parser.c (cp_ensure_no_oacc_routine): Update error message.

[official-gcc.git] / gcc / stor-layout.c

/* C-compiler utilities for types and variables storage layout
   Copyright (C) 1987-2015 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 3, 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 COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */


#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "target.h"
#include "function.h"
#include "rtl.h"
#include "tree.h"
#include "tm_p.h"
#include "stringpool.h"
#include "regs.h"
#include "emit-rtl.h"
#include "cgraph.h"
#include "diagnostic-core.h"
#include "fold-const.h"
#include "stor-layout.h"
#include "varasm.h"
#include "print-tree.h"
#include "langhooks.h"
#include "tree-inline.h"
#include "tree-dump.h"
#include "gimplify.h"

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

/* Nonzero if all REFERENCE_TYPEs are internal and hence should be allocated
   in the address spaces' address_mode, not pointer_mode.   Set only by
   internal_reference_types called only by a front end.  */
static int reference_types_internal = 0;

static tree self_referential_size (tree);
static void finalize_record_size (record_layout_info);
static void finalize_type_size (tree);
static void place_union_field (record_layout_info, tree);
static int excess_unit_span (HOST_WIDE_INT, HOST_WIDE_INT, HOST_WIDE_INT,
                             HOST_WIDE_INT, tree);
extern void debug_rli (record_layout_info);
\f
/* Show that REFERENCE_TYPES are internal and should use address_mode.
   Called only by front end.  */

void
internal_reference_types (void)
{
  reference_types_internal = 1;
}

/* 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 (tree size)
{
  /* Obviously.  */
  if (TREE_CONSTANT (size))
    return size;

  /* If the size is self-referential, we can't make a SAVE_EXPR (see
     save_expr for the rationale).  But we can do something else.  */
  if (CONTAINS_PLACEHOLDER_P (size))
    return self_referential_size (size);

  /* If we are in the global binding level, we can't make a SAVE_EXPR
     since it may end up being shared across functions, so it is up
     to the front-end to deal with this case.  */
  if (lang_hooks.decls.global_bindings_p ())
    return size;

  return save_expr (size);
}

/* An array of functions used for self-referential size computation.  */
static GTY(()) vec<tree, va_gc> *size_functions;

/* Return true if T is a self-referential component reference.  */

static bool
self_referential_component_ref_p (tree t)
{
  if (TREE_CODE (t) != COMPONENT_REF)
    return false;

  while (REFERENCE_CLASS_P (t))
    t = TREE_OPERAND (t, 0);

  return (TREE_CODE (t) == PLACEHOLDER_EXPR);
}

/* Similar to copy_tree_r but do not copy component references involving
   PLACEHOLDER_EXPRs.  These nodes are spotted in find_placeholder_in_expr
   and substituted in substitute_in_expr.  */

static tree
copy_self_referential_tree_r (tree *tp, int *walk_subtrees, void *data)
{
  enum tree_code code = TREE_CODE (*tp);

  /* Stop at types, decls, constants like copy_tree_r.  */
  if (TREE_CODE_CLASS (code) == tcc_type
      || TREE_CODE_CLASS (code) == tcc_declaration
      || TREE_CODE_CLASS (code) == tcc_constant)
    {
      *walk_subtrees = 0;
      return NULL_TREE;
    }

  /* This is the pattern built in ada/make_aligning_type.  */
  else if (code == ADDR_EXPR
           && TREE_CODE (TREE_OPERAND (*tp, 0)) == PLACEHOLDER_EXPR)
    {
      *walk_subtrees = 0;
      return NULL_TREE;
    }

  /* Default case: the component reference.  */
  else if (self_referential_component_ref_p (*tp))
    {
      *walk_subtrees = 0;
      return NULL_TREE;
    }

  /* We're not supposed to have them in self-referential size trees
     because we wouldn't properly control when they are evaluated.
     However, not creating superfluous SAVE_EXPRs requires accurate
     tracking of readonly-ness all the way down to here, which we
     cannot always guarantee in practice.  So punt in this case.  */
  else if (code == SAVE_EXPR)
    return error_mark_node;

  else if (code == STATEMENT_LIST)
    gcc_unreachable ();

  return copy_tree_r (tp, walk_subtrees, data);
}

/* Given a SIZE expression that is self-referential, return an equivalent
   expression to serve as the actual size expression for a type.  */

static tree
self_referential_size (tree size)
{
  static unsigned HOST_WIDE_INT fnno = 0;
  vec<tree> self_refs = vNULL;
  tree param_type_list = NULL, param_decl_list = NULL;
  tree t, ref, return_type, fntype, fnname, fndecl;
  unsigned int i;
  char buf[128];
  vec<tree, va_gc> *args = NULL;

  /* Do not factor out simple operations.  */
  t = skip_simple_constant_arithmetic (size);
  if (TREE_CODE (t) == CALL_EXPR || self_referential_component_ref_p (t))
    return size;

  /* Collect the list of self-references in the expression.  */
  find_placeholder_in_expr (size, &self_refs);
  gcc_assert (self_refs.length () > 0);

  /* Obtain a private copy of the expression.  */
  t = size;
  if (walk_tree (&t, copy_self_referential_tree_r, NULL, NULL) != NULL_TREE)
    return size;
  size = t;

  /* Build the parameter and argument lists in parallel; also
     substitute the former for the latter in the expression.  */
  vec_alloc (args, self_refs.length ());
  FOR_EACH_VEC_ELT (self_refs, i, ref)
    {
      tree subst, param_name, param_type, param_decl;

      if (DECL_P (ref))
        {
          /* We shouldn't have true variables here.  */
          gcc_assert (TREE_READONLY (ref));
          subst = ref;
        }
      /* This is the pattern built in ada/make_aligning_type.  */
      else if (TREE_CODE (ref) == ADDR_EXPR)
        subst = ref;
      /* Default case: the component reference.  */
      else
        subst = TREE_OPERAND (ref, 1);

      sprintf (buf, "p%d", i);
      param_name = get_identifier (buf);
      param_type = TREE_TYPE (ref);
      param_decl
        = build_decl (input_location, PARM_DECL, param_name, param_type);
      DECL_ARG_TYPE (param_decl) = param_type;
      DECL_ARTIFICIAL (param_decl) = 1;
      TREE_READONLY (param_decl) = 1;

      size = substitute_in_expr (size, subst, param_decl);

      param_type_list = tree_cons (NULL_TREE, param_type, param_type_list);
      param_decl_list = chainon (param_decl, param_decl_list);
      args->quick_push (ref);
    }

  self_refs.release ();

  /* Append 'void' to indicate that the number of parameters is fixed.  */
  param_type_list = tree_cons (NULL_TREE, void_type_node, param_type_list);

  /* The 3 lists have been created in reverse order.  */
  param_type_list = nreverse (param_type_list);
  param_decl_list = nreverse (param_decl_list);

  /* Build the function type.  */
  return_type = TREE_TYPE (size);
  fntype = build_function_type (return_type, param_type_list);

  /* Build the function declaration.  */
  sprintf (buf, "SZ" HOST_WIDE_INT_PRINT_UNSIGNED, fnno++);
  fnname = get_file_function_name (buf);
  fndecl = build_decl (input_location, FUNCTION_DECL, fnname, fntype);
  for (t = param_decl_list; t; t = DECL_CHAIN (t))
    DECL_CONTEXT (t) = fndecl;
  DECL_ARGUMENTS (fndecl) = param_decl_list;
  DECL_RESULT (fndecl)
    = build_decl (input_location, RESULT_DECL, 0, return_type);
  DECL_CONTEXT (DECL_RESULT (fndecl)) = fndecl;

  /* The function has been created by the compiler and we don't
     want to emit debug info for it.  */
  DECL_ARTIFICIAL (fndecl) = 1;
  DECL_IGNORED_P (fndecl) = 1;

  /* It is supposed to be "const" and never throw.  */
  TREE_READONLY (fndecl) = 1;
  TREE_NOTHROW (fndecl) = 1;

  /* We want it to be inlined when this is deemed profitable, as
     well as discarded if every call has been integrated.  */
  DECL_DECLARED_INLINE_P (fndecl) = 1;

  /* It is made up of a unique return statement.  */
  DECL_INITIAL (fndecl) = make_node (BLOCK);
  BLOCK_SUPERCONTEXT (DECL_INITIAL (fndecl)) = fndecl;
  t = build2 (MODIFY_EXPR, return_type, DECL_RESULT (fndecl), size);
  DECL_SAVED_TREE (fndecl) = build1 (RETURN_EXPR, void_type_node, t);
  TREE_STATIC (fndecl) = 1;

  /* Put it onto the list of size functions.  */
  vec_safe_push (size_functions, fndecl);

  /* Replace the original expression with a call to the size function.  */
  return build_call_expr_loc_vec (UNKNOWN_LOCATION, fndecl, args);
}

/* Take, queue and compile all the size functions.  It is essential that
   the size functions be gimplified at the very end of the compilation
   in order to guarantee transparent handling of self-referential sizes.
   Otherwise the GENERIC inliner would not be able to inline them back
   at each of their call sites, thus creating artificial non-constant
   size expressions which would trigger nasty problems later on.  */

void
finalize_size_functions (void)
{
  unsigned int i;
  tree fndecl;

  for (i = 0; size_functions && size_functions->iterate (i, &fndecl); i++)
    {
      allocate_struct_function (fndecl, false);
      set_cfun (NULL);
      dump_function (TDI_original, fndecl);
      gimplify_function_tree (fndecl);
      cgraph_node::finalize_function (fndecl, false);
    }

  vec_free (size_functions);
}
\f
/* Return the machine mode to use for a nonscalar of SIZE bits.  The
   mode must be in class MCLASS, and have exactly that many value bits;
   it may have padding as well.  If LIMIT is nonzero, modes of wider
   than MAX_FIXED_MODE_SIZE will not be used.  */

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

  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 (mclass); mode != VOIDmode;
       mode = GET_MODE_WIDER_MODE (mode))
    if (GET_MODE_PRECISION (mode) == size)
      return mode;

  if (mclass == MODE_INT || mclass == MODE_PARTIAL_INT)
    for (i = 0; i < NUM_INT_N_ENTS; i ++)
      if (int_n_data[i].bitsize == size
          && int_n_enabled_p[i])
        return int_n_data[i].m;

  return BLKmode;
}

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

machine_mode
mode_for_size_tree (const_tree size, enum mode_class mclass, int limit)
{
  unsigned HOST_WIDE_INT uhwi;
  unsigned int ui;

  if (!tree_fits_uhwi_p (size))
    return BLKmode;
  uhwi = tree_to_uhwi (size);
  ui = uhwi;
  if (uhwi != ui)
    return BLKmode;
  return mode_for_size (ui, mclass, limit);
}

