fortran/

[pf3gnuchains/gcc-fork.git] / gcc / fortran / trans-array.c

/* Array translation routines
   Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation,
   Inc.
   Contributed by Paul Brook <paul@nowt.org>
   and Steven Bosscher <s.bosscher@student.tudelft.nl>

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2, or (at your option) any later
version.

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

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

/* trans-array.c-- Various array related code, including scalarization,
                   allocation, initialization and other support routines.  */

/* How the scalarizer works.
   In gfortran, array expressions use the same core routines as scalar
   expressions.
   First, a Scalarization State (SS) chain is built.  This is done by walking
   the expression tree, and building a linear list of the terms in the
   expression.  As the tree is walked, scalar subexpressions are translated.

   The scalarization parameters are stored in a gfc_loopinfo structure.
   First the start and stride of each term is calculated by
   gfc_conv_ss_startstride.  During this process the expressions for the array
   descriptors and data pointers are also translated.

   If the expression is an assignment, we must then resolve any dependencies.
   In fortran all the rhs values of an assignment must be evaluated before
   any assignments take place.  This can require a temporary array to store the
   values.  We also require a temporary when we are passing array expressions
   or vector subecripts as procedure parameters.

   Array sections are passed without copying to a temporary.  These use the
   scalarizer to determine the shape of the section.  The flag
   loop->array_parameter tells the scalarizer that the actual values and loop
   variables will not be required.

   The function gfc_conv_loop_setup generates the scalarization setup code.
   It determines the range of the scalarizing loop variables.  If a temporary
   is required, this is created and initialized.  Code for scalar expressions
   taken outside the loop is also generated at this time.  Next the offset and
   scaling required to translate from loop variables to array indices for each
   term is calculated.

   A call to gfc_start_scalarized_body marks the start of the scalarized
   expression.  This creates a scope and declares the loop variables.  Before
   calling this gfc_make_ss_chain_used must be used to indicate which terms
   will be used inside this loop.

   The scalar gfc_conv_* functions are then used to build the main body of the
   scalarization loop.  Scalarization loop variables and precalculated scalar
   values are automatically substituted.  Note that gfc_advance_se_ss_chain
   must be used, rather than changing the se->ss directly.

   For assignment expressions requiring a temporary two sub loops are
   generated.  The first stores the result of the expression in the temporary,
   the second copies it to the result.  A call to
   gfc_trans_scalarized_loop_boundary marks the end of the main loop code and
   the start of the copying loop.  The temporary may be less than full rank.

   Finally gfc_trans_scalarizing_loops is called to generate the implicit do
   loops.  The loops are added to the pre chain of the loopinfo.  The post
   chain may still contain cleanup code.

   After the loop code has been added into its parent scope gfc_cleanup_loop
   is called to free all the SS allocated by the scalarizer.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tree.h"
#include "tree-gimple.h"
#include "ggc.h"
#include "toplev.h"
#include "real.h"
#include "flags.h"
#include "gfortran.h"
#include "trans.h"
#include "trans-stmt.h"
#include "trans-types.h"
#include "trans-array.h"
#include "trans-const.h"
#include "dependency.h"

static gfc_ss *gfc_walk_subexpr (gfc_ss *, gfc_expr *);
static bool gfc_get_array_constructor_size (mpz_t *, gfc_constructor *);

/* The contents of this structure aren't actually used, just the address.  */
static gfc_ss gfc_ss_terminator_var;
gfc_ss * const gfc_ss_terminator = &gfc_ss_terminator_var;


static tree
gfc_array_dataptr_type (tree desc)
{
  return (GFC_TYPE_ARRAY_DATAPTR_TYPE (TREE_TYPE (desc)));
}


/* Build expressions to access the members of an array descriptor.
   It's surprisingly easy to mess up here, so never access
   an array descriptor by "brute force", always use these
   functions.  This also avoids problems if we change the format
   of an array descriptor.

   To understand these magic numbers, look at the comments
   before gfc_build_array_type() in trans-types.c.

   The code within these defines should be the only code which knows the format
   of an array descriptor.

   Any code just needing to read obtain the bounds of an array should use
   gfc_conv_array_* rather than the following functions as these will return
   know constant values, and work with arrays which do not have descriptors.

   Don't forget to #undef these!  */

#define DATA_FIELD 0
#define OFFSET_FIELD 1
#define DTYPE_FIELD 2
#define DIMENSION_FIELD 3

#define STRIDE_SUBFIELD 0
#define LBOUND_SUBFIELD 1
#define UBOUND_SUBFIELD 2

/* This provides READ-ONLY access to the data field.  The field itself
   doesn't have the proper type.  */

tree
gfc_conv_descriptor_data_get (tree desc)
{
  tree field, type, t;

  type = TREE_TYPE (desc);
  gcc_assert (GFC_DESCRIPTOR_TYPE_P (type));

  field = TYPE_FIELDS (type);
  gcc_assert (DATA_FIELD == 0);

  t = build3 (COMPONENT_REF, TREE_TYPE (field), desc, field, NULL_TREE);
  t = fold_convert (GFC_TYPE_ARRAY_DATAPTR_TYPE (type), t);

  return t;
}

/* This provides WRITE access to the data field.  */

void
gfc_conv_descriptor_data_set (stmtblock_t *block, tree desc, tree value)
{
  tree field, type, t;

  type = TREE_TYPE (desc);
  gcc_assert (GFC_DESCRIPTOR_TYPE_P (type));

  field = TYPE_FIELDS (type);
  gcc_assert (DATA_FIELD == 0);

  t = build3 (COMPONENT_REF, TREE_TYPE (field), desc, field, NULL_TREE);
  gfc_add_modify_expr (block, t, fold_convert (TREE_TYPE (field), value));
}


/* This provides address access to the data field.  This should only be
   used by array allocation, passing this on to the runtime.  */

tree
gfc_conv_descriptor_data_addr (tree desc)
{
  tree field, type, t;

  type = TREE_TYPE (desc);
  gcc_assert (GFC_DESCRIPTOR_TYPE_P (type));

  field = TYPE_FIELDS (type);
  gcc_assert (DATA_FIELD == 0);

  t = build3 (COMPONENT_REF, TREE_TYPE (field), desc, field, NULL_TREE);
  return build_fold_addr_expr (t);
}

tree
gfc_conv_descriptor_offset (tree desc)
{
  tree type;
  tree field;

  type = TREE_TYPE (desc);
  gcc_assert (GFC_DESCRIPTOR_TYPE_P (type));

  field = gfc_advance_chain (TYPE_FIELDS (type), OFFSET_FIELD);
  gcc_assert (field != NULL_TREE && TREE_TYPE (field) == gfc_array_index_type);

  return build3 (COMPONENT_REF, TREE_TYPE (field), desc, field, NULL_TREE);
}

tree
gfc_conv_descriptor_dtype (tree desc)
{
  tree field;
  tree type;

  type = TREE_TYPE (desc);
  gcc_assert (GFC_DESCRIPTOR_TYPE_P (type));

  field = gfc_advance_chain (TYPE_FIELDS (type), DTYPE_FIELD);
  gcc_assert (field != NULL_TREE && TREE_TYPE (field) == gfc_array_index_type);

  return build3 (COMPONENT_REF, TREE_TYPE (field), desc, field, NULL_TREE);
}

static tree
gfc_conv_descriptor_dimension (tree desc, tree dim)
{
  tree field;
  tree type;
  tree tmp;

  type = TREE_TYPE (desc);
  gcc_assert (GFC_DESCRIPTOR_TYPE_P (type));

  field = gfc_advance_chain (TYPE_FIELDS (type), DIMENSION_FIELD);
  gcc_assert (field != NULL_TREE
          && TREE_CODE (TREE_TYPE (field)) == ARRAY_TYPE
          && TREE_CODE (TREE_TYPE (TREE_TYPE (field))) == RECORD_TYPE);

  tmp = build3 (COMPONENT_REF, TREE_TYPE (field), desc, field, NULL_TREE);
  tmp = gfc_build_array_ref (tmp, dim);
  return tmp;
}

tree
gfc_conv_descriptor_stride (tree desc, tree dim)
{
  tree tmp;
  tree field;

  tmp = gfc_conv_descriptor_dimension (desc, dim);
  field = TYPE_FIELDS (TREE_TYPE (tmp));
  field = gfc_advance_chain (field, STRIDE_SUBFIELD);
  gcc_assert (field != NULL_TREE && TREE_TYPE (field) == gfc_array_index_type);

  tmp = build3 (COMPONENT_REF, TREE_TYPE (field), tmp, field, NULL_TREE);
  return tmp;
}

tree
gfc_conv_descriptor_lbound (tree desc, tree dim)
{
  tree tmp;
  tree field;

  tmp = gfc_conv_descriptor_dimension (desc, dim);
  field = TYPE_FIELDS (TREE_TYPE (tmp));
  field = gfc_advance_chain (field, LBOUND_SUBFIELD);
  gcc_assert (field != NULL_TREE && TREE_TYPE (field) == gfc_array_index_type);

  tmp = build3 (COMPONENT_REF, TREE_TYPE (field), tmp, field, NULL_TREE);
  return tmp;
}

tree
gfc_conv_descriptor_ubound (tree desc, tree dim)
{
  tree tmp;
  tree field;

  tmp = gfc_conv_descriptor_dimension (desc, dim);
  field = TYPE_FIELDS (TREE_TYPE (tmp));
  field = gfc_advance_chain (field, UBOUND_SUBFIELD);
  gcc_assert (field != NULL_TREE && TREE_TYPE (field) == gfc_array_index_type);

  tmp = build3 (COMPONENT_REF, TREE_TYPE (field), tmp, field, NULL_TREE);
  return tmp;
}


/* Build a null array descriptor constructor.  */

tree
gfc_build_null_descriptor (tree type)
{
  tree field;
  tree tmp;

  gcc_assert (GFC_DESCRIPTOR_TYPE_P (type));
  gcc_assert (DATA_FIELD == 0);
  field = TYPE_FIELDS (type);

  /* Set a NULL data pointer.  */
  tmp = build_constructor_single (type, field, null_pointer_node);
  TREE_CONSTANT (tmp) = 1;
  TREE_INVARIANT (tmp) = 1;
  /* All other fields are ignored.  */

  return tmp;
}


/* Cleanup those #defines.  */

#undef DATA_FIELD
#undef OFFSET_FIELD
#undef DTYPE_FIELD
#undef DIMENSION_FIELD
#undef STRIDE_SUBFIELD
#undef LBOUND_SUBFIELD
#undef UBOUND_SUBFIELD


/* Mark a SS chain as used.  Flags specifies in which loops the SS is used.
   flags & 1 = Main loop body.
   flags & 2 = temp copy loop.  */

void
gfc_mark_ss_chain_used (gfc_ss * ss, unsigned flags)
{
  for (; ss != gfc_ss_terminator; ss = ss->next)
    ss->useflags = flags;
}

static void gfc_free_ss (gfc_ss *);


/* Free a gfc_ss chain.  */

static void
gfc_free_ss_chain (gfc_ss * ss)
{
  gfc_ss *next;

  while (ss != gfc_ss_terminator)
    {
      gcc_assert (ss != NULL);
      next = ss->next;
      gfc_free_ss (ss);
      ss = next;
    }
}


/* Free a SS.  */

static void
gfc_free_ss (gfc_ss * ss)
{
  int n;

  switch (ss->type)
    {
    case GFC_SS_SECTION:
      for (n = 0; n < GFC_MAX_DIMENSIONS; n++)
        {
          if (ss->data.info.subscript[n])
            gfc_free_ss_chain (ss->data.info.subscript[n]);
        }
      break;

    default:
      break;
    }

  gfc_free (ss);
}


/* Free all the SS associated with a loop.  */

void
gfc_cleanup_loop (gfc_loopinfo * loop)
{
  gfc_ss *ss;
  gfc_ss *next;

  ss = loop->ss;
  while (ss != gfc_ss_terminator)
    {
      gcc_assert (ss != NULL);
      next = ss->loop_chain;
      gfc_free_ss (ss);
      ss = next;
    }
}


/* Associate a SS chain with a loop.  */

void
gfc_add_ss_to_loop (gfc_loopinfo * loop, gfc_ss * head)
{
  gfc_ss *ss;

  if (head == gfc_ss_terminator)
    return;

  ss = head;
  for (; ss && ss != gfc_ss_terminator; ss = ss->next)
    {
      if (ss->next == gfc_ss_terminator)
        ss->loop_chain = loop->ss;
      else
        ss->loop_chain = ss->next;
    }
  gcc_assert (ss == gfc_ss_terminator);
  loop->ss = head;
}


/* Generate an initializer for a static pointer or allocatable array.  */

void
gfc_trans_static_array_pointer (gfc_symbol * sym)
{
  tree type;

  gcc_assert (TREE_STATIC (sym->backend_decl));
  /* Just zero the data member.  */
  type = TREE_TYPE (sym->backend_decl);
  DECL_INITIAL (sym->backend_decl) = gfc_build_null_descriptor (type);
}


/* If the bounds of SE's loop have not yet been set, see if they can be
   determined from array spec AS, which is the array spec of a called
   function.  MAPPING maps the callee's dummy arguments to the values
   that the caller is passing.  Add any initialization and finalization
   code to SE.  */

void
gfc_set_loop_bounds_from_array_spec (gfc_interface_mapping * mapping,
                                     gfc_se * se, gfc_array_spec * as)
{
  int n, dim;
  gfc_se tmpse;
  tree lower;
  tree upper;
  tree tmp;

  if (as && as->type == AS_EXPLICIT)
    for (dim = 0; dim < se->loop->dimen; dim++)
      {
        n = se->loop->order[dim];
        if (se->loop->to[n] == NULL_TREE)
          {
            /* Evaluate the lower bound.  */
            gfc_init_se (&tmpse, NULL);
            gfc_apply_interface_mapping (mapping, &tmpse, as->lower[dim]);
            gfc_add_block_to_block (&se->pre, &tmpse.pre);
            gfc_add_block_to_block (&se->post, &tmpse.post);
            lower = tmpse.expr;

            /* ...and the upper bound.  */
            gfc_init_se (&tmpse, NULL);
            gfc_apply_interface_mapping (mapping, &tmpse, as->upper[dim]);
            gfc_add_block_to_block (&se->pre, &tmpse.pre);
            gfc_add_block_to_block (&se->post, &tmpse.post);
            upper = tmpse.expr;

            /* Set the upper bound of the loop to UPPER - LOWER.  */
            tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type, upper, lower);
            tmp = gfc_evaluate_now (tmp, &se->pre);
            se->loop->to[n] = tmp;
          }
      }
}


/* Generate code to allocate an array temporary, or create a variable to
   hold the data.  If size is NULL, zero the descriptor so that the
   callee will allocate the array.  If DEALLOC is true, also generate code to
   free the array afterwards.

