node (INTEGER_TYPE);

  TYPE_PRECISION (type) = precision;

  fixup_signed_type (type);
  return type;
}

/* Create and return a type for unsigned integers of PRECISION bits.  */

tree
make_unsigned_type (precision)
     int precision;
{
  tree type = make_node (INTEGER_TYPE);

  TYPE_PRECISION (type) = precision;

  fixup_unsigned_type (type);
  return type;
}
\f
/* Initialize sizetype and bitsizetype to a reasonable and temporary
   value to enable integer types to be created.  */

void
initialize_sizetypes ()
{
  tree t = make_node (INTEGER_TYPE);

  /* Set this so we do something reasonable for the build_int_2 calls
     below.  */
  integer_type_node = t;

  TYPE_MODE (t) = SImode;
  TYPE_ALIGN (t) = GET_MODE_ALIGNMENT (SImode);
  TYPE_USER_ALIGN (t) = 0;
  TYPE_SIZE (t) = build_int_2 (GET_MODE_BITSIZE (SImode), 0);
  TYPE_SIZE_UNIT (t) = build_int_2 (GET_MODE_SIZE (SImode), 0);
  TREE_UNSIGNED (t) = 1;
  TYPE_PRECISION (t) = GET_MODE_BITSIZE (SImode);
  TYPE_MIN_VALUE (t) = build_int_2 (0, 0);
  TYPE_IS_SIZETYPE (t) = 1;

  /* 1000 avoids problems with possible overflow and is certainly
     larger than any size value we'd want to be storing.  */
  TYPE_MAX_VALUE (t) = build_int_2 (1000, 0);

  /* These two must be different nodes because of the caching done in
     size_int_wide.  */
  sizetype = t;
  bitsizetype = copy_node (t);
  integer_type_node = 0;
}

/* Set sizetype to TYPE, and initialize *sizetype accordingly.
   Also update the type of any standard type's sizes made so far.  */

void
set_sizetype (type)
     tree type;
{
  int oprecision = TYPE_PRECISION (type);
  /* The *bitsizetype types use a precision that avoids overflows when
     calculating signed sizes / offsets in bits.  However, when
     cross-compiling from a 32 bit to a 64 bit host, we are limited to 64 bit
     precision.  */
  int precision = MIN (oprecision + BITS_PER_UNIT_LOG + 1,
                       2 * HOST_BITS_PER_WIDE_INT);
  unsigned int i;
  tree t;

  if (sizetype_set)
    abort ();

  /* Make copies of nodes since we'll be setting TYPE_IS_SIZETYPE.  */
  sizetype = copy_node (type);
  TYPE_DOMAIN (sizetype) = type;
  TYPE_IS_SIZETYPE (sizetype) = 1;
  bitsizetype = make_node (INTEGER_TYPE);
  TYPE_NAME (bitsizetype) = TYPE_NAME (type);
  TYPE_PRECISION (bitsizetype) = precision;
  TYPE_IS_SIZETYPE (bitsizetype) = 1;

  if (TREE_UNSIGNED (type))
    fixup_unsigned_type (bitsizetype);
  else
    fixup_signed_type (bitsizetype);

  layout_type (bitsizetype);

  if (TREE_UNSIGNED (type))
    {
      usizetype = sizetype;
      ubitsizetype = bitsizetype;
      ssizetype = copy_node (make_signed_type (oprecision));
      sbitsizetype = copy_node (make_signed_type (precision));
    }
  else
    {
      ssizetype = sizetype;
      sbitsizetype = bitsizetype;
      usizetype = copy_node (make_unsigned_type (oprecision));
      ubitsizetype = copy_node (make_unsigned_type (precision));
    }

  TYPE_NAME (bitsizetype) = get_identifier ("bit_size_type");

  /* Show is a sizetype, is a main type, and has no pointers to it.  */
  for (i = 0; i < ARRAY_SIZE (sizetype_tab); i++)
    {
      TYPE_IS_SIZETYPE (sizetype_tab[i]) = 1;
      TYPE_MAIN_VARIANT (sizetype_tab[i]) = sizetype_tab[i];
      TYPE_NEXT_VARIANT (sizetype_tab[i]) = 0;
      TYPE_POINTER_TO (sizetype_tab[i]) = 0;
      TYPE_REFERENCE_TO (sizetype_tab[i]) = 0;
    }

  ggc_add_tree_root ((tree *) &sizetype_tab,
                     sizeof sizetype_tab / sizeof (tree));

  /* Go down each of the types we already made and set the proper type
     for the sizes in them.  */
  for (t = early_type_list; t != 0; t = TREE_CHAIN (t))
    {
      if (TREE_CODE (TREE_VALUE (t)) != INTEGER_TYPE)
        abort ();

      TREE_TYPE (TYPE_SIZE (TREE_VALUE (t))) = bitsizetype;
      TREE_TYPE (TYPE_SIZE_UNIT (TREE_VALUE (t))) = sizetype;
    }

  early_type_list = 0;
  sizetype_set = 1;
}
\f
/* Set the extreme values of TYPE based on its precision in bits,
   then lay it out.  Used when make_signed_type won't do
   because the tree code is not INTEGER_TYPE.
   E.g. for Pascal, when the -fsigned-char option is given.  */

void
fixup_signed_type (type)
     tree type;
{
  int precision = TYPE_PRECISION (type);

  /* We can not represent properly constants greater then
     2 * HOST_BITS_PER_WIDE_INT, still we need the types
     as they are used by i386 vector extensions and friends.  */
  if (precision > HOST_BITS_PER_WIDE_INT * 2)
    precision = HOST_BITS_PER_WIDE_INT * 2;