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

machine_mode
smallest_mode_for_size (unsigned int size, enum mode_class mclass)
{
  machine_mode mode = VOIDmode;
  int i;

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

  if (mclass == MODE_INT || mclass == MODE_PARTIAL_INT)
    for (i = 0; i < NUM_INT_N_ENTS; i ++)
      if (int_n_data[i].bitsize >= size
          && int_n_data[i].bitsize < GET_MODE_PRECISION (mode)
          && int_n_enabled_p[i])
        mode = int_n_data[i].m;

  if (mode == VOIDmode)
    gcc_unreachable ();

  return mode;
}

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

machine_mode
int_mode_for_mode (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_DECIMAL_FLOAT:
    case MODE_VECTOR_INT:
    case MODE_VECTOR_FLOAT:
    case MODE_FRACT:
    case MODE_ACCUM:
    case MODE_UFRACT:
    case MODE_UACCUM:
    case MODE_VECTOR_FRACT:
    case MODE_VECTOR_ACCUM:
    case MODE_VECTOR_UFRACT:
    case MODE_VECTOR_UACCUM:
    case MODE_POINTER_BOUNDS:
      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:
      gcc_unreachable ();
    }

  return mode;
}

/* Find a mode that can be used for efficient bitwise operations on MODE.
   Return BLKmode if no such mode exists.  */

machine_mode
bitwise_mode_for_mode (machine_mode mode)
{
  /* Quick exit if we already have a suitable mode.  */
  unsigned int bitsize = GET_MODE_BITSIZE (mode);
  if (SCALAR_INT_MODE_P (mode) && bitsize <= MAX_FIXED_MODE_SIZE)
    return mode;

  /* Reuse the sanity checks from int_mode_for_mode.  */
  gcc_checking_assert ((int_mode_for_mode (mode), true));

  /* Try to replace complex modes with complex modes.  In general we
     expect both components to be processed independently, so we only
     care whether there is a register for the inner mode.  */
  if (COMPLEX_MODE_P (mode))
    {
      machine_mode trial = mode;
      if (GET_MODE_CLASS (mode) != MODE_COMPLEX_INT)
        trial = mode_for_size (bitsize, MODE_COMPLEX_INT, false);
      if (trial != BLKmode
          && have_regs_of_mode[GET_MODE_INNER (trial)])
        return trial;
    }

  /* Try to replace vector modes with vector modes.  Also try using vector
     modes if an integer mode would be too big.  */
  if (VECTOR_MODE_P (mode) || bitsize > MAX_FIXED_MODE_SIZE)
    {
      machine_mode trial = mode;
      if (GET_MODE_CLASS (mode) != MODE_VECTOR_INT)
        trial = mode_for_size (bitsize, MODE_VECTOR_INT, 0);
      if (trial != BLKmode
          && have_regs_of_mode[trial]
          && targetm.vector_mode_supported_p (trial))
        return trial;
    }

  /* Otherwise fall back on integers while honoring MAX_FIXED_MODE_SIZE.  */
  return mode_for_size (bitsize, MODE_INT, true);
}

/* Find a type that can be used for efficient bitwise operations on MODE.
   Return null if no such mode exists.  */

tree
bitwise_type_for_mode (machine_mode mode)
{
  mode = bitwise_mode_for_mode (mode);
  if (mode == BLKmode)
    return NULL_TREE;

  unsigned int inner_size = GET_MODE_UNIT_BITSIZE (mode);
  tree inner_type = build_nonstandard_integer_type (inner_size, true);

  if (VECTOR_MODE_P (mode))
    return build_vector_type_for_mode (inner_type, mode);

  if (COMPLEX_MODE_P (mode))
    return build_complex_type (inner_type);

  gcc_checking_assert (GET_MODE_INNER (mode) == mode);
  return inner_type;
}

/* Find a mode that is suitable for representing a vector with
   NUNITS elements of mode INNERMODE.  Returns BLKmode if there
   is no suitable mode.  */

machine_mode
mode_for_vector (machine_mode innermode, unsigned nunits)
{
  machine_mode mode;

  /* First, look for a supported vector type.  */
  if (SCALAR_FLOAT_MODE_P (innermode))
    mode = MIN_MODE_VECTOR_FLOAT;
  else if (SCALAR_FRACT_MODE_P (innermode))
    mode = MIN_MODE_VECTOR_FRACT;
  else if (SCALAR_UFRACT_MODE_P (innermode))
    mode = MIN_MODE_VECTOR_UFRACT;
  else if (SCALAR_ACCUM_MODE_P (innermode))
    mode = MIN_MODE_VECTOR_ACCUM;
  else if (SCALAR_UACCUM_MODE_P (innermode))
    mode = MIN_MODE_VECTOR_UACCUM;
  else
    mode = MIN_MODE_VECTOR_INT;

  /* Do not check vector_mode_supported_p here.  We'll do that
     later in vector_type_mode.  */
  for (; mode != VOIDmode ; mode = GET_MODE_WIDER_MODE (mode))
    if (GET_MODE_NUNITS (mode) == nunits
        && GET_MODE_INNER (mode) == innermode)
      break;

  /* For integers, try mapping it to a same-sized scalar mode.  */
  if (mode == VOIDmode
      && GET_MODE_CLASS (innermode) == MODE_INT)
    mode = mode_for_size (nunits * GET_MODE_BITSIZE (innermode),
                          MODE_INT, 0);

  if (mode == VOIDmode
      || (GET_MODE_CLASS (mode) == MODE_INT
          && !have_regs_of_mode[mode]))
    return BLKmode;

  return mode;
}

/* Return the alignment of MODE. This will be bounded by 1 and
   BIGGEST_ALIGNMENT.  */

unsigned int
get_mode_alignment (machine_mode mode)
{
  return MIN (BIGGEST_ALIGNMENT, MAX (1, mode_base_align[mode]*BITS_PER_UNIT));
}

/* Return the natural mode of an array, given that it is SIZE bytes in
   total and has elements of type ELEM_TYPE.  */

static machine_mode
mode_for_array (tree elem_type, tree size)
{
  tree elem_size;
  unsigned HOST_WIDE_INT int_size, int_elem_size;
  bool limit_p;

  /* One-element arrays get the component type's mode.  */
  elem_size = TYPE_SIZE (elem_type);
  if (simple_cst_equal (size, elem_size))
    return TYPE_MODE (elem_type);

  limit_p = true;
  if (tree_fits_uhwi_p (size) && tree_fits_uhwi_p (elem_size))
    {
      int_size = tree_to_uhwi (size);
      int_elem_size = tree_to_uhwi (elem_size);
      if (int_elem_size > 0
          && int_size % int_elem_size == 0
          && targetm.array_mode_supported_p (TYPE_MODE (elem_type),
                                             int_size / int_elem_size))
        limit_p = false;
    }
  return mode_for_size_tree (size, MODE_INT, limit_p);
}
\f
/* Subroutine of layout_decl: Force alignment required for the data type.
   But if the decl itself wants greater alignment, don't override that.  */

static inline void
do_type_align (tree type, tree decl)
{
  if (TYPE_ALIGN (type) > DECL_ALIGN (decl))
    {
      DECL_ALIGN (decl) = TYPE_ALIGN (type);
      if (TREE_CODE (decl) == FIELD_DECL)
        DECL_USER_ALIGN (decl) = TYPE_USER_ALIGN (type);
    }
}

/* 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 (tree decl, unsigned int known_align)
{
  tree type = TREE_TYPE (decl);
  enum tree_code code = TREE_CODE (decl);
  rtx rtl = NULL_RTX;
  location_t loc = DECL_SOURCE_LOCATION (decl);

  if (code == CONST_DECL)
    return;

  gcc_assert (code == VAR_DECL || code == PARM_DECL || code == RESULT_DECL
              || code == TYPE_DECL ||code == FIELD_DECL);

  rtl = DECL_RTL_IF_SET (decl);

  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.  */

  DECL_UNSIGNED (decl) = TYPE_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 if (DECL_SIZE_UNIT (decl) == 0)
    DECL_SIZE_UNIT (decl)
      = fold_convert_loc (loc, sizetype,
                          size_binop_loc (loc, CEIL_DIV_EXPR, DECL_SIZE (decl),
                                          bitsize_unit_node));

  if (code != FIELD_DECL)
    /* For non-fields, update the alignment from the type.  */
    do_type_align (type, decl);
  else
    /* For fields, it's a bit more complicated...  */
    {
      bool old_user_align = DECL_USER_ALIGN (decl);
      bool zero_bitfield = false;
      bool packed_p = DECL_PACKED (decl);
      unsigned int mfa;

      if (DECL_BIT_FIELD (decl))
        {
          DECL_BIT_FIELD_TYPE (decl) = type;

          /* A zero-length bit-field affects the alignment of the next
             field.  In essence such bit-fields are not influenced by
             any packing due to #pragma pack or attribute packed.  */
          if (integer_zerop (DECL_SIZE (decl))
              && ! targetm.ms_bitfield_layout_p (DECL_FIELD_CONTEXT (decl)))
            {
              zero_bitfield = true;
              packed_p = false;
              if (PCC_BITFIELD_TYPE_MATTERS)
                do_type_align (type, decl);
              else
                {
#ifdef EMPTY_FIELD_BOUNDARY
                  if (EMPTY_FIELD_BOUNDARY > DECL_ALIGN (decl))
                    {
                      DECL_ALIGN (decl) = EMPTY_FIELD_BOUNDARY;
                      DECL_USER_ALIGN (decl) = 0;
                    }
#endif
                }
            }

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

              if (xmode != BLKmode
                  && !(xalign > BITS_PER_UNIT && DECL_PACKED (decl))
                  && (known_align == 0 || known_align >= xalign))
                {
                  DECL_ALIGN (decl) = MAX (xalign, 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 (TYPE_MODE (type) == BLKmode && DECL_MODE (decl) == BLKmode
              && known_align >= TYPE_ALIGN (type)
              && DECL_ALIGN (decl) >= TYPE_ALIGN (type))
            DECL_BIT_FIELD (decl) = 0;
        }
      else if (packed_p && DECL_USER_ALIGN (decl))
        /* Don't touch DECL_ALIGN.  For other packed fields, go ahead and
           round up; we'll reduce it again below.  We want packing to
           supersede USER_ALIGN inherited from the type, but defer to
           alignment explicitly specified on the field decl.  */;
      else
        do_type_align (type, decl);