   Initialization code is added to PRE and finalization code to POST.
   DYNAMIC is true if the caller may want to extend the array later
   using realloc.  This prevents us from putting the array on the stack.  */

static void
gfc_trans_allocate_array_storage (stmtblock_t * pre, stmtblock_t * post,
                                  gfc_ss_info * info, tree size, tree nelem,
                                  bool dynamic, bool dealloc)
{
  tree tmp;
  tree args;
  tree desc;
  bool onstack;

  desc = info->descriptor;
  info->offset = gfc_index_zero_node;
  if (size == NULL_TREE || integer_zerop (size))
    {
      /* A callee allocated array.  */
      gfc_conv_descriptor_data_set (pre, desc, null_pointer_node);
      onstack = FALSE;
    }
  else
    {
      /* Allocate the temporary.  */
      onstack = !dynamic && gfc_can_put_var_on_stack (size);

      if (onstack)
        {
          /* Make a temporary variable to hold the data.  */
          tmp = fold_build2 (MINUS_EXPR, TREE_TYPE (nelem), nelem,
                             integer_one_node);
          tmp = build_range_type (gfc_array_index_type, gfc_index_zero_node,
                                  tmp);
          tmp = build_array_type (gfc_get_element_type (TREE_TYPE (desc)),
                                  tmp);
          tmp = gfc_create_var (tmp, "A");
          tmp = build_fold_addr_expr (tmp);
          gfc_conv_descriptor_data_set (pre, desc, tmp);
        }
      else
        {
          /* Allocate memory to hold the data.  */
          args = gfc_chainon_list (NULL_TREE, size);

          if (gfc_index_integer_kind == 4)
            tmp = gfor_fndecl_internal_malloc;
          else if (gfc_index_integer_kind == 8)
            tmp = gfor_fndecl_internal_malloc64;
          else
            gcc_unreachable ();
          tmp = build_function_call_expr (tmp, args);
          tmp = gfc_evaluate_now (tmp, pre);
          gfc_conv_descriptor_data_set (pre, desc, tmp);
        }
    }
  info->data = gfc_conv_descriptor_data_get (desc);

  /* The offset is zero because we create temporaries with a zero
     lower bound.  */
  tmp = gfc_conv_descriptor_offset (desc);
  gfc_add_modify_expr (pre, tmp, gfc_index_zero_node);

  if (dealloc && !onstack)
    {
      /* Free the temporary.  */
      tmp = gfc_conv_descriptor_data_get (desc);
      tmp = fold_convert (pvoid_type_node, tmp);
      tmp = gfc_chainon_list (NULL_TREE, tmp);
      tmp = build_function_call_expr (gfor_fndecl_internal_free, tmp);
      gfc_add_expr_to_block (post, tmp);
    }
}


/* Generate code to create and initialize the descriptor for a temporary
   array.  This is used for both temporaries needed by the scalarizer, and
   functions returning arrays.  Adjusts the loop variables to be
   zero-based, and calculates the loop bounds for callee allocated arrays.
   Allocate the array unless it's callee allocated (we have a callee
   allocated array if 'callee_alloc' is true, or if loop->to[n] is
   NULL_TREE for any n).  Also fills in the descriptor, data and offset
   fields of info if known.  Returns the size of the array, or NULL for a
   callee allocated array.

   PRE, POST, DYNAMIC and DEALLOC are as for gfc_trans_allocate_array_storage.
 */

tree
gfc_trans_create_temp_array (stmtblock_t * pre, stmtblock_t * post,
                             gfc_loopinfo * loop, gfc_ss_info * info,
                             tree eltype, bool dynamic, bool dealloc,
                             bool callee_alloc)
{
  tree type;
  tree desc;
  tree tmp;
  tree size;
  tree nelem;
  int n;
  int dim;

  gcc_assert (info->dimen > 0);
  /* Set the lower bound to zero.  */
  for (dim = 0; dim < info->dimen; dim++)
    {
      n = loop->order[dim];
      if (n < loop->temp_dim)
        gcc_assert (integer_zerop (loop->from[n]));
      else
        {
          /* Callee allocated arrays may not have a known bound yet.  */
          if (loop->to[n])
              loop->to[n] = fold_build2 (MINUS_EXPR, gfc_array_index_type,
                                         loop->to[n], loop->from[n]);
          loop->from[n] = gfc_index_zero_node;
        }

      info->delta[dim] = gfc_index_zero_node;
      info->start[dim] = gfc_index_zero_node;
      info->stride[dim] = gfc_index_one_node;
      info->dim[dim] = dim;
    }

  /* Initialize the descriptor.  */
  type =
    gfc_get_array_type_bounds (eltype, info->dimen, loop->from, loop->to, 1);
  desc = gfc_create_var (type, "atmp");
  GFC_DECL_PACKED_ARRAY (desc) = 1;

  info->descriptor = desc;
  size = gfc_index_one_node;

  /* Fill in the array dtype.  */
  tmp = gfc_conv_descriptor_dtype (desc);
  gfc_add_modify_expr (pre, tmp, gfc_get_dtype (TREE_TYPE (desc)));

  /*
     Fill in the bounds and stride.  This is a packed array, so:

     size = 1;
     for (n = 0; n < rank; n++)
       {
         stride[n] = size
         delta = ubound[n] + 1 - lbound[n];
         size = size * delta;
       }
     size = size * sizeof(element);
  */

  for (n = 0; n < info->dimen; n++)
    {
      if (loop->to[n] == NULL_TREE)
        {
          /* For a callee allocated array express the loop bounds in terms
             of the descriptor fields.  */
          tmp = build2 (MINUS_EXPR, gfc_array_index_type,
                        gfc_conv_descriptor_ubound (desc, gfc_rank_cst[n]),
                        gfc_conv_descriptor_lbound (desc, gfc_rank_cst[n]));
          loop->to[n] = tmp;
          size = NULL_TREE;
          continue;
        }
        
      /* Store the stride and bound components in the descriptor.  */
      tmp = gfc_conv_descriptor_stride (desc, gfc_rank_cst[n]);
      gfc_add_modify_expr (pre, tmp, size);

      tmp = gfc_conv_descriptor_lbound (desc, gfc_rank_cst[n]);
      gfc_add_modify_expr (pre, tmp, gfc_index_zero_node);

      tmp = gfc_conv_descriptor_ubound (desc, gfc_rank_cst[n]);
      gfc_add_modify_expr (pre, tmp, loop->to[n]);

      tmp = fold_build2 (PLUS_EXPR, gfc_array_index_type,
                         loop->to[n], gfc_index_one_node);

      size = fold_build2 (MULT_EXPR, gfc_array_index_type, size, tmp);
      size = gfc_evaluate_now (size, pre);
    }

  /* Get the size of the array.  */
  nelem = size;
  if (size && !callee_alloc)
    size = fold_build2 (MULT_EXPR, gfc_array_index_type, size,
                        TYPE_SIZE_UNIT (gfc_get_element_type (type)));
  else
    size = NULL_TREE;

  gfc_trans_allocate_array_storage (pre, post, info, size, nelem, dynamic,
                                    dealloc);

  if (info->dimen > loop->temp_dim)
    loop->temp_dim = info->dimen;

  return size;
}


/* Generate code to transpose array EXPR by creating a new descriptor
   in which the dimension specifications have been reversed.  */

void
gfc_conv_array_transpose (gfc_se * se, gfc_expr * expr)
{
  tree dest, src, dest_index, src_index;
  gfc_loopinfo *loop;
  gfc_ss_info *dest_info, *src_info;
  gfc_ss *dest_ss, *src_ss;
  gfc_se src_se;
  int n;

  loop = se->loop;

  src_ss = gfc_walk_expr (expr);
  dest_ss = se->ss;

  src_info = &src_ss->data.info;
  dest_info = &dest_ss->data.info;

  /* Get a descriptor for EXPR.  */
  gfc_init_se (&src_se, NULL);
  gfc_conv_expr_descriptor (&src_se, expr, src_ss);
  gfc_add_block_to_block (&se->pre, &src_se.pre);
  gfc_add_block_to_block (&se->post, &src_se.post);
  src = src_se.expr;

  /* Allocate a new descriptor for the return value.  */
  dest = gfc_create_var (TREE_TYPE (src), "atmp");
  dest_info->descriptor = dest;
  se->expr = dest;

  /* Copy across the dtype field.  */
  gfc_add_modify_expr (&se->pre,
                       gfc_conv_descriptor_dtype (dest),
                       gfc_conv_descriptor_dtype (src));

  /* Copy the dimension information, renumbering dimension 1 to 0 and
     0 to 1.  */
  gcc_assert (dest_info->dimen == 2);
  gcc_assert (src_info->dimen == 2);
  for (n = 0; n < 2; n++)
    {
      dest_info->delta[n] = integer_zero_node;
      dest_info->start[n] = integer_zero_node;
      dest_info->stride[n] = integer_one_node;
      dest_info->dim[n] = n;

      dest_index = gfc_rank_cst[n];
      src_index = gfc_rank_cst[1 - n];

      gfc_add_modify_expr (&se->pre,
                           gfc_conv_descriptor_stride (dest, dest_index),
                           gfc_conv_descriptor_stride (src, src_index));

      gfc_add_modify_expr (&se->pre,
                           gfc_conv_descriptor_lbound (dest, dest_index),
                           gfc_conv_descriptor_lbound (src, src_index));

      gfc_add_modify_expr (&se->pre,
                           gfc_conv_descriptor_ubound (dest, dest_index),
                           gfc_conv_descriptor_ubound (src, src_index));

      if (!loop->to[n])
        {
          gcc_assert (integer_zerop (loop->from[n]));
          loop->to[n] = build2 (MINUS_EXPR, gfc_array_index_type,
                                gfc_conv_descriptor_ubound (dest, dest_index),
                                gfc_conv_descriptor_lbound (dest, dest_index));
        }
    }

  /* Copy the data pointer.  */
  dest_info->data = gfc_conv_descriptor_data_get (src);
  gfc_conv_descriptor_data_set (&se->pre, dest, dest_info->data);

  /* Copy the offset.  This is not changed by transposition: the top-left
     element is still at the same offset as before.  */
  dest_info->offset = gfc_conv_descriptor_offset (src);
  gfc_add_modify_expr (&se->pre,
                       gfc_conv_descriptor_offset (dest),
                       dest_info->offset);

  if (dest_info->dimen > loop->temp_dim)
    loop->temp_dim = dest_info->dimen;
}


/* Return the number of iterations in a loop that starts at START,
   ends at END, and has step STEP.  */

static tree
gfc_get_iteration_count (tree start, tree end, tree step)
{
  tree tmp;
  tree type;

  type = TREE_TYPE (step);
  tmp = fold_build2 (MINUS_EXPR, type, end, start);
  tmp = fold_build2 (FLOOR_DIV_EXPR, type, tmp, step);
  tmp = fold_build2 (PLUS_EXPR, type, tmp, build_int_cst (type, 1));
  tmp = fold_build2 (MAX_EXPR, type, tmp, build_int_cst (type, 0));
  return fold_convert (gfc_array_index_type, tmp);
}


/* Extend the data in array DESC by EXTRA elements.  */

static void
gfc_grow_array (stmtblock_t * pblock, tree desc, tree extra)
{
  tree args;
  tree tmp;
  tree size;
  tree ubound;

  if (integer_zerop (extra))
    return;

  ubound = gfc_conv_descriptor_ubound (desc, gfc_rank_cst[0]);

  /* Add EXTRA to the upper bound.  */
  tmp = build2 (PLUS_EXPR, gfc_array_index_type, ubound, extra);
  gfc_add_modify_expr (pblock, ubound, tmp);

  /* Get the value of the current data pointer.  */
  tmp = gfc_conv_descriptor_data_get (desc);
  args = gfc_chainon_list (NULL_TREE, tmp);

  /* Calculate the new array size.  */
  size = TYPE_SIZE_UNIT (gfc_get_element_type (TREE_TYPE (desc)));
  tmp = build2 (PLUS_EXPR, gfc_array_index_type, ubound, gfc_index_one_node);
  tmp = build2 (MULT_EXPR, gfc_array_index_type, tmp, size);
  args = gfc_chainon_list (args, tmp);

  /* Pick the appropriate realloc function.  */
  if (gfc_index_integer_kind == 4)
    tmp = gfor_fndecl_internal_realloc;
  else if (gfc_index_integer_kind == 8)
    tmp = gfor_fndecl_internal_realloc64;
  else
    gcc_unreachable ();

  /* Set the new data pointer.  */
  tmp = build_function_call_expr (tmp, args);
  gfc_conv_descriptor_data_set (pblock, desc, tmp);
}


/* Return true if the bounds of iterator I can only be determined
   at run time.  */

static inline bool
gfc_iterator_has_dynamic_bounds (gfc_iterator * i)
{
  return (i->start->expr_type != EXPR_CONSTANT
          || i->end->expr_type != EXPR_CONSTANT
          || i->step->expr_type != EXPR_CONSTANT);
}


/* Split the size of constructor element EXPR into the sum of two terms,
   one of which can be determined at compile time and one of which must
   be calculated at run time.  Set *SIZE to the former and return true
   if the latter might be nonzero.  */

static bool
gfc_get_array_constructor_element_size (mpz_t * size, gfc_expr * expr)
{
  if (expr->expr_type == EXPR_ARRAY)
    return gfc_get_array_constructor_size (size, expr->value.constructor);
  else if (expr->rank > 0)
    {
      /* Calculate everything at run time.  */
      mpz_set_ui (*size, 0);
      return true;
    }
  else
    {
      /* A single element.  */
      mpz_set_ui (*size, 1);
      return false;
    }
}


/* Like gfc_get_array_constructor_element_size, but applied to the whole
   of array constructor C.  */

static bool
gfc_get_array_constructor_size (mpz_t * size, gfc_constructor * c)
{
  gfc_iterator *i;
  mpz_t val;
  mpz_t len;
  bool dynamic;

  mpz_set_ui (*size, 0);
  mpz_init (len);
  mpz_init (val);

  dynamic = false;
  for (; c; c = c->next)
    {
      i = c->iterator;
      if (i && gfc_iterator_has_dynamic_bounds (i))
        dynamic = true;
      else
        {
          dynamic |= gfc_get_array_constructor_element_size (&len, c->expr);
          if (i)
            {
              /* Multiply the static part of the element size by the
                 number of iterations.  */
              mpz_sub (val, i->end->value.integer, i->start->value.integer);
              mpz_fdiv_q (val, val, i->step->value.integer);
              mpz_add_ui (val, val, 1);
              if (mpz_sgn (val) > 0)
                mpz_mul (len, len, val);
              else
                mpz_set_ui (len, 0);
            }
          mpz_add (*size, *size, len);
        }
    }
  mpz_clear (len);
  mpz_clear (val);
  return dynamic;
}


/* Make sure offset is a variable.  */

static void
gfc_put_offset_into_var (stmtblock_t * pblock, tree * poffset,
                         tree * offsetvar)
{
  /* We should have already created the offset variable.  We cannot
     create it here because we may be in an inner scope.  */
  gcc_assert (*offsetvar != NULL_TREE);
  gfc_add_modify_expr (pblock, *offsetvar, *poffset);
  *poffset = *offsetvar;
  TREE_USED (*offsetvar) = 1;
}


/* Assign an element of an array constructor.  */

static void
gfc_trans_array_ctor_element (stmtblock_t * pblock, tree desc,
                              tree offset, gfc_se * se, gfc_expr * expr)
{
  tree tmp;
  tree args;

  gfc_conv_expr (se, expr);

