[multiple changes]

[gcc.git] / gcc / ada / utils.c

/****************************************************************************
 *                                                                          *
 *                         GNAT COMPILER COMPONENTS                         *
 *                                                                          *
 *                                U T I L S                                 *
 *                                                                          *
 *                          C Implementation File                           *
 *                                                                          *
 *          Copyright (C) 1992-2004, Free Software Foundation, Inc.         *
 *                                                                          *
 * GNAT is free software;  you can  redistribute it  and/or modify it under *
 * terms of the  GNU General Public License as published  by the Free Soft- *
 * ware  Foundation;  either version 2,  or (at your option) any later ver- *
 * sion.  GNAT is distributed in the hope that it will be useful, but WITH- *
 * OUT 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  distributed with GNAT;  see file COPYING.  If not, write *
 * to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, *
 * MA 02111-1307, USA.                                                      *
 *                                                                          *
 * GNAT was originally developed  by the GNAT team at  New York University. *
 * Extensive contributions were provided by Ada Core Technologies Inc.      *
 *                                                                          *
 ****************************************************************************/

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "flags.h"
#include "defaults.h"
#include "toplev.h"
#include "output.h"
#include "ggc.h"
#include "debug.h"
#include "convert.h"
#include "target.h"
#include "function.h"

#include "ada.h"
#include "types.h"
#include "atree.h"
#include "elists.h"
#include "namet.h"
#include "nlists.h"
#include "stringt.h"
#include "uintp.h"
#include "fe.h"
#include "sinfo.h"
#include "einfo.h"
#include "ada-tree.h"
#include "gigi.h"

#ifndef MAX_FIXED_MODE_SIZE
#define MAX_FIXED_MODE_SIZE GET_MODE_BITSIZE (DImode)
#endif

#ifndef MAX_BITS_PER_WORD
#define MAX_BITS_PER_WORD  BITS_PER_WORD
#endif

/* If nonzero, pretend we are allocating at global level.  */
int force_global;

/* Tree nodes for the various types and decls we create.  */
tree gnat_std_decls[(int) ADT_LAST];

/* Functions to call for each of the possible raise reasons.  */
tree gnat_raise_decls[(int) LAST_REASON_CODE + 1];

/* Associates a GNAT tree node to a GCC tree node. It is used in
   `save_gnu_tree', `get_gnu_tree' and `present_gnu_tree'. See documentation
   of `save_gnu_tree' for more info.  */
static GTY((length ("max_gnat_nodes"))) tree *associate_gnat_to_gnu;

/* This listhead is used to record any global objects that need elaboration.
   TREE_PURPOSE is the variable to be elaborated and TREE_VALUE is the
   initial value to assign.  */

static GTY(()) tree pending_elaborations;

/* This stack allows us to momentarily switch to generating elaboration
   lists for an inner context.  */

struct e_stack GTY((chain_next ("%h.next"))) {
  struct e_stack *next;
  tree elab_list;
};
static GTY(()) struct e_stack *elist_stack;

/* This variable keeps a table for types for each precision so that we only
   allocate each of them once. Signed and unsigned types are kept separate.

   Note that these types are only used when fold-const requests something
   special.  Perhaps we should NOT share these types; we'll see how it
   goes later.  */
static GTY(()) tree signed_and_unsigned_types[2 * MAX_BITS_PER_WORD + 1][2];

/* Likewise for float types, but record these by mode.  */
static GTY(()) tree float_types[NUM_MACHINE_MODES];

/* For each binding contour we allocate a binding_level structure which records
   the entities defined or declared in that contour. Contours include:

        the global one
        one for each subprogram definition
        one for each compound statement (declare block)

   Binding contours are used to create GCC tree BLOCK nodes.  */

struct ada_binding_level GTY((chain_next ("%h.chain")))
{
  /* The binding level containing this one (the enclosing binding level). */
  struct ada_binding_level *chain;
  /* The BLOCK node for this level.  */
  tree block;
};

/* The binding level currently in effect.  */
static GTY(()) struct ada_binding_level *current_binding_level;

/* A chain of ada_binding_level structures awaiting reuse.  */
static GTY((deletable)) struct ada_binding_level *free_binding_level;

/* A chain of unused BLOCK nodes. */
static GTY((deletable)) tree free_block_chain;

struct language_function GTY(())
{
  int unused;
};

static tree merge_sizes (tree, tree, tree, int, int);
static tree compute_related_constant (tree, tree);
static tree split_plus (tree, tree *);
static int value_zerop (tree);
static tree float_type_for_precision (int, enum machine_mode);
static tree convert_to_fat_pointer (tree, tree);
static tree convert_to_thin_pointer (tree, tree);
static tree make_descriptor_field (const char *,tree, tree, tree);
static int value_factor_p (tree, int);
static int potential_alignment_gap (tree, tree, tree);
\f
/* Initialize the association of GNAT nodes to GCC trees.  */

void
init_gnat_to_gnu (void)
{
  associate_gnat_to_gnu
    = (tree *) ggc_alloc_cleared (max_gnat_nodes * sizeof (tree));

  pending_elaborations = build_tree_list (NULL_TREE, NULL_TREE);
}

/* GNAT_ENTITY is a GNAT tree node for an entity.   GNU_DECL is the GCC tree
   which is to be associated with GNAT_ENTITY. Such GCC tree node is always
   a ..._DECL node.  If NO_CHECK is nonzero, the latter check is suppressed.

   If GNU_DECL is zero, a previous association is to be reset.  */

void
save_gnu_tree (Entity_Id gnat_entity, tree gnu_decl, int no_check)
{
  /* Check that GNAT_ENTITY is not already defined and that it is being set
     to something which is a decl.  Raise gigi 401 if not.  Usually, this
     means GNAT_ENTITY is defined twice, but occasionally is due to some
     Gigi problem.  */
  if (gnu_decl
      && (associate_gnat_to_gnu[gnat_entity - First_Node_Id]
          || (! no_check && ! DECL_P (gnu_decl))))
    gigi_abort (401);

  associate_gnat_to_gnu[gnat_entity - First_Node_Id] = gnu_decl;
}

/* GNAT_ENTITY is a GNAT tree node for a defining identifier.
   Return the ..._DECL node that was associated with it.  If there is no tree
   node associated with GNAT_ENTITY, abort.

   In some cases, such as delayed elaboration or expressions that need to
   be elaborated only once, GNAT_ENTITY is really not an entity.  */

tree
get_gnu_tree (Entity_Id gnat_entity)
{
  if (! associate_gnat_to_gnu[gnat_entity - First_Node_Id])
    gigi_abort (402);

  return associate_gnat_to_gnu[gnat_entity - First_Node_Id];
}

/* Return nonzero if a GCC tree has been associated with GNAT_ENTITY.  */

int
present_gnu_tree (Entity_Id gnat_entity)
{
  return (associate_gnat_to_gnu[gnat_entity - First_Node_Id] != NULL_TREE);
}

\f
/* Return non-zero if we are currently in the global binding level.  */

int
global_bindings_p (void)
{
  return (force_global != 0 || current_binding_level->chain == 0 ? -1 : 0);
}

/* Return the list of declarations in the current level. Note that this list
   is in reverse order (it has to be so for back-end compatibility).  */

tree
getdecls (void)
{
  return BLOCK_VARS (current_binding_level->block);
}

/* Enter a new binding level. */

void
gnat_pushlevel ()
{
  struct ada_binding_level *newlevel = NULL;

  /* Reuse a struct for this binding level, if there is one.  */
  if (free_binding_level)
    {
      newlevel = free_binding_level;
      free_binding_level = free_binding_level->chain;
    }
  else
    newlevel
      = (struct ada_binding_level *)
        ggc_alloc (sizeof (struct ada_binding_level));

  /* Use a free BLOCK, if any; otherwise, allocate one.  */
  if (free_block_chain)
    {
      newlevel->block = free_block_chain;
      free_block_chain = TREE_CHAIN (free_block_chain);
      TREE_CHAIN (newlevel->block) = NULL_TREE;
    }
  else
    newlevel->block = make_node (BLOCK);

  /* Point the BLOCK we just made to its parent.  */
  if (current_binding_level)
    BLOCK_SUPERCONTEXT (newlevel->block) = current_binding_level->block;

  BLOCK_VARS (newlevel->block) = BLOCK_SUBBLOCKS (newlevel->block) = NULL_TREE;

  /* Add this level to the front of the chain (stack) of levels that are
     active.  */
  newlevel->chain = current_binding_level;
  current_binding_level = newlevel;
}

/* Exit a binding level.  Return the BLOCK node, if any.  */

tree
gnat_poplevel ()
{
  struct ada_binding_level *level = current_binding_level;
  tree block = level->block;
  tree decl;

  BLOCK_VARS (block) = nreverse (BLOCK_VARS (block));
  BLOCK_SUBBLOCKS (block) = nreverse (BLOCK_SUBBLOCKS (block));

  /* Output any nested inline functions within this block which must be
     compiled because their address is needed. */
  for (decl =  BLOCK_VARS (block); decl; decl = TREE_CHAIN (decl))
    if (TREE_CODE (decl) == FUNCTION_DECL
        && ! TREE_ASM_WRITTEN (decl) && TREE_ADDRESSABLE (decl)
        && DECL_INITIAL (decl) != 0)
      {
        push_function_context ();
        /* ??? This is temporary.  */
        ggc_push_context ();
        output_inline_function (decl);
        ggc_pop_context ();
        pop_function_context ();
      }

  /* If this is a function-level BLOCK don't do anything.  Otherwise, if there
     are no variables free the block and merge its subblocks into those of its
     parent block. Otherwise, add it to the list of its parent.  */
  if (TREE_CODE (BLOCK_SUPERCONTEXT (block)) == FUNCTION_DECL)
    ;
  else if (BLOCK_VARS (block) == NULL_TREE)
    {
      BLOCK_SUBBLOCKS (level->chain->block)
        = chainon (BLOCK_SUBBLOCKS (block),
                   BLOCK_SUBBLOCKS (level->chain->block));
      TREE_CHAIN (block) = free_block_chain;
      free_block_chain = block;
      block = NULL_TREE;
    }
  else
    {
      TREE_CHAIN (block) = BLOCK_SUBBLOCKS (level->chain->block);
      BLOCK_SUBBLOCKS (level->chain->block) = block;
      TREE_USED (block) = 1;
    }

  /* Free this binding structure.  */
  current_binding_level = level->chain;
  level->chain = free_binding_level;
  free_binding_level = level;
  return block;
}

/* Insert BLOCK at the end of the list of subblocks of the
   current binding level.  This is used when a BIND_EXPR is expanded,
   to handle the BLOCK node inside the BIND_EXPR.  */

void
insert_block (tree block)
{
  TREE_USED (block) = 1;
  TREE_CHAIN (block) = BLOCK_SUBBLOCKS (current_binding_level->block);
  BLOCK_SUBBLOCKS (current_binding_level->block) = block;
}

/* Return nonzero if the current binding has any variables.  This means
   it will have a BLOCK node.  */

int
block_has_vars ()
{
  return BLOCK_VARS (current_binding_level->block) != 0;
}
\f
/* Records a ..._DECL node DECL as belonging to the current lexical scope.
   Returns the ..._DECL node. */

tree
pushdecl (tree decl)
{
  /* If at top level, there is no context. But PARM_DECLs always go in the
     level of its function. */
  if (global_bindings_p () && TREE_CODE (decl) != PARM_DECL)
    DECL_CONTEXT (decl) = 0;
  else
    DECL_CONTEXT (decl) = current_function_decl;

  /* Put the declaration on the list.  The list of declarations is in reverse
     order. The list will be reversed later.

     Don't put TYPE_DECLs for UNCONSTRAINED_ARRAY_TYPE into the list.  They
     will cause trouble with the debugger and aren't needed anyway.  */
  if (TREE_CODE (decl) != TYPE_DECL
      || TREE_CODE (TREE_TYPE (decl)) != UNCONSTRAINED_ARRAY_TYPE)
    {
      TREE_CHAIN (decl) = BLOCK_VARS (current_binding_level->block);
      BLOCK_VARS (current_binding_level->block) = decl;
    }

  /* For the declaration of a type, set its name if it either is not already
     set, was set to an IDENTIFIER_NODE, indicating an internal name,
     or if the previous type name was not derived from a source name.
     We'd rather have the type named with a real name and all the pointer
     types to the same object have the same POINTER_TYPE node.  Code in this
     function in c-decl.c makes a copy of the type node here, but that may
     cause us trouble with incomplete types, so let's not try it (at least
     for now).  */

  if (TREE_CODE (decl) == TYPE_DECL
      && DECL_NAME (decl) != 0
      && (TYPE_NAME (TREE_TYPE (decl)) == 0
          || TREE_CODE (TYPE_NAME (TREE_TYPE (decl))) == IDENTIFIER_NODE
          || (TREE_CODE (TYPE_NAME (TREE_TYPE (decl))) == TYPE_DECL
              && DECL_ARTIFICIAL (TYPE_NAME (TREE_TYPE (decl)))
              && ! DECL_ARTIFICIAL (decl))))
    TYPE_NAME (TREE_TYPE (decl)) = decl;

  return decl;
}
\f
/* Do little here.  Set up the standard declarations later after the
   front end has been run.  */

void
gnat_init_decl_processing (void)
{
  input_line = 0;

  /* Make the binding_level structure for global names.  */
  current_function_decl = 0;
  current_binding_level = 0;
  free_binding_level = 0;
  gnat_pushlevel ();

  build_common_tree_nodes (0);

  /* In Ada, we use a signed type for SIZETYPE.  Use the signed type
     corresponding to the size of Pmode.  In most cases when ptr_mode and
     Pmode differ, C will use the width of ptr_mode as sizetype.  But we get
     far better code using the width of Pmode.  Make this here since we need
     this before we can expand the GNAT types.  */
  set_sizetype (gnat_type_for_size (GET_MODE_BITSIZE (Pmode), 0));
  build_common_tree_nodes_2 (0);

  pushdecl (build_decl (TYPE_DECL, get_identifier (SIZE_TYPE), sizetype));

  /* We need to make the integer type before doing anything else.
     We stitch this in to the appropriate GNAT type later.  */
  pushdecl (build_decl (TYPE_DECL, get_identifier ("integer"),
                        integer_type_node));
  pushdecl (build_decl (TYPE_DECL, get_identifier ("unsigned char"),
                        char_type_node));

  ptr_void_type_node = build_pointer_type (void_type_node);

}

/* Create the predefined scalar types such as `integer_type_node' needed
   in the gcc back-end and initialize the global binding level.  */

void
init_gigi_decls (tree long_long_float_type, tree exception_type)
{
  tree endlink, decl;
  unsigned int i;

  /* Set the types that GCC and Gigi use from the front end.  We would like
     to do this for char_type_node, but it needs to correspond to the C
     char type.  */
  if (TREE_CODE (TREE_TYPE (long_long_float_type)) == INTEGER_TYPE)
    {
      /* In this case, the builtin floating point types are VAX float,
         so make up a type for use.  */
      longest_float_type_node = make_node (REAL_TYPE);
      TYPE_PRECISION (longest_float_type_node) = LONG_DOUBLE_TYPE_SIZE;
      layout_type (longest_float_type_node);
      pushdecl (build_decl (TYPE_DECL, get_identifier ("longest float type"),
                            longest_float_type_node));
    }
  else
    longest_float_type_node = TREE_TYPE (long_long_float_type);

  except_type_node = TREE_TYPE (exception_type);

  unsigned_type_node = gnat_type_for_size (INT_TYPE_SIZE, 1);
  pushdecl (build_decl (TYPE_DECL, get_identifier ("unsigned int"),
                        unsigned_type_node));

  void_type_decl_node
    = pushdecl (build_decl (TYPE_DECL, get_identifier ("void"),
                            void_type_node));

  void_ftype = build_function_type (void_type_node, NULL_TREE);
  ptr_void_ftype = build_pointer_type (void_ftype);