      /* If the field is packed and not explicitly aligned, give it the
         minimum alignment.  Note that do_type_align may set
         DECL_USER_ALIGN, so we need to check old_user_align instead.  */
      if (packed_p
          && !old_user_align)
        DECL_ALIGN (decl) = MIN (DECL_ALIGN (decl), BITS_PER_UNIT);

      if (! packed_p && ! DECL_USER_ALIGN (decl))
        {
          /* 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
          DECL_ALIGN (decl)
            = MIN (DECL_ALIGN (decl), (unsigned) BIGGEST_FIELD_ALIGNMENT);
#endif
#ifdef ADJUST_FIELD_ALIGN
          DECL_ALIGN (decl) = ADJUST_FIELD_ALIGN (decl, DECL_ALIGN (decl));
#endif
        }

      if (zero_bitfield)
        mfa = initial_max_fld_align * BITS_PER_UNIT;
      else
        mfa = maximum_field_alignment;
      /* Should this be controlled by DECL_USER_ALIGN, too?  */
      if (mfa != 0)
        DECL_ALIGN (decl) = MIN (DECL_ALIGN (decl), mfa);
    }

  /* 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)
        {
          int size_as_int = TREE_INT_CST_LOW (size);

          if (compare_tree_int (size, size_as_int) == 0)
            warning (OPT_Wlarger_than_, "size of %q+D is %d bytes", decl, size_as_int);
          else
            warning (OPT_Wlarger_than_, "size of %q+D is larger than %wd bytes",
                     decl, larger_than_size);
        }
    }

  /* If the RTL was already set, update its mode and mem attributes.  */
  if (rtl)
    {
      PUT_MODE (rtl, DECL_MODE (decl));
      SET_DECL_RTL (decl, 0);
      if (MEM_P (rtl))
        set_mem_attributes (rtl, decl, 1);
      SET_DECL_RTL (decl, rtl);
    }
}

/* Given a VAR_DECL, PARM_DECL or RESULT_DECL, clears the results of
   a previous call to layout_decl and calls it again.  */

void
relayout_decl (tree decl)
{
  DECL_SIZE (decl) = DECL_SIZE_UNIT (decl) = 0;
  DECL_MODE (decl) = VOIDmode;
  if (!DECL_USER_ALIGN (decl))
    DECL_ALIGN (decl) = 0;
  SET_DECL_RTL (decl, 0);

  layout_decl (decl, 0);
}
\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 (tree t)
{
  record_layout_info rli = XNEW (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->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))
    {
      unsigned tmp;

      /* #pragma pack overrides STRUCTURE_SIZE_BOUNDARY.  */
      tmp = (unsigned) STRUCTURE_SIZE_BOUNDARY;
      if (maximum_field_alignment != 0)
        tmp = MIN (tmp, maximum_field_alignment);
      rli->record_align = MAX (rli->record_align, tmp);
    }
#endif

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

  return rli;
}

/* Return the combined bit position for the byte offset OFFSET and the
   bit position BITPOS.

   These functions operate on byte and bit positions present in FIELD_DECLs
   and assume that these expressions result in no (intermediate) overflow.
   This assumption is necessary to fold the expressions as much as possible,
   so as to avoid creating artificially variable-sized types in languages
   supporting variable-sized types like Ada.  */

tree
bit_from_pos (tree offset, tree bitpos)
{
  if (TREE_CODE (offset) == PLUS_EXPR)
    offset = size_binop (PLUS_EXPR,
                         fold_convert (bitsizetype, TREE_OPERAND (offset, 0)),
                         fold_convert (bitsizetype, TREE_OPERAND (offset, 1)));
  else
    offset = fold_convert (bitsizetype, offset);
  return size_binop (PLUS_EXPR, bitpos,
                     size_binop (MULT_EXPR, offset, bitsize_unit_node));
}

/* Return the combined truncated byte position for the byte offset OFFSET and
   the bit position BITPOS.  */

tree
byte_from_pos (tree offset, tree bitpos)
{
  tree bytepos;
  if (TREE_CODE (bitpos) == MULT_EXPR
      && tree_int_cst_equal (TREE_OPERAND (bitpos, 1), bitsize_unit_node))
    bytepos = TREE_OPERAND (bitpos, 0);
  else
    bytepos = size_binop (TRUNC_DIV_EXPR, bitpos, bitsize_unit_node);
  return size_binop (PLUS_EXPR, offset, fold_convert (sizetype, bytepos));
}

/* Split the bit position POS into a byte offset *POFFSET and a bit
   position *PBITPOS with the byte offset aligned to OFF_ALIGN bits.  */

void
pos_from_bit (tree *poffset, tree *pbitpos, unsigned int off_align,
              tree pos)
{
  tree toff_align = bitsize_int (off_align);
  if (TREE_CODE (pos) == MULT_EXPR
      && tree_int_cst_equal (TREE_OPERAND (pos, 1), toff_align))
    {
      *poffset = size_binop (MULT_EXPR,
                             fold_convert (sizetype, TREE_OPERAND (pos, 0)),
                             size_int (off_align / BITS_PER_UNIT));
      *pbitpos = bitsize_zero_node;
    }
  else
    {
      *poffset = size_binop (MULT_EXPR,
                             fold_convert (sizetype,
                                           size_binop (FLOOR_DIV_EXPR, pos,
                                                       toff_align)),
                             size_int (off_align / BITS_PER_UNIT));
      *pbitpos = size_binop (FLOOR_MOD_EXPR, pos, toff_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 (tree *poffset, tree *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 offset, bitpos;
      pos_from_bit (&offset, &bitpos, off_align, *pbitpos);
      *poffset = size_binop (PLUS_EXPR, *poffset, offset);
      *pbitpos = bitpos;
    }
}

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

DEBUG_FUNCTION void
debug_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, off = %u\n",
           rli->record_align, rli->unpacked_align,
           rli->offset_align);

  /* The ms_struct code is the only that uses this.  */
  if (targetm.ms_bitfield_layout_p (rli->t))
    fprintf (stderr, "remaining in alignment = %u\n", rli->remaining_in_alignment);

  if (rli->packed_maybe_necessary)
    fprintf (stderr, "packed may be necessary\n");

  if (!vec_safe_is_empty (rli->pending_statics))
    {
      fprintf (stderr, "pending statics:\n");
      debug_vec_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 (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 (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 (record_layout_info rli)
{
  return bit_from_pos (rli->offset, rli->bitpos);
}

/* FIELD is about to be added to RLI->T.  The alignment (in bits) of
   the next available location within the record is given by KNOWN_ALIGN.
   Update the variable alignment fields in RLI, and return the alignment
   to give the FIELD.  */

unsigned int
update_alignment_for_field (record_layout_info rli, tree field,
                            unsigned int known_align)
{
  /* The alignment required for FIELD.  */
  unsigned int desired_align;
  /* The type of this field.  */
  tree type = TREE_TYPE (field);
  /* True if the field was explicitly aligned by the user.  */
  bool user_align;
  bool is_bitfield;

  /* Do not attempt to align an ERROR_MARK node */
  if (TREE_CODE (type) == ERROR_MARK)
    return 0;

  /* Lay out the field so we know what alignment it needs.  */
  layout_decl (field, known_align);
  desired_align = DECL_ALIGN (field);
  user_align = DECL_USER_ALIGN (field);

  is_bitfield = (type != error_mark_node
                 && DECL_BIT_FIELD_TYPE (field)
                 && ! integer_zerop (TYPE_SIZE (type)));

  /* 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))
    {
      /* Here, the alignment of the underlying type of a bitfield can
         affect the alignment of a record; even a zero-sized field
         can do this.  The alignment should be to the alignment of
         the type, except that for zero-size bitfields this only
         applies if there was an immediately prior, nonzero-size
         bitfield.  (That's the way it is, experimentally.) */
      if ((!is_bitfield && !DECL_PACKED (field))
          || ((DECL_SIZE (field) == NULL_TREE
               || !integer_zerop (DECL_SIZE (field)))
              ? !DECL_PACKED (field)
              : (rli->prev_field
                 && DECL_BIT_FIELD_TYPE (rli->prev_field)
                 && ! integer_zerop (DECL_SIZE (rli->prev_field)))))
        {
          unsigned int type_align = TYPE_ALIGN (type);
          type_align = MAX (type_align, desired_align);
          if (maximum_field_alignment != 0)
            type_align = MIN (type_align, maximum_field_alignment);
          rli->record_align = MAX (rli->record_align, type_align);
          rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
        }
    }
  else if (is_bitfield && PCC_BITFIELD_TYPE_MATTERS)
    {
      /* Named bit-fields cause the entire structure to have the
         alignment implied by their type.  Some targets also apply the same
         rules to unnamed bitfields.  */
      if (DECL_NAME (field) != 0
          || targetm.align_anon_bitfield ())
        {
          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

          /* Targets might chose to handle unnamed and hence possibly
             zero-width bitfield.  Those are not influenced by #pragmas
             or packed attributes.  */
          if (integer_zerop (DECL_SIZE (field)))
            {
              if (initial_max_fld_align)
                type_align = MIN (type_align,
                                  initial_max_fld_align * BITS_PER_UNIT);
            }
          else 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);

          /* The alignment of the record is increased to the maximum
             of the current alignment, the alignment indicated on the
             field (i.e., the alignment specified by an __aligned__
             attribute), and the alignment indicated by the type of
             the field.  */
          rli->record_align = MAX (rli->record_align, desired_align);
          rli->record_align = MAX (rli->record_align, type_align);

          if (warn_packed)
            rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
          user_align |= TYPE_USER_ALIGN (type);
        }
    }
  else
    {
      rli->record_align = MAX (rli->record_align, desired_align);
      rli->unpacked_align = MAX (rli->unpacked_align, TYPE_ALIGN (type));
    }

  TYPE_USER_ALIGN (rli->t) |= user_align;

  return desired_align;
}

/* Called from place_field to handle unions.  */

static void
place_union_field (record_layout_info rli, tree field)
{
  update_alignment_for_field (rli, field, /*known_align=*/0);

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

  /* If this is an ERROR_MARK return *after* having set the
     field at the start of the union. This helps when parsing
     invalid fields. */
  if (TREE_CODE (TREE_TYPE (field)) == ERROR_MARK)
    return;

  /* 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_build3 (COND_EXPR, sizetype, DECL_QUALIFIER (field),
                               DECL_SIZE_UNIT (field), rli->offset);
}