  /* Store the value.  */
  tmp = build_fold_indirect_ref (gfc_conv_descriptor_data_get (desc));
  tmp = gfc_build_array_ref (tmp, offset);
  if (expr->ts.type == BT_CHARACTER)
    {
      gfc_conv_string_parameter (se);
      if (POINTER_TYPE_P (TREE_TYPE (tmp)))
        {
          /* The temporary is an array of pointers.  */
          se->expr = fold_convert (TREE_TYPE (tmp), se->expr);
          gfc_add_modify_expr (&se->pre, tmp, se->expr);
        }
      else
        {
          /* The temporary is an array of string values.  */
          tmp = gfc_build_addr_expr (pchar_type_node, tmp);
          /* We know the temporary and the value will be the same length,
             so can use memcpy.  */
          args = gfc_chainon_list (NULL_TREE, tmp);
          args = gfc_chainon_list (args, se->expr);
          args = gfc_chainon_list (args, se->string_length);
          tmp = built_in_decls[BUILT_IN_MEMCPY];
          tmp = build_function_call_expr (tmp, args);
          gfc_add_expr_to_block (&se->pre, tmp);
        }
    }
  else
    {
      /* TODO: Should the frontend already have done this conversion?  */
      se->expr = fold_convert (TREE_TYPE (tmp), se->expr);
      gfc_add_modify_expr (&se->pre, tmp, se->expr);
    }

  gfc_add_block_to_block (pblock, &se->pre);
  gfc_add_block_to_block (pblock, &se->post);
}


/* Add the contents of an array to the constructor.  DYNAMIC is as for
   gfc_trans_array_constructor_value.  */

static void
gfc_trans_array_constructor_subarray (stmtblock_t * pblock,
                                      tree type ATTRIBUTE_UNUSED,
                                      tree desc, gfc_expr * expr,
                                      tree * poffset, tree * offsetvar,
                                      bool dynamic)
{
  gfc_se se;
  gfc_ss *ss;
  gfc_loopinfo loop;
  stmtblock_t body;
  tree tmp;
  tree size;
  int n;

  /* We need this to be a variable so we can increment it.  */
  gfc_put_offset_into_var (pblock, poffset, offsetvar);

  gfc_init_se (&se, NULL);

  /* Walk the array expression.  */
  ss = gfc_walk_expr (expr);
  gcc_assert (ss != gfc_ss_terminator);

  /* Initialize the scalarizer.  */
  gfc_init_loopinfo (&loop);
  gfc_add_ss_to_loop (&loop, ss);

  /* Initialize the loop.  */
  gfc_conv_ss_startstride (&loop);
  gfc_conv_loop_setup (&loop);

  /* Make sure the constructed array has room for the new data.  */
  if (dynamic)
    {
      /* Set SIZE to the total number of elements in the subarray.  */
      size = gfc_index_one_node;
      for (n = 0; n < loop.dimen; n++)
        {
          tmp = gfc_get_iteration_count (loop.from[n], loop.to[n],
                                         gfc_index_one_node);
          size = fold_build2 (MULT_EXPR, gfc_array_index_type, size, tmp);
        }

      /* Grow the constructed array by SIZE elements.  */
      gfc_grow_array (&loop.pre, desc, size);
    }

  /* Make the loop body.  */
  gfc_mark_ss_chain_used (ss, 1);
  gfc_start_scalarized_body (&loop, &body);
  gfc_copy_loopinfo_to_se (&se, &loop);
  se.ss = ss;

  if (expr->ts.type == BT_CHARACTER)
    gfc_todo_error ("character arrays in constructors");

  gfc_trans_array_ctor_element (&body, desc, *poffset, &se, expr);
  gcc_assert (se.ss == gfc_ss_terminator);

  /* Increment the offset.  */
  tmp = build2 (PLUS_EXPR, gfc_array_index_type, *poffset, gfc_index_one_node);
  gfc_add_modify_expr (&body, *poffset, tmp);

  /* Finish the loop.  */
  gfc_trans_scalarizing_loops (&loop, &body);
  gfc_add_block_to_block (&loop.pre, &loop.post);
  tmp = gfc_finish_block (&loop.pre);
  gfc_add_expr_to_block (pblock, tmp);

  gfc_cleanup_loop (&loop);
}


/* Assign the values to the elements of an array constructor.  DYNAMIC
   is true if descriptor DESC only contains enough data for the static
   size calculated by gfc_get_array_constructor_size.  When true, memory
   for the dynamic parts must be allocated using realloc.  */

static void
gfc_trans_array_constructor_value (stmtblock_t * pblock, tree type,
                                   tree desc, gfc_constructor * c,
                                   tree * poffset, tree * offsetvar,
                                   bool dynamic)
{
  tree tmp;
  stmtblock_t body;
  gfc_se se;
  mpz_t size;

  mpz_init (size);
  for (; c; c = c->next)
    {
      /* If this is an iterator or an array, the offset must be a variable.  */
      if ((c->iterator || c->expr->rank > 0) && INTEGER_CST_P (*poffset))
        gfc_put_offset_into_var (pblock, poffset, offsetvar);

      gfc_start_block (&body);

      if (c->expr->expr_type == EXPR_ARRAY)
        {
          /* Array constructors can be nested.  */
          gfc_trans_array_constructor_value (&body, type, desc,
                                             c->expr->value.constructor,
                                             poffset, offsetvar, dynamic);
        }
      else if (c->expr->rank > 0)
        {
          gfc_trans_array_constructor_subarray (&body, type, desc, c->expr,
                                                poffset, offsetvar, dynamic);
        }
      else
        {
          /* This code really upsets the gimplifier so don't bother for now.  */
          gfc_constructor *p;
          HOST_WIDE_INT n;
          HOST_WIDE_INT size;

          p = c;
          n = 0;
          while (p && !(p->iterator || p->expr->expr_type != EXPR_CONSTANT))
            {
              p = p->next;
              n++;
            }
          if (n < 4)
            {
              /* Scalar values.  */
              gfc_init_se (&se, NULL);
              gfc_trans_array_ctor_element (&body, desc, *poffset,
                                            &se, c->expr);

              *poffset = fold_build2 (PLUS_EXPR, gfc_array_index_type,
                                      *poffset, gfc_index_one_node);
            }
          else
            {
              /* Collect multiple scalar constants into a constructor.  */
              tree list;
              tree init;
              tree bound;
              tree tmptype;

              p = c;
              list = NULL_TREE;
              /* Count the number of consecutive scalar constants.  */
              while (p && !(p->iterator
                            || p->expr->expr_type != EXPR_CONSTANT))
                {
                  gfc_init_se (&se, NULL);
                  gfc_conv_constant (&se, p->expr);
                  if (p->expr->ts.type == BT_CHARACTER
                      && POINTER_TYPE_P (type))
                    {
                      /* For constant character array constructors we build
                         an array of pointers.  */
                      se.expr = gfc_build_addr_expr (pchar_type_node,
                                                     se.expr);
                    }
                    
                  list = tree_cons (NULL_TREE, se.expr, list);
                  c = p;
                  p = p->next;
                }

              bound = build_int_cst (NULL_TREE, n - 1);
              /* Create an array type to hold them.  */
              tmptype = build_range_type (gfc_array_index_type,
                                          gfc_index_zero_node, bound);
              tmptype = build_array_type (type, tmptype);

              init = build_constructor_from_list (tmptype, nreverse (list));
              TREE_CONSTANT (init) = 1;
              TREE_INVARIANT (init) = 1;
              TREE_STATIC (init) = 1;
              /* Create a static variable to hold the data.  */
              tmp = gfc_create_var (tmptype, "data");
              TREE_STATIC (tmp) = 1;
              TREE_CONSTANT (tmp) = 1;
              TREE_INVARIANT (tmp) = 1;
              DECL_INITIAL (tmp) = init;
              init = tmp;

              /* Use BUILTIN_MEMCPY to assign the values.  */
              tmp = gfc_conv_descriptor_data_get (desc);
              tmp = build_fold_indirect_ref (tmp);
              tmp = gfc_build_array_ref (tmp, *poffset);
              tmp = build_fold_addr_expr (tmp);
              init = build_fold_addr_expr (init);

              size = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (type));
              bound = build_int_cst (NULL_TREE, n * size);
              tmp = gfc_chainon_list (NULL_TREE, tmp);
              tmp = gfc_chainon_list (tmp, init);
              tmp = gfc_chainon_list (tmp, bound);
              tmp = build_function_call_expr (built_in_decls[BUILT_IN_MEMCPY],
                                             tmp);
              gfc_add_expr_to_block (&body, tmp);

              *poffset = fold_build2 (PLUS_EXPR, gfc_array_index_type,
                                      *poffset, build_int_cst (NULL_TREE, n));
            }
          if (!INTEGER_CST_P (*poffset))
            {
              gfc_add_modify_expr (&body, *offsetvar, *poffset);
              *poffset = *offsetvar;
            }
        }

      /* The frontend should already have done any expansions possible
         at compile-time.  */
      if (!c->iterator)
        {
          /* Pass the code as is.  */
          tmp = gfc_finish_block (&body);
          gfc_add_expr_to_block (pblock, tmp);
        }
      else
        {
          /* Build the implied do-loop.  */
          tree cond;
          tree end;
          tree step;
          tree loopvar;
          tree exit_label;
          tree loopbody;
          tree tmp2;

          loopbody = gfc_finish_block (&body);

          gfc_init_se (&se, NULL);
          gfc_conv_expr (&se, c->iterator->var);
          gfc_add_block_to_block (pblock, &se.pre);
          loopvar = se.expr;

          /* Initialize the loop.  */
          gfc_init_se (&se, NULL);
          gfc_conv_expr_val (&se, c->iterator->start);
          gfc_add_block_to_block (pblock, &se.pre);
          gfc_add_modify_expr (pblock, loopvar, se.expr);

          gfc_init_se (&se, NULL);
          gfc_conv_expr_val (&se, c->iterator->end);
          gfc_add_block_to_block (pblock, &se.pre);
          end = gfc_evaluate_now (se.expr, pblock);

          gfc_init_se (&se, NULL);
          gfc_conv_expr_val (&se, c->iterator->step);
          gfc_add_block_to_block (pblock, &se.pre);
          step = gfc_evaluate_now (se.expr, pblock);

          /* If this array expands dynamically, and the number of iterations
             is not constant, we won't have allocated space for the static
             part of C->EXPR's size.  Do that now.  */
          if (dynamic && gfc_iterator_has_dynamic_bounds (c->iterator))
            {
              /* Get the number of iterations.  */
              tmp = gfc_get_iteration_count (loopvar, end, step);

              /* Get the static part of C->EXPR's size.  */
              gfc_get_array_constructor_element_size (&size, c->expr);
              tmp2 = gfc_conv_mpz_to_tree (size, gfc_index_integer_kind);

              /* Grow the array by TMP * TMP2 elements.  */
              tmp = fold_build2 (MULT_EXPR, gfc_array_index_type, tmp, tmp2);
              gfc_grow_array (pblock, desc, tmp);
            }

          /* Generate the loop body.  */
          exit_label = gfc_build_label_decl (NULL_TREE);
          gfc_start_block (&body);

          /* Generate the exit condition.  Depending on the sign of
             the step variable we have to generate the correct
             comparison.  */
          tmp = fold_build2 (GT_EXPR, boolean_type_node, step, 
                             build_int_cst (TREE_TYPE (step), 0));
          cond = fold_build3 (COND_EXPR, boolean_type_node, tmp,
                              build2 (GT_EXPR, boolean_type_node,
                                      loopvar, end),
                              build2 (LT_EXPR, boolean_type_node,
                                      loopvar, end));
          tmp = build1_v (GOTO_EXPR, exit_label);
          TREE_USED (exit_label) = 1;
          tmp = build3_v (COND_EXPR, cond, tmp, build_empty_stmt ());
          gfc_add_expr_to_block (&body, tmp);

          /* The main loop body.  */
          gfc_add_expr_to_block (&body, loopbody);

          /* Increase loop variable by step.  */
          tmp = build2 (PLUS_EXPR, TREE_TYPE (loopvar), loopvar, step);
          gfc_add_modify_expr (&body, loopvar, tmp);

          /* Finish the loop.  */
          tmp = gfc_finish_block (&body);
          tmp = build1_v (LOOP_EXPR, tmp);
          gfc_add_expr_to_block (pblock, tmp);

          /* Add the exit label.  */
          tmp = build1_v (LABEL_EXPR, exit_label);
          gfc_add_expr_to_block (pblock, tmp);
        }
    }
  mpz_clear (size);
}


/* Figure out the string length of a variable reference expression.
   Used by get_array_ctor_strlen.  */

static void
get_array_ctor_var_strlen (gfc_expr * expr, tree * len)
{
  gfc_ref *ref;
  gfc_typespec *ts;

  /* Don't bother if we already know the length is a constant.  */
  if (*len && INTEGER_CST_P (*len))
    return;

  ts = &expr->symtree->n.sym->ts;
  for (ref = expr->ref; ref; ref = ref->next)
    {
      switch (ref->type)
        {
        case REF_ARRAY:
          /* Array references don't change the string length.  */
          break;

        case COMPONENT_REF:
          /* Use the length of the component.  */
          ts = &ref->u.c.component->ts;
          break;

        default:
          /* TODO: Substrings are tricky because we can't evaluate the
             expression more than once.  For now we just give up, and hope
             we can figure it out elsewhere.  */
          return;
        }
    }

  *len = ts->cl->backend_decl;
}


/* Figure out the string length of a character array constructor.
   Returns TRUE if all elements are character constants.  */

static bool
get_array_ctor_strlen (gfc_constructor * c, tree * len)
{
  bool is_const;
  
  is_const = TRUE;
  for (; c; c = c->next)
    {
      switch (c->expr->expr_type)
        {
        case EXPR_CONSTANT:
          if (!(*len && INTEGER_CST_P (*len)))
            *len = build_int_cstu (gfc_charlen_type_node,
                                   c->expr->value.character.length);
          break;

        case EXPR_ARRAY:
          if (!get_array_ctor_strlen (c->expr->value.constructor, len))
            is_const = FALSE;
          break;

        case EXPR_VARIABLE:
          is_const = false;
          get_array_ctor_var_strlen (c->expr, len);
          break;

        default:
          is_const = FALSE;
          /* TODO: For now we just ignore anything we don't know how to
             handle, and hope we can figure it out a different way.  */
          break;
        }
    }

  return is_const;
}


/* Array constructors are handled by constructing a temporary, then using that
   within the scalarization loop.  This is not optimal, but seems by far the
   simplest method.  */

static void
gfc_trans_array_constructor (gfc_loopinfo * loop, gfc_ss * ss)
{
  gfc_constructor *c;
  tree offset;
  tree offsetvar;
  tree desc;
  tree type;
  bool const_string;
  bool dynamic;

  ss->data.info.dimen = loop->dimen;

  c = ss->expr->value.constructor;
  if (ss->expr->ts.type == BT_CHARACTER)
    {
      const_string = get_array_ctor_strlen (c, &ss->string_length);
      if (!ss->string_length)
        gfc_todo_error ("complex character array constructors");

      type = gfc_get_character_type_len (ss->expr->ts.kind, ss->string_length);
      if (const_string)
        type = build_pointer_type (type);
    }
  else
    {
      const_string = TRUE;
      type = gfc_typenode_for_spec (&ss->expr->ts);
    }