  /* Now declare runtime functions. */
  endlink = tree_cons (NULL_TREE, void_type_node, NULL_TREE);

  /* malloc is a function declaration tree for a function to allocate
     memory.  */
  malloc_decl = create_subprog_decl (get_identifier ("__gnat_malloc"),
                                     NULL_TREE,
                                     build_function_type (ptr_void_type_node,
                                                          tree_cons (NULL_TREE,
                                                                     sizetype,
                                                                     endlink)),
                                     NULL_TREE, 0, 1, 1, 0);

  /* free is a function declaration tree for a function to free memory.  */
  free_decl
    = create_subprog_decl (get_identifier ("__gnat_free"), NULL_TREE,
                           build_function_type (void_type_node,
                                                tree_cons (NULL_TREE,
                                                           ptr_void_type_node,
                                                           endlink)),
                           NULL_TREE, 0, 1, 1, 0);

  /* Make the types and functions used for exception processing.    */
  jmpbuf_type
    = build_array_type (gnat_type_for_mode (Pmode, 0),
                        build_index_type (build_int_2 (5, 0)));
  pushdecl (build_decl (TYPE_DECL, get_identifier ("JMPBUF_T"), jmpbuf_type));
  jmpbuf_ptr_type = build_pointer_type (jmpbuf_type);

  /* Functions to get and set the jumpbuf pointer for the current thread.  */
  get_jmpbuf_decl
    = create_subprog_decl
    (get_identifier ("system__soft_links__get_jmpbuf_address_soft"),
     NULL_TREE, build_function_type (jmpbuf_ptr_type, NULL_TREE),
     NULL_TREE, 0, 1, 1, 0);

  set_jmpbuf_decl
    = create_subprog_decl
    (get_identifier ("system__soft_links__set_jmpbuf_address_soft"),
     NULL_TREE,
     build_function_type (void_type_node,
                          tree_cons (NULL_TREE, jmpbuf_ptr_type, endlink)),
     NULL_TREE, 0, 1, 1, 0);

  /* Function to get the current exception.  */
  get_excptr_decl
    = create_subprog_decl
    (get_identifier ("system__soft_links__get_gnat_exception"),
     NULL_TREE,
     build_function_type (build_pointer_type (except_type_node), NULL_TREE),
     NULL_TREE, 0, 1, 1, 0);

  /* Functions that raise exceptions. */
  raise_nodefer_decl
    = create_subprog_decl
      (get_identifier ("__gnat_raise_nodefer_with_msg"), NULL_TREE,
       build_function_type (void_type_node,
                            tree_cons (NULL_TREE,
                                       build_pointer_type (except_type_node),
                                       endlink)),
       NULL_TREE, 0, 1, 1, 0);

  /* Hooks to call when entering/leaving an exception handler.  */
  begin_handler_decl
    = create_subprog_decl (get_identifier ("__gnat_begin_handler"), NULL_TREE,
                           build_function_type (void_type_node,
                                                tree_cons (NULL_TREE,
                                                           ptr_void_type_node,
                                                           endlink)),
                           NULL_TREE, 0, 1, 1, 0);

  end_handler_decl
    = create_subprog_decl (get_identifier ("__gnat_end_handler"), NULL_TREE,
                           build_function_type (void_type_node,
                                                tree_cons (NULL_TREE,
                                                           ptr_void_type_node,
                                                           endlink)),
                           NULL_TREE, 0, 1, 1, 0);

  /* If in no exception handlers mode, all raise statements are redirected to
     __gnat_last_chance_handler. No need to redefine raise_nodefer_decl, since
     this procedure will never be called in this mode.  */
  if (No_Exception_Handlers_Set ())
    {
      decl
        = create_subprog_decl
          (get_identifier ("__gnat_last_chance_handler"), NULL_TREE,
           build_function_type (void_type_node,
                                tree_cons (NULL_TREE,
                                           build_pointer_type (char_type_node),
                                           tree_cons (NULL_TREE,
                                                      integer_type_node,
                                                      endlink))),
           NULL_TREE, 0, 1, 1, 0);

      for (i = 0; i < ARRAY_SIZE (gnat_raise_decls); i++)
        gnat_raise_decls[i] = decl;
    }
  else
    /* Otherwise, make one decl for each exception reason.  */
    for (i = 0; i < ARRAY_SIZE (gnat_raise_decls); i++)
      {
        char name[17];

        sprintf (name, "__gnat_rcheck_%.2d", i);
        gnat_raise_decls[i]
          = create_subprog_decl
            (get_identifier (name), NULL_TREE,
             build_function_type (void_type_node,
                                  tree_cons (NULL_TREE,
                                             build_pointer_type
                                             (char_type_node),
                                             tree_cons (NULL_TREE,
                                                        integer_type_node,
                                                        endlink))),
             NULL_TREE, 0, 1, 1, 0);
      }

  /* Indicate that these never return.  */
  TREE_THIS_VOLATILE (raise_nodefer_decl) = 1;
  TREE_SIDE_EFFECTS (raise_nodefer_decl) = 1;
  TREE_TYPE (raise_nodefer_decl)
    = build_qualified_type (TREE_TYPE (raise_nodefer_decl),
                            TYPE_QUAL_VOLATILE);

  for (i = 0; i < ARRAY_SIZE (gnat_raise_decls); i++)
    {
      TREE_THIS_VOLATILE (gnat_raise_decls[i]) = 1;
      TREE_SIDE_EFFECTS (gnat_raise_decls[i]) = 1;
      TREE_TYPE (gnat_raise_decls[i])
        = build_qualified_type (TREE_TYPE (gnat_raise_decls[i]),
                                TYPE_QUAL_VOLATILE);
    }

  /* setjmp returns an integer and has one operand, which is a pointer to
     a jmpbuf.  */
  setjmp_decl
    = create_subprog_decl
      (get_identifier ("__builtin_setjmp"), NULL_TREE,
       build_function_type (integer_type_node,
                            tree_cons (NULL_TREE,  jmpbuf_ptr_type, endlink)),
       NULL_TREE, 0, 1, 1, 0);

  DECL_BUILT_IN_CLASS (setjmp_decl) = BUILT_IN_NORMAL;
  DECL_FUNCTION_CODE (setjmp_decl) = BUILT_IN_SETJMP;

  /* update_setjmp_buf updates a setjmp buffer from the current stack pointer
     address.  */
  update_setjmp_buf_decl
    = create_subprog_decl
      (get_identifier ("__builtin_update_setjmp_buf"), NULL_TREE,
       build_function_type (void_type_node,
                            tree_cons (NULL_TREE,  jmpbuf_ptr_type, endlink)),
       NULL_TREE, 0, 1, 1, 0);

  DECL_BUILT_IN_CLASS (update_setjmp_buf_decl) = BUILT_IN_NORMAL;
  DECL_FUNCTION_CODE (update_setjmp_buf_decl) = BUILT_IN_UPDATE_SETJMP_BUF;

  main_identifier_node = get_identifier ("main");
}
\f
/* Given a record type (RECORD_TYPE) and a chain of FIELD_DECL
   nodes (FIELDLIST), finish constructing the record or union type.
   If HAS_REP is nonzero, this record has a rep clause; don't call
   layout_type but merely set the size and alignment ourselves.
   If DEFER_DEBUG is nonzero, do not call the debugging routines
   on this type; it will be done later. */

void
finish_record_type (tree record_type,
                    tree fieldlist,
                    int has_rep,
                    int defer_debug)
{
  enum tree_code code = TREE_CODE (record_type);
  tree ada_size = bitsize_zero_node;
  tree size = bitsize_zero_node;
  tree size_unit = size_zero_node;
  int var_size = 0;
  tree field;

  TYPE_FIELDS (record_type) = fieldlist;

  if (TYPE_NAME (record_type) != 0
      && TREE_CODE (TYPE_NAME (record_type)) == TYPE_DECL)
    TYPE_STUB_DECL (record_type) = TYPE_NAME (record_type);
  else
    TYPE_STUB_DECL (record_type)
      = pushdecl (build_decl (TYPE_DECL, TYPE_NAME (record_type),
                              record_type));

  /* We don't need both the typedef name and the record name output in
     the debugging information, since they are the same.  */
  DECL_ARTIFICIAL (TYPE_STUB_DECL (record_type)) = 1;

  /* Globally initialize the record first.  If this is a rep'ed record,
     that just means some initializations; otherwise, layout the record.  */

  if (has_rep)
    {
      TYPE_ALIGN (record_type) = MAX (BITS_PER_UNIT, TYPE_ALIGN (record_type));
      TYPE_MODE (record_type) = BLKmode;
      if (TYPE_SIZE (record_type) == 0)
        {
          TYPE_SIZE (record_type) = bitsize_zero_node;
          TYPE_SIZE_UNIT (record_type) = size_zero_node;
        }
      /* For all-repped records with a size specified, lay the QUAL_UNION_TYPE
         out just like a UNION_TYPE, since the size will be fixed.  */
      else if (code == QUAL_UNION_TYPE)
        code = UNION_TYPE;
    }
  else
    {
      /* Ensure there isn't a size already set.  There can be in an error
         case where there is a rep clause but all fields have errors and
         no longer have a position.  */
      TYPE_SIZE (record_type) = 0;
      layout_type (record_type);
    }

  /* At this point, the position and size of each field is known.  It was
     either set before entry by a rep clause, or by laying out the type above.

     We now run a pass over the fields (in reverse order for QUAL_UNION_TYPEs)
     to compute the Ada size; the GCC size and alignment (for rep'ed records
     that are not padding types); and the mode (for rep'ed records).  We also
     clear the DECL_BIT_FIELD indication for the cases we know have not been
     handled yet, and adjust DECL_NONADDRESSABLE_P accordingly.  */

  if (code == QUAL_UNION_TYPE)
    fieldlist = nreverse (fieldlist);

  for (field = fieldlist; field; field = TREE_CHAIN (field))
    {
      tree pos = bit_position (field);

      tree type = TREE_TYPE (field);
      tree this_size = DECL_SIZE (field);
      tree this_size_unit = DECL_SIZE_UNIT (field);
      tree this_ada_size = DECL_SIZE (field);

      /* We need to make an XVE/XVU record if any field has variable size,
         whether or not the record does.  For example, if we have an union,
         it may be that all fields, rounded up to the alignment, have the
         same size, in which case we'll use that size.  But the debug
         output routines (except Dwarf2) won't be able to output the fields,
         so we need to make the special record.  */
      if (TREE_CODE (this_size) != INTEGER_CST)
        var_size = 1;

      if ((TREE_CODE (type) == RECORD_TYPE || TREE_CODE (type) == UNION_TYPE
          || TREE_CODE (type) == QUAL_UNION_TYPE)
          && ! TYPE_IS_FAT_POINTER_P (type)
          && ! TYPE_CONTAINS_TEMPLATE_P (type)
          && TYPE_ADA_SIZE (type) != 0)
        this_ada_size = TYPE_ADA_SIZE (type);

      /* Clear DECL_BIT_FIELD for the cases layout_decl does not handle.  */
      if (DECL_BIT_FIELD (field) && !STRICT_ALIGNMENT
          && value_factor_p (pos, BITS_PER_UNIT)
          && operand_equal_p (this_size, TYPE_SIZE (type), 0))
        DECL_BIT_FIELD (field) = 0;

      /* If we still have DECL_BIT_FIELD set at this point, we know the field
         is technically not addressable.  Except that it can actually be
         addressed if the field is BLKmode and happens to be properly
         aligned.  */
      DECL_NONADDRESSABLE_P (field)
        |= DECL_BIT_FIELD (field) && DECL_MODE (field) != BLKmode;

      if (has_rep && ! DECL_BIT_FIELD (field))
        TYPE_ALIGN (record_type)
          = MAX (TYPE_ALIGN (record_type), DECL_ALIGN (field));

      switch (code)
        {
        case UNION_TYPE:
          ada_size = size_binop (MAX_EXPR, ada_size, this_ada_size);
          size = size_binop (MAX_EXPR, size, this_size);
          size_unit = size_binop (MAX_EXPR, size_unit, this_size_unit);
          break;

        case QUAL_UNION_TYPE:
          ada_size
            = fold (build (COND_EXPR, bitsizetype, DECL_QUALIFIER (field),
                           this_ada_size, ada_size));
          size = fold (build (COND_EXPR, bitsizetype, DECL_QUALIFIER (field),
                              this_size, size));
          size_unit = fold (build (COND_EXPR, sizetype, DECL_QUALIFIER (field),
                                   this_size_unit, size_unit));
          break;

        case RECORD_TYPE:
          /* Since we know here that all fields are sorted in order of
             increasing bit position, the size of the record is one
             higher than the ending bit of the last field processed
             unless we have a rep clause, since in that case we might
             have a field outside a QUAL_UNION_TYPE that has a higher ending
             position.  So use a MAX in that case.  Also, if this field is a
             QUAL_UNION_TYPE, we need to take into account the previous size in
             the case of empty variants.  */
          ada_size
            = merge_sizes (ada_size, pos, this_ada_size,
                           TREE_CODE (type) == QUAL_UNION_TYPE, has_rep);
          size = merge_sizes (size, pos, this_size,
                              TREE_CODE (type) == QUAL_UNION_TYPE, has_rep);
          size_unit
            = merge_sizes (size_unit, byte_position (field), this_size_unit,
                           TREE_CODE (type) == QUAL_UNION_TYPE, has_rep);
          break;

        default:
          abort ();
        }
    }

  if (code == QUAL_UNION_TYPE)
    nreverse (fieldlist);

  /* If this is a padding record, we never want to make the size smaller than
     what was specified in it, if any.  */
  if (TREE_CODE (record_type) == RECORD_TYPE
      && TYPE_IS_PADDING_P (record_type) && TYPE_SIZE (record_type) != 0)
    {
      size = TYPE_SIZE (record_type);
      size_unit = TYPE_SIZE_UNIT (record_type);
    }

  /* Now set any of the values we've just computed that apply.  */
  if (! TYPE_IS_FAT_POINTER_P (record_type)
      && ! TYPE_CONTAINS_TEMPLATE_P (record_type))
    SET_TYPE_ADA_SIZE (record_type, ada_size);

  if (has_rep)
    {
      if (! (TREE_CODE (record_type) == RECORD_TYPE
             && TYPE_IS_PADDING_P (record_type)
             && CONTAINS_PLACEHOLDER_P (size)))
        {
          TYPE_SIZE (record_type) = round_up (size, TYPE_ALIGN (record_type));
          TYPE_SIZE_UNIT (record_type)
            = round_up (size_unit,
                        TYPE_ALIGN (record_type) / BITS_PER_UNIT);
        }

      compute_record_mode (record_type);
    }

  if (! defer_debug)
    {
      /* If this record is of variable size, rename it so that the
         debugger knows it is and make a new, parallel, record
         that tells the debugger how the record is laid out.  See
         exp_dbug.ads.  But don't do this for records that are padding
         since they confuse GDB.  */
      if (var_size
          && ! (TREE_CODE (record_type) == RECORD_TYPE
                && TYPE_IS_PADDING_P (record_type)))
        {
          tree new_record_type
            = make_node (TREE_CODE (record_type) == QUAL_UNION_TYPE
                         ? UNION_TYPE : TREE_CODE (record_type));
          tree orig_id = DECL_NAME (TYPE_STUB_DECL (record_type));
          tree new_id
            = concat_id_with_name (orig_id,
                                   TREE_CODE (record_type) == QUAL_UNION_TYPE
                                   ? "XVU" : "XVE");
          tree last_pos = bitsize_zero_node;
          tree old_field;
          tree prev_old_field = 0;

          TYPE_NAME (new_record_type) = new_id;
          TYPE_ALIGN (new_record_type) = BIGGEST_ALIGNMENT;
          TYPE_STUB_DECL (new_record_type)
            = pushdecl (build_decl (TYPE_DECL, new_id, new_record_type));
          DECL_ARTIFICIAL (TYPE_STUB_DECL (new_record_type)) = 1;
          DECL_IGNORED_P (TYPE_STUB_DECL (new_record_type))
            = DECL_IGNORED_P (TYPE_STUB_DECL (record_type));
          TYPE_SIZE (new_record_type) = size_int (TYPE_ALIGN (record_type));

          /* Now scan all the fields, replacing each field with a new
             field corresponding to the new encoding.  */
          for (old_field = TYPE_FIELDS (record_type); old_field != 0;
               old_field = TREE_CHAIN (old_field))
            {
              tree field_type = TREE_TYPE (old_field);
              tree field_name = DECL_NAME (old_field);
              tree new_field;
              tree curpos = bit_position (old_field);
              int var = 0;
              unsigned int align = 0;
              tree pos;

              /* See how the position was modified from the last position.