  TYPE_MIN_VALUE (type)
    = build_int_2 ((precision - HOST_BITS_PER_WIDE_INT > 0
                    ? 0 : (HOST_WIDE_INT) (-1) << (precision - 1)),
                   (((HOST_WIDE_INT) (-1)
                     << (precision - HOST_BITS_PER_WIDE_INT - 1 > 0
                         ? precision - HOST_BITS_PER_WIDE_INT - 1
                         : 0))));
  TYPE_MAX_VALUE (type)
    = build_int_2 ((precision - HOST_BITS_PER_WIDE_INT > 0
                    ? -1 : ((HOST_WIDE_INT) 1 << (precision - 1)) - 1),
                   (precision - HOST_BITS_PER_WIDE_INT - 1 > 0
                    ? (((HOST_WIDE_INT) 1
                        << (precision - HOST_BITS_PER_WIDE_INT - 1))) - 1
                    : 0));

  TREE_TYPE (TYPE_MIN_VALUE (type)) = type;
  TREE_TYPE (TYPE_MAX_VALUE (type)) = type;

  /* Lay out the type: set its alignment, size, etc.  */
  layout_type (type);
}

/* Set the extreme values of TYPE based on its precision in bits,
   then lay it out.  This is used both in `make_unsigned_type'
   and for enumeral types.  */

void
fixup_unsigned_type (type)
     tree type;
{
  int precision = TYPE_PRECISION (type);

  /* We can not represent properly constants greater then
     2 * HOST_BITS_PER_WIDE_INT, still we need the types
     as they are used by i386 vector extensions and friends.  */
  if (precision > HOST_BITS_PER_WIDE_INT * 2)
    precision = HOST_BITS_PER_WIDE_INT * 2;

  TYPE_MIN_VALUE (type) = build_int_2 (0, 0);
  TYPE_MAX_VALUE (type)
    = build_int_2 (precision - HOST_BITS_PER_WIDE_INT >= 0
                   ? -1 : ((HOST_WIDE_INT) 1 << precision) - 1,
                   precision - HOST_BITS_PER_WIDE_INT > 0
                   ? ((unsigned HOST_WIDE_INT) ~0
                      >> (HOST_BITS_PER_WIDE_INT
                          - (precision - HOST_BITS_PER_WIDE_INT)))
                   : 0);
  TREE_TYPE (TYPE_MIN_VALUE (type)) = type;
  TREE_TYPE (TYPE_MAX_VALUE (type)) = type;

  /* Lay out the type: set its alignment, size, etc.  */
  layout_type (type);
}
\f
/* Find the best machine mode to use when referencing a bit field of length
   BITSIZE bits starting at BITPOS.

   The underlying object is known to be aligned to a boundary of ALIGN bits.
   If LARGEST_MODE is not VOIDmode, it means that we should not use a mode
   larger than LARGEST_MODE (usually SImode).

   If no mode meets all these conditions, we return VOIDmode.  Otherwise, if
   VOLATILEP is true or SLOW_BYTE_ACCESS is false, we return the smallest
   mode meeting these conditions.

   Otherwise (VOLATILEP is false and SLOW_BYTE_ACCESS is true), we return
   the largest mode (but a mode no wider than UNITS_PER_WORD) that meets
   all the conditions.  */

enum machine_mode
get_best_mode (bitsize, bitpos, align, largest_mode, volatilep)
     int bitsize, bitpos;
     unsigned int align;
     enum machine_mode largest_mode;
     int volatilep;
{
  enum machine_mode mode;
  unsigned int unit = 0;

  /* Find the narrowest integer mode that contains the bit field.  */
  for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != VOIDmode;
       mode = GET_MODE_WIDER_MODE (mode))
    {
      unit = GET_MODE_BITSIZE (mode);
      if ((bitpos % unit) + bitsize <= unit)
        break;
    }

  if (mode == VOIDmode
      /* It is tempting to omit the following line
         if STRICT_ALIGNMENT is true.
         But that is incorrect, since if the bitfield uses part of 3 bytes
         and we use a 4-byte mode, we could get a spurious segv
         if the extra 4th byte is past the end of memory.
         (Though at least one Unix compiler ignores this problem:
         that on the Sequent 386 machine.  */
      || MIN (unit, BIGGEST_ALIGNMENT) > align
      || (largest_mode != VOIDmode && unit > GET_MODE_BITSIZE (largest_mode)))
    return VOIDmode;

  if (SLOW_BYTE_ACCESS && ! volatilep)
    {
      enum machine_mode wide_mode = VOIDmode, tmode;

      for (tmode = GET_CLASS_NARROWEST_MODE (MODE_INT); tmode != VOIDmode;
           tmode = GET_MODE_WIDER_MODE (tmode))
        {
          unit = GET_MODE_BITSIZE (tmode);
          if (bitpos / unit == (bitpos + bitsize - 1) / unit
              && unit <= BITS_PER_WORD
              && unit <= MIN (align, BIGGEST_ALIGNMENT)
              && (largest_mode == VOIDmode
                  || unit <= GET_MODE_BITSIZE (largest_mode)))
            wide_mode = tmode;
        }

      if (wide_mode != VOIDmode)
        return wide_mode;
    }

  return mode;
}

/* This function is run once to initialize stor-layout.c.  */

void
init_stor_layout_once ()
{
  ggc_add_tree_root (&pending_sizes, 1);
}