  /* See if the constructor determines the loop bounds.  */
  dynamic = false;
  if (loop->to[0] == NULL_TREE)
    {
      mpz_t size;

      /* We should have a 1-dimensional, zero-based loop.  */
      gcc_assert (loop->dimen == 1);
      gcc_assert (integer_zerop (loop->from[0]));

      /* Split the constructor size into a static part and a dynamic part.
         Allocate the static size up-front and record whether the dynamic
         size might be nonzero.  */
      mpz_init (size);
      dynamic = gfc_get_array_constructor_size (&size, c);
      mpz_sub_ui (size, size, 1);
      loop->to[0] = gfc_conv_mpz_to_tree (size, gfc_index_integer_kind);
      mpz_clear (size);
    }

  gfc_trans_create_temp_array (&loop->pre, &loop->post, loop, &ss->data.info,
                               type, dynamic, true, false);

  desc = ss->data.info.descriptor;
  offset = gfc_index_zero_node;
  offsetvar = gfc_create_var_np (gfc_array_index_type, "offset");
  TREE_USED (offsetvar) = 0;
  gfc_trans_array_constructor_value (&loop->pre, type, desc, c,
                                     &offset, &offsetvar, dynamic);

  /* If the array grows dynamically, the upper bound of the loop variable
     is determined by the array's final upper bound.  */
  if (dynamic)
    loop->to[0] = gfc_conv_descriptor_ubound (desc, gfc_rank_cst[0]);

  if (TREE_USED (offsetvar))
    pushdecl (offsetvar);
  else
    gcc_assert (INTEGER_CST_P (offset));
#if 0
  /* Disable bound checking for now because it's probably broken.  */
  if (flag_bounds_check)
    {
      gcc_unreachable ();
    }
#endif
}


/* INFO describes a GFC_SS_SECTION in loop LOOP, and this function is
   called after evaluating all of INFO's vector dimensions.  Go through
   each such vector dimension and see if we can now fill in any missing
   loop bounds.  */

static void
gfc_set_vector_loop_bounds (gfc_loopinfo * loop, gfc_ss_info * info)
{
  gfc_se se;
  tree tmp;
  tree desc;
  tree zero;
  int n;
  int dim;

  for (n = 0; n < loop->dimen; n++)
    {
      dim = info->dim[n];
      if (info->ref->u.ar.dimen_type[dim] == DIMEN_VECTOR
          && loop->to[n] == NULL)
        {
          /* Loop variable N indexes vector dimension DIM, and we don't
             yet know the upper bound of loop variable N.  Set it to the
             difference between the vector's upper and lower bounds.  */
          gcc_assert (loop->from[n] == gfc_index_zero_node);
          gcc_assert (info->subscript[dim]
                      && info->subscript[dim]->type == GFC_SS_VECTOR);

          gfc_init_se (&se, NULL);
          desc = info->subscript[dim]->data.info.descriptor;
          zero = gfc_rank_cst[0];
          tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type,
                             gfc_conv_descriptor_ubound (desc, zero),
                             gfc_conv_descriptor_lbound (desc, zero));
          tmp = gfc_evaluate_now (tmp, &loop->pre);
          loop->to[n] = tmp;
        }
    }
}


/* Add the pre and post chains for all the scalar expressions in a SS chain
   to loop.  This is called after the loop parameters have been calculated,
   but before the actual scalarizing loops.  */

static void
gfc_add_loop_ss_code (gfc_loopinfo * loop, gfc_ss * ss, bool subscript)
{
  gfc_se se;
  int n;

  /* TODO: This can generate bad code if there are ordering dependencies.
     eg. a callee allocated function and an unknown size constructor.  */
  gcc_assert (ss != NULL);

  for (; ss != gfc_ss_terminator; ss = ss->loop_chain)
    {
      gcc_assert (ss);

      switch (ss->type)
        {
        case GFC_SS_SCALAR:
          /* Scalar expression.  Evaluate this now.  This includes elemental
             dimension indices, but not array section bounds.  */
          gfc_init_se (&se, NULL);
          gfc_conv_expr (&se, ss->expr);
          gfc_add_block_to_block (&loop->pre, &se.pre);

          if (ss->expr->ts.type != BT_CHARACTER)
            {
              /* Move the evaluation of scalar expressions outside the
                 scalarization loop.  */
              if (subscript)
                se.expr = convert(gfc_array_index_type, se.expr);
              se.expr = gfc_evaluate_now (se.expr, &loop->pre);
              gfc_add_block_to_block (&loop->pre, &se.post);
            }
          else
            gfc_add_block_to_block (&loop->post, &se.post);

          ss->data.scalar.expr = se.expr;
          ss->string_length = se.string_length;
          break;

        case GFC_SS_REFERENCE:
          /* Scalar reference.  Evaluate this now.  */
          gfc_init_se (&se, NULL);
          gfc_conv_expr_reference (&se, ss->expr);
          gfc_add_block_to_block (&loop->pre, &se.pre);
          gfc_add_block_to_block (&loop->post, &se.post);

          ss->data.scalar.expr = gfc_evaluate_now (se.expr, &loop->pre);
          ss->string_length = se.string_length;
          break;

        case GFC_SS_SECTION:
          /* Add the expressions for scalar and vector subscripts.  */
          for (n = 0; n < GFC_MAX_DIMENSIONS; n++)
            if (ss->data.info.subscript[n])
              gfc_add_loop_ss_code (loop, ss->data.info.subscript[n], true);

          gfc_set_vector_loop_bounds (loop, &ss->data.info);
          break;

        case GFC_SS_VECTOR:
          /* Get the vector's descriptor and store it in SS.  */
          gfc_init_se (&se, NULL);
          gfc_conv_expr_descriptor (&se, ss->expr, gfc_walk_expr (ss->expr));
          gfc_add_block_to_block (&loop->pre, &se.pre);
          gfc_add_block_to_block (&loop->post, &se.post);
          ss->data.info.descriptor = se.expr;
          break;

        case GFC_SS_INTRINSIC:
          gfc_add_intrinsic_ss_code (loop, ss);
          break;

        case GFC_SS_FUNCTION:
          /* Array function return value.  We call the function and save its
             result in a temporary for use inside the loop.  */
          gfc_init_se (&se, NULL);
          se.loop = loop;
          se.ss = ss;
          gfc_conv_expr (&se, ss->expr);
          gfc_add_block_to_block (&loop->pre, &se.pre);
          gfc_add_block_to_block (&loop->post, &se.post);
          ss->string_length = se.string_length;
          break;

        case GFC_SS_CONSTRUCTOR:
          gfc_trans_array_constructor (loop, ss);
          break;

        case GFC_SS_TEMP:
        case GFC_SS_COMPONENT:
          /* Do nothing.  These are handled elsewhere.  */
          break;

        default:
          gcc_unreachable ();
        }
    }
}


/* Translate expressions for the descriptor and data pointer of a SS.  */
/*GCC ARRAYS*/

static void
gfc_conv_ss_descriptor (stmtblock_t * block, gfc_ss * ss, int base)
{
  gfc_se se;
  tree tmp;

  /* Get the descriptor for the array to be scalarized.  */
  gcc_assert (ss->expr->expr_type == EXPR_VARIABLE);
  gfc_init_se (&se, NULL);
  se.descriptor_only = 1;
  gfc_conv_expr_lhs (&se, ss->expr);
  gfc_add_block_to_block (block, &se.pre);
  ss->data.info.descriptor = se.expr;
  ss->string_length = se.string_length;

  if (base)
    {
      /* Also the data pointer.  */
      tmp = gfc_conv_array_data (se.expr);
      /* If this is a variable or address of a variable we use it directly.
         Otherwise we must evaluate it now to avoid breaking dependency
         analysis by pulling the expressions for elemental array indices
         inside the loop.  */
      if (!(DECL_P (tmp)
            || (TREE_CODE (tmp) == ADDR_EXPR
                && DECL_P (TREE_OPERAND (tmp, 0)))))
        tmp = gfc_evaluate_now (tmp, block);
      ss->data.info.data = tmp;

      tmp = gfc_conv_array_offset (se.expr);
      ss->data.info.offset = gfc_evaluate_now (tmp, block);
    }
}


/* Initialize a gfc_loopinfo structure.  */

void
gfc_init_loopinfo (gfc_loopinfo * loop)
{
  int n;

  memset (loop, 0, sizeof (gfc_loopinfo));
  gfc_init_block (&loop->pre);
  gfc_init_block (&loop->post);

  /* Initially scalarize in order.  */
  for (n = 0; n < GFC_MAX_DIMENSIONS; n++)
    loop->order[n] = n;

  loop->ss = gfc_ss_terminator;
}


/* Copies the loop variable info to a gfc_se structure. Does not copy the SS
   chain.  */

void
gfc_copy_loopinfo_to_se (gfc_se * se, gfc_loopinfo * loop)
{
  se->loop = loop;
}


/* Return an expression for the data pointer of an array.  */

tree
gfc_conv_array_data (tree descriptor)
{
  tree type;

  type = TREE_TYPE (descriptor);
  if (GFC_ARRAY_TYPE_P (type))
    {
      if (TREE_CODE (type) == POINTER_TYPE)
        return descriptor;
      else
        {
          /* Descriptorless arrays.  */
          return build_fold_addr_expr (descriptor);
        }
    }
  else
    return gfc_conv_descriptor_data_get (descriptor);
}


/* Return an expression for the base offset of an array.  */

tree
gfc_conv_array_offset (tree descriptor)
{
  tree type;

  type = TREE_TYPE (descriptor);
  if (GFC_ARRAY_TYPE_P (type))
    return GFC_TYPE_ARRAY_OFFSET (type);
  else
    return gfc_conv_descriptor_offset (descriptor);
}


/* Get an expression for the array stride.  */

tree
gfc_conv_array_stride (tree descriptor, int dim)
{
  tree tmp;
  tree type;

  type = TREE_TYPE (descriptor);

  /* For descriptorless arrays use the array size.  */
  tmp = GFC_TYPE_ARRAY_STRIDE (type, dim);
  if (tmp != NULL_TREE)
    return tmp;

  tmp = gfc_conv_descriptor_stride (descriptor, gfc_rank_cst[dim]);
  return tmp;
}


/* Like gfc_conv_array_stride, but for the lower bound.  */

tree
gfc_conv_array_lbound (tree descriptor, int dim)
{
  tree tmp;
  tree type;

  type = TREE_TYPE (descriptor);

  tmp = GFC_TYPE_ARRAY_LBOUND (type, dim);
  if (tmp != NULL_TREE)
    return tmp;

  tmp = gfc_conv_descriptor_lbound (descriptor, gfc_rank_cst[dim]);
  return tmp;
}


/* Like gfc_conv_array_stride, but for the upper bound.  */

tree
gfc_conv_array_ubound (tree descriptor, int dim)
{
  tree tmp;
  tree type;

  type = TREE_TYPE (descriptor);

  tmp = GFC_TYPE_ARRAY_UBOUND (type, dim);
  if (tmp != NULL_TREE)
    return tmp;

  /* This should only ever happen when passing an assumed shape array
     as an actual parameter.  The value will never be used.  */
  if (GFC_ARRAY_TYPE_P (TREE_TYPE (descriptor)))
    return gfc_index_zero_node;

  tmp = gfc_conv_descriptor_ubound (descriptor, gfc_rank_cst[dim]);
  return tmp;
}


/* Generate code to perform an array index bound check.  */

static tree
gfc_trans_array_bound_check (gfc_se * se, tree descriptor, tree index, int n)
{
  tree cond;
  tree fault;
  tree tmp;

  if (!flag_bounds_check)
    return index;

  index = gfc_evaluate_now (index, &se->pre);
  /* Check lower bound.  */
  tmp = gfc_conv_array_lbound (descriptor, n);
  fault = fold_build2 (LT_EXPR, boolean_type_node, index, tmp);
  /* Check upper bound.  */
  tmp = gfc_conv_array_ubound (descriptor, n);
  cond = fold_build2 (GT_EXPR, boolean_type_node, index, tmp);
  fault = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, fault, cond);

  gfc_trans_runtime_check (fault, gfc_strconst_fault, &se->pre);

  return index;
}


/* Return the offset for an index.  Performs bound checking for elemental
   dimensions.  Single element references are processed separately.  */

static tree
gfc_conv_array_index_offset (gfc_se * se, gfc_ss_info * info, int dim, int i,
                             gfc_array_ref * ar, tree stride)
{
  tree index;
  tree desc;
  tree data;

  /* Get the index into the array for this dimension.  */
  if (ar)
    {
      gcc_assert (ar->type != AR_ELEMENT);
      switch (ar->dimen_type[dim])
        {
        case DIMEN_ELEMENT:
          gcc_assert (i == -1);
          /* Elemental dimension.  */
          gcc_assert (info->subscript[dim]
                      && info->subscript[dim]->type == GFC_SS_SCALAR);
          /* We've already translated this value outside the loop.  */
          index = info->subscript[dim]->data.scalar.expr;

          index =
            gfc_trans_array_bound_check (se, info->descriptor, index, dim);
          break;

        case DIMEN_VECTOR:
          gcc_assert (info && se->loop);
          gcc_assert (info->subscript[dim]
                      && info->subscript[dim]->type == GFC_SS_VECTOR);
          desc = info->subscript[dim]->data.info.descriptor;

          /* Get a zero-based index into the vector.  */
          index = fold_build2 (MINUS_EXPR, gfc_array_index_type,
                               se->loop->loopvar[i], se->loop->from[i]);

          /* Multiply the index by the stride.  */
          index = fold_build2 (MULT_EXPR, gfc_array_index_type,
                               index, gfc_conv_array_stride (desc, 0));

          /* Read the vector to get an index into info->descriptor.  */
          data = build_fold_indirect_ref (gfc_conv_array_data (desc));
          index = gfc_build_array_ref (data, index);
          index = gfc_evaluate_now (index, &se->pre);

          /* Do any bounds checking on the final info->descriptor index.  */
          index = gfc_trans_array_bound_check (se, info->descriptor,
                                               index, dim);
          break;

        case DIMEN_RANGE:
          /* Scalarized dimension.  */
          gcc_assert (info && se->loop);

          /* Multiply the loop variable by the stride and delta.  */
          index = se->loop->loopvar[i];
          index = fold_build2 (MULT_EXPR, gfc_array_index_type, index,
                               info->stride[i]);
          index = fold_build2 (PLUS_EXPR, gfc_array_index_type, index,
                               info->delta[i]);
          break;

        default:
          gcc_unreachable ();
        }
    }
  else
    {
      /* Temporary array or derived type component.  */
      gcc_assert (se->loop);
      index = se->loop->loopvar[se->loop->order[i]];
      if (!integer_zerop (info->delta[i]))
        index = fold_build2 (PLUS_EXPR, gfc_array_index_type,
                             index, info->delta[i]);
    }