                 There are two basic cases we support: a value was added
                 to the last position or the last position was rounded to
                 a boundary and they something was added.  Check for the
                 first case first.  If not, see if there is any evidence
                 of rounding.  If so, round the last position and try
                 again.

                 If this is a union, the position can be taken as zero. */

              if (TREE_CODE (new_record_type) == UNION_TYPE)
                pos = bitsize_zero_node, align = 0;
              else
                pos = compute_related_constant (curpos, last_pos);

              if (pos == 0 && TREE_CODE (curpos) == MULT_EXPR
                  && TREE_CODE (TREE_OPERAND (curpos, 1)) == INTEGER_CST)
                {
                  align = TREE_INT_CST_LOW (TREE_OPERAND (curpos, 1));
                  pos = compute_related_constant (curpos,
                                                  round_up (last_pos, align));
                }
              else if (pos == 0 && TREE_CODE (curpos) == PLUS_EXPR
                       && TREE_CODE (TREE_OPERAND (curpos, 1)) == INTEGER_CST
                       && TREE_CODE (TREE_OPERAND (curpos, 0)) == MULT_EXPR
                       && host_integerp (TREE_OPERAND
                                         (TREE_OPERAND (curpos, 0), 1),
                                         1))
                {
                  align
                    = tree_low_cst
                      (TREE_OPERAND (TREE_OPERAND (curpos, 0), 1), 1);
                  pos = compute_related_constant (curpos,
                                                  round_up (last_pos, align));
                }
              else if (potential_alignment_gap (prev_old_field, old_field,
                                                pos))
                {
                  align = TYPE_ALIGN (field_type);
                  pos = compute_related_constant (curpos,
                                                  round_up (last_pos, align));
                }

              /* If we can't compute a position, set it to zero.

                 ??? We really should abort here, but it's too much work
                 to get this correct for all cases.  */

              if (pos == 0)
                pos = bitsize_zero_node;

              /* See if this type is variable-size and make a new type
                 and indicate the indirection if so.  */
              if (TREE_CODE (DECL_SIZE (old_field)) != INTEGER_CST)
                {
                  field_type = build_pointer_type (field_type);
                  var = 1;
                }

              /* Make a new field name, if necessary.  */
              if (var || align != 0)
                {
                  char suffix[6];

                  if (align != 0)
                    sprintf (suffix, "XV%c%u", var ? 'L' : 'A',
                             align / BITS_PER_UNIT);
                  else
                    strcpy (suffix, "XVL");

                  field_name = concat_id_with_name (field_name, suffix);
                }

              new_field = create_field_decl (field_name, field_type,
                                             new_record_type, 0,
                                             DECL_SIZE (old_field), pos, 0);
              TREE_CHAIN (new_field) = TYPE_FIELDS (new_record_type);
              TYPE_FIELDS (new_record_type) = new_field;

              /* If old_field is a QUAL_UNION_TYPE, take its size as being
                 zero.  The only time it's not the last field of the record
                 is when there are other components at fixed positions after
                 it (meaning there was a rep clause for every field) and we
                 want to be able to encode them.  */
              last_pos = size_binop (PLUS_EXPR, bit_position (old_field),
                                     (TREE_CODE (TREE_TYPE (old_field))
                                      == QUAL_UNION_TYPE)
                                     ? bitsize_zero_node
                                     : DECL_SIZE (old_field));
              prev_old_field = old_field;
            }

          TYPE_FIELDS (new_record_type)
            = nreverse (TYPE_FIELDS (new_record_type));

          rest_of_type_compilation (new_record_type, global_bindings_p ());
        }

      rest_of_type_compilation (record_type, global_bindings_p ());
    }
}

/* Utility function of above to merge LAST_SIZE, the previous size of a record
   with FIRST_BIT and SIZE that describe a field.  SPECIAL is nonzero
   if this represents a QUAL_UNION_TYPE in which case we must look for
   COND_EXPRs and replace a value of zero with the old size.  If HAS_REP
   is nonzero, we must take the MAX of the end position of this field
   with LAST_SIZE.  In all other cases, we use FIRST_BIT plus SIZE.

   We return an expression for the size.  */

static tree
merge_sizes (tree last_size,
             tree first_bit,
             tree size,
             int special,
             int has_rep)
{
  tree type = TREE_TYPE (last_size);
  tree new;

  if (! special || TREE_CODE (size) != COND_EXPR)
    {
      new = size_binop (PLUS_EXPR, first_bit, size);
      if (has_rep)
        new = size_binop (MAX_EXPR, last_size, new);
    }

  else
    new = fold (build (COND_EXPR, type, TREE_OPERAND (size, 0),
                       integer_zerop (TREE_OPERAND (size, 1))
                       ? last_size : merge_sizes (last_size, first_bit,
                                                  TREE_OPERAND (size, 1),
                                                  1, has_rep),
                       integer_zerop (TREE_OPERAND (size, 2))
                      ? last_size : merge_sizes (last_size, first_bit,
                                                 TREE_OPERAND (size, 2),
                                                 1, has_rep)));

  /* We don't need any NON_VALUE_EXPRs and they can confuse us (especially
     when fed through substitute_in_expr) into thinking that a constant
     size is not constant.  */
  while (TREE_CODE (new) == NON_LVALUE_EXPR)
    new = TREE_OPERAND (new, 0);

  return new;
}

/* Utility function of above to see if OP0 and OP1, both of SIZETYPE, are
   related by the addition of a constant.  Return that constant if so.  */

static tree
compute_related_constant (tree op0, tree op1)
{
  tree op0_var, op1_var;
  tree op0_con = split_plus (op0, &op0_var);
  tree op1_con = split_plus (op1, &op1_var);
  tree result = size_binop (MINUS_EXPR, op0_con, op1_con);

  if (operand_equal_p (op0_var, op1_var, 0))
    return result;
  else if (operand_equal_p (op0, size_binop (PLUS_EXPR, op1_var, result), 0))
    return result;
  else
    return 0;
}

/* Utility function of above to split a tree OP which may be a sum, into a
   constant part, which is returned, and a variable part, which is stored
   in *PVAR.  *PVAR may be bitsize_zero_node.  All operations must be of
   bitsizetype.  */

static tree
split_plus (tree in, tree *pvar)
{
  /* Strip NOPS in order to ease the tree traversal and maximize the
     potential for constant or plus/minus discovery. We need to be careful
     to always return and set *pvar to bitsizetype trees, but it's worth
     the effort.  */
  STRIP_NOPS (in);

  *pvar = convert (bitsizetype, in);

  if (TREE_CODE (in) == INTEGER_CST)
    {
      *pvar = bitsize_zero_node;
      return convert (bitsizetype, in);
    }
  else if (TREE_CODE (in) == PLUS_EXPR || TREE_CODE (in) == MINUS_EXPR)
    {
      tree lhs_var, rhs_var;
      tree lhs_con = split_plus (TREE_OPERAND (in, 0), &lhs_var);
      tree rhs_con = split_plus (TREE_OPERAND (in, 1), &rhs_var);

      if (lhs_var == TREE_OPERAND (in, 0)
          && rhs_var == TREE_OPERAND (in, 1))
        return bitsize_zero_node;

      *pvar = size_binop (TREE_CODE (in), lhs_var, rhs_var);
      return size_binop (TREE_CODE (in), lhs_con, rhs_con);
    }
  else
    return bitsize_zero_node;
}
\f
/* Return a FUNCTION_TYPE node. RETURN_TYPE is the type returned by the
   subprogram. If it is void_type_node, then we are dealing with a procedure,
   otherwise we are dealing with a function. PARAM_DECL_LIST is a list of
   PARM_DECL nodes that are the subprogram arguments.  CICO_LIST is the
   copy-in/copy-out list to be stored into TYPE_CICO_LIST.
   RETURNS_UNCONSTRAINED is nonzero if the function returns an unconstrained
   object.  RETURNS_BY_REF is nonzero if the function returns by reference.
   RETURNS_WITH_DSP is nonzero if the function is to return with a
   depressed stack pointer.  */

tree
create_subprog_type (tree return_type,
                     tree param_decl_list,
                     tree cico_list,
                     int returns_unconstrained,
                     int returns_by_ref,
                     int returns_with_dsp)
{
  /* A chain of TREE_LIST nodes whose TREE_VALUEs are the data type nodes of
     the subprogram formal parameters. This list is generated by traversing the
     input list of PARM_DECL nodes.  */
  tree param_type_list = NULL;
  tree param_decl;
  tree type;

  for (param_decl = param_decl_list; param_decl;
       param_decl = TREE_CHAIN (param_decl))
    param_type_list = tree_cons (NULL_TREE, TREE_TYPE (param_decl),
                                          param_type_list);

  /* The list of the function parameter types has to be terminated by the void
     type to signal to the back-end that we are not dealing with a variable
     parameter subprogram, but that the subprogram has a fixed number of
     parameters.  */
  param_type_list = tree_cons (NULL_TREE, void_type_node, param_type_list);

  /* The list of argument types has been created in reverse
     so nreverse it.   */
  param_type_list = nreverse (param_type_list);

  type = build_function_type (return_type, param_type_list);

  /* TYPE may have been shared since GCC hashes types.  If it has a CICO_LIST
     or the new type should, make a copy of TYPE.  Likewise for
     RETURNS_UNCONSTRAINED and RETURNS_BY_REF.  */
  if (TYPE_CI_CO_LIST (type) != 0 || cico_list != 0
      || TYPE_RETURNS_UNCONSTRAINED_P (type) != returns_unconstrained
      || TYPE_RETURNS_BY_REF_P (type) != returns_by_ref)
    type = copy_type (type);

  SET_TYPE_CI_CO_LIST (type, cico_list);
  TYPE_RETURNS_UNCONSTRAINED_P (type) = returns_unconstrained;
  TYPE_RETURNS_STACK_DEPRESSED (type) = returns_with_dsp;
  TYPE_RETURNS_BY_REF_P (type) = returns_by_ref;
  return type;
}
\f
/* Return a copy of TYPE but safe to modify in any way.  */

tree
copy_type (tree type)
{
  tree new = copy_node (type);

  /* copy_node clears this field instead of copying it, because it is
     aliased with TREE_CHAIN.  */
  TYPE_STUB_DECL (new) = TYPE_STUB_DECL (type);

  TYPE_POINTER_TO (new) = 0;
  TYPE_REFERENCE_TO (new) = 0;
  TYPE_MAIN_VARIANT (new) = new;
  TYPE_NEXT_VARIANT (new) = 0;

  return new;
}
\f
/* Return an INTEGER_TYPE of SIZETYPE with range MIN to MAX and whose
   TYPE_INDEX_TYPE is INDEX.  */

tree
create_index_type (tree min, tree max, tree index)
{
  /* First build a type for the desired range.  */
  tree type = build_index_2_type (min, max);

  /* If this type has the TYPE_INDEX_TYPE we want, return it.  Otherwise, if it
     doesn't have TYPE_INDEX_TYPE set, set it to INDEX.  If TYPE_INDEX_TYPE
     is set, but not to INDEX, make a copy of this type with the requested
     index type.  Note that we have no way of sharing these types, but that's
     only a small hole.  */
  if (TYPE_INDEX_TYPE (type) == index)
    return type;
  else if (TYPE_INDEX_TYPE (type) != 0)
    type = copy_type (type);

  SET_TYPE_INDEX_TYPE (type, index);
  return type;
}
\f
/* Return a TYPE_DECL node. TYPE_NAME gives the name of the type (a character
   string) and TYPE is a ..._TYPE node giving its data type.
   ARTIFICIAL_P is nonzero if this is a declaration that was generated
   by the compiler.  DEBUG_INFO_P is nonzero if we need to write debugging
   information about this type.  */

tree
create_type_decl (tree type_name,
                  tree type,
                  struct attrib *attr_list,
                  int artificial_p,
                  int debug_info_p)
{
  tree type_decl = build_decl (TYPE_DECL, type_name, type);
  enum tree_code code = TREE_CODE (type);

  DECL_ARTIFICIAL (type_decl) = artificial_p;
  pushdecl (type_decl);
  process_attributes (type_decl, attr_list);

  /* Pass type declaration information to the debugger unless this is an
     UNCONSTRAINED_ARRAY_TYPE, which the debugger does not support,
     and ENUMERAL_TYPE or RECORD_TYPE which is handled separately,
     a dummy type, which will be completed later, or a type for which
     debugging information was not requested.  */
  if (code == UNCONSTRAINED_ARRAY_TYPE || TYPE_IS_DUMMY_P (type)
      || ! debug_info_p)
    DECL_IGNORED_P (type_decl) = 1;
  else if (code != ENUMERAL_TYPE && code != RECORD_TYPE
      && ! ((code == POINTER_TYPE || code == REFERENCE_TYPE)
            && TYPE_IS_DUMMY_P (TREE_TYPE (type))))
    rest_of_decl_compilation (type_decl, NULL, global_bindings_p (), 0);

  return type_decl;
}

/* Returns a GCC VAR_DECL node. VAR_NAME gives the name of the variable.
   ASM_NAME is its assembler name (if provided).  TYPE is its data type
   (a GCC ..._TYPE node).  VAR_INIT is the GCC tree for an optional initial
   expression; NULL_TREE if none.

   CONST_FLAG is nonzero if this variable is constant.

   PUBLIC_FLAG is nonzero if this definition is to be made visible outside of
   the current compilation unit. This flag should be set when processing the
   variable definitions in a package specification.  EXTERN_FLAG is nonzero
   when processing an external variable declaration (as opposed to a
   definition: no storage is to be allocated for the variable here).