/* A bitfield of SIZE with a required access alignment of ALIGN is allocated
   at BYTE_OFFSET / BIT_OFFSET.  Return nonzero if the field would span more
   units of alignment than the underlying TYPE.  */
static int
excess_unit_span (HOST_WIDE_INT byte_offset, HOST_WIDE_INT bit_offset,
                  HOST_WIDE_INT size, HOST_WIDE_INT align, tree type)
{
  /* Note that the calculation of OFFSET might overflow; we calculate it so
     that we still get the right result as long as ALIGN is a power of two.  */
  unsigned HOST_WIDE_INT offset = byte_offset * BITS_PER_UNIT + bit_offset;

  offset = offset % align;
  return ((offset + size + align - 1) / align
          > tree_to_uhwi (TYPE_SIZE (type)) / align);
}

/* 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 (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;
  /* The type of this field.  */
  tree type = TREE_TYPE (field);

  gcc_assert (TREE_CODE (field) != ERROR_MARK);

  /* 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)
    {
      vec_safe_push (rli->pending_statics, field);
      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;
    }

  else if (TREE_CODE (type) == ERROR_MARK)
    {
      /* Place this field at the current allocation position, so we
         maintain monotonicity.  */
      DECL_FIELD_OFFSET (field) = rli->offset;
      DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
      SET_DECL_OFFSET_ALIGN (field, rli->offset_align);
      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_to_uhwi (rli->bitpos)
                   & - tree_to_uhwi (rli->bitpos));
  else if (integer_zerop (rli->offset))
    known_align = 0;
  else if (tree_fits_uhwi_p (rli->offset))
    known_align = (BITS_PER_UNIT
                   * (tree_to_uhwi (rli->offset)
                      & - tree_to_uhwi (rli->offset)));
  else
    known_align = rli->offset_align;

  desired_align = update_alignment_for_field (rli, field, known_align);
  if (known_align == 0)
    known_align = MAX (BIGGEST_ALIGNMENT, rli->record_align);

  if (warn_packed && DECL_PACKED (field))
    {
      if (known_align >= TYPE_ALIGN (type))
        {
          if (TYPE_ALIGN (type) > desired_align)
            {
              if (STRICT_ALIGNMENT)
                warning (OPT_Wattributes, "packed attribute causes "
                         "inefficient alignment for %q+D", field);
              /* Don't warn if DECL_PACKED was set by the type.  */
              else if (!TYPE_PACKED (rli->t))
                warning (OPT_Wattributes, "packed attribute is "
                         "unnecessary for %q+D", field);
            }
        }
      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 (!targetm.ms_bitfield_layout_p (rli->t)
          && DECL_SOURCE_LOCATION (field) != BUILTINS_LOCATION)
        warning (OPT_Wpadded, "padding struct to align %q+D", field);

      /* 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,
                          fold_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;
      if (targetm.ms_bitfield_layout_p (rli->t))
        rli->prev_field = NULL;
    }

  /* Handle compatibility with PCC.  Note that if the record has any
     variable-sized fields, we need not worry about compatibility.  */
  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)
          /* Enter for these packed fields only to issue a warning.  */
          || TYPE_ALIGN (type) <= BITS_PER_UNIT)
      && maximum_field_alignment == 0
      && ! integer_zerop (DECL_SIZE (field))
      && tree_fits_uhwi_p (DECL_SIZE (field))
      && tree_fits_uhwi_p (rli->offset)
      && tree_fits_uhwi_p (TYPE_SIZE (type)))
    {
      unsigned int type_align = TYPE_ALIGN (type);
      tree dsize = DECL_SIZE (field);
      HOST_WIDE_INT field_size = tree_to_uhwi (dsize);
      HOST_WIDE_INT offset = tree_to_uhwi (rli->offset);
      HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos);

#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 (excess_unit_span (offset, bit_offset, field_size, type_align, type))
        {
          if (DECL_PACKED (field))
            {
              if (warn_packed_bitfield_compat == 1)
                inform
                  (input_location,
                   "offset of packed bit-field %qD has changed in GCC 4.4",
                   field);
            }
          else
            rli->bitpos = round_up (rli->bitpos, type_align);
        }

      if (! DECL_PACKED (field))
        TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (type);
    }

#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))
      && tree_fits_uhwi_p (DECL_SIZE (field))
      && tree_fits_uhwi_p (rli->offset)
      && tree_fits_uhwi_p (TYPE_SIZE (type)))
    {
      unsigned int type_align = TYPE_ALIGN (type);
      tree dsize = DECL_SIZE (field);
      HOST_WIDE_INT field_size = tree_to_uhwi (dsize);
      HOST_WIDE_INT offset = tree_to_uhwi (rli->offset);
      HOST_WIDE_INT bit_offset = tree_to_shwi (rli->bitpos);

#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.  */
      if (excess_unit_span (offset, bit_offset, field_size, type_align, type))
        rli->bitpos = round_up (rli->bitpos, type_align);

      TYPE_USER_ALIGN (rli->t) |= TYPE_USER_ALIGN (type);
    }
#endif

  /* See the docs for TARGET_MS_BITFIELD_LAYOUT_P for details.
     A subtlety:
        When a bit field is inserted into a packed record, the whole
        size of the underlying type is used by one or more same-size
        adjacent bitfields.  (That is, if its long:3, 32 bits is
        used in the record, and any additional adjacent long bitfields are
        packed into the same chunk of 32 bits. However, if the size
        changes, a new field of that size is allocated.)  In an unpacked
        record, this is the same as using alignment, but not equivalent
        when packing.

     Note: for compatibility, we use the type size, not the type alignment
     to determine alignment, since that matches the documentation */

  if (targetm.ms_bitfield_layout_p (rli->t))
    {
      tree prev_saved = rli->prev_field;
      tree prev_type = prev_saved ? DECL_BIT_FIELD_TYPE (prev_saved) : NULL;

      /* This is a bitfield if it exists.  */
      if (rli->prev_field)
        {
          /* If both are bitfields, nonzero, and the same size, this is
             the middle of a run.  Zero declared size fields are special
             and handled as "end of run". (Note: it's nonzero declared
             size, but equal type sizes!) (Since we know that both
             the current and previous fields are bitfields by the
             time we check it, DECL_SIZE must be present for both.) */
          if (DECL_BIT_FIELD_TYPE (field)
              && !integer_zerop (DECL_SIZE (field))
              && !integer_zerop (DECL_SIZE (rli->prev_field))
              && tree_fits_shwi_p (DECL_SIZE (rli->prev_field))
              && tree_fits_uhwi_p (TYPE_SIZE (type))
              && simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type)))
            {
              /* We're in the middle of a run of equal type size fields; make
                 sure we realign if we run out of bits.  (Not decl size,
                 type size!) */
              HOST_WIDE_INT bitsize = tree_to_uhwi (DECL_SIZE (field));

              if (rli->remaining_in_alignment < bitsize)
                {
                  HOST_WIDE_INT typesize = tree_to_uhwi (TYPE_SIZE (type));

                  /* out of bits; bump up to next 'word'.  */
                  rli->bitpos
                    = size_binop (PLUS_EXPR, rli->bitpos,
                                  bitsize_int (rli->remaining_in_alignment));
                  rli->prev_field = field;
                  if (typesize < bitsize)
                    rli->remaining_in_alignment = 0;
                  else
                    rli->remaining_in_alignment = typesize - bitsize;
                }
              else
                rli->remaining_in_alignment -= bitsize;
            }
          else
            {
              /* End of a run: if leaving a run of bitfields of the same type
                 size, we have to "use up" the rest of the bits of the type
                 size.

                 Compute the new position as the sum of the size for the prior
                 type and where we first started working on that type.
                 Note: since the beginning of the field was aligned then
                 of course the end will be too.  No round needed.  */

              if (!integer_zerop (DECL_SIZE (rli->prev_field)))
                {
                  rli->bitpos
                    = size_binop (PLUS_EXPR, rli->bitpos,
                                  bitsize_int (rli->remaining_in_alignment));
                }
              else
                /* We "use up" size zero fields; the code below should behave
                   as if the prior field was not a bitfield.  */
                prev_saved = NULL;

              /* Cause a new bitfield to be captured, either this time (if
                 currently a bitfield) or next time we see one.  */
              if (!DECL_BIT_FIELD_TYPE (field)
                  || integer_zerop (DECL_SIZE (field)))
                rli->prev_field = NULL;
            }

          normalize_rli (rli);
        }

      /* If we're starting a new run of same type size bitfields
         (or a run of non-bitfields), set up the "first of the run"
         fields.

         That is, if the current field is not a bitfield, or if there
         was a prior bitfield the type sizes differ, or if there wasn't
         a prior bitfield the size of the current field is nonzero.

         Note: we must be sure to test ONLY the type size if there was
         a prior bitfield and ONLY for the current field being zero if
         there wasn't.  */

      if (!DECL_BIT_FIELD_TYPE (field)
          || (prev_saved != NULL
              ? !simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type))
              : !integer_zerop (DECL_SIZE (field)) ))
        {
          /* Never smaller than a byte for compatibility.  */
          unsigned int type_align = BITS_PER_UNIT;

          /* (When not a bitfield), we could be seeing a flex array (with
             no DECL_SIZE).  Since we won't be using remaining_in_alignment
             until we see a bitfield (and come by here again) we just skip
             calculating it.  */
          if (DECL_SIZE (field) != NULL
              && tree_fits_uhwi_p (TYPE_SIZE (TREE_TYPE (field)))
              && tree_fits_uhwi_p (DECL_SIZE (field)))
            {
              unsigned HOST_WIDE_INT bitsize
                = tree_to_uhwi (DECL_SIZE (field));
              unsigned HOST_WIDE_INT typesize
                = tree_to_uhwi (TYPE_SIZE (TREE_TYPE (field)));

              if (typesize < bitsize)
                rli->remaining_in_alignment = 0;
              else
                rli->remaining_in_alignment = typesize - bitsize;
            }

          /* Now align (conventionally) for the new type.  */
          type_align = TYPE_ALIGN (TREE_TYPE (field));

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

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

          /* If we really aligned, don't allow subsequent bitfields
             to undo that.  */
          rli->prev_field = NULL;
        }
    }

  /* 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);

  /* Evaluate nonconstant offsets only once, either now or as soon as safe.  */
  if (TREE_CODE (DECL_FIELD_OFFSET (field)) != INTEGER_CST)
    DECL_FIELD_OFFSET (field) = variable_size (DECL_FIELD_OFFSET (field));