  /* Multiply by the stride.  */
  index = fold_build2 (MULT_EXPR, gfc_array_index_type, index, stride);

  return index;
}


/* Build a scalarized reference to an array.  */

static void
gfc_conv_scalarized_array_ref (gfc_se * se, gfc_array_ref * ar)
{
  gfc_ss_info *info;
  tree index;
  tree tmp;
  int n;

  info = &se->ss->data.info;
  if (ar)
    n = se->loop->order[0];
  else
    n = 0;

  index = gfc_conv_array_index_offset (se, info, info->dim[n], n, ar,
                                       info->stride0);
  /* Add the offset for this dimension to the stored offset for all other
     dimensions.  */
  index = fold_build2 (PLUS_EXPR, gfc_array_index_type, index, info->offset);

  tmp = build_fold_indirect_ref (info->data);
  se->expr = gfc_build_array_ref (tmp, index);
}


/* Translate access of temporary array.  */

void
gfc_conv_tmp_array_ref (gfc_se * se)
{
  se->string_length = se->ss->string_length;
  gfc_conv_scalarized_array_ref (se, NULL);
}


/* Build an array reference.  se->expr already holds the array descriptor.
   This should be either a variable, indirect variable reference or component
   reference.  For arrays which do not have a descriptor, se->expr will be
   the data pointer.
   a(i, j, k) = base[offset + i * stride[0] + j * stride[1] + k * stride[2]]*/

void
gfc_conv_array_ref (gfc_se * se, gfc_array_ref * ar)
{
  int n;
  tree index;
  tree tmp;
  tree stride;
  tree fault;
  gfc_se indexse;

  /* Handle scalarized references separately.  */
  if (ar->type != AR_ELEMENT)
    {
      gfc_conv_scalarized_array_ref (se, ar);
      gfc_advance_se_ss_chain (se);
      return;
    }

  index = gfc_index_zero_node;

  fault = gfc_index_zero_node;

  /* Calculate the offsets from all the dimensions.  */
  for (n = 0; n < ar->dimen; n++)
    {
      /* Calculate the index for this dimension.  */
      gfc_init_se (&indexse, se);
      gfc_conv_expr_type (&indexse, ar->start[n], gfc_array_index_type);
      gfc_add_block_to_block (&se->pre, &indexse.pre);

      if (flag_bounds_check)
        {
          /* Check array bounds.  */
          tree cond;

          indexse.expr = gfc_evaluate_now (indexse.expr, &se->pre);

          tmp = gfc_conv_array_lbound (se->expr, n);
          cond = fold_build2 (LT_EXPR, boolean_type_node, 
                              indexse.expr, tmp);
          fault =
            fold_build2 (TRUTH_OR_EXPR, boolean_type_node, fault, cond);

          tmp = gfc_conv_array_ubound (se->expr, n);
          cond = fold_build2 (GT_EXPR, boolean_type_node, 
                              indexse.expr, tmp);
          fault =
            fold_build2 (TRUTH_OR_EXPR, boolean_type_node, fault, cond);
        }

      /* Multiply the index by the stride.  */
      stride = gfc_conv_array_stride (se->expr, n);
      tmp = fold_build2 (MULT_EXPR, gfc_array_index_type, indexse.expr,
                         stride);

      /* And add it to the total.  */
      index = fold_build2 (PLUS_EXPR, gfc_array_index_type, index, tmp);
    }

  if (flag_bounds_check)
    gfc_trans_runtime_check (fault, gfc_strconst_fault, &se->pre);

  tmp = gfc_conv_array_offset (se->expr);
  if (!integer_zerop (tmp))
    index = fold_build2 (PLUS_EXPR, gfc_array_index_type, index, tmp);
      
  /* Access the calculated element.  */
  tmp = gfc_conv_array_data (se->expr);
  tmp = build_fold_indirect_ref (tmp);
  se->expr = gfc_build_array_ref (tmp, index);
}


/* Generate the code to be executed immediately before entering a
   scalarization loop.  */

static void
gfc_trans_preloop_setup (gfc_loopinfo * loop, int dim, int flag,
                         stmtblock_t * pblock)
{
  tree index;
  tree stride;
  gfc_ss_info *info;
  gfc_ss *ss;
  gfc_se se;
  int i;

  /* This code will be executed before entering the scalarization loop
     for this dimension.  */
  for (ss = loop->ss; ss != gfc_ss_terminator; ss = ss->loop_chain)
    {
      if ((ss->useflags & flag) == 0)
        continue;

      if (ss->type != GFC_SS_SECTION
          && ss->type != GFC_SS_FUNCTION && ss->type != GFC_SS_CONSTRUCTOR
          && ss->type != GFC_SS_COMPONENT)
        continue;

      info = &ss->data.info;

      if (dim >= info->dimen)
        continue;

      if (dim == info->dimen - 1)
        {
          /* For the outermost loop calculate the offset due to any
             elemental dimensions.  It will have been initialized with the
             base offset of the array.  */
          if (info->ref)
            {
              for (i = 0; i < info->ref->u.ar.dimen; i++)
                {
                  if (info->ref->u.ar.dimen_type[i] != DIMEN_ELEMENT)
                    continue;

                  gfc_init_se (&se, NULL);
                  se.loop = loop;
                  se.expr = info->descriptor;
                  stride = gfc_conv_array_stride (info->descriptor, i);
                  index = gfc_conv_array_index_offset (&se, info, i, -1,
                                                       &info->ref->u.ar,
                                                       stride);
                  gfc_add_block_to_block (pblock, &se.pre);

                  info->offset = fold_build2 (PLUS_EXPR, gfc_array_index_type,
                                              info->offset, index);
                  info->offset = gfc_evaluate_now (info->offset, pblock);
                }

              i = loop->order[0];
              stride = gfc_conv_array_stride (info->descriptor, info->dim[i]);
            }
          else
            stride = gfc_conv_array_stride (info->descriptor, 0);

          /* Calculate the stride of the innermost loop.  Hopefully this will
             allow the backend optimizers to do their stuff more effectively.
           */
          info->stride0 = gfc_evaluate_now (stride, pblock);
        }
      else
        {
          /* Add the offset for the previous loop dimension.  */
          gfc_array_ref *ar;

          if (info->ref)
            {
              ar = &info->ref->u.ar;
              i = loop->order[dim + 1];
            }
          else
            {
              ar = NULL;
              i = dim + 1;
            }

          gfc_init_se (&se, NULL);
          se.loop = loop;
          se.expr = info->descriptor;
          stride = gfc_conv_array_stride (info->descriptor, info->dim[i]);
          index = gfc_conv_array_index_offset (&se, info, info->dim[i], i,
                                               ar, stride);
          gfc_add_block_to_block (pblock, &se.pre);
          info->offset = fold_build2 (PLUS_EXPR, gfc_array_index_type,
                                      info->offset, index);
          info->offset = gfc_evaluate_now (info->offset, pblock);
        }

      /* Remember this offset for the second loop.  */
      if (dim == loop->temp_dim - 1)
        info->saved_offset = info->offset;
    }
}


/* Start a scalarized expression.  Creates a scope and declares loop
   variables.  */

void
gfc_start_scalarized_body (gfc_loopinfo * loop, stmtblock_t * pbody)
{
  int dim;
  int n;
  int flags;

  gcc_assert (!loop->array_parameter);

  for (dim = loop->dimen - 1; dim >= 0; dim--)
    {
      n = loop->order[dim];

      gfc_start_block (&loop->code[n]);

      /* Create the loop variable.  */
      loop->loopvar[n] = gfc_create_var (gfc_array_index_type, "S");

      if (dim < loop->temp_dim)
        flags = 3;
      else
        flags = 1;
      /* Calculate values that will be constant within this loop.  */
      gfc_trans_preloop_setup (loop, dim, flags, &loop->code[n]);
    }
  gfc_start_block (pbody);
}


/* Generates the actual loop code for a scalarization loop.  */

static void
gfc_trans_scalarized_loop_end (gfc_loopinfo * loop, int n,
                               stmtblock_t * pbody)
{
  stmtblock_t block;
  tree cond;
  tree tmp;
  tree loopbody;
  tree exit_label;

  loopbody = gfc_finish_block (pbody);

  /* Initialize the loopvar.  */
  gfc_add_modify_expr (&loop->code[n], loop->loopvar[n], loop->from[n]);

  exit_label = gfc_build_label_decl (NULL_TREE);

  /* Generate the loop body.  */
  gfc_init_block (&block);

  /* The exit condition.  */
  cond = build2 (GT_EXPR, boolean_type_node, loop->loopvar[n], loop->to[n]);
  tmp = build1_v (GOTO_EXPR, exit_label);
  TREE_USED (exit_label) = 1;
  tmp = build3_v (COND_EXPR, cond, tmp, build_empty_stmt ());
  gfc_add_expr_to_block (&block, tmp);

  /* The main body.  */
  gfc_add_expr_to_block (&block, loopbody);

  /* Increment the loopvar.  */
  tmp = build2 (PLUS_EXPR, gfc_array_index_type,
                loop->loopvar[n], gfc_index_one_node);
  gfc_add_modify_expr (&block, loop->loopvar[n], tmp);

  /* Build the loop.  */
  tmp = gfc_finish_block (&block);
  tmp = build1_v (LOOP_EXPR, tmp);
  gfc_add_expr_to_block (&loop->code[n], tmp);

  /* Add the exit label.  */
  tmp = build1_v (LABEL_EXPR, exit_label);
  gfc_add_expr_to_block (&loop->code[n], tmp);
}


/* Finishes and generates the loops for a scalarized expression.  */

void
gfc_trans_scalarizing_loops (gfc_loopinfo * loop, stmtblock_t * body)
{
  int dim;
  int n;
  gfc_ss *ss;
  stmtblock_t *pblock;
  tree tmp;

  pblock = body;
  /* Generate the loops.  */
  for (dim = 0; dim < loop->dimen; dim++)
    {
      n = loop->order[dim];
      gfc_trans_scalarized_loop_end (loop, n, pblock);
      loop->loopvar[n] = NULL_TREE;
      pblock = &loop->code[n];
    }

  tmp = gfc_finish_block (pblock);
  gfc_add_expr_to_block (&loop->pre, tmp);

  /* Clear all the used flags.  */
  for (ss = loop->ss; ss; ss = ss->loop_chain)
    ss->useflags = 0;
}


/* Finish the main body of a scalarized expression, and start the secondary
   copying body.  */

void
gfc_trans_scalarized_loop_boundary (gfc_loopinfo * loop, stmtblock_t * body)
{
  int dim;
  int n;
  stmtblock_t *pblock;
  gfc_ss *ss;

  pblock = body;
  /* We finish as many loops as are used by the temporary.  */
  for (dim = 0; dim < loop->temp_dim - 1; dim++)
    {
      n = loop->order[dim];
      gfc_trans_scalarized_loop_end (loop, n, pblock);
      loop->loopvar[n] = NULL_TREE;
      pblock = &loop->code[n];
    }

  /* We don't want to finish the outermost loop entirely.  */
  n = loop->order[loop->temp_dim - 1];
  gfc_trans_scalarized_loop_end (loop, n, pblock);

  /* Restore the initial offsets.  */
  for (ss = loop->ss; ss != gfc_ss_terminator; ss = ss->loop_chain)
    {
      if ((ss->useflags & 2) == 0)
        continue;

      if (ss->type != GFC_SS_SECTION
          && ss->type != GFC_SS_FUNCTION && ss->type != GFC_SS_CONSTRUCTOR
          && ss->type != GFC_SS_COMPONENT)
        continue;

      ss->data.info.offset = ss->data.info.saved_offset;
    }

  /* Restart all the inner loops we just finished.  */
  for (dim = loop->temp_dim - 2; dim >= 0; dim--)
    {
      n = loop->order[dim];

      gfc_start_block (&loop->code[n]);

      loop->loopvar[n] = gfc_create_var (gfc_array_index_type, "Q");

      gfc_trans_preloop_setup (loop, dim, 2, &loop->code[n]);
    }

  /* Start a block for the secondary copying code.  */
  gfc_start_block (body);
}


/* Calculate the upper bound of an array section.  */

static tree
gfc_conv_section_upper_bound (gfc_ss * ss, int n, stmtblock_t * pblock)
{
  int dim;
  gfc_expr *end;
  tree desc;
  tree bound;
  gfc_se se;
  gfc_ss_info *info;

  gcc_assert (ss->type == GFC_SS_SECTION);

  info = &ss->data.info;
  dim = info->dim[n];

  if (info->ref->u.ar.dimen_type[dim] == DIMEN_VECTOR)
    /* We'll calculate the upper bound once we have access to the
       vector's descriptor.  */
    return NULL;

  gcc_assert (info->ref->u.ar.dimen_type[dim] == DIMEN_RANGE);
  desc = info->descriptor;
  end = info->ref->u.ar.end[dim];

  if (end)
    {
      /* The upper bound was specified.  */
      gfc_init_se (&se, NULL);
      gfc_conv_expr_type (&se, end, gfc_array_index_type);
      gfc_add_block_to_block (pblock, &se.pre);
      bound = se.expr;
    }
  else
    {
      /* No upper bound was specified, so use the bound of the array.  */
      bound = gfc_conv_array_ubound (desc, dim);
    }

  return bound;
}


/* Calculate the lower bound of an array section.  */

static void
gfc_conv_section_startstride (gfc_loopinfo * loop, gfc_ss * ss, int n)
{
  gfc_expr *start;
  gfc_expr *stride;
  tree desc;
  gfc_se se;
  gfc_ss_info *info;
  int dim;

  gcc_assert (ss->type == GFC_SS_SECTION);

  info = &ss->data.info;
  dim = info->dim[n];

  if (info->ref->u.ar.dimen_type[dim] == DIMEN_VECTOR)
    {
      /* We use a zero-based index to access the vector.  */
      info->start[n] = gfc_index_zero_node;
      info->stride[n] = gfc_index_one_node;
      return;
    }

  gcc_assert (info->ref->u.ar.dimen_type[dim] == DIMEN_RANGE);
  desc = info->descriptor;
  start = info->ref->u.ar.start[dim];
  stride = info->ref->u.ar.stride[dim];

  /* Calculate the start of the range.  For vector subscripts this will
     be the range of the vector.  */
  if (start)
    {
      /* Specified section start.  */
      gfc_init_se (&se, NULL);
      gfc_conv_expr_type (&se, start, gfc_array_index_type);
      gfc_add_block_to_block (&loop->pre, &se.pre);
      info->start[n] = se.expr;
    }
  else
    {
      /* No lower bound specified so use the bound of the array.  */
      info->start[n] = gfc_conv_array_lbound (desc, dim);
    }
  info->start[n] = gfc_evaluate_now (info->start[n], &loop->pre);

  /* Calculate the stride.  */
  if (stride == NULL)
    info->stride[n] = gfc_index_one_node;
  else
    {
      gfc_init_se (&se, NULL);
      gfc_conv_expr_type (&se, stride, gfc_array_index_type);
      gfc_add_block_to_block (&loop->pre, &se.pre);
      info->stride[n] = gfc_evaluate_now (se.expr, &loop->pre);
    }
}