   STATIC_FLAG is only relevant when not at top level.  In that case
   it indicates whether to always allocate storage to the variable.   */

tree
create_var_decl (tree var_name, tree asm_name, tree type, tree var_init,
                 int const_flag, int public_flag, int extern_flag,
                 int static_flag, struct attrib *attr_list)
{
  int init_const
    = (var_init == 0
       ? 0
       : (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (var_init))
          && (global_bindings_p () || static_flag
              ? 0 != initializer_constant_valid_p (var_init,
                                                   TREE_TYPE (var_init))
              : TREE_CONSTANT (var_init))));
  tree var_decl
    = build_decl ((const_flag && init_const
                   /* Only make a CONST_DECL for sufficiently-small objects.
                      We consider complex double "sufficiently-small"  */
                   && TYPE_SIZE (type) != 0
                   && host_integerp (TYPE_SIZE_UNIT (type), 1)
                   && 0 >= compare_tree_int (TYPE_SIZE_UNIT (type),
                                             GET_MODE_SIZE (DCmode)))
                  ? CONST_DECL : VAR_DECL, var_name, type);

  /* If this is external, throw away any initializations unless this is a
     CONST_DECL (meaning we have a constant); they will be done elsewhere.  If
     we are defining a global here, leave a constant initialization and save
     any variable elaborations for the elaboration routine.  Otherwise, if
     the initializing expression is not the same as TYPE, generate the
     initialization with an assignment statement, since it knows how
     to do the required adjustents.  If we are just annotating types,
     throw away the initialization if it isn't a constant.  */

  if ((extern_flag && TREE_CODE (var_decl) != CONST_DECL)
      || (type_annotate_only && var_init != 0 && ! TREE_CONSTANT (var_init)))
    var_init = 0;

  if (global_bindings_p () && var_init != 0 && ! init_const)
    {
      add_pending_elaborations (var_decl, var_init);
      var_init = 0;
    }

  else if (var_init != 0
           && ((TYPE_MAIN_VARIANT (TREE_TYPE (var_init))
                != TYPE_MAIN_VARIANT (type))
               || (static_flag && ! init_const)))
    DECL_INIT_BY_ASSIGN_P (var_decl) = 1;

  DECL_INITIAL  (var_decl) = var_init;
  TREE_READONLY (var_decl) = const_flag;
  DECL_EXTERNAL (var_decl) = extern_flag;
  TREE_PUBLIC   (var_decl) = public_flag || extern_flag;
  TREE_CONSTANT (var_decl) = TREE_CODE (var_decl) == CONST_DECL;
  TREE_THIS_VOLATILE (var_decl) = TREE_SIDE_EFFECTS (var_decl)
    = TYPE_VOLATILE (type);

  /* At the global binding level we need to allocate static storage for the
     variable if and only if its not external. If we are not at the top level
     we allocate automatic storage unless requested not to.  */
  TREE_STATIC (var_decl) = global_bindings_p () ? !extern_flag : static_flag;

  if (asm_name != 0)
    SET_DECL_ASSEMBLER_NAME (var_decl, asm_name);

  process_attributes (var_decl, attr_list);

  /* Add this decl to the current binding level and generate any
     needed code and RTL. */
  var_decl = pushdecl (var_decl);

  if (TREE_SIDE_EFFECTS (var_decl))
    TREE_ADDRESSABLE (var_decl) = 1;

  if (TREE_CODE (var_decl) != CONST_DECL)
    rest_of_decl_compilation (var_decl, 0, global_bindings_p (), 0);

  return var_decl;
}
\f
/* Returns a FIELD_DECL node. FIELD_NAME the field name, FIELD_TYPE is its
   type, and RECORD_TYPE is the type of the parent.  PACKED is nonzero if
   this field is in a record type with a "pragma pack".  If SIZE is nonzero
   it is the specified size for this field.  If POS is nonzero, it is the bit
   position.  If ADDRESSABLE is nonzero, it means we are allowed to take
   the address of this field for aliasing purposes.  */

tree
create_field_decl (tree field_name,
                   tree field_type,
                   tree record_type,
                   int packed,
                   tree size,
                   tree pos,
                   int addressable)
{
  tree field_decl = build_decl (FIELD_DECL, field_name, field_type);

  DECL_CONTEXT (field_decl) = record_type;
  TREE_READONLY (field_decl) = TYPE_READONLY (field_type);

  /* If FIELD_TYPE is BLKmode, we must ensure this is aligned to at least a
     byte boundary since GCC cannot handle less-aligned BLKmode bitfields.  */
  if (packed && TYPE_MODE (field_type) == BLKmode)
    DECL_ALIGN (field_decl) = BITS_PER_UNIT;

  /* If a size is specified, use it.  Otherwise, if the record type is packed
     compute a size to use, which may differ from the object's natural size.
     We always set a size in this case to trigger the checks for bitfield
     creation below, which is typically required when no position has been
     specified.  */
  if (size != 0)
    size = convert (bitsizetype, size);
  else if (packed == 1)
    {
      size = rm_size (field_type);

      /* For a constant size larger than MAX_FIXED_MODE_SIZE, round up to
         byte.  */
      if (TREE_CODE (size) == INTEGER_CST
          && compare_tree_int (size, MAX_FIXED_MODE_SIZE) > 0)
        size = round_up (size, BITS_PER_UNIT);
    }

  /* Make a bitfield if a size is specified for two reasons: first if the size
     differs from the natural size.  Second, if the alignment is insufficient.
     There are a number of ways the latter can be true.

     We never make a bitfield if the type of the field has a nonconstant size,
     or if it is claimed to be addressable, because no such entity requiring
     bitfield operations should reach here.

     We do *preventively* make a bitfield when there might be the need for it
     but we don't have all the necessary information to decide, as is the case
     of a field with no specified position in a packed record.

     We also don't look at STRICT_ALIGNMENT here, and rely on later processing
     in layout_decl or finish_record_type to clear the bit_field indication if
     it is in fact not needed. */
  if (size != 0 && TREE_CODE (size) == INTEGER_CST
      && TREE_CODE (TYPE_SIZE (field_type)) == INTEGER_CST
      && ! addressable
      && (! operand_equal_p (TYPE_SIZE (field_type), size, 0)
          || (pos != 0
              && ! value_zerop (size_binop (TRUNC_MOD_EXPR, pos,
                                            bitsize_int (TYPE_ALIGN
                                                         (field_type)))))
          || packed
          || (TYPE_ALIGN (record_type) != 0
              && TYPE_ALIGN (record_type) < TYPE_ALIGN (field_type))))
    {
      DECL_BIT_FIELD (field_decl) = 1;
      DECL_SIZE (field_decl) = size;
      if (! packed && pos == 0)
        DECL_ALIGN (field_decl)
          = (TYPE_ALIGN (record_type) != 0
             ? MIN (TYPE_ALIGN (record_type), TYPE_ALIGN (field_type))
             : TYPE_ALIGN (field_type));
    }

  DECL_PACKED (field_decl) = pos != 0 ? DECL_BIT_FIELD (field_decl) : packed;
  DECL_ALIGN (field_decl)
    = MAX (DECL_ALIGN (field_decl),
           DECL_BIT_FIELD (field_decl) ? 1
           : packed && TYPE_MODE (field_type) != BLKmode ? BITS_PER_UNIT
           : TYPE_ALIGN (field_type));

  if (pos != 0)
    {
      /* We need to pass in the alignment the DECL is known to have.
         This is the lowest-order bit set in POS, but no more than
         the alignment of the record, if one is specified.  Note
         that an alignment of 0 is taken as infinite.  */
      unsigned int known_align;

      if (host_integerp (pos, 1))
        known_align = tree_low_cst (pos, 1) & - tree_low_cst (pos, 1);
      else
        known_align = BITS_PER_UNIT;

      if (TYPE_ALIGN (record_type)
          && (known_align == 0 || known_align > TYPE_ALIGN (record_type)))
        known_align = TYPE_ALIGN (record_type);

      layout_decl (field_decl, known_align);
      SET_DECL_OFFSET_ALIGN (field_decl,
                             host_integerp (pos, 1) ? BIGGEST_ALIGNMENT
                             : BITS_PER_UNIT);
      pos_from_bit (&DECL_FIELD_OFFSET (field_decl),
                    &DECL_FIELD_BIT_OFFSET (field_decl),
                    DECL_OFFSET_ALIGN (field_decl), pos);

      DECL_HAS_REP_P (field_decl) = 1;
    }

  /* If the field type is passed by reference, we will have pointers to the
     field, so it is addressable. */
  if (must_pass_by_ref (field_type) || default_pass_by_ref (field_type))
    addressable = 1;

  /* ??? For now, we say that any field of aggregate type is addressable
     because the front end may take 'Reference of it.  */
  if (AGGREGATE_TYPE_P (field_type))
    addressable = 1;

  /* Mark the decl as nonaddressable if it is indicated so semantically,
     meaning we won't ever attempt to take the address of the field.

     It may also be "technically" nonaddressable, meaning that even if we
     attempt to take the field's address we will actually get the address of a
     copy. This is the case for true bitfields, but the DECL_BIT_FIELD value
     we have at this point is not accurate enough, so we don't account for
     this here and let finish_record_type decide.  */
  DECL_NONADDRESSABLE_P (field_decl) = ! addressable;

  return field_decl;
}

/* Subroutine of previous function: return nonzero if EXP, ignoring any side
   effects, has the value of zero.  */

static int
value_zerop (tree exp)
{
  if (TREE_CODE (exp) == COMPOUND_EXPR)
    return value_zerop (TREE_OPERAND (exp, 1));

  return integer_zerop (exp);
}
\f
/* Returns a PARM_DECL node. PARAM_NAME is the name of the parameter,
   PARAM_TYPE is its type.  READONLY is nonzero if the parameter is
   readonly (either an IN parameter or an address of a pass-by-ref
   parameter). */

tree
create_param_decl (tree param_name, tree param_type, int readonly)
{
  tree param_decl = build_decl (PARM_DECL, param_name, param_type);

  /* Honor targetm.calls.promote_prototypes(), as not doing so can
     lead to various ABI violations.  */
  if (targetm.calls.promote_prototypes (param_type)
      && (TREE_CODE (param_type) == INTEGER_TYPE
          || TREE_CODE (param_type) == ENUMERAL_TYPE)
      && TYPE_PRECISION (param_type) < TYPE_PRECISION (integer_type_node))
    {
      /* We have to be careful about biased types here.  Make a subtype
         of integer_type_node with the proper biasing.  */
      if (TREE_CODE (param_type) == INTEGER_TYPE
          && TYPE_BIASED_REPRESENTATION_P (param_type))
        {
          param_type
            = copy_type (build_range_type (integer_type_node,
                                           TYPE_MIN_VALUE (param_type),
                                           TYPE_MAX_VALUE (param_type)));

          TYPE_BIASED_REPRESENTATION_P (param_type) = 1;
        }
      else
        param_type = integer_type_node;
    }

  DECL_ARG_TYPE (param_decl) = param_type;
  DECL_ARG_TYPE_AS_WRITTEN (param_decl) = param_type;
  TREE_READONLY (param_decl) = readonly;
  return param_decl;
}
\f
/* Given a DECL and ATTR_LIST, process the listed attributes.  */

void
process_attributes (tree decl, struct attrib *attr_list)
{
  for (; attr_list; attr_list = attr_list->next)
    switch (attr_list->type)
      {
      case ATTR_MACHINE_ATTRIBUTE:
        decl_attributes (&decl, tree_cons (attr_list->name, attr_list->arg,
                                           NULL_TREE),
                         ATTR_FLAG_TYPE_IN_PLACE);
        break;

      case ATTR_LINK_ALIAS:
        TREE_STATIC (decl) = 1;
        assemble_alias (decl, attr_list->name);
        break;

      case ATTR_WEAK_EXTERNAL:
        if (SUPPORTS_WEAK)
          declare_weak (decl);
        else
          post_error ("?weak declarations not supported on this target",
                      attr_list->error_point);
        break;

      case ATTR_LINK_SECTION:
        if (targetm.have_named_sections)
          {
            DECL_SECTION_NAME (decl)
              = build_string (IDENTIFIER_LENGTH (attr_list->name),
                              IDENTIFIER_POINTER (attr_list->name));
          }
        else
          post_error ("?section attributes are not supported for this target",
                      attr_list->error_point);
        break;
      }
}
\f
/* Add some pending elaborations on the list.  */

void
add_pending_elaborations (tree var_decl, tree var_init)
{
  if (var_init != 0)
    Check_Elaboration_Code_Allowed (error_gnat_node);

  pending_elaborations
    = chainon (pending_elaborations, build_tree_list (var_decl, var_init));
}

/* Obtain any pending elaborations and clear the old list.  */

tree
get_pending_elaborations (void)
{
  /* Each thing added to the list went on the end; we want it on the
     beginning.  */
  tree result = TREE_CHAIN (pending_elaborations);

  TREE_CHAIN (pending_elaborations) = 0;
  return result;
}

/* Return true if VALUE is a multiple of FACTOR. FACTOR must be a power
   of 2. */

static int
value_factor_p (tree value, int factor)
{
  if (host_integerp (value, 1))
    return tree_low_cst (value, 1) % factor == 0;

  if (TREE_CODE (value) == MULT_EXPR)
    return (value_factor_p (TREE_OPERAND (value, 0), factor)
            || value_factor_p (TREE_OPERAND (value, 1), factor));

  return 0;
}

/* Given 2 consecutive field decls PREV_FIELD and CURR_FIELD, return true
   unless we can prove these 2 fields are laid out in such a way that no gap
   exist between the end of PREV_FIELD and the begining of CURR_FIELD.  OFFSET
   is the distance in bits between the end of PREV_FIELD and the starting
   position of CURR_FIELD. It is ignored if null. */

static int
potential_alignment_gap (tree prev_field, tree curr_field, tree offset)
{
  /* If this is the first field of the record, there cannot be any gap */
  if (!prev_field)
    return 0;

  /* If the previous field is a union type, then return False: The only
     time when such a field is not the last field of the record is when
     there are other components at fixed positions after it (meaning there
     was a rep clause for every field), in which case we don't want the
     alignment constraint to override them. */
  if (TREE_CODE (TREE_TYPE (prev_field)) == QUAL_UNION_TYPE)
    return 0;

  /* If the distance between the end of prev_field and the begining of
     curr_field is constant, then there is a gap if the value of this
     constant is not null. */
  if (offset && host_integerp (offset, 1))
    return (!integer_zerop (offset));

  /* If the size and position of the previous field are constant,
     then check the sum of this size and position. There will be a gap
     iff it is not multiple of the current field alignment. */
  if (host_integerp (DECL_SIZE (prev_field), 1)
      && host_integerp (bit_position (prev_field), 1))
    return ((tree_low_cst (bit_position (prev_field), 1)
             + tree_low_cst (DECL_SIZE (prev_field), 1))
            % DECL_ALIGN (curr_field) != 0);

  /* If both the position and size of the previous field are multiples
     of the current field alignment, there can not be any gap. */
  if (value_factor_p (bit_position (prev_field), DECL_ALIGN (curr_field))
      && value_factor_p (DECL_SIZE (prev_field), DECL_ALIGN (curr_field)))
    return 0;

  /* Fallback, return that there may be a potential gap */
  return 1;
}

/* Return nonzero if there are pending elaborations.  */

int
pending_elaborations_p (void)
{
  return TREE_CHAIN (pending_elaborations) != 0;
}

/* Save a copy of the current pending elaboration list and make a new
   one.  */

void
push_pending_elaborations (void)
{
  struct e_stack *p = (struct e_stack *) ggc_alloc (sizeof (struct e_stack));

  p->next = elist_stack;
  p->elab_list = pending_elaborations;
  elist_stack = p;
  pending_elaborations = build_tree_list (NULL_TREE, NULL_TREE);
}

/* Pop the stack of pending elaborations.  */

void
pop_pending_elaborations (void)
{
  struct e_stack *p = elist_stack;

  pending_elaborations = p->elab_list;
  elist_stack = p->next;
}

/* Return the current position in pending_elaborations so we can insert
   elaborations after that point.  */

tree
get_elaboration_location (void)
{
  return tree_last (pending_elaborations);
}

/* Insert the current elaborations after ELAB, which is in some elaboration
   list.  */

void
insert_elaboration_list (tree elab)
{
  tree next = TREE_CHAIN (elab);

  if (TREE_CHAIN (pending_elaborations))
    {
      TREE_CHAIN (elab) = TREE_CHAIN (pending_elaborations);
      TREE_CHAIN (tree_last (pending_elaborations)) = next;
      TREE_CHAIN (pending_elaborations) = 0;
    }
}

/* Returns a LABEL_DECL node for LABEL_NAME.  */

tree
create_label_decl (tree label_name)
{
  tree label_decl = build_decl (LABEL_DECL, label_name, void_type_node);

  DECL_CONTEXT (label_decl)     = current_function_decl;
  DECL_MODE (label_decl)        = VOIDmode;
  DECL_SOURCE_LOCATION (label_decl) = input_location;

  return label_decl;
}
\f
/* Returns a FUNCTION_DECL node.  SUBPROG_NAME is the name of the subprogram,
   ASM_NAME is its assembler name, SUBPROG_TYPE is its type (a FUNCTION_TYPE
   node), PARAM_DECL_LIST is the list of the subprogram arguments (a list of
   PARM_DECL nodes chained through the TREE_CHAIN field).