  /* 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_to_uhwi (DECL_FIELD_BIT_OFFSET (field))
                    & - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)));
  else if (integer_zerop (DECL_FIELD_OFFSET (field)))
    actual_align = MAX (BIGGEST_ALIGNMENT, rli->record_align);
  else if (tree_fits_uhwi_p (DECL_FIELD_OFFSET (field)))
    actual_align = (BITS_PER_UNIT
                   * (tree_to_uhwi (DECL_FIELD_OFFSET (field))
                      & - tree_to_uhwi (DECL_FIELD_OFFSET (field))));
  else
    actual_align = DECL_OFFSET_ALIGN (field);
  /* ACTUAL_ALIGN is still the actual alignment *within the record* .
     store / extract bit field operations will check the alignment of the
     record against the mode of bit fields.  */

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

  if (rli->prev_field == NULL && DECL_BIT_FIELD_TYPE (field))
    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 (field)) != INTEGER_CST
           || TREE_OVERFLOW (DECL_SIZE (field)))
    {
      rli->offset
        = size_binop (PLUS_EXPR, rli->offset,
                      fold_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, desired_align);
    }
  else if (targetm.ms_bitfield_layout_p (rli->t))
    {
      rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos, DECL_SIZE (field));

      /* If we ended a bitfield before the full length of the type then
         pad the struct out to the full length of the last type.  */
      if ((DECL_CHAIN (field) == NULL
           || TREE_CODE (DECL_CHAIN (field)) != FIELD_DECL)
          && DECL_BIT_FIELD_TYPE (field)
          && !integer_zerop (DECL_SIZE (field)))
        rli->bitpos = size_binop (PLUS_EXPR, rli->bitpos,
                                  bitsize_int (rli->remaining_in_alignment));

      normalize_rli (rli);
    }
  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
   indicated by RLI.  */

static void
finalize_record_size (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);

  /* Round the size up to be a multiple of the required alignment.  */
  TYPE_SIZE (rli->t) = round_up (unpadded_size, TYPE_ALIGN (rli->t));
  TYPE_SIZE_UNIT (rli->t)
    = round_up (unpadded_size_unit, TYPE_ALIGN_UNIT (rli->t));

  if (TREE_CONSTANT (unpadded_size)
      && simple_cst_equal (unpadded_size, TYPE_SIZE (rli->t)) == 0
      && input_location != BUILTINS_LOCATION)
    warning (OPT_Wpadded, "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

      unpacked_size = round_up (TYPE_SIZE (rli->t), rli->unpacked_align);
      if (simple_cst_equal (unpacked_size, TYPE_SIZE (rli->t)))
        {
          if (TYPE_NAME (rli->t))
            {
              tree name;

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

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

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

void
compute_record_mode (tree type)
{
  tree field;
  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.  */
  SET_TYPE_MODE (type, BLKmode);

  if (! tree_fits_uhwi_p (TYPE_SIZE (type)))
    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 = DECL_CHAIN (field))
    {
      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))
              && !(TYPE_SIZE (TREE_TYPE (field)) != 0
                   && integer_zerop (TYPE_SIZE (TREE_TYPE (field)))))
          || ! tree_fits_uhwi_p (bit_position (field))
          || DECL_SIZE (field) == 0
          || ! tree_fits_uhwi_p (DECL_SIZE (field)))
        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);

      /* With some targets, it is sub-optimal to access an aligned
         BLKmode structure as a scalar.  */
      if (targetm.member_type_forces_blk (field, mode))
        return;
    }

  /* If we only have one real field; use its mode if that mode's size
     matches the type's size.  This only applies to RECORD_TYPE.  This
     does not apply to unions.  */
  if (TREE_CODE (type) == RECORD_TYPE && mode != VOIDmode
      && tree_fits_uhwi_p (TYPE_SIZE (type))
      && GET_MODE_BITSIZE (mode) == tree_to_uhwi (TYPE_SIZE (type)))
    SET_TYPE_MODE (type, mode);
  else
    SET_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;
      SET_TYPE_MODE (type, BLKmode);
    }
}

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

static void
finalize_type_size (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 || !AGGREGATE_TYPE_P (type)))
    {
      unsigned mode_align = GET_MODE_ALIGNMENT (TYPE_MODE (type));

      /* Don't override a larger alignment requirement coming from a user
         alignment of one of the fields.  */
      if (mode_align >= TYPE_ALIGN (type))
        {
          TYPE_ALIGN (type) = mode_align;
          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)
      = fold_convert (sizetype,
                      size_binop (FLOOR_DIV_EXPR, TYPE_SIZE (type),
                                  bitsize_unit_node));

  if (TYPE_SIZE (type) != 0)
    {
      TYPE_SIZE (type) = round_up (TYPE_SIZE (type), TYPE_ALIGN (type));
      TYPE_SIZE_UNIT (type)
        = round_up (TYPE_SIZE_UNIT (type), TYPE_ALIGN_UNIT (type));
    }

  /* 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 precision = TYPE_PRECISION (type);
      unsigned int user_align = TYPE_USER_ALIGN (type);
      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;
          unsigned valign = align;
          if (TYPE_USER_ALIGN (variant))
            valign = MAX (valign, TYPE_ALIGN (variant));
          else
            TYPE_USER_ALIGN (variant) = user_align;
          TYPE_ALIGN (variant) = valign;
          TYPE_PRECISION (variant) = precision;
          SET_TYPE_MODE (variant, mode);
        }
    }
}

/* Return a new underlying object for a bitfield started with FIELD.  */

static tree
start_bitfield_representative (tree field)
{
  tree repr = make_node (FIELD_DECL);
  DECL_FIELD_OFFSET (repr) = DECL_FIELD_OFFSET (field);
  /* Force the representative to begin at a BITS_PER_UNIT aligned
     boundary - C++ may use tail-padding of a base object to
     continue packing bits so the bitfield region does not start
     at bit zero (see g++.dg/abi/bitfield5.C for example).
     Unallocated bits may happen for other reasons as well,
     for example Ada which allows explicit bit-granular structure layout.  */
  DECL_FIELD_BIT_OFFSET (repr)
    = size_binop (BIT_AND_EXPR,
                  DECL_FIELD_BIT_OFFSET (field),
                  bitsize_int (~(BITS_PER_UNIT - 1)));
  SET_DECL_OFFSET_ALIGN (repr, DECL_OFFSET_ALIGN (field));
  DECL_SIZE (repr) = DECL_SIZE (field);
  DECL_SIZE_UNIT (repr) = DECL_SIZE_UNIT (field);
  DECL_PACKED (repr) = DECL_PACKED (field);
  DECL_CONTEXT (repr) = DECL_CONTEXT (field);
  return repr;
}

/* Finish up a bitfield group that was started by creating the underlying
   object REPR with the last field in the bitfield group FIELD.  */

static void
finish_bitfield_representative (tree repr, tree field)
{
  unsigned HOST_WIDE_INT bitsize, maxbitsize;
  machine_mode mode;
  tree nextf, size;

  size = size_diffop (DECL_FIELD_OFFSET (field),
                      DECL_FIELD_OFFSET (repr));
  while (TREE_CODE (size) == COMPOUND_EXPR)
    size = TREE_OPERAND (size, 1);
  gcc_assert (tree_fits_uhwi_p (size));
  bitsize = (tree_to_uhwi (size) * BITS_PER_UNIT
             + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field))
             - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr))
             + tree_to_uhwi (DECL_SIZE (field)));

  /* Round up bitsize to multiples of BITS_PER_UNIT.  */
  bitsize = (bitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1);

  /* Now nothing tells us how to pad out bitsize ...  */
  nextf = DECL_CHAIN (field);
  while (nextf && TREE_CODE (nextf) != FIELD_DECL)
    nextf = DECL_CHAIN (nextf);
  if (nextf)
    {
      tree maxsize;
      /* If there was an error, the field may be not laid out
         correctly.  Don't bother to do anything.  */
      if (TREE_TYPE (nextf) == error_mark_node)
        return;
      maxsize = size_diffop (DECL_FIELD_OFFSET (nextf),
                             DECL_FIELD_OFFSET (repr));
      if (tree_fits_uhwi_p (maxsize))
        {
          maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT
                        + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (nextf))
                        - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr)));
          /* If the group ends within a bitfield nextf does not need to be
             aligned to BITS_PER_UNIT.  Thus round up.  */
          maxbitsize = (maxbitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1);
        }
      else
        maxbitsize = bitsize;
    }
  else
    {
      /* ???  If you consider that tail-padding of this struct might be
         re-used when deriving from it we cannot really do the following
         and thus need to set maxsize to bitsize?  Also we cannot
         generally rely on maxsize to fold to an integer constant, so
         use bitsize as fallback for this case.  */
      tree maxsize = size_diffop (TYPE_SIZE_UNIT (DECL_CONTEXT (field)),
                                  DECL_FIELD_OFFSET (repr));
      if (tree_fits_uhwi_p (maxsize))
        maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT
                      - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr)));
      else
        maxbitsize = bitsize;
    }

  /* Only if we don't artificially break up the representative in
     the middle of a large bitfield with different possibly
     overlapping representatives.  And all representatives start
     at byte offset.  */
  gcc_assert (maxbitsize % BITS_PER_UNIT == 0);

  /* Find the smallest nice mode to use.  */
  for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != VOIDmode;
       mode = GET_MODE_WIDER_MODE (mode))
    if (GET_MODE_BITSIZE (mode) >= bitsize)
      break;
  if (mode != VOIDmode
      && (GET_MODE_BITSIZE (mode) > maxbitsize
          || GET_MODE_BITSIZE (mode) > MAX_FIXED_MODE_SIZE))
    mode = VOIDmode;

  if (mode == VOIDmode)
    {
      /* We really want a BLKmode representative only as a last resort,
         considering the member b in
           struct { int a : 7; int b : 17; int c; } __attribute__((packed));
         Otherwise we simply want to split the representative up
         allowing for overlaps within the bitfield region as required for
           struct { int a : 7; int b : 7;
                    int c : 10; int d; } __attribute__((packed));
         [0, 15] HImode for a and b, [8, 23] HImode for c.  */
      DECL_SIZE (repr) = bitsize_int (bitsize);
      DECL_SIZE_UNIT (repr) = size_int (bitsize / BITS_PER_UNIT);
      DECL_MODE (repr) = BLKmode;
      TREE_TYPE (repr) = build_array_type_nelts (unsigned_char_type_node,
                                                 bitsize / BITS_PER_UNIT);
    }
  else
    {
      unsigned HOST_WIDE_INT modesize = GET_MODE_BITSIZE (mode);
      DECL_SIZE (repr) = bitsize_int (modesize);
      DECL_SIZE_UNIT (repr) = size_int (modesize / BITS_PER_UNIT);
      DECL_MODE (repr) = mode;
      TREE_TYPE (repr) = lang_hooks.types.type_for_mode (mode, 1);
    }