/* Calculates the range start and stride for a SS chain.  Also gets the
   descriptor and data pointer.  The range of vector subscripts is the size
   of the vector.  Array bounds are also checked.  */

void
gfc_conv_ss_startstride (gfc_loopinfo * loop)
{
  int n;
  tree tmp;
  gfc_ss *ss;
  tree desc;

  loop->dimen = 0;
  /* Determine the rank of the loop.  */
  for (ss = loop->ss;
       ss != gfc_ss_terminator && loop->dimen == 0; ss = ss->loop_chain)
    {
      switch (ss->type)
        {
        case GFC_SS_SECTION:
        case GFC_SS_CONSTRUCTOR:
        case GFC_SS_FUNCTION:
        case GFC_SS_COMPONENT:
          loop->dimen = ss->data.info.dimen;
          break;

        default:
          break;
        }
    }

  if (loop->dimen == 0)
    gfc_todo_error ("Unable to determine rank of expression");


  /* Loop over all the SS in the chain.  */
  for (ss = loop->ss; ss != gfc_ss_terminator; ss = ss->loop_chain)
    {
      if (ss->expr && ss->expr->shape && !ss->shape)
        ss->shape = ss->expr->shape;

      switch (ss->type)
        {
        case GFC_SS_SECTION:
          /* Get the descriptor for the array.  */
          gfc_conv_ss_descriptor (&loop->pre, ss, !loop->array_parameter);

          for (n = 0; n < ss->data.info.dimen; n++)
            gfc_conv_section_startstride (loop, ss, n);
          break;

        case GFC_SS_CONSTRUCTOR:
        case GFC_SS_FUNCTION:
          for (n = 0; n < ss->data.info.dimen; n++)
            {
              ss->data.info.start[n] = gfc_index_zero_node;
              ss->data.info.stride[n] = gfc_index_one_node;
            }
          break;

        default:
          break;
        }
    }

  /* The rest is just runtime bound checking.  */
  if (flag_bounds_check)
    {
      stmtblock_t block;
      tree fault;
      tree bound;
      tree end;
      tree size[GFC_MAX_DIMENSIONS];
      gfc_ss_info *info;
      int dim;

      gfc_start_block (&block);

      fault = integer_zero_node;
      for (n = 0; n < loop->dimen; n++)
        size[n] = NULL_TREE;

      for (ss = loop->ss; ss != gfc_ss_terminator; ss = ss->loop_chain)
        {
          if (ss->type != GFC_SS_SECTION)
            continue;

          /* TODO: range checking for mapped dimensions.  */
          info = &ss->data.info;

          /* This code only checks ranges.  Elemental and vector
             dimensions are checked later.  */
          for (n = 0; n < loop->dimen; n++)
            {
              dim = info->dim[n];
              if (info->ref->u.ar.dimen_type[dim] != DIMEN_RANGE)
                continue;

              desc = ss->data.info.descriptor;

              /* Check lower bound.  */
              bound = gfc_conv_array_lbound (desc, dim);
              tmp = info->start[n];
              tmp = fold_build2 (LT_EXPR, boolean_type_node, tmp, bound);
              fault = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, fault,
                                   tmp);

              /* Check the upper bound.  */
              bound = gfc_conv_array_ubound (desc, dim);
              end = gfc_conv_section_upper_bound (ss, n, &block);
              tmp = fold_build2 (GT_EXPR, boolean_type_node, end, bound);
              fault = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, fault,
                                   tmp);

              /* Check the section sizes match.  */
              tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type, end,
                                 info->start[n]);
              tmp = fold_build2 (FLOOR_DIV_EXPR, gfc_array_index_type, tmp,
                                 info->stride[n]);
              /* We remember the size of the first section, and check all the
                 others against this.  */
              if (size[n])
                {
                  tmp =
                    fold_build2 (NE_EXPR, boolean_type_node, tmp, size[n]);
                  fault =
                    build2 (TRUTH_OR_EXPR, boolean_type_node, fault, tmp);
                }
              else
                size[n] = gfc_evaluate_now (tmp, &block);
            }
        }
      gfc_trans_runtime_check (fault, gfc_strconst_bounds, &block);

      tmp = gfc_finish_block (&block);
      gfc_add_expr_to_block (&loop->pre, tmp);
    }
}


/* Return true if the two SS could be aliased, i.e. both point to the same data
   object.  */
/* TODO: resolve aliases based on frontend expressions.  */

static int
gfc_could_be_alias (gfc_ss * lss, gfc_ss * rss)
{
  gfc_ref *lref;
  gfc_ref *rref;
  gfc_symbol *lsym;
  gfc_symbol *rsym;

  lsym = lss->expr->symtree->n.sym;
  rsym = rss->expr->symtree->n.sym;
  if (gfc_symbols_could_alias (lsym, rsym))
    return 1;

  if (rsym->ts.type != BT_DERIVED
      && lsym->ts.type != BT_DERIVED)
    return 0;

  /* For derived types we must check all the component types.  We can ignore
     array references as these will have the same base type as the previous
     component ref.  */
  for (lref = lss->expr->ref; lref != lss->data.info.ref; lref = lref->next)
    {
      if (lref->type != REF_COMPONENT)
        continue;

      if (gfc_symbols_could_alias (lref->u.c.sym, rsym))
        return 1;

      for (rref = rss->expr->ref; rref != rss->data.info.ref;
           rref = rref->next)
        {
          if (rref->type != REF_COMPONENT)
            continue;

          if (gfc_symbols_could_alias (lref->u.c.sym, rref->u.c.sym))
            return 1;
        }
    }

  for (rref = rss->expr->ref; rref != rss->data.info.ref; rref = rref->next)
    {
      if (rref->type != REF_COMPONENT)
        break;

      if (gfc_symbols_could_alias (rref->u.c.sym, lsym))
        return 1;
    }

  return 0;
}


/* Resolve array data dependencies.  Creates a temporary if required.  */
/* TODO: Calc dependencies with gfc_expr rather than gfc_ss, and move to
   dependency.c.  */

void
gfc_conv_resolve_dependencies (gfc_loopinfo * loop, gfc_ss * dest,
                               gfc_ss * rss)
{
  gfc_ss *ss;
  gfc_ref *lref;
  gfc_ref *rref;
  gfc_ref *aref;
  int nDepend = 0;
  int temp_dim = 0;

  loop->temp_ss = NULL;
  aref = dest->data.info.ref;
  temp_dim = 0;

  for (ss = rss; ss != gfc_ss_terminator; ss = ss->next)
    {
      if (ss->type != GFC_SS_SECTION)
        continue;

      if (gfc_could_be_alias (dest, ss)
            || gfc_are_equivalenced_arrays (dest->expr, ss->expr))
        {
          nDepend = 1;
          break;
        }

      if (dest->expr->symtree->n.sym == ss->expr->symtree->n.sym)
        {
          lref = dest->expr->ref;
          rref = ss->expr->ref;

          nDepend = gfc_dep_resolver (lref, rref);
#if 0
          /* TODO : loop shifting.  */
          if (nDepend == 1)
            {
              /* Mark the dimensions for LOOP SHIFTING */
              for (n = 0; n < loop->dimen; n++)
                {
                  int dim = dest->data.info.dim[n];

                  if (lref->u.ar.dimen_type[dim] == DIMEN_VECTOR)
                    depends[n] = 2;
                  else if (! gfc_is_same_range (&lref->u.ar,
                                                &rref->u.ar, dim, 0))
                    depends[n] = 1;
                 }

              /* Put all the dimensions with dependencies in the
                 innermost loops.  */
              dim = 0;
              for (n = 0; n < loop->dimen; n++)
                {
                  gcc_assert (loop->order[n] == n);
                  if (depends[n])
                  loop->order[dim++] = n;
                }
              temp_dim = dim;
              for (n = 0; n < loop->dimen; n++)
                {
                  if (! depends[n])
                  loop->order[dim++] = n;
                }

              gcc_assert (dim == loop->dimen);
              break;
            }
#endif
        }
    }

  if (nDepend == 1)
    {
      tree base_type = gfc_typenode_for_spec (&dest->expr->ts);
      if (GFC_ARRAY_TYPE_P (base_type)
          || GFC_DESCRIPTOR_TYPE_P (base_type))
        base_type = gfc_get_element_type (base_type);
      loop->temp_ss = gfc_get_ss ();
      loop->temp_ss->type = GFC_SS_TEMP;
      loop->temp_ss->data.temp.type = base_type;
      loop->temp_ss->string_length = dest->string_length;
      loop->temp_ss->data.temp.dimen = loop->dimen;
      loop->temp_ss->next = gfc_ss_terminator;
      gfc_add_ss_to_loop (loop, loop->temp_ss);
    }
  else
    loop->temp_ss = NULL;
}


/* Initialize the scalarization loop.  Creates the loop variables.  Determines
   the range of the loop variables.  Creates a temporary if required.
   Calculates how to transform from loop variables to array indices for each
   expression.  Also generates code for scalar expressions which have been
   moved outside the loop.  */

void
gfc_conv_loop_setup (gfc_loopinfo * loop)
{
  int n;
  int dim;
  gfc_ss_info *info;
  gfc_ss_info *specinfo;
  gfc_ss *ss;
  tree tmp;
  tree len;
  gfc_ss *loopspec[GFC_MAX_DIMENSIONS];
  bool dynamic[GFC_MAX_DIMENSIONS];
  gfc_constructor *c;
  mpz_t *cshape;
  mpz_t i;

  mpz_init (i);
  for (n = 0; n < loop->dimen; n++)
    {
      loopspec[n] = NULL;
      dynamic[n] = false;
      /* We use one SS term, and use that to determine the bounds of the
         loop for this dimension.  We try to pick the simplest term.  */
      for (ss = loop->ss; ss != gfc_ss_terminator; ss = ss->loop_chain)
        {
          if (ss->shape)
            {
              /* The frontend has worked out the size for us.  */
              loopspec[n] = ss;
              continue;
            }

          if (ss->type == GFC_SS_CONSTRUCTOR)
            {
              /* An unknown size constructor will always be rank one.
                 Higher rank constructors will either have known shape,
                 or still be wrapped in a call to reshape.  */
              gcc_assert (loop->dimen == 1);

              /* Always prefer to use the constructor bounds if the size
                 can be determined at compile time.  Prefer not to otherwise,
                 since the general case involves realloc, and it's better to
                 avoid that overhead if possible.  */
              c = ss->expr->value.constructor;
              dynamic[n] = gfc_get_array_constructor_size (&i, c);
              if (!dynamic[n] || !loopspec[n])
                loopspec[n] = ss;
              continue;
            }

          /* TODO: Pick the best bound if we have a choice between a
             function and something else.  */
          if (ss->type == GFC_SS_FUNCTION)
            {
              loopspec[n] = ss;
              continue;
            }

          if (ss->type != GFC_SS_SECTION)
            continue;

          if (loopspec[n])
            specinfo = &loopspec[n]->data.info;
          else
            specinfo = NULL;
          info = &ss->data.info;

          if (!specinfo)
            loopspec[n] = ss;
          /* Criteria for choosing a loop specifier (most important first):
             doesn't need realloc
             stride of one
             known stride
             known lower bound
             known upper bound
           */
          else if (loopspec[n]->type == GFC_SS_CONSTRUCTOR && dynamic[n])
            loopspec[n] = ss;
          else if (integer_onep (info->stride[n])
                   && !integer_onep (specinfo->stride[n]))
            loopspec[n] = ss;
          else if (INTEGER_CST_P (info->stride[n])
                   && !INTEGER_CST_P (specinfo->stride[n]))
            loopspec[n] = ss;
          else if (INTEGER_CST_P (info->start[n])
                   && !INTEGER_CST_P (specinfo->start[n]))
            loopspec[n] = ss;
          /* We don't work out the upper bound.
             else if (INTEGER_CST_P (info->finish[n])
             && ! INTEGER_CST_P (specinfo->finish[n]))
             loopspec[n] = ss; */
        }

      if (!loopspec[n])
        gfc_todo_error ("Unable to find scalarization loop specifier");

      info = &loopspec[n]->data.info;

      /* Set the extents of this range.  */
      cshape = loopspec[n]->shape;
      if (cshape && INTEGER_CST_P (info->start[n])
          && INTEGER_CST_P (info->stride[n]))
        {
          loop->from[n] = info->start[n];
          mpz_set (i, cshape[n]);
          mpz_sub_ui (i, i, 1);
          /* To = from + (size - 1) * stride.  */
          tmp = gfc_conv_mpz_to_tree (i, gfc_index_integer_kind);
          if (!integer_onep (info->stride[n]))
            tmp = fold_build2 (MULT_EXPR, gfc_array_index_type,
                               tmp, info->stride[n]);
          loop->to[n] = fold_build2 (PLUS_EXPR, gfc_array_index_type,
                                     loop->from[n], tmp);
        }
      else
        {
          loop->from[n] = info->start[n];
          switch (loopspec[n]->type)
            {
            case GFC_SS_CONSTRUCTOR:
              /* The upper bound is calculated when we expand the
                 constructor.  */
              gcc_assert (loop->to[n] == NULL_TREE);
              break;

            case GFC_SS_SECTION:
              loop->to[n] = gfc_conv_section_upper_bound (loopspec[n], n,
                                                          &loop->pre);
              break;

            case GFC_SS_FUNCTION:
              /* The loop bound will be set when we generate the call.  */
              gcc_assert (loop->to[n] == NULL_TREE);
              break;

            default:
              gcc_unreachable ();
            }
        }

      /* Transform everything so we have a simple incrementing variable.  */
      if (integer_onep (info->stride[n]))
        info->delta[n] = gfc_index_zero_node;
      else
        {
          /* Set the delta for this section.  */
          info->delta[n] = gfc_evaluate_now (loop->from[n], &loop->pre);
          /* Number of iterations is (end - start + step) / step.
             with start = 0, this simplifies to
             last = end / step;
             for (i = 0; i<=last; i++){...};  */
          tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type,
                             loop->to[n], loop->from[n]);
          tmp = fold_build2 (TRUNC_DIV_EXPR, gfc_array_index_type, 
                             tmp, info->stride[n]);
          loop->to[n] = gfc_evaluate_now (tmp, &loop->pre);
          /* Make the loop variable start at 0.  */
          loop->from[n] = gfc_index_zero_node;
        }
    }

  /* Add all the scalar code that can be taken out of the loops.
     This may include calculating the loop bounds, so do it before
     allocating the temporary.  */
  gfc_add_loop_ss_code (loop, loop->ss, false);

  /* If we want a temporary then create it.  */
  if (loop->temp_ss != NULL)
    {
      gcc_assert (loop->temp_ss->type == GFC_SS_TEMP);
      tmp = loop->temp_ss->data.temp.type;
      len = loop->temp_ss->string_length;
      n = loop->temp_ss->data.temp.dimen;
      memset (&loop->temp_ss->data.info, 0, sizeof (gfc_ss_info));
      loop->temp_ss->type = GFC_SS_SECTION;
      loop->temp_ss->data.info.dimen = n;
      gfc_trans_create_temp_array (&loop->pre, &loop->post, loop,
                                   &loop->temp_ss->data.info, tmp, false, true,
                                   false);
    }

  for (n = 0; n < loop->temp_dim; n++)
    loopspec[loop->order[n]] = NULL;

  mpz_clear (i);