   INLINE_FLAG, PUBLIC_FLAG, EXTERN_FLAG, and ATTR_LIST are used to set the
   appropriate fields in the FUNCTION_DECL.  */

tree
create_subprog_decl (tree subprog_name,
                     tree asm_name,
                     tree subprog_type,
                     tree param_decl_list,
                     int inline_flag,
                     int public_flag,
                     int extern_flag,
                     struct attrib *attr_list)
{
  tree return_type  = TREE_TYPE (subprog_type);
  tree subprog_decl = build_decl (FUNCTION_DECL, subprog_name, subprog_type);

  /* If this is a function nested inside an inlined external function, it
     means we aren't going to compile the outer function unless it is
     actually inlined, so do the same for us.  */
  if (current_function_decl != 0 && DECL_INLINE (current_function_decl)
      && DECL_EXTERNAL (current_function_decl))
    extern_flag = 1;

  DECL_EXTERNAL (subprog_decl)  = extern_flag;
  TREE_PUBLIC (subprog_decl)    = public_flag;
  DECL_INLINE (subprog_decl)    = inline_flag;
  TREE_READONLY (subprog_decl)  = TYPE_READONLY (subprog_type);
  TREE_THIS_VOLATILE (subprog_decl) = TYPE_VOLATILE (subprog_type);
  TREE_SIDE_EFFECTS (subprog_decl) = TYPE_VOLATILE (subprog_type);
  DECL_ARGUMENTS (subprog_decl) = param_decl_list;
  DECL_RESULT (subprog_decl)    = build_decl (RESULT_DECL, 0, return_type);

  if (asm_name != 0)
    SET_DECL_ASSEMBLER_NAME (subprog_decl, asm_name);

  process_attributes (subprog_decl, attr_list);

  /* Add this decl to the current binding level.  */
  subprog_decl = pushdecl (subprog_decl);

  /* Output the assembler code and/or RTL for the declaration.  */
  rest_of_decl_compilation (subprog_decl, 0, global_bindings_p (), 0);

  return subprog_decl;
}
\f
/* Count how deep we are into nested functions.  This is because
   we shouldn't call the backend function context routines unless we
   are in a nested function.  */

static int function_nesting_depth;

/* Set up the framework for generating code for SUBPROG_DECL, a subprogram
   body. This routine needs to be invoked before processing the declarations
   appearing in the subprogram.  */

void
begin_subprog_body (tree subprog_decl)
{
  tree param_decl;

  if (function_nesting_depth++ != 0)
    push_function_context ();

  announce_function (subprog_decl);

  /* Make this field nonzero so further routines know that this is not
     tentative. error_mark_node is replaced below with the adequate BLOCK.  */
  DECL_INITIAL (subprog_decl)  = error_mark_node;

  /* This function exists in static storage. This does not mean `static' in
     the C sense!  */
  TREE_STATIC (subprog_decl)   = 1;

  /* Enter a new binding level and show that all the parameters belong to
     this function.  */
  current_function_decl = subprog_decl;
  gnat_pushlevel ();

  for (param_decl = DECL_ARGUMENTS (subprog_decl); param_decl;
       param_decl = TREE_CHAIN (param_decl))
    DECL_CONTEXT (param_decl) = subprog_decl;

  init_function_start (subprog_decl);
  expand_function_start (subprog_decl, 0);

  /* If this function is `main', emit a call to `__main'
     to run global initializers, etc.  */
  if (DECL_ASSEMBLER_NAME (subprog_decl) != 0
      && MAIN_NAME_P (DECL_ASSEMBLER_NAME (subprog_decl))
      && DECL_CONTEXT (subprog_decl) == NULL_TREE)
    expand_main_function ();
}

/* Finish the definition of the current subprogram and compile it all the way
   to assembler language output.  */

void
end_subprog_body (void)
{
  tree decl;
  tree cico_list;

  /* Mark the BLOCK for this level as being for this function and pop the
     level.  Since the vars in it are the parameters, clear them.  */
  BLOCK_VARS (current_binding_level->block) = 0;
  BLOCK_SUPERCONTEXT (current_binding_level->block) = current_function_decl;
  DECL_INITIAL (current_function_decl) = current_binding_level->block;
  gnat_poplevel ();

  /* Mark the RESULT_DECL as being in this subprogram. */
  DECL_CONTEXT (DECL_RESULT (current_function_decl)) = current_function_decl;

  expand_function_end ();

  /* If this is a nested function, push a new GC context.  That will keep
     local variables on the stack from being collected while we're doing
     the compilation of this function.  */
  if (function_nesting_depth > 1)
    ggc_push_context ();

  /* If we're only annotating types, don't actually compile this
     function.  */
  if (!type_annotate_only)
    {
      rest_of_compilation (current_function_decl);
      if (! DECL_DEFER_OUTPUT (current_function_decl))
        {
          free_after_compilation (cfun);
          DECL_STRUCT_FUNCTION (current_function_decl) = 0;
        }
      cfun = 0;
    }

  if (function_nesting_depth > 1)
    ggc_pop_context ();

  /* Throw away any VAR_DECLs we made for OUT parameters; they must
     not be seen when we call this function and will be in
     unallocated memory anyway.  */
  for (cico_list = TYPE_CI_CO_LIST (TREE_TYPE (current_function_decl));
       cico_list != 0; cico_list = TREE_CHAIN (cico_list))
    TREE_VALUE (cico_list) = 0;

  if (DECL_STRUCT_FUNCTION (current_function_decl) == 0)
    {
      /* Throw away DECL_RTL in any PARM_DECLs unless this function
         was saved for inline, in which case the DECL_RTLs are in
         preserved memory.  */
      for (decl = DECL_ARGUMENTS (current_function_decl);
           decl != 0; decl = TREE_CHAIN (decl))
        {
          SET_DECL_RTL (decl, 0);
          DECL_INCOMING_RTL (decl) = 0;
        }

      /* Similarly, discard DECL_RTL of the return value.  */
      SET_DECL_RTL (DECL_RESULT (current_function_decl), 0);

      /* But DECL_INITIAL must remain nonzero so we know this
         was an actual function definition unless toplev.c decided not
         to inline it.  */
      if (DECL_INITIAL (current_function_decl) != 0)
        DECL_INITIAL (current_function_decl) = error_mark_node;

      DECL_ARGUMENTS (current_function_decl) = 0;
    }

  /* If we are not at the bottom of the function nesting stack, pop up to
     the containing function.  Otherwise show we aren't in any function.  */
  if (--function_nesting_depth != 0)
    pop_function_context ();
  else
    current_function_decl = 0;
}
\f
/* Return a definition for a builtin function named NAME and whose data type
   is TYPE.  TYPE should be a function type with argument types.
   FUNCTION_CODE tells later passes how to compile calls to this function.
   See tree.h for its possible values.

   If LIBRARY_NAME is nonzero, use that for DECL_ASSEMBLER_NAME,
   the name to be called if we can't opencode the function.  If
   ATTRS is nonzero, use that for the function attribute list.  */

tree
builtin_function (const char *name,
                  tree type,
                  int function_code,
                  enum built_in_class class,
                  const char *library_name,
                  tree attrs)
{
  tree decl = build_decl (FUNCTION_DECL, get_identifier (name), type);

  DECL_EXTERNAL (decl) = 1;
  TREE_PUBLIC (decl) = 1;
  if (library_name)
    SET_DECL_ASSEMBLER_NAME (decl, get_identifier (library_name));

  pushdecl (decl);
  DECL_BUILT_IN_CLASS (decl) = class;
  DECL_FUNCTION_CODE (decl) = function_code;
  if (attrs)
      decl_attributes (&decl, attrs, ATTR_FLAG_BUILT_IN);
  return decl;
}

/* Return an integer type with the number of bits of precision given by
   PRECISION.  UNSIGNEDP is nonzero if the type is unsigned; otherwise
   it is a signed type.  */

tree
gnat_type_for_size (unsigned precision, int unsignedp)
{
  tree t;
  char type_name[20];

  if (precision <= 2 * MAX_BITS_PER_WORD
      && signed_and_unsigned_types[precision][unsignedp] != 0)
    return signed_and_unsigned_types[precision][unsignedp];

 if (unsignedp)
    t = make_unsigned_type (precision);
  else
    t = make_signed_type (precision);

  if (precision <= 2 * MAX_BITS_PER_WORD)
    signed_and_unsigned_types[precision][unsignedp] = t;

  if (TYPE_NAME (t) == 0)
    {
      sprintf (type_name, "%sSIGNED_%d", unsignedp ? "UN" : "", precision);
      TYPE_NAME (t) = get_identifier (type_name);
    }

  return t;
}

/* Likewise for floating-point types.  */

static tree
float_type_for_precision (int precision, enum machine_mode mode)
{
  tree t;
  char type_name[20];

  if (float_types[(int) mode] != 0)
    return float_types[(int) mode];

  float_types[(int) mode] = t = make_node (REAL_TYPE);
  TYPE_PRECISION (t) = precision;
  layout_type (t);

  if (TYPE_MODE (t) != mode)
    gigi_abort (414);

  if (TYPE_NAME (t) == 0)
    {
      sprintf (type_name, "FLOAT_%d", precision);
      TYPE_NAME (t) = get_identifier (type_name);
    }

  return t;
}

/* Return a data type that has machine mode MODE.  UNSIGNEDP selects
   an unsigned type; otherwise a signed type is returned.  */

tree
gnat_type_for_mode (enum machine_mode mode, int unsignedp)
{
  if (mode == BLKmode)
    return NULL_TREE;
  else if (mode == VOIDmode)
    return void_type_node;
  else if (GET_MODE_CLASS (mode) == MODE_FLOAT)
    return float_type_for_precision (GET_MODE_PRECISION (mode), mode);
  else
    return gnat_type_for_size (GET_MODE_BITSIZE (mode), unsignedp);
}

/* Return the unsigned version of a TYPE_NODE, a scalar type.  */

tree
gnat_unsigned_type (tree type_node)
{
  tree type = gnat_type_for_size (TYPE_PRECISION (type_node), 1);

  if (TREE_CODE (type_node) == INTEGER_TYPE && TYPE_MODULAR_P (type_node))
    {
      type = copy_node (type);
      TREE_TYPE (type) = type_node;
    }
  else if (TREE_TYPE (type_node) != 0
           && TREE_CODE (TREE_TYPE (type_node)) == INTEGER_TYPE
           && TYPE_MODULAR_P (TREE_TYPE (type_node)))
    {
      type = copy_node (type);
      TREE_TYPE (type) = TREE_TYPE (type_node);
    }

  return type;
}

/* Return the signed version of a TYPE_NODE, a scalar type.  */

tree
gnat_signed_type (tree type_node)
{
  tree type = gnat_type_for_size (TYPE_PRECISION (type_node), 0);

  if (TREE_CODE (type_node) == INTEGER_TYPE && TYPE_MODULAR_P (type_node))
    {
      type = copy_node (type);
      TREE_TYPE (type) = type_node;
    }
  else if (TREE_TYPE (type_node) != 0
           && TREE_CODE (TREE_TYPE (type_node)) == INTEGER_TYPE
           && TYPE_MODULAR_P (TREE_TYPE (type_node)))
    {
      type = copy_node (type);
      TREE_TYPE (type) = TREE_TYPE (type_node);
    }

  return type;
}

/* Return a type the same as TYPE except unsigned or signed according to
   UNSIGNEDP.  */

tree
gnat_signed_or_unsigned_type (int unsignedp, tree type)
{
  if (! INTEGRAL_TYPE_P (type) || TYPE_UNSIGNED (type) == unsignedp)
    return type;
  else
    return gnat_type_for_size (TYPE_PRECISION (type), unsignedp);
}
\f
/* EXP is an expression for the size of an object.  If this size contains
   discriminant references, replace them with the maximum (if MAX_P) or
   minimum (if ! MAX_P) possible value of the discriminant.  */

tree
max_size (tree exp, int max_p)
{
  enum tree_code code = TREE_CODE (exp);
  tree type = TREE_TYPE (exp);

  switch (TREE_CODE_CLASS (code))
    {
    case 'd':
    case 'c':
      return exp;

    case 'x':
      if (code == TREE_LIST)
        return tree_cons (TREE_PURPOSE (exp),
                          max_size (TREE_VALUE (exp), max_p),
                          TREE_CHAIN (exp) != 0
                          ? max_size (TREE_CHAIN (exp), max_p) : 0);
      break;

    case 'r':
      /* If this contains a PLACEHOLDER_EXPR, it is the thing we want to
         modify.  Otherwise, we treat it like a variable.  */
      if (! CONTAINS_PLACEHOLDER_P (exp))
        return exp;

      type = TREE_TYPE (TREE_OPERAND (exp, 1));
      return
        max_size (max_p ? TYPE_MAX_VALUE (type) : TYPE_MIN_VALUE (type), 1);

    case '<':
      return max_p ? size_one_node : size_zero_node;

    case '1':
    case '2':
    case 'e':
      switch (TREE_CODE_LENGTH (code))
        {
        case 1:
          if (code == NON_LVALUE_EXPR)
            return max_size (TREE_OPERAND (exp, 0), max_p);
          else
            return
              fold (build1 (code, type,
                            max_size (TREE_OPERAND (exp, 0),
                                      code == NEGATE_EXPR ? ! max_p : max_p)));

        case 2:
          if (code == RTL_EXPR)
            gigi_abort (407);
          else if (code == COMPOUND_EXPR)
            return max_size (TREE_OPERAND (exp, 1), max_p);

          {
            tree lhs = max_size (TREE_OPERAND (exp, 0), max_p);
            tree rhs = max_size (TREE_OPERAND (exp, 1),
                                 code == MINUS_EXPR ? ! max_p : max_p);

            /* Special-case wanting the maximum value of a MIN_EXPR.
               In that case, if one side overflows, return the other.
               sizetype is signed, but we know sizes are non-negative.
               Likewise, handle a MINUS_EXPR or PLUS_EXPR with the LHS
               overflowing or the maximum possible value and the RHS
               a variable.  */
            if (max_p && code == MIN_EXPR && TREE_OVERFLOW (rhs))
              return lhs;
            else if (max_p && code == MIN_EXPR && TREE_OVERFLOW (lhs))
              return rhs;
            else if ((code == MINUS_EXPR || code == PLUS_EXPR)
                     && ((TREE_CONSTANT (lhs) && TREE_OVERFLOW (lhs))
                         || operand_equal_p (lhs, TYPE_MAX_VALUE (type), 0))
                     && ! TREE_CONSTANT (rhs))
              return lhs;
            else
              return fold (build (code, type, lhs, rhs));
          }

        case 3:
          if (code == SAVE_EXPR)
            return exp;
          else if (code == COND_EXPR)
            return fold (build (max_p ? MAX_EXPR : MIN_EXPR, type,
                                max_size (TREE_OPERAND (exp, 1), max_p),
                                max_size (TREE_OPERAND (exp, 2), max_p)));
          else if (code == CALL_EXPR && TREE_OPERAND (exp, 1) != 0)
            return build (CALL_EXPR, type, TREE_OPERAND (exp, 0),
                          max_size (TREE_OPERAND (exp, 1), max_p), NULL);
        }
    }

  gigi_abort (408);
}
\f
/* Build a template of type TEMPLATE_TYPE from the array bounds of ARRAY_TYPE.
   EXPR is an expression that we can use to locate any PLACEHOLDER_EXPRs.
   Return a constructor for the template.  */

tree
build_template (tree template_type, tree array_type, tree expr)
{
  tree template_elts = NULL_TREE;
  tree bound_list = NULL_TREE;
  tree field;

  if (TREE_CODE (array_type) == RECORD_TYPE
      && (TYPE_IS_PADDING_P (array_type)
          || TYPE_LEFT_JUSTIFIED_MODULAR_P (array_type)))
    array_type = TREE_TYPE (TYPE_FIELDS (array_type));

  if (TREE_CODE (array_type) == ARRAY_TYPE
      || (TREE_CODE (array_type) == INTEGER_TYPE
          && TYPE_HAS_ACTUAL_BOUNDS_P (array_type)))
    bound_list = TYPE_ACTUAL_BOUNDS (array_type);