  /* Remember whether the bitfield group is at the end of the
     structure or not.  */
  DECL_CHAIN (repr) = nextf;
}

/* Compute and set FIELD_DECLs for the underlying objects we should
   use for bitfield access for the structure T.  */

void
finish_bitfield_layout (tree t)
{
  tree field, prev;
  tree repr = NULL_TREE;

  /* Unions would be special, for the ease of type-punning optimizations
     we could use the underlying type as hint for the representative
     if the bitfield would fit and the representative would not exceed
     the union in size.  */
  if (TREE_CODE (t) != RECORD_TYPE)
    return;

  for (prev = NULL_TREE, field = TYPE_FIELDS (t);
       field; field = DECL_CHAIN (field))
    {
      if (TREE_CODE (field) != FIELD_DECL)
        continue;

      /* In the C++ memory model, consecutive bit fields in a structure are
         considered one memory location and updating a memory location
         may not store into adjacent memory locations.  */
      if (!repr
          && DECL_BIT_FIELD_TYPE (field))
        {
          /* Start new representative.  */
          repr = start_bitfield_representative (field);
        }
      else if (repr
               && ! DECL_BIT_FIELD_TYPE (field))
        {
          /* Finish off new representative.  */
          finish_bitfield_representative (repr, prev);
          repr = NULL_TREE;
        }
      else if (DECL_BIT_FIELD_TYPE (field))
        {
          gcc_assert (repr != NULL_TREE);

          /* Zero-size bitfields finish off a representative and
             do not have a representative themselves.  This is
             required by the C++ memory model.  */
          if (integer_zerop (DECL_SIZE (field)))
            {
              finish_bitfield_representative (repr, prev);
              repr = NULL_TREE;
            }

          /* We assume that either DECL_FIELD_OFFSET of the representative
             and each bitfield member is a constant or they are equal.
             This is because we need to be able to compute the bit-offset
             of each field relative to the representative in get_bit_range
             during RTL expansion.
             If these constraints are not met, simply force a new
             representative to be generated.  That will at most
             generate worse code but still maintain correctness with
             respect to the C++ memory model.  */
          else if (!((tree_fits_uhwi_p (DECL_FIELD_OFFSET (repr))
                      && tree_fits_uhwi_p (DECL_FIELD_OFFSET (field)))
                     || operand_equal_p (DECL_FIELD_OFFSET (repr),
                                         DECL_FIELD_OFFSET (field), 0)))
            {
              finish_bitfield_representative (repr, prev);
              repr = start_bitfield_representative (field);
            }
        }
      else
        continue;

      if (repr)
        DECL_BIT_FIELD_REPRESENTATIVE (field) = repr;

      prev = field;
    }

  if (repr)
    finish_bitfield_representative (repr, prev);
}

/* 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, unless FREE_P is false.  Passing a value other than false
   for FREE_P is bad practice; this option only exists to support the
   G++ 3.2 ABI.  */

void
finish_record_layout (record_layout_info rli, int free_p)
{
  tree variant;

  /* 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);

  /* Compute bitfield representatives.  */
  finish_bitfield_layout (rli->t);

  /* Propagate TYPE_PACKED and TYPE_REVERSE_STORAGE_ORDER to variants.
     With C++ templates, it is too early to do this when the attribute
     is being parsed.  */
  for (variant = TYPE_NEXT_VARIANT (rli->t); variant;
       variant = TYPE_NEXT_VARIANT (variant))
    {
      TYPE_PACKED (variant) = TYPE_PACKED (rli->t);
      TYPE_REVERSE_STORAGE_ORDER (variant)
        = TYPE_REVERSE_STORAGE_ORDER (rli->t);
    }

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

  /* Clean up.  */
  if (free_p)
    {
      vec_free (rli->pending_statics);
      free (rli);
    }
}
\f

/* Finish processing a builtin RECORD_TYPE type TYPE.  It's name is
   NAME, its fields are chained in reverse on FIELDS.

   If ALIGN_TYPE is non-null, it is given the same alignment as
   ALIGN_TYPE.  */

void
finish_builtin_struct (tree type, const char *name, tree fields,
                       tree align_type)
{
  tree tail, next;

  for (tail = NULL_TREE; fields; tail = fields, fields = next)
    {
      DECL_FIELD_CONTEXT (fields) = type;
      next = DECL_CHAIN (fields);
      DECL_CHAIN (fields) = tail;
    }
  TYPE_FIELDS (type) = tail;

  if (align_type)
    {
      TYPE_ALIGN (type) = TYPE_ALIGN (align_type);
      TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (align_type);
    }

  layout_type (type);
#if 0 /* not yet, should get fixed properly later */
  TYPE_NAME (type) = make_type_decl (get_identifier (name), type);
#else
  TYPE_NAME (type) = build_decl (BUILTINS_LOCATION,
                                 TYPE_DECL, get_identifier (name), type);
#endif
  TYPE_STUB_DECL (type) = TYPE_NAME (type);
  layout_decl (TYPE_NAME (type), 0);
}

/* 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 (tree type)
{
  gcc_assert (type);

  if (type == error_mark_node)
    return;

  /* We don't want finalize_type_size to copy an alignment attribute to
     variants that don't have it.  */
  type = TYPE_MAIN_VARIANT (type);

  /* 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.  */
      gcc_unreachable ();

    case BOOLEAN_TYPE:
    case INTEGER_TYPE:
    case ENUMERAL_TYPE:
      SET_TYPE_MODE (type,
                     smallest_mode_for_size (TYPE_PRECISION (type), MODE_INT));
      TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
      /* Don't set TYPE_PRECISION here, as it may be set by a bitfield.  */
      TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
      break;

    case REAL_TYPE:
      SET_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 FIXED_POINT_TYPE:
     /* TYPE_MODE (type) has been set already.  */
     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:
      TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type));
      SET_TYPE_MODE (type,
                     mode_for_size (2 * TYPE_PRECISION (TREE_TYPE (type)),
                                    (TREE_CODE (TREE_TYPE (type)) == REAL_TYPE
                                     ? MODE_COMPLEX_FLOAT : MODE_COMPLEX_INT),
                                     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:
      {
        int nunits = TYPE_VECTOR_SUBPARTS (type);
        tree innertype = TREE_TYPE (type);

        gcc_assert (!(nunits & (nunits - 1)));

        /* Find an appropriate mode for the vector type.  */
        if (TYPE_MODE (type) == VOIDmode)
          SET_TYPE_MODE (type,
                         mode_for_vector (TYPE_MODE (innertype), nunits));

        TYPE_SATURATING (type) = TYPE_SATURATING (TREE_TYPE (type));
        TYPE_UNSIGNED (type) = TYPE_UNSIGNED (TREE_TYPE (type));
        /* Several boolean vector elements may fit in a single unit.  */
        if (VECTOR_BOOLEAN_TYPE_P (type)
            && type->type_common.mode != BLKmode)
          TYPE_SIZE_UNIT (type)
            = size_int (GET_MODE_SIZE (type->type_common.mode));
        else
          TYPE_SIZE_UNIT (type) = int_const_binop (MULT_EXPR,
                                                   TYPE_SIZE_UNIT (innertype),
                                                   size_int (nunits));
        TYPE_SIZE (type) = int_const_binop (MULT_EXPR,
                                            TYPE_SIZE (innertype),
                                            bitsize_int (nunits));

        /* For vector types, we do not default to the mode's alignment.
           Instead, query a target hook, defaulting to natural alignment.
           This prevents ABI changes depending on whether or not native
           vector modes are supported.  */
        TYPE_ALIGN (type) = targetm.vector_alignment (type);

        /* However, if the underlying mode requires a bigger alignment than
           what the target hook provides, we cannot use the mode.  For now,
           simply reject that case.  */
        gcc_assert (TYPE_ALIGN (type)
                    >= GET_MODE_ALIGNMENT (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;
      SET_TYPE_MODE (type, VOIDmode);
      break;

    case POINTER_BOUNDS_TYPE:
      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 OFFSET_TYPE:
      TYPE_SIZE (type) = bitsize_int (POINTER_SIZE);
      TYPE_SIZE_UNIT (type) = size_int (POINTER_SIZE_UNITS);
      /* A pointer might be MODE_PARTIAL_INT, but ptrdiff_t must be
         integral, which may be an __intN.  */
      SET_TYPE_MODE (type, mode_for_size (POINTER_SIZE, MODE_INT, 0));
      TYPE_PRECISION (type) = POINTER_SIZE;
      break;

    case FUNCTION_TYPE:
    case METHOD_TYPE:
      /* It's hard to see what the mode and size of a function ought to
         be, but we do know the alignment is FUNCTION_BOUNDARY, so
         make it consistent with that.  */
      SET_TYPE_MODE (type, mode_for_size (FUNCTION_BOUNDARY, MODE_INT, 0));
      TYPE_SIZE (type) = bitsize_int (FUNCTION_BOUNDARY);
      TYPE_SIZE_UNIT (type) = size_int (FUNCTION_BOUNDARY / BITS_PER_UNIT);
      break;

    case POINTER_TYPE:
    case REFERENCE_TYPE:
      {
        machine_mode mode = TYPE_MODE (type);
        if (TREE_CODE (type) == REFERENCE_TYPE && reference_types_internal)
          {
            addr_space_t as = TYPE_ADDR_SPACE (TREE_TYPE (type));
            mode = targetm.addr_space.address_mode (as);
          }

        TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
        TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
        TYPE_UNSIGNED (type) = 1;
        TYPE_PRECISION (type) = GET_MODE_PRECISION (mode);
      }
      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 element_size = TYPE_SIZE (element);
            tree length;

            /* Make sure that an array of zero-sized element is zero-sized
               regardless of its extent.  */
            if (integer_zerop (element_size))
              length = size_zero_node;