  /* For array parameters we don't have loop variables, so don't calculate the
     translations.  */
  if (loop->array_parameter)
    return;

  /* Calculate the translation from loop variables to array indices.  */
  for (ss = loop->ss; ss != gfc_ss_terminator; ss = ss->loop_chain)
    {
      if (ss->type != GFC_SS_SECTION && ss->type != GFC_SS_COMPONENT)
        continue;

      info = &ss->data.info;

      for (n = 0; n < info->dimen; n++)
        {
          dim = info->dim[n];

          /* If we are specifying the range the delta is already set.  */
          if (loopspec[n] != ss)
            {
              /* Calculate the offset relative to the loop variable.
                 First multiply by the stride.  */
              tmp = fold_build2 (MULT_EXPR, gfc_array_index_type,
                                 loop->from[n], info->stride[n]);

              /* Then subtract this from our starting value.  */
              tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type,
                                 info->start[n], tmp);

              info->delta[n] = gfc_evaluate_now (tmp, &loop->pre);
            }
        }
    }
}


/* Fills in an array descriptor, and returns the size of the array.  The size
   will be a simple_val, ie a variable or a constant.  Also calculates the
   offset of the base.  Returns the size of the array.
   {
    stride = 1;
    offset = 0;
    for (n = 0; n < rank; n++)
      {
        a.lbound[n] = specified_lower_bound;
        offset = offset + a.lbond[n] * stride;
        size = 1 - lbound;
        a.ubound[n] = specified_upper_bound;
        a.stride[n] = stride;
        size = ubound + size; //size = ubound + 1 - lbound
        stride = stride * size;
      }
    return (stride);
   }  */
/*GCC ARRAYS*/

static tree
gfc_array_init_size (tree descriptor, int rank, tree * poffset,
                     gfc_expr ** lower, gfc_expr ** upper,
                     stmtblock_t * pblock)
{
  tree type;
  tree tmp;
  tree size;
  tree offset;
  tree stride;
  gfc_expr *ubound;
  gfc_se se;
  int n;

  type = TREE_TYPE (descriptor);

  stride = gfc_index_one_node;
  offset = gfc_index_zero_node;

  /* Set the dtype.  */
  tmp = gfc_conv_descriptor_dtype (descriptor);
  gfc_add_modify_expr (pblock, tmp, gfc_get_dtype (TREE_TYPE (descriptor)));

  for (n = 0; n < rank; n++)
    {
      /* We have 3 possibilities for determining the size of the array:
         lower == NULL    => lbound = 1, ubound = upper[n]
         upper[n] = NULL  => lbound = 1, ubound = lower[n]
         upper[n] != NULL => lbound = lower[n], ubound = upper[n]  */
      ubound = upper[n];

      /* Set lower bound.  */
      gfc_init_se (&se, NULL);
      if (lower == NULL)
        se.expr = gfc_index_one_node;
      else
        {
          gcc_assert (lower[n]);
          if (ubound)
            {
              gfc_conv_expr_type (&se, lower[n], gfc_array_index_type);
              gfc_add_block_to_block (pblock, &se.pre);
            }
          else
            {
              se.expr = gfc_index_one_node;
              ubound = lower[n];
            }
        }
      tmp = gfc_conv_descriptor_lbound (descriptor, gfc_rank_cst[n]);
      gfc_add_modify_expr (pblock, tmp, se.expr);

      /* Work out the offset for this component.  */
      tmp = fold_build2 (MULT_EXPR, gfc_array_index_type, se.expr, stride);
      offset = fold_build2 (MINUS_EXPR, gfc_array_index_type, offset, tmp);

      /* Start the calculation for the size of this dimension.  */
      size = build2 (MINUS_EXPR, gfc_array_index_type,
                     gfc_index_one_node, se.expr);

      /* Set upper bound.  */
      gfc_init_se (&se, NULL);
      gcc_assert (ubound);
      gfc_conv_expr_type (&se, ubound, gfc_array_index_type);
      gfc_add_block_to_block (pblock, &se.pre);

      tmp = gfc_conv_descriptor_ubound (descriptor, gfc_rank_cst[n]);
      gfc_add_modify_expr (pblock, tmp, se.expr);

      /* Store the stride.  */
      tmp = gfc_conv_descriptor_stride (descriptor, gfc_rank_cst[n]);
      gfc_add_modify_expr (pblock, tmp, stride);

      /* Calculate the size of this dimension.  */
      size = fold_build2 (PLUS_EXPR, gfc_array_index_type, se.expr, size);

      /* Multiply the stride by the number of elements in this dimension.  */
      stride = fold_build2 (MULT_EXPR, gfc_array_index_type, stride, size);
      stride = gfc_evaluate_now (stride, pblock);
    }

  /* The stride is the number of elements in the array, so multiply by the
     size of an element to get the total size.  */
  tmp = TYPE_SIZE_UNIT (gfc_get_element_type (type));
  size = fold_build2 (MULT_EXPR, gfc_array_index_type, stride, tmp);

  if (poffset != NULL)
    {
      offset = gfc_evaluate_now (offset, pblock);
      *poffset = offset;
    }

  size = gfc_evaluate_now (size, pblock);
  return size;
}


/* Initializes the descriptor and generates a call to _gfor_allocate.  Does
   the work for an ALLOCATE statement.  */
/*GCC ARRAYS*/

bool
gfc_array_allocate (gfc_se * se, gfc_expr * expr, tree pstat)
{
  tree tmp;
  tree pointer;
  tree allocate;
  tree offset;
  tree size;
  gfc_expr **lower;
  gfc_expr **upper;
  gfc_ref *ref;
  int allocatable_array;

  ref = expr->ref;

  /* Find the last reference in the chain.  */
  while (ref && ref->next != NULL)
    {
      gcc_assert (ref->type != REF_ARRAY || ref->u.ar.type == AR_ELEMENT);
      ref = ref->next;
    }

  if (ref == NULL || ref->type != REF_ARRAY)
    return false;

  /* Figure out the size of the array.  */
  switch (ref->u.ar.type)
    {
    case AR_ELEMENT:
      lower = NULL;
      upper = ref->u.ar.start;
      break;

    case AR_FULL:
      gcc_assert (ref->u.ar.as->type == AS_EXPLICIT);

      lower = ref->u.ar.as->lower;
      upper = ref->u.ar.as->upper;
      break;

    case AR_SECTION:
      lower = ref->u.ar.start;
      upper = ref->u.ar.end;
      break;

    default:
      gcc_unreachable ();
      break;
    }

  size = gfc_array_init_size (se->expr, ref->u.ar.as->rank, &offset,
                              lower, upper, &se->pre);

  /* Allocate memory to store the data.  */
  tmp = gfc_conv_descriptor_data_addr (se->expr);
  pointer = gfc_evaluate_now (tmp, &se->pre);

  allocatable_array = expr->symtree->n.sym->attr.allocatable;

  if (TYPE_PRECISION (gfc_array_index_type) == 32)
    {
      if (allocatable_array)
        allocate = gfor_fndecl_allocate_array;
      else
        allocate = gfor_fndecl_allocate;
    }
  else if (TYPE_PRECISION (gfc_array_index_type) == 64)
    {
      if (allocatable_array)
        allocate = gfor_fndecl_allocate64_array;
      else
        allocate = gfor_fndecl_allocate64;
    }
  else
    gcc_unreachable ();

  tmp = gfc_chainon_list (NULL_TREE, pointer);
  tmp = gfc_chainon_list (tmp, size);
  tmp = gfc_chainon_list (tmp, pstat);
  tmp = build_function_call_expr (allocate, tmp);
  gfc_add_expr_to_block (&se->pre, tmp);

  tmp = gfc_conv_descriptor_offset (se->expr);
  gfc_add_modify_expr (&se->pre, tmp, offset);

  return true;
}


/* Deallocate an array variable.  Also used when an allocated variable goes
   out of scope.  */
/*GCC ARRAYS*/

tree
gfc_array_deallocate (tree descriptor, tree pstat)
{
  tree var;
  tree tmp;
  stmtblock_t block;

  gfc_start_block (&block);
  /* Get a pointer to the data.  */
  tmp = gfc_conv_descriptor_data_addr (descriptor);
  var = gfc_evaluate_now (tmp, &block);

  /* Parameter is the address of the data component.  */
  tmp = gfc_chainon_list (NULL_TREE, var);
  tmp = gfc_chainon_list (tmp, pstat);
  tmp = build_function_call_expr (gfor_fndecl_deallocate, tmp);
  gfc_add_expr_to_block (&block, tmp);

  return gfc_finish_block (&block);
}


/* Create an array constructor from an initialization expression.
   We assume the frontend already did any expansions and conversions.  */

tree
gfc_conv_array_initializer (tree type, gfc_expr * expr)
{
  gfc_constructor *c;
  tree tmp;
  mpz_t maxval;
  gfc_se se;
  HOST_WIDE_INT hi;
  unsigned HOST_WIDE_INT lo;
  tree index, range;
  VEC(constructor_elt,gc) *v = NULL;

  switch (expr->expr_type)
    {
    case EXPR_CONSTANT:
    case EXPR_STRUCTURE:
      /* A single scalar or derived type value.  Create an array with all
         elements equal to that value.  */
      gfc_init_se (&se, NULL);
      
      if (expr->expr_type == EXPR_CONSTANT)
        gfc_conv_constant (&se, expr);
      else
        gfc_conv_structure (&se, expr, 1);

      tmp = TYPE_MAX_VALUE (TYPE_DOMAIN (type));
      gcc_assert (tmp && INTEGER_CST_P (tmp));
      hi = TREE_INT_CST_HIGH (tmp);
      lo = TREE_INT_CST_LOW (tmp);
      lo++;
      if (lo == 0)
        hi++;
      /* This will probably eat buckets of memory for large arrays.  */
      while (hi != 0 || lo != 0)
        {
          CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, se.expr);
          if (lo == 0)
            hi--;
          lo--;
        }
      break;

    case EXPR_ARRAY:
      /* Create a vector of all the elements.  */
      for (c = expr->value.constructor; c; c = c->next)
        {
          if (c->iterator)
            {
              /* Problems occur when we get something like
                 integer :: a(lots) = (/(i, i=1,lots)/)  */
              /* TODO: Unexpanded array initializers.  */
              internal_error
                ("Possible frontend bug: array constructor not expanded");
            }
          if (mpz_cmp_si (c->n.offset, 0) != 0)
            index = gfc_conv_mpz_to_tree (c->n.offset, gfc_index_integer_kind);
          else
            index = NULL_TREE;
          mpz_init (maxval);
          if (mpz_cmp_si (c->repeat, 0) != 0)
            {
              tree tmp1, tmp2;

              mpz_set (maxval, c->repeat);
              mpz_add (maxval, c->n.offset, maxval);
              mpz_sub_ui (maxval, maxval, 1);
              tmp2 = gfc_conv_mpz_to_tree (maxval, gfc_index_integer_kind);
              if (mpz_cmp_si (c->n.offset, 0) != 0)
                {
                  mpz_add_ui (maxval, c->n.offset, 1);
                  tmp1 = gfc_conv_mpz_to_tree (maxval, gfc_index_integer_kind);
                }
              else
                tmp1 = gfc_conv_mpz_to_tree (c->n.offset, gfc_index_integer_kind);

              range = build2 (RANGE_EXPR, integer_type_node, tmp1, tmp2);
            }
          else
            range = NULL;
          mpz_clear (maxval);

          gfc_init_se (&se, NULL);
          switch (c->expr->expr_type)
            {
            case EXPR_CONSTANT:
              gfc_conv_constant (&se, c->expr);
              if (range == NULL_TREE)
                CONSTRUCTOR_APPEND_ELT (v, index, se.expr);
              else
                {
                  if (index != NULL_TREE)
                    CONSTRUCTOR_APPEND_ELT (v, index, se.expr);
                  CONSTRUCTOR_APPEND_ELT (v, range, se.expr);
                }
              break;

            case EXPR_STRUCTURE:
              gfc_conv_structure (&se, c->expr, 1);
              CONSTRUCTOR_APPEND_ELT (v, index, se.expr);
              break;

            default:
              gcc_unreachable ();
            }
        }
      break;

    default:
      gcc_unreachable ();
    }

  /* Create a constructor from the list of elements.  */
  tmp = build_constructor (type, v);
  TREE_CONSTANT (tmp) = 1;
  TREE_INVARIANT (tmp) = 1;
  return tmp;
}


/* Generate code to evaluate non-constant array bounds.  Sets *poffset and
   returns the size (in elements) of the array.  */

static tree
gfc_trans_array_bounds (tree type, gfc_symbol * sym, tree * poffset,
                        stmtblock_t * pblock)
{
  gfc_array_spec *as;
  tree size;
  tree stride;
  tree offset;
  tree ubound;
  tree lbound;
  tree tmp;
  gfc_se se;

  int dim;

  as = sym->as;

  size = gfc_index_one_node;
  offset = gfc_index_zero_node;
  for (dim = 0; dim < as->rank; dim++)
    {
      /* Evaluate non-constant array bound expressions.  */
      lbound = GFC_TYPE_ARRAY_LBOUND (type, dim);
      if (as->lower[dim] && !INTEGER_CST_P (lbound))
        {
          gfc_init_se (&se, NULL);
          gfc_conv_expr_type (&se, as->lower[dim], gfc_array_index_type);
          gfc_add_block_to_block (pblock, &se.pre);
          gfc_add_modify_expr (pblock, lbound, se.expr);
        }
      ubound = GFC_TYPE_ARRAY_UBOUND (type, dim);
      if (as->upper[dim] && !INTEGER_CST_P (ubound))
        {
          gfc_init_se (&se, NULL);
          gfc_conv_expr_type (&se, as->upper[dim], gfc_array_index_type);
          gfc_add_block_to_block (pblock, &se.pre);
          gfc_add_modify_expr (pblock, ubound, se.expr);
        }
      /* The offset of this dimension.  offset = offset - lbound * stride.  */
      tmp = fold_build2 (MULT_EXPR, gfc_array_index_type, lbound, size);
      offset = fold_build2 (MINUS_EXPR, gfc_array_index_type, offset, tmp);

      /* The size of this dimension, and the stride of the next.  */
      if (dim + 1 < as->rank)
        stride = GFC_TYPE_ARRAY_STRIDE (type, dim + 1);
      else
        stride = GFC_TYPE_ARRAY_SIZE (type);

      if (ubound != NULL_TREE && !(stride && INTEGER_CST_P (stride)))
        {
          /* Calculate stride = size * (ubound + 1 - lbound).  */
          tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type,
                             gfc_index_one_node, lbound);
          tmp = fold_build2 (PLUS_EXPR, gfc_array_index_type, ubound, tmp);
          tmp = fold_build2 (MULT_EXPR, gfc_array_index_type, size, tmp);
          if (stride)
            gfc_add_modify_expr (pblock, stride, tmp);
          else
            stride = gfc_evaluate_now (tmp, pblock);
        }

      size = stride;
    }

  gfc_trans_vla_type_sizes (sym, pblock);