  /* First make the list for a CONSTRUCTOR for the template.   Go down the
     field list of the template instead of the type chain because this
     array might be an Ada array of arrays and we can't tell where the
     nested arrays stop being the underlying object.  */

  for (field = TYPE_FIELDS (template_type); field;
       (bound_list != 0
        ? (bound_list = TREE_CHAIN (bound_list))
        : (array_type = TREE_TYPE (array_type))),
       field = TREE_CHAIN (TREE_CHAIN (field)))
    {
      tree bounds, min, max;

      /* If we have a bound list, get the bounds from there.  Likewise
         for an ARRAY_TYPE.  Otherwise, if expr is a PARM_DECL with
         DECL_BY_COMPONENT_PTR_P, use the bounds of the field in the template.
         This will give us a maximum range.  */
      if (bound_list != 0)
        bounds = TREE_VALUE (bound_list);
      else if (TREE_CODE (array_type) == ARRAY_TYPE)
        bounds = TYPE_INDEX_TYPE (TYPE_DOMAIN (array_type));
      else if (expr != 0 && TREE_CODE (expr) == PARM_DECL
               && DECL_BY_COMPONENT_PTR_P (expr))
        bounds = TREE_TYPE (field);
      else
        gigi_abort (411);

      min = convert (TREE_TYPE (TREE_CHAIN (field)), TYPE_MIN_VALUE (bounds));
      max = convert (TREE_TYPE (field), TYPE_MAX_VALUE (bounds));

      /* If either MIN or MAX involve a PLACEHOLDER_EXPR, we must
         substitute it from OBJECT.  */
      min = SUBSTITUTE_PLACEHOLDER_IN_EXPR (min, expr);
      max = SUBSTITUTE_PLACEHOLDER_IN_EXPR (max, expr);

      template_elts = tree_cons (TREE_CHAIN (field), max,
                                 tree_cons (field, min, template_elts));
    }

  return gnat_build_constructor (template_type, nreverse (template_elts));
}
\f
/* Build a VMS descriptor from a Mechanism_Type, which must specify
   a descriptor type, and the GCC type of an object.  Each FIELD_DECL
   in the type contains in its DECL_INITIAL the expression to use when
   a constructor is made for the type.  GNAT_ENTITY is a gnat node used
   to print out an error message if the mechanism cannot be applied to
   an object of that type and also for the name.  */

tree
build_vms_descriptor (tree type, Mechanism_Type mech, Entity_Id gnat_entity)
{
  tree record_type = make_node (RECORD_TYPE);
  tree field_list = 0;
  int class;
  int dtype = 0;
  tree inner_type;
  int ndim;
  int i;
  tree *idx_arr;
  tree tem;

  /* If TYPE is an unconstrained array, use the underlying array type.  */
  if (TREE_CODE (type) == UNCONSTRAINED_ARRAY_TYPE)
    type = TREE_TYPE (TREE_TYPE (TYPE_FIELDS (TREE_TYPE (type))));

  /* If this is an array, compute the number of dimensions in the array,
     get the index types, and point to the inner type.  */
  if (TREE_CODE (type) != ARRAY_TYPE)
    ndim = 0;
  else
    for (ndim = 1, inner_type = type;
         TREE_CODE (TREE_TYPE (inner_type)) == ARRAY_TYPE
         && TYPE_MULTI_ARRAY_P (TREE_TYPE (inner_type));
         ndim++, inner_type = TREE_TYPE (inner_type))
      ;

  idx_arr = (tree *) alloca (ndim * sizeof (tree));

  if (mech != By_Descriptor_NCA
      && TREE_CODE (type) == ARRAY_TYPE && TYPE_CONVENTION_FORTRAN_P (type))
    for (i = ndim - 1, inner_type = type;
         i >= 0;
         i--, inner_type = TREE_TYPE (inner_type))
      idx_arr[i] = TYPE_DOMAIN (inner_type);
  else
    for (i = 0, inner_type = type;
         i < ndim;
         i++, inner_type = TREE_TYPE (inner_type))
      idx_arr[i] = TYPE_DOMAIN (inner_type);

  /* Now get the DTYPE value.  */
  switch (TREE_CODE (type))
    {
    case INTEGER_TYPE:
    case ENUMERAL_TYPE:
      if (TYPE_VAX_FLOATING_POINT_P (type))
        switch (tree_low_cst (TYPE_DIGITS_VALUE (type), 1))
          {
          case 6:
            dtype = 10;
            break;
          case 9:
            dtype = 11;
            break;
          case 15:
            dtype = 27;
            break;
          }
      else
        switch (GET_MODE_BITSIZE (TYPE_MODE (type)))
          {
          case 8:
            dtype = TYPE_UNSIGNED (type) ? 2 : 6;
            break;
          case 16:
            dtype = TYPE_UNSIGNED (type) ? 3 : 7;
            break;
          case 32:
            dtype = TYPE_UNSIGNED (type) ? 4 : 8;
            break;
          case 64:
            dtype = TYPE_UNSIGNED (type) ? 5 : 9;
            break;
          case 128:
            dtype = TYPE_UNSIGNED (type) ? 25 : 26;
            break;
          }
      break;

    case REAL_TYPE:
      dtype = GET_MODE_BITSIZE (TYPE_MODE (type)) == 32 ? 52 : 53;
      break;

    case COMPLEX_TYPE:
      if (TREE_CODE (TREE_TYPE (type)) == INTEGER_TYPE
          && TYPE_VAX_FLOATING_POINT_P (type))
        switch (tree_low_cst (TYPE_DIGITS_VALUE (type), 1))
          {
          case 6:
            dtype = 12;
            break;
          case 9:
            dtype = 13;
            break;
          case 15:
            dtype = 29;
          }
      else
        dtype = GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (type))) == 32 ? 54: 55;
      break;

    case ARRAY_TYPE:
      dtype = 14;
      break;

    default:
      break;
    }

  /* Get the CLASS value.  */
  switch (mech)
    {
    case By_Descriptor_A:
      class = 4;
      break;
    case By_Descriptor_NCA:
      class = 10;
      break;
    case By_Descriptor_SB:
      class = 15;
      break;
    default:
      class = 1;
    }

  /* Make the type for a descriptor for VMS.  The first four fields
     are the same for all types.  */

  field_list
    = chainon (field_list,
               make_descriptor_field
               ("LENGTH", gnat_type_for_size (16, 1), record_type,
                size_in_bytes (mech == By_Descriptor_A ? inner_type : type)));

  field_list = chainon (field_list,
                        make_descriptor_field ("DTYPE",
                                               gnat_type_for_size (8, 1),
                                               record_type, size_int (dtype)));
  field_list = chainon (field_list,
                        make_descriptor_field ("CLASS",
                                               gnat_type_for_size (8, 1),
                                               record_type, size_int (class)));

  field_list
    = chainon (field_list,
               make_descriptor_field
               ("POINTER",
                build_pointer_type_for_mode (type, SImode, false), record_type,
                build1 (ADDR_EXPR,
                        build_pointer_type_for_mode (type, SImode, false),
                        build (PLACEHOLDER_EXPR, type))));

  switch (mech)
    {
    case By_Descriptor:
    case By_Descriptor_S:
      break;

    case By_Descriptor_SB:
      field_list
        = chainon (field_list,
                   make_descriptor_field
                   ("SB_L1", gnat_type_for_size (32, 1), record_type,
                    TREE_CODE (type) == ARRAY_TYPE
                    ? TYPE_MIN_VALUE (TYPE_DOMAIN (type)) : size_zero_node));
      field_list
        = chainon (field_list,
                   make_descriptor_field
                   ("SB_L2", gnat_type_for_size (32, 1), record_type,
                    TREE_CODE (type) == ARRAY_TYPE
                    ? TYPE_MAX_VALUE (TYPE_DOMAIN (type)) : size_zero_node));
      break;

    case By_Descriptor_A:
    case By_Descriptor_NCA:
      field_list = chainon (field_list,
                            make_descriptor_field ("SCALE",
                                                   gnat_type_for_size (8, 1),
                                                   record_type,
                                                   size_zero_node));

      field_list = chainon (field_list,
                            make_descriptor_field ("DIGITS",
                                                   gnat_type_for_size (8, 1),
                                                   record_type,
                                                   size_zero_node));

      field_list
        = chainon (field_list,
                   make_descriptor_field
                   ("AFLAGS", gnat_type_for_size (8, 1), record_type,
                    size_int (mech == By_Descriptor_NCA
                              ? 0
                              /* Set FL_COLUMN, FL_COEFF, and FL_BOUNDS.  */
                              : (TREE_CODE (type) == ARRAY_TYPE
                                 && TYPE_CONVENTION_FORTRAN_P (type)
                                 ? 224 : 192))));

      field_list = chainon (field_list,
                            make_descriptor_field ("DIMCT",
                                                   gnat_type_for_size (8, 1),
                                                   record_type,
                                                   size_int (ndim)));

      field_list = chainon (field_list,
                            make_descriptor_field ("ARSIZE",
                                                   gnat_type_for_size (32, 1),
                                                   record_type,
                                                   size_in_bytes (type)));

      /* Now build a pointer to the 0,0,0... element.  */
      tem = build (PLACEHOLDER_EXPR, type);
      for (i = 0, inner_type = type; i < ndim;
           i++, inner_type = TREE_TYPE (inner_type))
        tem = build (ARRAY_REF, TREE_TYPE (inner_type), tem,
                     convert (TYPE_DOMAIN (inner_type), size_zero_node));

      field_list
        = chainon (field_list,
                   make_descriptor_field
                   ("A0",
                    build_pointer_type_for_mode (inner_type, SImode, false),
                    record_type,
                    build1 (ADDR_EXPR,
                            build_pointer_type_for_mode (inner_type, SImode,
                                                         false),
                            tem)));

      /* Next come the addressing coefficients.  */
      tem = size_int (1);
      for (i = 0; i < ndim; i++)
        {
          char fname[3];
          tree idx_length
            = size_binop (MULT_EXPR, tem,
                          size_binop (PLUS_EXPR,
                                      size_binop (MINUS_EXPR,
                                                  TYPE_MAX_VALUE (idx_arr[i]),
                                                  TYPE_MIN_VALUE (idx_arr[i])),
                                      size_int (1)));

          fname[0] = (mech == By_Descriptor_NCA ? 'S' : 'M');
          fname[1] = '0' + i, fname[2] = 0;
          field_list
            = chainon (field_list,
                       make_descriptor_field (fname,
                                              gnat_type_for_size (32, 1),
                                              record_type, idx_length));

          if (mech == By_Descriptor_NCA)
            tem = idx_length;
        }

      /* Finally here are the bounds.  */
      for (i = 0; i < ndim; i++)
        {
          char fname[3];

          fname[0] = 'L', fname[1] = '0' + i, fname[2] = 0;
          field_list
            = chainon (field_list,
                       make_descriptor_field
                       (fname, gnat_type_for_size (32, 1), record_type,
                        TYPE_MIN_VALUE (idx_arr[i])));

          fname[0] = 'U';
          field_list
            = chainon (field_list,
                       make_descriptor_field
                       (fname, gnat_type_for_size (32, 1), record_type,
                        TYPE_MAX_VALUE (idx_arr[i])));
        }
      break;

    default:
      post_error ("unsupported descriptor type for &", gnat_entity);
    }

  finish_record_type (record_type, field_list, 0, 1);
  pushdecl (build_decl (TYPE_DECL, create_concat_name (gnat_entity, "DESC"),
                        record_type));

  return record_type;
}

/* Utility routine for above code to make a field.  */

static tree
make_descriptor_field (const char *name, tree type,
                       tree rec_type, tree initial)
{
  tree field
    = create_field_decl (get_identifier (name), type, rec_type, 0, 0, 0, 0);

  DECL_INITIAL (field) = initial;
  return field;
}
\f
/* Build a type to be used to represent an aliased object whose nominal
   type is an unconstrained array.  This consists of a RECORD_TYPE containing
   a field of TEMPLATE_TYPE and a field of OBJECT_TYPE, which is an
   ARRAY_TYPE.  If ARRAY_TYPE is that of the unconstrained array, this
   is used to represent an arbitrary unconstrained object.  Use NAME
   as the name of the record.  */

tree
build_unc_object_type (tree template_type, tree object_type, tree name)
{
  tree type = make_node (RECORD_TYPE);
  tree template_field = create_field_decl (get_identifier ("BOUNDS"),
                                           template_type, type, 0, 0, 0, 1);
  tree array_field = create_field_decl (get_identifier ("ARRAY"), object_type,
                                        type, 0, 0, 0, 1);

  TYPE_NAME (type) = name;
  TYPE_CONTAINS_TEMPLATE_P (type) = 1;
  finish_record_type (type,
                      chainon (chainon (NULL_TREE, template_field),
                               array_field),
                      0, 0);

  return type;
}
\f
/* Update anything previously pointing to OLD_TYPE to point to NEW_TYPE.  In
   the normal case this is just two adjustments, but we have more to do
   if NEW is an UNCONSTRAINED_ARRAY_TYPE.  */

void
update_pointer_to (tree old_type, tree new_type)
{
  tree ptr = TYPE_POINTER_TO (old_type);
  tree ref = TYPE_REFERENCE_TO (old_type);
  tree type;

  /* If this is the main variant, process all the other variants first.  */
  if (TYPE_MAIN_VARIANT (old_type) == old_type)
    for (type = TYPE_NEXT_VARIANT (old_type); type != 0;
         type = TYPE_NEXT_VARIANT (type))
      update_pointer_to (type, new_type);

  /* If no pointer or reference, we are done.  */
  if (ptr == 0 && ref == 0)
    return;

  /* Merge the old type qualifiers in the new type.

     Each old variant has qualifiers for specific reasons, and the new
     designated type as well. Each set of qualifiers represents useful
     information grabbed at some point, and merging the two simply unifies
     these inputs into the final type description.

     Consider for instance a volatile type frozen after an access to constant
     type designating it. After the designated type freeze, we get here with a
     volatile new_type and a dummy old_type with a readonly variant, created
     when the access type was processed. We shall make a volatile and readonly
     designated type, because that's what it really is.

     We might also get here for a non-dummy old_type variant with different
     qualifiers than the new_type ones, for instance in some cases of pointers
     to private record type elaboration (see the comments around the call to
     this routine from gnat_to_gnu_entity/E_Access_Type). We have to merge the
     qualifiers in thoses cases too, to avoid accidentally discarding the
     initial set, and will often end up with old_type == new_type then.  */
  new_type = build_qualified_type (new_type,
                                   TYPE_QUALS (old_type)
                                   | TYPE_QUALS (new_type));

  /* If the new type and the old one are identical, there is nothing to
     update.  */
  if (old_type == new_type)
    return;

  /* Otherwise, first handle the simple case.  */
  if (TREE_CODE (new_type) != UNCONSTRAINED_ARRAY_TYPE)
    {
      TYPE_POINTER_TO (new_type) = ptr;
      TYPE_REFERENCE_TO (new_type) = ref;

      for (; ptr; ptr = TYPE_NEXT_PTR_TO (ptr))
        {
          TREE_TYPE (ptr) = new_type;

          if (TYPE_NAME (ptr) != 0
              && TREE_CODE (TYPE_NAME (ptr)) == TYPE_DECL
              && TREE_CODE (new_type) != ENUMERAL_TYPE)
            rest_of_decl_compilation (TYPE_NAME (ptr), NULL,
                                      global_bindings_p (), 0);
        }

      for (; ref; ref = TYPE_NEXT_PTR_TO (ref))
        {
          TREE_TYPE (ref) = new_type;

          if (TYPE_NAME (ref) != 0
              && TREE_CODE (TYPE_NAME (ref)) == TYPE_DECL
              && TREE_CODE (new_type) != ENUMERAL_TYPE)
            rest_of_decl_compilation (TYPE_NAME (ref), NULL,
                                      global_bindings_p (), 0);
        }
    }

  /* Now deal with the unconstrained array case. In this case the "pointer"
     is actually a RECORD_TYPE where the types of both fields are
     pointers to void.  In that case, copy the field list from the
     old type to the new one and update the fields' context. */
  else if (TREE_CODE (ptr) != RECORD_TYPE || ! TYPE_IS_FAT_POINTER_P (ptr))
    gigi_abort (412);

  else
    {
      tree new_obj_rec = TYPE_OBJECT_RECORD_TYPE (new_type);
      tree ptr_temp_type;
      tree new_ref;
      tree var;

      TYPE_FIELDS (ptr) = TYPE_FIELDS (TYPE_POINTER_TO (new_type));
      DECL_CONTEXT (TYPE_FIELDS (ptr)) = ptr;
      DECL_CONTEXT (TREE_CHAIN (TYPE_FIELDS (ptr))) = ptr;

      /* Rework the PLACEHOLDER_EXPR inside the reference to the
         template bounds.