            /* The computation should happen in the original signedness so
               that (possible) negative values are handled appropriately
               when determining overflow.  */
            else
              {
                /* ???  When it is obvious that the range is signed
                   represent it using ssizetype.  */
                if (TREE_CODE (lb) == INTEGER_CST
                    && TREE_CODE (ub) == INTEGER_CST
                    && TYPE_UNSIGNED (TREE_TYPE (lb))
                    && tree_int_cst_lt (ub, lb))
                  {
                    lb = wide_int_to_tree (ssizetype,
                                           offset_int::from (lb, SIGNED));
                    ub = wide_int_to_tree (ssizetype,
                                           offset_int::from (ub, SIGNED));
                  }
                length
                  = fold_convert (sizetype,
                                  size_binop (PLUS_EXPR,
                                              build_int_cst (TREE_TYPE (lb), 1),
                                              size_binop (MINUS_EXPR, ub, lb)));
              }

            /* ??? We have no way to distinguish a null-sized array from an
               array spanning the whole sizetype range, so we arbitrarily
               decide that [0, -1] is the only valid representation.  */
            if (integer_zerop (length)
                && TREE_OVERFLOW (length)
                && integer_zerop (lb))
              length = size_zero_node;

            TYPE_SIZE (type) = size_binop (MULT_EXPR, element_size,
                                           fold_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.  */
            if (TYPE_SIZE_UNIT (element))
              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.  */

        unsigned align = TYPE_ALIGN (element);
        if (TYPE_USER_ALIGN (type))
          align = MAX (align, TYPE_ALIGN (type));
        else
          TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (element);
#ifdef ROUND_TYPE_ALIGN
        align = ROUND_TYPE_ALIGN (type, align, BITS_PER_UNIT);
#else
        align = MAX (align, BITS_PER_UNIT);
#endif
        TYPE_ALIGN (type) = align;
        SET_TYPE_MODE (type, BLKmode);
        if (TYPE_SIZE (type) != 0
            && ! targetm.member_type_forces_blk (type, VOIDmode)
            /* BLKmode elements force BLKmode aggregate;
               else extract/store fields may lose.  */
            && (TYPE_MODE (TREE_TYPE (type)) != BLKmode
                || TYPE_NO_FORCE_BLK (TREE_TYPE (type))))
          {
            SET_TYPE_MODE (type, mode_for_array (TREE_TYPE (type),
                                                 TYPE_SIZE (type)));
            if (TYPE_MODE (type) != BLKmode
                && STRICT_ALIGNMENT && TYPE_ALIGN (type) < BIGGEST_ALIGNMENT
                && TYPE_ALIGN (type) < GET_MODE_ALIGNMENT (TYPE_MODE (type)))
              {
                TYPE_NO_FORCE_BLK (type) = 1;
                SET_TYPE_MODE (type, BLKmode);
              }
          }
        /* When the element size is constant, check that it is at least as
           large as the element alignment.  */
        if (TYPE_SIZE_UNIT (element)
            && TREE_CODE (TYPE_SIZE_UNIT (element)) == INTEGER_CST
            /* If TYPE_SIZE_UNIT overflowed, then it is certainly larger than
               TYPE_ALIGN_UNIT.  */
            && !TREE_OVERFLOW (TYPE_SIZE_UNIT (element))
            && !integer_zerop (TYPE_SIZE_UNIT (element))
            && compare_tree_int (TYPE_SIZE_UNIT (element),
                                 TYPE_ALIGN_UNIT (element)) < 0)
          error ("alignment of array elements is greater than element size");
        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 = DECL_CHAIN (field))
          place_field (rli, field);

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

        /* Finish laying out the record.  */
        finish_record_layout (rli, /*free_p=*/true);
      }
      break;

    default:
      gcc_unreachable ();
    }

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

  /* We should never see alias sets on incomplete aggregates.  And we
     should not call layout_type on not incomplete aggregates.  */
  if (AGGREGATE_TYPE_P (type))
    gcc_assert (!TYPE_ALIAS_SET_KNOWN_P (type));
}

/* Return the least alignment required for type TYPE.  */

unsigned int
min_align_of_type (tree type)
{
  unsigned int align = TYPE_ALIGN (type);
  if (!TYPE_USER_ALIGN (type))
    {
      align = MIN (align, BIGGEST_ALIGNMENT);
#ifdef BIGGEST_FIELD_ALIGNMENT
      align = MIN (align, BIGGEST_FIELD_ALIGNMENT);
#endif
      unsigned int field_align = align;
#ifdef ADJUST_FIELD_ALIGN
      tree field = build_decl (UNKNOWN_LOCATION, FIELD_DECL, NULL_TREE, type);
      field_align = ADJUST_FIELD_ALIGN (field, field_align);
      ggc_free (field);
#endif
      align = MIN (align, field_align);
    }
  return align / BITS_PER_UNIT;
}

/* Vector types need to re-check the target flags each time we report
   the machine mode.  We need to do this because attribute target can
   change the result of vector_mode_supported_p and have_regs_of_mode
   on a per-function basis.  Thus the TYPE_MODE of a VECTOR_TYPE can
   change on a per-function basis.  */
/* ??? Possibly a better solution is to run through all the types
   referenced by a function and re-compute the TYPE_MODE once, rather
   than make the TYPE_MODE macro call a function.  */

machine_mode
vector_type_mode (const_tree t)
{
  machine_mode mode;

  gcc_assert (TREE_CODE (t) == VECTOR_TYPE);

  mode = t->type_common.mode;
  if (VECTOR_MODE_P (mode)
      && (!targetm.vector_mode_supported_p (mode)
          || !have_regs_of_mode[mode]))
    {
      machine_mode innermode = TREE_TYPE (t)->type_common.mode;

      /* For integers, try mapping it to a same-sized scalar mode.  */
      if (GET_MODE_CLASS (innermode) == MODE_INT)
        {
          mode = mode_for_size (TYPE_VECTOR_SUBPARTS (t)
                                * GET_MODE_BITSIZE (innermode), MODE_INT, 0);

          if (mode != VOIDmode && have_regs_of_mode[mode])
            return mode;
        }

      return BLKmode;
    }

  return mode;
}
\f
/* Create and return a type for signed integers of PRECISION bits.  */

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

  TYPE_PRECISION (type) = precision;

  fixup_unsigned_type (type);
  return type;
}
\f
/* Create and return a type for fract of PRECISION bits, UNSIGNEDP,
   and SATP.  */

tree
make_fract_type (int precision, int unsignedp, int satp)
{
  tree type = make_node (FIXED_POINT_TYPE);

  TYPE_PRECISION (type) = precision;

  if (satp)
    TYPE_SATURATING (type) = 1;

  /* Lay out the type: set its alignment, size, etc.  */
  if (unsignedp)
    {
      TYPE_UNSIGNED (type) = 1;
      SET_TYPE_MODE (type, mode_for_size (precision, MODE_UFRACT, 0));
    }
  else
    SET_TYPE_MODE (type, mode_for_size (precision, MODE_FRACT, 0));
  layout_type (type);

  return type;
}

/* Create and return a type for accum of PRECISION bits, UNSIGNEDP,
   and SATP.  */

tree
make_accum_type (int precision, int unsignedp, int satp)
{
  tree type = make_node (FIXED_POINT_TYPE);

  TYPE_PRECISION (type) = precision;

  if (satp)
    TYPE_SATURATING (type) = 1;

  /* Lay out the type: set its alignment, size, etc.  */
  if (unsignedp)
    {
      TYPE_UNSIGNED (type) = 1;
      SET_TYPE_MODE (type, mode_for_size (precision, MODE_UACCUM, 0));
    }
  else
    SET_TYPE_MODE (type, mode_for_size (precision, MODE_ACCUM, 0));
  layout_type (type);

  return type;
}

/* Initialize sizetypes so layout_type can use them.  */

void
initialize_sizetypes (void)
{
  int precision, bprecision;

  /* Get sizetypes precision from the SIZE_TYPE target macro.  */
  if (strcmp (SIZETYPE, "unsigned int") == 0)
    precision = INT_TYPE_SIZE;
  else if (strcmp (SIZETYPE, "long unsigned int") == 0)
    precision = LONG_TYPE_SIZE;
  else if (strcmp (SIZETYPE, "long long unsigned int") == 0)
    precision = LONG_LONG_TYPE_SIZE;
  else if (strcmp (SIZETYPE, "short unsigned int") == 0)
    precision = SHORT_TYPE_SIZE;
  else
    {
      int i;

      precision = -1;
      for (i = 0; i < NUM_INT_N_ENTS; i++)
        if (int_n_enabled_p[i])
          {
            char name[50];
            sprintf (name, "__int%d unsigned", int_n_data[i].bitsize);

            if (strcmp (name, SIZETYPE) == 0)
              {
                precision = int_n_data[i].bitsize;
              }
          }
      if (precision == -1)
        gcc_unreachable ();
    }

  bprecision
    = MIN (precision + BITS_PER_UNIT_LOG + 1, MAX_FIXED_MODE_SIZE);
  bprecision
    = GET_MODE_PRECISION (smallest_mode_for_size (bprecision, MODE_INT));
  if (bprecision > HOST_BITS_PER_DOUBLE_INT)
    bprecision = HOST_BITS_PER_DOUBLE_INT;

  /* Create stubs for sizetype and bitsizetype so we can create constants.  */
  sizetype = make_node (INTEGER_TYPE);
  TYPE_NAME (sizetype) = get_identifier ("sizetype");
  TYPE_PRECISION (sizetype) = precision;
  TYPE_UNSIGNED (sizetype) = 1;
  bitsizetype = make_node (INTEGER_TYPE);
  TYPE_NAME (bitsizetype) = get_identifier ("bitsizetype");
  TYPE_PRECISION (bitsizetype) = bprecision;
  TYPE_UNSIGNED (bitsizetype) = 1;

  /* Now layout both types manually.  */
  SET_TYPE_MODE (sizetype, smallest_mode_for_size (precision, MODE_INT));
  TYPE_ALIGN (sizetype) = GET_MODE_ALIGNMENT (TYPE_MODE (sizetype));
  TYPE_SIZE (sizetype) = bitsize_int (precision);
  TYPE_SIZE_UNIT (sizetype) = size_int (GET_MODE_SIZE (TYPE_MODE (sizetype)));
  set_min_and_max_values_for_integral_type (sizetype, precision, UNSIGNED);

  SET_TYPE_MODE (bitsizetype, smallest_mode_for_size (bprecision, MODE_INT));
  TYPE_ALIGN (bitsizetype) = GET_MODE_ALIGNMENT (TYPE_MODE (bitsizetype));
  TYPE_SIZE (bitsizetype) = bitsize_int (bprecision);
  TYPE_SIZE_UNIT (bitsizetype)
    = size_int (GET_MODE_SIZE (TYPE_MODE (bitsizetype)));
  set_min_and_max_values_for_integral_type (bitsizetype, bprecision, UNSIGNED);