         ??? This is now the only use of gnat_substitute_in_type, which
         is now a very "heavy" routine to do this, so it should be replaced
         at some point.  */
      ptr_temp_type = TREE_TYPE (TREE_CHAIN (TYPE_FIELDS (ptr)));
      new_ref = build (COMPONENT_REF, ptr_temp_type,
                       build (PLACEHOLDER_EXPR, ptr),
                       TREE_CHAIN (TYPE_FIELDS (ptr)));

      update_pointer_to
        (TREE_TYPE (TREE_TYPE (TYPE_FIELDS (ptr))),
         gnat_substitute_in_type (TREE_TYPE (TREE_TYPE (TYPE_FIELDS (ptr))),
                                  TREE_CHAIN (TYPE_FIELDS (ptr)), new_ref));

      for (var = TYPE_MAIN_VARIANT (ptr); var; var = TYPE_NEXT_VARIANT (var))
        SET_TYPE_UNCONSTRAINED_ARRAY (var, new_type);

      TYPE_POINTER_TO (new_type) = TYPE_REFERENCE_TO (new_type)
        = TREE_TYPE (new_type) = ptr;

      /* Now handle updating the allocation record, what the thin pointer
         points to.  Update all pointers from the old record into the new
         one, update the types of the fields, and recompute the size.  */

      update_pointer_to (TYPE_OBJECT_RECORD_TYPE (old_type), new_obj_rec);

      TREE_TYPE (TYPE_FIELDS (new_obj_rec)) = TREE_TYPE (ptr_temp_type);
      TREE_TYPE (TREE_CHAIN (TYPE_FIELDS (new_obj_rec)))
        = TREE_TYPE (TREE_TYPE (TYPE_FIELDS (ptr)));
      DECL_SIZE (TREE_CHAIN (TYPE_FIELDS (new_obj_rec)))
        = TYPE_SIZE (TREE_TYPE (TREE_TYPE (TYPE_FIELDS (ptr))));
      DECL_SIZE_UNIT (TREE_CHAIN (TYPE_FIELDS (new_obj_rec)))
        = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (TYPE_FIELDS (ptr))));

      TYPE_SIZE (new_obj_rec)
        = size_binop (PLUS_EXPR,
                      DECL_SIZE (TYPE_FIELDS (new_obj_rec)),
                      DECL_SIZE (TREE_CHAIN (TYPE_FIELDS (new_obj_rec))));
      TYPE_SIZE_UNIT (new_obj_rec)
        = size_binop (PLUS_EXPR,
                      DECL_SIZE_UNIT (TYPE_FIELDS (new_obj_rec)),
                      DECL_SIZE_UNIT (TREE_CHAIN (TYPE_FIELDS (new_obj_rec))));
      rest_of_type_compilation (ptr, global_bindings_p ());
    }
}
\f
/* Convert a pointer to a constrained array into a pointer to a fat
   pointer.  This involves making or finding a template.  */

static tree
convert_to_fat_pointer (tree type, tree expr)
{
  tree template_type = TREE_TYPE (TREE_TYPE (TREE_CHAIN (TYPE_FIELDS (type))));
  tree template, template_addr;
  tree etype = TREE_TYPE (expr);

  /* If EXPR is a constant of zero, we make a fat pointer that has a null
     pointer to the template and array.  */
  if (integer_zerop (expr))
    return
      gnat_build_constructor
        (type,
         tree_cons (TYPE_FIELDS (type),
                    convert (TREE_TYPE (TYPE_FIELDS (type)), expr),
                    tree_cons (TREE_CHAIN (TYPE_FIELDS (type)),
                               convert (build_pointer_type (template_type),
                                        expr),
                               NULL_TREE)));

  /* If EXPR is a thin pointer, make the template and data from the record.  */

  else if (TYPE_THIN_POINTER_P (etype))
    {
      tree fields = TYPE_FIELDS (TREE_TYPE (etype));

      expr = save_expr (expr);
      if (TREE_CODE (expr) == ADDR_EXPR)
        expr = TREE_OPERAND (expr, 0);
      else
        expr = build1 (INDIRECT_REF, TREE_TYPE (etype), expr);

      template = build_component_ref (expr, NULL_TREE, fields, 0);
      expr = build_unary_op (ADDR_EXPR, NULL_TREE,
                             build_component_ref (expr, NULL_TREE,
                                                  TREE_CHAIN (fields), 0));
    }
  else
    /* Otherwise, build the constructor for the template.  */
    template = build_template (template_type, TREE_TYPE (etype), expr);

  template_addr = build_unary_op (ADDR_EXPR, NULL_TREE, template);

  /* The result is a CONSTRUCTOR for the fat pointer.

     If expr is an argument of a foreign convention subprogram, the type it
     points to is directly the component type. In this case, the expression
     type may not match the corresponding FIELD_DECL type at this point, so we
     call "convert" here to fix that up if necessary. This type consistency is
     required, for instance because it ensures that possible later folding of
     component_refs against this constructor always yields something of the
     same type as the initial reference.

     Note that the call to "build_template" above is still fine, because it
     will only refer to the provided template_type in this case.  */
   return
     gnat_build_constructor
     (type, tree_cons (TYPE_FIELDS (type),
                      convert (TREE_TYPE (TYPE_FIELDS (type)), expr),
                      tree_cons (TREE_CHAIN (TYPE_FIELDS (type)),
                                 template_addr, NULL_TREE)));
}
\f
/* Convert to a thin pointer type, TYPE.  The only thing we know how to convert
   is something that is a fat pointer, so convert to it first if it EXPR
   is not already a fat pointer.  */

static tree
convert_to_thin_pointer (tree type, tree expr)
{
  if (! TYPE_FAT_POINTER_P (TREE_TYPE (expr)))
    expr
      = convert_to_fat_pointer
        (TREE_TYPE (TYPE_UNCONSTRAINED_ARRAY (TREE_TYPE (type))), expr);

  /* We get the pointer to the data and use a NOP_EXPR to make it the
     proper GCC type.  */
  expr
    = build_component_ref (expr, NULL_TREE, TYPE_FIELDS (TREE_TYPE (expr)), 0);
  expr = build1 (NOP_EXPR, type, expr);

  return expr;
}
\f
/* Create an expression whose value is that of EXPR,
   converted to type TYPE.  The TREE_TYPE of the value
   is always TYPE.  This function implements all reasonable
   conversions; callers should filter out those that are
   not permitted by the language being compiled.  */

tree
convert (tree type, tree expr)
{
  enum tree_code code = TREE_CODE (type);
  tree etype = TREE_TYPE (expr);
  enum tree_code ecode = TREE_CODE (etype);
  tree tem;

  /* If EXPR is already the right type, we are done.  */
  if (type == etype)
    return expr;
  /* If we're converting between two aggregate types that have the same main
     variant, just make a NOP_EXPR.  */
  else if (AGGREGATE_TYPE_P (type)
           && TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (etype))
    return build1 (NOP_EXPR, type, expr);

  /* If the input type has padding, remove it by doing a component reference
     to the field.  If the output type has padding, make a constructor
     to build the record.  If both input and output have padding and are
     of variable size, do this as an unchecked conversion.  */
  else if (ecode == RECORD_TYPE && code == RECORD_TYPE
      && TYPE_IS_PADDING_P (type) && TYPE_IS_PADDING_P (etype)
      && (! TREE_CONSTANT (TYPE_SIZE (type))
          || ! TREE_CONSTANT (TYPE_SIZE (etype))))
    ;
  else if (ecode == RECORD_TYPE && TYPE_IS_PADDING_P (etype))
    {
      /* If we have just converted to this padded type, just get
         the inner expression.  */
      if (TREE_CODE (expr) == CONSTRUCTOR
          && CONSTRUCTOR_ELTS (expr) != 0
          && TREE_PURPOSE (CONSTRUCTOR_ELTS (expr)) == TYPE_FIELDS (etype))
        return TREE_VALUE (CONSTRUCTOR_ELTS (expr));
      else
        return convert (type, build_component_ref (expr, NULL_TREE,
                                                   TYPE_FIELDS (etype), 0));
    }
  else if (code == RECORD_TYPE && TYPE_IS_PADDING_P (type))
    {
      /* If we previously converted from another type and our type is
         of variable size, remove the conversion to avoid the need for
         variable-size temporaries.  */
      if (TREE_CODE (expr) == VIEW_CONVERT_EXPR
          && ! TREE_CONSTANT (TYPE_SIZE (type)))
        expr = TREE_OPERAND (expr, 0);

      /* If we are just removing the padding from expr, convert the original
         object if we have variable size.  That will avoid the need
         for some variable-size temporaries.  */
      if (TREE_CODE (expr) == COMPONENT_REF
          && TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0))) == RECORD_TYPE
          && TYPE_IS_PADDING_P (TREE_TYPE (TREE_OPERAND (expr, 0)))
          && ! TREE_CONSTANT (TYPE_SIZE (type)))
        return convert (type, TREE_OPERAND (expr, 0));

      /* If the result type is a padded type with a self-referentially-sized
         field and the expression type is a record, do this as an
         unchecked converstion.  */
      else if (TREE_CODE (etype) == RECORD_TYPE
               && CONTAINS_PLACEHOLDER_P (DECL_SIZE (TYPE_FIELDS (type))))
        return unchecked_convert (type, expr, 0);

      else
        return
          gnat_build_constructor (type,
                             tree_cons (TYPE_FIELDS (type),
                                        convert (TREE_TYPE
                                                 (TYPE_FIELDS (type)),
                                                 expr),
                                        NULL_TREE));
    }

  /* If the input is a biased type, adjust first.  */
  if (ecode == INTEGER_TYPE && TYPE_BIASED_REPRESENTATION_P (etype))
    return convert (type, fold (build (PLUS_EXPR, TREE_TYPE (etype),
                                       fold (build1 (GNAT_NOP_EXPR,
                                                     TREE_TYPE (etype), expr)),
                                       TYPE_MIN_VALUE (etype))));

  /* If the input is a left-justified modular type, we need to extract
     the actual object before converting it to any other type with the
     exception of an unconstrained array.  */
  if (ecode == RECORD_TYPE && TYPE_LEFT_JUSTIFIED_MODULAR_P (etype)
      && code != UNCONSTRAINED_ARRAY_TYPE)
    return convert (type, build_component_ref (expr, NULL_TREE,
                                               TYPE_FIELDS (etype), 0));

  /* If converting to a type that contains a template, convert to the data
     type and then build the template. */
  if (code == RECORD_TYPE && TYPE_CONTAINS_TEMPLATE_P (type))
    {
      tree obj_type = TREE_TYPE (TREE_CHAIN (TYPE_FIELDS (type)));

      /* If the source already has a template, get a reference to the
         associated array only, as we are going to rebuild a template
         for the target type anyway.  */
      expr = maybe_unconstrained_array (expr);

      return
        gnat_build_constructor
          (type,
           tree_cons (TYPE_FIELDS (type),
                      build_template (TREE_TYPE (TYPE_FIELDS (type)),
                                      obj_type, NULL_TREE),
                      tree_cons (TREE_CHAIN (TYPE_FIELDS (type)),
                                 convert (obj_type, expr), NULL_TREE)));
    }

  /* There are some special cases of expressions that we process
     specially.  */
  switch (TREE_CODE (expr))
    {
    case ERROR_MARK:
      return expr;

    case TRANSFORM_EXPR:
    case NULL_EXPR:
      /* Just set its type here.  For TRANSFORM_EXPR, we will do the actual
         conversion in gnat_expand_expr.  NULL_EXPR does not represent
         and actual value, so no conversion is needed.  */
      expr = copy_node (expr);
      TREE_TYPE (expr) = type;
      return expr;

    case STRING_CST:
    case CONSTRUCTOR:
      /* If we are converting a STRING_CST to another constrained array type,
         just make a new one in the proper type.  Likewise for
         CONSTRUCTOR if the alias sets are the same.  */
      if (code == ecode && AGGREGATE_TYPE_P (etype)
          && ! (TREE_CODE (TYPE_SIZE (etype)) == INTEGER_CST
                && TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST)
          && (TREE_CODE (expr) == STRING_CST
              || get_alias_set (etype) == get_alias_set (type)))
        {
          expr = copy_node (expr);
          TREE_TYPE (expr) = type;
          return expr;
        }
      break;

    case COMPONENT_REF:
      /* If we are converting between two aggregate types of the same
         kind, size, mode, and alignment, just make a new COMPONENT_REF.
         This avoid unneeded conversions which makes reference computations
         more complex.  */
      if (code == ecode && TYPE_MODE (type) == TYPE_MODE (etype)
          && AGGREGATE_TYPE_P (type) && AGGREGATE_TYPE_P (etype)
          && TYPE_ALIGN (type) == TYPE_ALIGN (etype)
          && operand_equal_p (TYPE_SIZE (type), TYPE_SIZE (etype), 0)
          && get_alias_set (type) == get_alias_set (etype))
        return build (COMPONENT_REF, type, TREE_OPERAND (expr, 0),
                      TREE_OPERAND (expr, 1));

      break;

    case UNCONSTRAINED_ARRAY_REF:
      /* Convert this to the type of the inner array by getting the address of
         the array from the template.  */
      expr = build_unary_op (INDIRECT_REF, NULL_TREE,
                             build_component_ref (TREE_OPERAND (expr, 0),
                                                  get_identifier ("P_ARRAY"),
                                                  NULL_TREE, 0));
      etype = TREE_TYPE (expr);
      ecode = TREE_CODE (etype);
      break;

    case VIEW_CONVERT_EXPR:
      if (AGGREGATE_TYPE_P (type) && AGGREGATE_TYPE_P (etype)
          && ! TYPE_FAT_POINTER_P (type) && ! TYPE_FAT_POINTER_P (etype))
        return convert (type, TREE_OPERAND (expr, 0));
      break;

    case INDIRECT_REF:
      /* If both types are record types, just convert the pointer and
         make a new INDIRECT_REF.