  /* Create the signed variants of *sizetype.  */
  ssizetype = make_signed_type (TYPE_PRECISION (sizetype));
  TYPE_NAME (ssizetype) = get_identifier ("ssizetype");
  sbitsizetype = make_signed_type (TYPE_PRECISION (bitsizetype));
  TYPE_NAME (sbitsizetype) = get_identifier ("sbitsizetype");
}
\f
/* TYPE is an integral type, i.e., an INTEGRAL_TYPE, ENUMERAL_TYPE
   or BOOLEAN_TYPE.  Set TYPE_MIN_VALUE and TYPE_MAX_VALUE
   for TYPE, based on the PRECISION and whether or not the TYPE
   IS_UNSIGNED.  PRECISION need not correspond to a width supported
   natively by the hardware; for example, on a machine with 8-bit,
   16-bit, and 32-bit register modes, PRECISION might be 7, 23, or
   61.  */

void
set_min_and_max_values_for_integral_type (tree type,
                                          int precision,
                                          signop sgn)
{
  /* For bitfields with zero width we end up creating integer types
     with zero precision.  Don't assign any minimum/maximum values
     to those types, they don't have any valid value.  */
  if (precision < 1)
    return;

  TYPE_MIN_VALUE (type)
    = wide_int_to_tree (type, wi::min_value (precision, sgn));
  TYPE_MAX_VALUE (type)
    = wide_int_to_tree (type, wi::max_value (precision, sgn));
}

/* 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 (tree type)
{
  int precision = TYPE_PRECISION (type);

  set_min_and_max_values_for_integral_type (type, precision, SIGNED);

  /* 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 (tree type)
{
  int precision = TYPE_PRECISION (type);

  TYPE_UNSIGNED (type) = 1;

  set_min_and_max_values_for_integral_type (type, precision, UNSIGNED);

  /* Lay out the type: set its alignment, size, etc.  */
  layout_type (type);
}
\f
/* Construct an iterator for a bitfield that spans BITSIZE bits,
   starting at BITPOS.

   BITREGION_START is the bit position of the first bit in this
   sequence of bit fields.  BITREGION_END is the last bit in this
   sequence.  If these two fields are non-zero, we should restrict the
   memory access to that range.  Otherwise, we are allowed to touch
   any adjacent non bit-fields.

   ALIGN is the alignment of the underlying object in bits.
   VOLATILEP says whether the bitfield is volatile.  */

bit_field_mode_iterator
::bit_field_mode_iterator (HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
                           HOST_WIDE_INT bitregion_start,
                           HOST_WIDE_INT bitregion_end,
                           unsigned int align, bool volatilep)
: m_mode (GET_CLASS_NARROWEST_MODE (MODE_INT)), m_bitsize (bitsize),
  m_bitpos (bitpos), m_bitregion_start (bitregion_start),
  m_bitregion_end (bitregion_end), m_align (align),
  m_volatilep (volatilep), m_count (0)
{
  if (!m_bitregion_end)
    {
      /* We can assume that any aligned chunk of ALIGN bits that overlaps
         the bitfield is mapped and won't trap, provided that ALIGN isn't
         too large.  The cap is the biggest required alignment for data,
         or at least the word size.  And force one such chunk at least.  */
      unsigned HOST_WIDE_INT units
        = MIN (align, MAX (BIGGEST_ALIGNMENT, BITS_PER_WORD));
      if (bitsize <= 0)
        bitsize = 1;
      m_bitregion_end = bitpos + bitsize + units - 1;
      m_bitregion_end -= m_bitregion_end % units + 1;
    }
}

/* Calls to this function return successively larger modes that can be used
   to represent the bitfield.  Return true if another bitfield mode is
   available, storing it in *OUT_MODE if so.  */

bool
bit_field_mode_iterator::next_mode (machine_mode *out_mode)
{
  for (; m_mode != VOIDmode; m_mode = GET_MODE_WIDER_MODE (m_mode))
    {
      unsigned int unit = GET_MODE_BITSIZE (m_mode);

      /* Skip modes that don't have full precision.  */
      if (unit != GET_MODE_PRECISION (m_mode))
        continue;

      /* Stop if the mode is too wide to handle efficiently.  */
      if (unit > MAX_FIXED_MODE_SIZE)
        break;

      /* Don't deliver more than one multiword mode; the smallest one
         should be used.  */
      if (m_count > 0 && unit > BITS_PER_WORD)
        break;

      /* Skip modes that are too small.  */
      unsigned HOST_WIDE_INT substart = (unsigned HOST_WIDE_INT) m_bitpos % unit;
      unsigned HOST_WIDE_INT subend = substart + m_bitsize;
      if (subend > unit)
        continue;

      /* Stop if the mode goes outside the bitregion.  */
      HOST_WIDE_INT start = m_bitpos - substart;
      if (m_bitregion_start && start < m_bitregion_start)
        break;
      HOST_WIDE_INT end = start + unit;
      if (end > m_bitregion_end + 1)
        break;

      /* Stop if the mode requires too much alignment.  */
      if (GET_MODE_ALIGNMENT (m_mode) > m_align
          && SLOW_UNALIGNED_ACCESS (m_mode, m_align))
        break;

      *out_mode = m_mode;
      m_mode = GET_MODE_WIDER_MODE (m_mode);
      m_count++;
      return true;
    }
  return false;
}

/* Return true if smaller modes are generally preferred for this kind
   of bitfield.  */

bool
bit_field_mode_iterator::prefer_smaller_modes ()
{
  return (m_volatilep
          ? targetm.narrow_volatile_bitfield ()
          : !SLOW_BYTE_ACCESS);
}

/* Find the best machine mode to use when referencing a bit field of length
   BITSIZE bits starting at BITPOS.

   BITREGION_START is the bit position of the first bit in this
   sequence of bit fields.  BITREGION_END is the last bit in this
   sequence.  If these two fields are non-zero, we should restrict the
   memory access to that range.  Otherwise, we are allowed to touch
   any adjacent non bit-fields.

   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.

   If VOLATILEP is false and SLOW_BYTE_ACCESS is false, we return the
   smallest mode meeting these conditions.

   If 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.

   If VOLATILEP is true the narrow_volatile_bitfields target hook is used to
   decide which of the above modes should be used.  */

machine_mode
get_best_mode (int bitsize, int bitpos,
               unsigned HOST_WIDE_INT bitregion_start,
               unsigned HOST_WIDE_INT bitregion_end,
               unsigned int align,
               machine_mode largest_mode, bool volatilep)
{
  bit_field_mode_iterator iter (bitsize, bitpos, bitregion_start,
                                bitregion_end, align, volatilep);
  machine_mode widest_mode = VOIDmode;
  machine_mode mode;
  while (iter.next_mode (&mode)
         /* ??? For historical reasons, reject modes that would normally
            receive greater alignment, even if unaligned accesses are
            acceptable.  This has both advantages and disadvantages.
            Removing this check means that something like:

               struct s { unsigned int x; unsigned int y; };
               int f (struct s *s) { return s->x == 0 && s->y == 0; }

            can be implemented using a single load and compare on
            64-bit machines that have no alignment restrictions.
            For example, on powerpc64-linux-gnu, we would generate:

                    ld 3,0(3)
                    cntlzd 3,3
                    srdi 3,3,6
                    blr

            rather than:

                    lwz 9,0(3)
                    cmpwi 7,9,0
                    bne 7,.L3
                    lwz 3,4(3)
                    cntlzw 3,3
                    srwi 3,3,5
                    extsw 3,3
                    blr
                    .p2align 4,,15
            .L3:
                    li 3,0
                    blr

            However, accessing more than one field can make life harder
            for the gimple optimizers.  For example, gcc.dg/vect/bb-slp-5.c
            has a series of unsigned short copies followed by a series of
            unsigned short comparisons.  With this check, both the copies
            and comparisons remain 16-bit accesses and FRE is able
            to eliminate the latter.  Without the check, the comparisons
            can be done using 2 64-bit operations, which FRE isn't able
            to handle in the same way.

            Either way, it would probably be worth disabling this check
            during expand.  One particular example where removing the
            check would help is the get_best_mode call in store_bit_field.
            If we are given a memory bitregion of 128 bits that is aligned
            to a 64-bit boundary, and the bitfield we want to modify is
            in the second half of the bitregion, this check causes
            store_bitfield to turn the memory into a 64-bit reference
            to the _first_ half of the region.  We later use
            adjust_bitfield_address to get a reference to the correct half,
            but doing so looks to adjust_bitfield_address as though we are
            moving past the end of the original object, so it drops the
            associated MEM_EXPR and MEM_OFFSET.  Removing the check
            causes store_bit_field to keep a 128-bit memory reference,
            so that the final bitfield reference still has a MEM_EXPR
            and MEM_OFFSET.  */
         && GET_MODE_ALIGNMENT (mode) <= align
         && (largest_mode == VOIDmode
             || GET_MODE_SIZE (mode) <= GET_MODE_SIZE (largest_mode)))
    {
      widest_mode = mode;
      if (iter.prefer_smaller_modes ())
        break;
    }
  return widest_mode;
}

/* Gets minimal and maximal values for MODE (signed or unsigned depending on
   SIGN).  The returned constants are made to be usable in TARGET_MODE.  */

void
get_mode_bounds (machine_mode mode, int sign,
                 machine_mode target_mode,
                 rtx *mmin, rtx *mmax)
{
  unsigned size = GET_MODE_PRECISION (mode);
  unsigned HOST_WIDE_INT min_val, max_val;

  gcc_assert (size <= HOST_BITS_PER_WIDE_INT);

  /* Special case BImode, which has values 0 and STORE_FLAG_VALUE.  */
  if (mode == BImode)
    {
      if (STORE_FLAG_VALUE < 0)
        {
          min_val = STORE_FLAG_VALUE;
          max_val = 0;
        }
      else
        {
          min_val = 0;
          max_val = STORE_FLAG_VALUE;
        }
    }
  else if (sign)
    {
      min_val = -((unsigned HOST_WIDE_INT) 1 << (size - 1));
      max_val = ((unsigned HOST_WIDE_INT) 1 << (size - 1)) - 1;
    }
  else
    {
      min_val = 0;
      max_val = ((unsigned HOST_WIDE_INT) 1 << (size - 1) << 1) - 1;
    }

  *mmin = gen_int_mode (min_val, target_mode);
  *mmax = gen_int_mode (max_val, target_mode);
}

#include "gt-stor-layout.h"