         ??? Disable this for now since it causes problems with the
         code in build_binary_op for MODIFY_EXPR which wants to
         strip off conversions.  But that code really is a mess and
         we need to do this a much better way some time.  */
      if (0
          && (TREE_CODE (type) == RECORD_TYPE
              || TREE_CODE (type) == UNION_TYPE)
          && (TREE_CODE (etype) == RECORD_TYPE
              || TREE_CODE (etype) == UNION_TYPE)
          && ! TYPE_FAT_POINTER_P (type) && ! TYPE_FAT_POINTER_P (etype))
        return build_unary_op (INDIRECT_REF, NULL_TREE,
                               convert (build_pointer_type (type),
                                        TREE_OPERAND (expr, 0)));
      break;

    default:
      break;
    }

  /* Check for converting to a pointer to an unconstrained array.  */
  if (TYPE_FAT_POINTER_P (type) && ! TYPE_FAT_POINTER_P (etype))
    return convert_to_fat_pointer (type, expr);

  if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (etype)
      || (code == INTEGER_CST && ecode == INTEGER_CST
          && (type == TREE_TYPE (etype) || etype == TREE_TYPE (type))))
    return fold (build1 (NOP_EXPR, type, expr));

  switch (code)
    {
    case VOID_TYPE:
      return build1 (CONVERT_EXPR, type, expr);

    case INTEGER_TYPE:
      if (TYPE_HAS_ACTUAL_BOUNDS_P (type)
          && (ecode == ARRAY_TYPE || ecode == UNCONSTRAINED_ARRAY_TYPE
              || (ecode == RECORD_TYPE && TYPE_CONTAINS_TEMPLATE_P (etype))))
        return unchecked_convert (type, expr, 0);
      else if (TYPE_BIASED_REPRESENTATION_P (type))
        return fold (build1 (CONVERT_EXPR, type,
                             fold (build (MINUS_EXPR, TREE_TYPE (type),
                                          convert (TREE_TYPE (type), expr),
                                          TYPE_MIN_VALUE (type)))));

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

    case ENUMERAL_TYPE:
      return fold (convert_to_integer (type, expr));

    case POINTER_TYPE:
    case REFERENCE_TYPE:
      /* If converting between two pointers to records denoting
         both a template and type, adjust if needed to account
         for any differing offsets, since one might be negative.  */
      if (TYPE_THIN_POINTER_P (etype) && TYPE_THIN_POINTER_P (type))
        {
          tree bit_diff
            = size_diffop (bit_position (TYPE_FIELDS (TREE_TYPE (etype))),
                           bit_position (TYPE_FIELDS (TREE_TYPE (type))));
          tree byte_diff = size_binop (CEIL_DIV_EXPR, bit_diff,
                                       sbitsize_int (BITS_PER_UNIT));

          expr = build1 (NOP_EXPR, type, expr);
          TREE_CONSTANT (expr) = TREE_CONSTANT (TREE_OPERAND (expr, 0));
          if (integer_zerop (byte_diff))
            return expr;

          return build_binary_op (PLUS_EXPR, type, expr,
                                  fold (convert_to_pointer (type, byte_diff)));
        }

      /* If converting to a thin pointer, handle specially.  */
      if (TYPE_THIN_POINTER_P (type)
          && TYPE_UNCONSTRAINED_ARRAY (TREE_TYPE (type)) != 0)
        return convert_to_thin_pointer (type, expr);

      /* If converting fat pointer to normal pointer, get the pointer to the
         array and then convert it.  */
      else if (TYPE_FAT_POINTER_P (etype))
        expr = build_component_ref (expr, get_identifier ("P_ARRAY"),
                                    NULL_TREE, 0);

      return fold (convert_to_pointer (type, expr));

    case REAL_TYPE:
      return fold (convert_to_real (type, expr));

    case RECORD_TYPE:
      if (TYPE_LEFT_JUSTIFIED_MODULAR_P (type) && ! AGGREGATE_TYPE_P (etype))
        return
          gnat_build_constructor
            (type, tree_cons (TYPE_FIELDS (type),
                              convert (TREE_TYPE (TYPE_FIELDS (type)), expr),
                              NULL_TREE));

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

    case ARRAY_TYPE:
      /* In these cases, assume the front-end has validated the conversion.
         If the conversion is valid, it will be a bit-wise conversion, so
         it can be viewed as an unchecked conversion.  */
      return unchecked_convert (type, expr, 0);

    case UNION_TYPE:
      /* Just validate that the type is indeed that of a field
         of the type.  Then make the simple conversion.  */
      for (tem = TYPE_FIELDS (type); tem; tem = TREE_CHAIN (tem))
        {
          if (TREE_TYPE (tem) == etype)
            return build1 (CONVERT_EXPR, type, expr);
          else if (TREE_CODE (TREE_TYPE (tem)) == RECORD_TYPE
                   && (TYPE_LEFT_JUSTIFIED_MODULAR_P (TREE_TYPE (tem))
                       || TYPE_IS_PADDING_P (TREE_TYPE (tem)))
                   && TREE_TYPE (TYPE_FIELDS (TREE_TYPE (tem))) == etype)
            return build1 (CONVERT_EXPR, type,
                           convert (TREE_TYPE (tem), expr));
        }

      gigi_abort (413);

    case UNCONSTRAINED_ARRAY_TYPE:
      /* If EXPR is a constrained array, take its address, convert it to a
         fat pointer, and then dereference it.  Likewise if EXPR is a
         record containing both a template and a constrained array.
         Note that a record representing a left justified modular type
         always represents a packed constrained array.  */
      if (ecode == ARRAY_TYPE
          || (ecode == INTEGER_TYPE && TYPE_HAS_ACTUAL_BOUNDS_P (etype))
          || (ecode == RECORD_TYPE && TYPE_CONTAINS_TEMPLATE_P (etype))
          || (ecode == RECORD_TYPE && TYPE_LEFT_JUSTIFIED_MODULAR_P (etype)))
        return
          build_unary_op
            (INDIRECT_REF, NULL_TREE,
             convert_to_fat_pointer (TREE_TYPE (type),
                                     build_unary_op (ADDR_EXPR,
                                                     NULL_TREE, expr)));

      /* Do something very similar for converting one unconstrained
         array to another.  */
      else if (ecode == UNCONSTRAINED_ARRAY_TYPE)
        return
          build_unary_op (INDIRECT_REF, NULL_TREE,
                          convert (TREE_TYPE (type),
                                   build_unary_op (ADDR_EXPR,
                                                   NULL_TREE, expr)));
      else
        gigi_abort (409);

    case COMPLEX_TYPE:
      return fold (convert_to_complex (type, expr));

    default:
      gigi_abort (410);
    }
}
\f
/* Remove all conversions that are done in EXP.  This includes converting
   from a padded type or to a left-justified modular type.  If TRUE_ADDRESS
   is nonzero, always return the address of the containing object even if
   the address is not bit-aligned.  */

tree
remove_conversions (tree exp, int true_address)
{
  switch (TREE_CODE (exp))
    {
    case CONSTRUCTOR:
      if (true_address
          && TREE_CODE (TREE_TYPE (exp)) == RECORD_TYPE
          && TYPE_LEFT_JUSTIFIED_MODULAR_P (TREE_TYPE (exp)))
        return remove_conversions (TREE_VALUE (CONSTRUCTOR_ELTS (exp)), 1);
      break;

    case COMPONENT_REF:
      if (TREE_CODE (TREE_TYPE (TREE_OPERAND (exp, 0))) == RECORD_TYPE
          && TYPE_IS_PADDING_P (TREE_TYPE (TREE_OPERAND (exp, 0))))
        return remove_conversions (TREE_OPERAND (exp, 0), true_address);
      break;

    case VIEW_CONVERT_EXPR:  case NON_LVALUE_EXPR:
    case NOP_EXPR:  case CONVERT_EXPR:  case GNAT_NOP_EXPR:
      return remove_conversions (TREE_OPERAND (exp, 0), true_address);

    default:
      break;
    }

  return exp;
}
\f
/* If EXP's type is an UNCONSTRAINED_ARRAY_TYPE, return an expression that
   refers to the underlying array.  If its type has TYPE_CONTAINS_TEMPLATE_P,
   likewise return an expression pointing to the underlying array.  */

tree
maybe_unconstrained_array (tree exp)
{
  enum tree_code code = TREE_CODE (exp);
  tree new;

  switch (TREE_CODE (TREE_TYPE (exp)))
    {
    case UNCONSTRAINED_ARRAY_TYPE:
      if (code == UNCONSTRAINED_ARRAY_REF)
        {
          new
            = build_unary_op (INDIRECT_REF, NULL_TREE,
                              build_component_ref (TREE_OPERAND (exp, 0),
                                                   get_identifier ("P_ARRAY"),
                                                   NULL_TREE, 0));
          TREE_READONLY (new) = TREE_STATIC (new) = TREE_READONLY (exp);
          return new;
        }

      else if (code == NULL_EXPR)
        return build1 (NULL_EXPR,
                       TREE_TYPE (TREE_TYPE (TYPE_FIELDS
                                             (TREE_TYPE (TREE_TYPE (exp))))),
                       TREE_OPERAND (exp, 0));

    case RECORD_TYPE:
      /* If this is a padded type, convert to the unpadded type and see if
         it contains a template.  */
      if (TYPE_IS_PADDING_P (TREE_TYPE (exp)))
        {
          new = convert (TREE_TYPE (TYPE_FIELDS (TREE_TYPE (exp))), exp);
          if (TREE_CODE (TREE_TYPE (new)) == RECORD_TYPE
              && TYPE_CONTAINS_TEMPLATE_P (TREE_TYPE (new)))
            return
              build_component_ref (new, NULL_TREE,
                                   TREE_CHAIN (TYPE_FIELDS (TREE_TYPE (new))),
                                   0);
        }
      else if (TYPE_CONTAINS_TEMPLATE_P (TREE_TYPE (exp)))
        return
          build_component_ref (exp, NULL_TREE,
                               TREE_CHAIN (TYPE_FIELDS (TREE_TYPE (exp))), 0);
      break;

    default:
      break;
    }

  return exp;
}
\f
/* Return an expression that does an unchecked converstion of EXPR to TYPE.
   If NOTRUNC_P is set, truncation operations should be suppressed.  */

tree
unchecked_convert (tree type, tree expr, int notrunc_p)
{
  tree etype = TREE_TYPE (expr);

  /* If the expression is already the right type, we are done.  */
  if (etype == type)
    return expr;

  /* If both types types are integral just do a normal conversion.
     Likewise for a conversion to an unconstrained array.  */
  if ((((INTEGRAL_TYPE_P (type)
         && ! (TREE_CODE (type) == INTEGER_TYPE
               && TYPE_VAX_FLOATING_POINT_P (type)))
        || (POINTER_TYPE_P (type) && ! TYPE_THIN_POINTER_P (type))
        || (TREE_CODE (type) == RECORD_TYPE
            && TYPE_LEFT_JUSTIFIED_MODULAR_P (type)))
       && ((INTEGRAL_TYPE_P (etype)
            && ! (TREE_CODE (etype) == INTEGER_TYPE
                  && TYPE_VAX_FLOATING_POINT_P (etype)))
           || (POINTER_TYPE_P (etype) && ! TYPE_THIN_POINTER_P (etype))
           || (TREE_CODE (etype) == RECORD_TYPE
               && TYPE_LEFT_JUSTIFIED_MODULAR_P (etype))))
      || TREE_CODE (type) == UNCONSTRAINED_ARRAY_TYPE)
    {
      tree rtype = type;

      if (TREE_CODE (etype) == INTEGER_TYPE
          && TYPE_BIASED_REPRESENTATION_P (etype))
        {
          tree ntype = copy_type (etype);

          TYPE_BIASED_REPRESENTATION_P (ntype) = 0;
          TYPE_MAIN_VARIANT (ntype) = ntype;
          expr = build1 (GNAT_NOP_EXPR, ntype, expr);
        }

      if (TREE_CODE (type) == INTEGER_TYPE
          && TYPE_BIASED_REPRESENTATION_P (type))
        {
          rtype = copy_type (type);
          TYPE_BIASED_REPRESENTATION_P (rtype) = 0;
          TYPE_MAIN_VARIANT (rtype) = rtype;
        }

      expr = convert (rtype, expr);
      if (type != rtype)
        expr = build1 (GNAT_NOP_EXPR, type, expr);
    }

  /* If we are converting TO an integral type whose precision is not the
     same as its size, first unchecked convert to a record that contains
     an object of the output type.  Then extract the field. */
  else if (INTEGRAL_TYPE_P (type) && TYPE_RM_SIZE (type) != 0
           && 0 != compare_tree_int (TYPE_RM_SIZE (type),
                                     GET_MODE_BITSIZE (TYPE_MODE (type))))
    {
      tree rec_type = make_node (RECORD_TYPE);
      tree field = create_field_decl (get_identifier ("OBJ"), type,
                                      rec_type, 1, 0, 0, 0);

      TYPE_FIELDS (rec_type) = field;
      layout_type (rec_type);

      expr = unchecked_convert (rec_type, expr, notrunc_p);
      expr = build_component_ref (expr, NULL_TREE, field, 0);
    }

  /* Similarly for integral input type whose precision is not equal to its
     size.  */
  else if (INTEGRAL_TYPE_P (etype) && TYPE_RM_SIZE (etype) != 0
      && 0 != compare_tree_int (TYPE_RM_SIZE (etype),
                                GET_MODE_BITSIZE (TYPE_MODE (etype))))
    {
      tree rec_type = make_node (RECORD_TYPE);
      tree field
        = create_field_decl (get_identifier ("OBJ"), etype, rec_type,
                             1, 0, 0, 0);

      TYPE_FIELDS (rec_type) = field;
      layout_type (rec_type);

      expr = gnat_build_constructor (rec_type, build_tree_list (field, expr));
      expr = unchecked_convert (type, expr, notrunc_p);
    }

  /* We have a special case when we are converting between two
     unconstrained array types.  In that case, take the address,
     convert the fat pointer types, and dereference.  */
  else if (TREE_CODE (etype) == UNCONSTRAINED_ARRAY_TYPE
           && TREE_CODE (type) == UNCONSTRAINED_ARRAY_TYPE)
    expr = build_unary_op (INDIRECT_REF, NULL_TREE,
                           build1 (VIEW_CONVERT_EXPR, TREE_TYPE (type),
                                   build_unary_op (ADDR_EXPR, NULL_TREE,
                                                   expr)));
  else
    {
      expr = maybe_unconstrained_array (expr);
      etype = TREE_TYPE (expr);
      expr = build1 (VIEW_CONVERT_EXPR, type, expr);
    }

  /* If the result is an integral type whose size is not equal to
     the size of the underlying machine type, sign- or zero-extend
     the result.  We need not do this in the case where the input is
     an integral type of the same precision and signedness or if the output
     is a biased type or if both the input and output are unsigned.  */
  if (! notrunc_p
      && INTEGRAL_TYPE_P (type) && TYPE_RM_SIZE (type) != 0
      && ! (TREE_CODE (type) == INTEGER_TYPE
            && TYPE_BIASED_REPRESENTATION_P (type))
      && 0 != compare_tree_int (TYPE_RM_SIZE (type),
                                GET_MODE_BITSIZE (TYPE_MODE (type)))
      && ! (INTEGRAL_TYPE_P (etype)
            && TYPE_UNSIGNED (type) == TYPE_UNSIGNED (etype)
            && operand_equal_p (TYPE_RM_SIZE (type),
                                (TYPE_RM_SIZE (etype) != 0
                                 ? TYPE_RM_SIZE (etype) : TYPE_SIZE (etype)),
                                0))
      && ! (TYPE_UNSIGNED (type) && TYPE_UNSIGNED (etype)))
    {
      tree base_type = gnat_type_for_mode (TYPE_MODE (type),
                                           TYPE_UNSIGNED (type));
      tree shift_expr
        = convert (base_type,
                   size_binop (MINUS_EXPR,
                               bitsize_int
                               (GET_MODE_BITSIZE (TYPE_MODE (type))),
                               TYPE_RM_SIZE (type)));
      expr
        = convert (type,
                   build_binary_op (RSHIFT_EXPR, base_type,
                                    build_binary_op (LSHIFT_EXPR, base_type,
                                                     convert (base_type, expr),
                                                     shift_expr),
                                    shift_expr));
    }

  /* An unchecked conversion should never raise Constraint_Error.  The code
     below assumes that GCC's conversion routines overflow the same way that
     the underlying hardware does.  This is probably true.  In the rare case
     when it is false, we can rely on the fact that such conversions are
     erroneous anyway.  */
  if (TREE_CODE (expr) == INTEGER_CST)
    TREE_OVERFLOW (expr) = TREE_CONSTANT_OVERFLOW (expr) = 0;

  /* If the sizes of the types differ and this is an VIEW_CONVERT_EXPR,
     show no longer constant.  */
  if (TREE_CODE (expr) == VIEW_CONVERT_EXPR
      && ! operand_equal_p (TYPE_SIZE_UNIT (type), TYPE_SIZE_UNIT (etype),
                            OEP_ONLY_CONST))
    TREE_CONSTANT (expr) = 0;

  return expr;
}

#include "gt-ada-utils.h"
#include "gtype-ada.h"