  *poffset = offset;
  return size;
}


/* Generate code to initialize/allocate an array variable.  */

tree
gfc_trans_auto_array_allocation (tree decl, gfc_symbol * sym, tree fnbody)
{
  stmtblock_t block;
  tree type;
  tree tmp;
  tree fndecl;
  tree size;
  tree offset;
  bool onstack;

  gcc_assert (!(sym->attr.pointer || sym->attr.allocatable));

  /* Do nothing for USEd variables.  */
  if (sym->attr.use_assoc)
    return fnbody;

  type = TREE_TYPE (decl);
  gcc_assert (GFC_ARRAY_TYPE_P (type));
  onstack = TREE_CODE (type) != POINTER_TYPE;

  gfc_start_block (&block);

  /* Evaluate character string length.  */
  if (sym->ts.type == BT_CHARACTER
      && onstack && !INTEGER_CST_P (sym->ts.cl->backend_decl))
    {
      gfc_trans_init_string_length (sym->ts.cl, &block);

      gfc_trans_vla_type_sizes (sym, &block);

      /* Emit a DECL_EXPR for this variable, which will cause the
         gimplifier to allocate storage, and all that good stuff.  */
      tmp = build1 (DECL_EXPR, TREE_TYPE (decl), decl);
      gfc_add_expr_to_block (&block, tmp);
    }

  if (onstack)
    {
      gfc_add_expr_to_block (&block, fnbody);
      return gfc_finish_block (&block);
    }

  type = TREE_TYPE (type);

  gcc_assert (!sym->attr.use_assoc);
  gcc_assert (!TREE_STATIC (decl));
  gcc_assert (!sym->module);

  if (sym->ts.type == BT_CHARACTER
      && !INTEGER_CST_P (sym->ts.cl->backend_decl))
    gfc_trans_init_string_length (sym->ts.cl, &block);

  size = gfc_trans_array_bounds (type, sym, &offset, &block);

  /* Don't actually allocate space for Cray Pointees.  */
  if (sym->attr.cray_pointee)
    {
      if (TREE_CODE (GFC_TYPE_ARRAY_OFFSET (type)) == VAR_DECL)
        gfc_add_modify_expr (&block, GFC_TYPE_ARRAY_OFFSET (type), offset);
      gfc_add_expr_to_block (&block, fnbody);
      return gfc_finish_block (&block);
    }

  /* The size is the number of elements in the array, so multiply by the
     size of an element to get the total size.  */
  tmp = TYPE_SIZE_UNIT (gfc_get_element_type (type));
  size = fold_build2 (MULT_EXPR, gfc_array_index_type, size, tmp);

  /* Allocate memory to hold the data.  */
  tmp = gfc_chainon_list (NULL_TREE, size);

  if (gfc_index_integer_kind == 4)
    fndecl = gfor_fndecl_internal_malloc;
  else if (gfc_index_integer_kind == 8)
    fndecl = gfor_fndecl_internal_malloc64;
  else
    gcc_unreachable ();
  tmp = build_function_call_expr (fndecl, tmp);
  tmp = fold (convert (TREE_TYPE (decl), tmp));
  gfc_add_modify_expr (&block, decl, tmp);

  /* Set offset of the array.  */
  if (TREE_CODE (GFC_TYPE_ARRAY_OFFSET (type)) == VAR_DECL)
    gfc_add_modify_expr (&block, GFC_TYPE_ARRAY_OFFSET (type), offset);


  /* Automatic arrays should not have initializers.  */
  gcc_assert (!sym->value);

  gfc_add_expr_to_block (&block, fnbody);

  /* Free the temporary.  */
  tmp = convert (pvoid_type_node, decl);
  tmp = gfc_chainon_list (NULL_TREE, tmp);
  tmp = build_function_call_expr (gfor_fndecl_internal_free, tmp);
  gfc_add_expr_to_block (&block, tmp);

  return gfc_finish_block (&block);
}


/* Generate entry and exit code for g77 calling convention arrays.  */

tree
gfc_trans_g77_array (gfc_symbol * sym, tree body)
{
  tree parm;
  tree type;
  locus loc;
  tree offset;
  tree tmp;
  stmtblock_t block;

  gfc_get_backend_locus (&loc);
  gfc_set_backend_locus (&sym->declared_at);

  /* Descriptor type.  */
  parm = sym->backend_decl;
  type = TREE_TYPE (parm);
  gcc_assert (GFC_ARRAY_TYPE_P (type));

  gfc_start_block (&block);

  if (sym->ts.type == BT_CHARACTER
      && TREE_CODE (sym->ts.cl->backend_decl) == VAR_DECL)
    gfc_trans_init_string_length (sym->ts.cl, &block);

  /* Evaluate the bounds of the array.  */
  gfc_trans_array_bounds (type, sym, &offset, &block);

  /* Set the offset.  */
  if (TREE_CODE (GFC_TYPE_ARRAY_OFFSET (type)) == VAR_DECL)
    gfc_add_modify_expr (&block, GFC_TYPE_ARRAY_OFFSET (type), offset);

  /* Set the pointer itself if we aren't using the parameter directly.  */
  if (TREE_CODE (parm) != PARM_DECL)
    {
      tmp = convert (TREE_TYPE (parm), GFC_DECL_SAVED_DESCRIPTOR (parm));
      gfc_add_modify_expr (&block, parm, tmp);
    }
  tmp = gfc_finish_block (&block);

  gfc_set_backend_locus (&loc);

  gfc_start_block (&block);
  /* Add the initialization code to the start of the function.  */
  gfc_add_expr_to_block (&block, tmp);
  gfc_add_expr_to_block (&block, body);

  return gfc_finish_block (&block);
}


/* Modify the descriptor of an array parameter so that it has the
   correct lower bound.  Also move the upper bound accordingly.
   If the array is not packed, it will be copied into a temporary.
   For each dimension we set the new lower and upper bounds.  Then we copy the
   stride and calculate the offset for this dimension.  We also work out
   what the stride of a packed array would be, and see it the two match.
   If the array need repacking, we set the stride to the values we just
   calculated, recalculate the offset and copy the array data.
   Code is also added to copy the data back at the end of the function.
   */

tree
gfc_trans_dummy_array_bias (gfc_symbol * sym, tree tmpdesc, tree body)
{
  tree size;
  tree type;
  tree offset;
  locus loc;
  stmtblock_t block;
  stmtblock_t cleanup;
  tree lbound;
  tree ubound;
  tree dubound;
  tree dlbound;
  tree dumdesc;
  tree tmp;
  tree stmt;
  tree stride;
  tree stmt_packed;
  tree stmt_unpacked;
  tree partial;
  gfc_se se;
  int n;
  int checkparm;
  int no_repack;
  bool optional_arg;

  /* Do nothing for pointer and allocatable arrays.  */
  if (sym->attr.pointer || sym->attr.allocatable)
    return body;

  if (sym->attr.dummy && gfc_is_nodesc_array (sym))
    return gfc_trans_g77_array (sym, body);

  gfc_get_backend_locus (&loc);
  gfc_set_backend_locus (&sym->declared_at);

  /* Descriptor type.  */
  type = TREE_TYPE (tmpdesc);
  gcc_assert (GFC_ARRAY_TYPE_P (type));
  dumdesc = GFC_DECL_SAVED_DESCRIPTOR (tmpdesc);
  dumdesc = build_fold_indirect_ref (dumdesc);
  gfc_start_block (&block);

  if (sym->ts.type == BT_CHARACTER
      && TREE_CODE (sym->ts.cl->backend_decl) == VAR_DECL)
    gfc_trans_init_string_length (sym->ts.cl, &block);

  checkparm = (sym->as->type == AS_EXPLICIT && flag_bounds_check);

  no_repack = !(GFC_DECL_PACKED_ARRAY (tmpdesc)
                || GFC_DECL_PARTIAL_PACKED_ARRAY (tmpdesc));

  if (GFC_DECL_PARTIAL_PACKED_ARRAY (tmpdesc))
    {
      /* For non-constant shape arrays we only check if the first dimension
         is contiguous.  Repacking higher dimensions wouldn't gain us
         anything as we still don't know the array stride.  */
      partial = gfc_create_var (boolean_type_node, "partial");
      TREE_USED (partial) = 1;
      tmp = gfc_conv_descriptor_stride (dumdesc, gfc_rank_cst[0]);
      tmp = fold_build2 (EQ_EXPR, boolean_type_node, tmp, integer_one_node);
      gfc_add_modify_expr (&block, partial, tmp);
    }
  else
    {
      partial = NULL_TREE;
    }

  /* The naming of stmt_unpacked and stmt_packed may be counter-intuitive
     here, however I think it does the right thing.  */
  if (no_repack)
    {
      /* Set the first stride.  */
      stride = gfc_conv_descriptor_stride (dumdesc, gfc_rank_cst[0]);
      stride = gfc_evaluate_now (stride, &block);

      tmp = build2 (EQ_EXPR, boolean_type_node, stride, integer_zero_node);
      tmp = build3 (COND_EXPR, gfc_array_index_type, tmp,
                    gfc_index_one_node, stride);
      stride = GFC_TYPE_ARRAY_STRIDE (type, 0);
      gfc_add_modify_expr (&block, stride, tmp);

      /* Allow the user to disable array repacking.  */
      stmt_unpacked = NULL_TREE;
    }
  else
    {
      gcc_assert (integer_onep (GFC_TYPE_ARRAY_STRIDE (type, 0)));
      /* A library call to repack the array if necessary.  */
      tmp = GFC_DECL_SAVED_DESCRIPTOR (tmpdesc);
      tmp = gfc_chainon_list (NULL_TREE, tmp);
      stmt_unpacked = build_function_call_expr (gfor_fndecl_in_pack, tmp);

      stride = gfc_index_one_node;
    }

  /* This is for the case where the array data is used directly without
     calling the repack function.  */
  if (no_repack || partial != NULL_TREE)
    stmt_packed = gfc_conv_descriptor_data_get (dumdesc);
  else
    stmt_packed = NULL_TREE;

  /* Assign the data pointer.  */
  if (stmt_packed != NULL_TREE && stmt_unpacked != NULL_TREE)
    {
      /* Don't repack unknown shape arrays when the first stride is 1.  */
      tmp = build3 (COND_EXPR, TREE_TYPE (stmt_packed), partial,
                    stmt_packed, stmt_unpacked);
    }
  else
    tmp = stmt_packed != NULL_TREE ? stmt_packed : stmt_unpacked;
  gfc_add_modify_expr (&block, tmpdesc, fold_convert (type, tmp));

  offset = gfc_index_zero_node;
  size = gfc_index_one_node;

  /* Evaluate the bounds of the array.  */
  for (n = 0; n < sym->as->rank; n++)
    {
      if (checkparm || !sym->as->upper[n])
        {
          /* Get the bounds of the actual parameter.  */
          dubound = gfc_conv_descriptor_ubound (dumdesc, gfc_rank_cst[n]);
          dlbound = gfc_conv_descriptor_lbound (dumdesc, gfc_rank_cst[n]);
        }
      else
        {
          dubound = NULL_TREE;
          dlbound = NULL_TREE;
        }

      lbound = GFC_TYPE_ARRAY_LBOUND (type, n);
      if (!INTEGER_CST_P (lbound))
        {
          gfc_init_se (&se, NULL);
          gfc_conv_expr_type (&se, sym->as->lower[n],
                              gfc_array_index_type);
          gfc_add_block_to_block (&block, &se.pre);
          gfc_add_modify_expr (&block, lbound, se.expr);
        }

      ubound = GFC_TYPE_ARRAY_UBOUND (type, n);
      /* Set the desired upper bound.  */
      if (sym->as->upper[n])
        {
          /* We know what we want the upper bound to be.  */
          if (!INTEGER_CST_P (ubound))
            {
              gfc_init_se (&se, NULL);
              gfc_conv_expr_type (&se, sym->as->upper[n],
                                  gfc_array_index_type);
              gfc_add_block_to_block (&block, &se.pre);
              gfc_add_modify_expr (&block, ubound, se.expr);
            }

          /* Check the sizes match.  */
          if (checkparm)
            {
              /* Check (ubound(a) - lbound(a) == ubound(b) - lbound(b)).  */

              tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type,
                                 ubound, lbound);
              stride = build2 (MINUS_EXPR, gfc_array_index_type,
                               dubound, dlbound);
              tmp = fold_build2 (NE_EXPR, gfc_array_index_type, tmp, stride);
              gfc_trans_runtime_check (tmp, gfc_strconst_bounds, &block);
            }
        }
      else
        {
          /* For assumed shape arrays move the upper bound by the same amount
             as the lower bound.  */
          tmp = build2 (MINUS_EXPR, gfc_array_index_type, dubound, dlbound);
          tmp = fold_build2 (PLUS_EXPR, gfc_array_index_type, tmp, lbound);
          gfc_add_modify_expr (&block, ubound, tmp);
        }
      /* The offset of this dimension.  offset = offset - lbound * stride.  */
      tmp = fold_build2 (MULT_EXPR, gfc_array_index_type, lbound, stride);
      offset = fold_build2 (MINUS_EXPR, gfc_array_index_type, offset, tmp);

      /* The size of this dimension, and the stride of the next.  */
      if (n + 1 < sym->as->rank)
        {
          stride = GFC_TYPE_ARRAY_STRIDE (type, n + 1);

          if (no_repack || partial != NULL_TREE)
            {
              stmt_unpacked =
                gfc_conv_descriptor_stride (dumdesc, gfc_rank_cst[n+1]);
            }

          /* Figure out the stride if not a known constant.  */
          if (!INTEGER_CST_P (stride))
            {
              if (no_repack)
                stmt_packed = NULL_TREE;
              else
                {
                  /* Calculate stride = size * (ubound + 1 - lbound).  */
                  tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type,
                                     gfc_index_one_node, lbound);
                  tmp = fold_build2 (PLUS_EXPR, gfc_array_index_type,
                                     ubound, tmp);
                  size = fold_build2 (MULT_EXPR, gfc_array_index_type,
                                      size, tmp);
                  stmt_packed = size;
                }

              /* Assign the stride.  */
              if (stmt_packed != NULL_TREE && stmt_unpacked != NULL_TREE)
                tmp = build3 (COND_EXPR, gfc_array_index_type, partial,
                              stmt_unpacked, stmt_packed);
              else
                tmp = (stmt_packed != NULL_TREE) ? stmt_packed : stmt_unpacked;
              gfc_add_modify_expr (&block, stride, tmp);
            }
        }
      else
        {
          stride = GFC_TYPE_ARRAY_SIZE (type);

          if (stride && !INTEGER_CST_P (stride))
            {
              /* Calculate size = stride * (ubound + 1 - lbound).  */
              tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type,
                                 gfc_index_one_node, lbound);
              tmp = fold_build2 (PLUS_EXPR, gfc_array_index_type,
                                 ubound, tmp);
              tmp = fold_build2 (MULT_EXPR, gfc_array_index_type,
                                 GFC_TYPE_ARRAY_STRIDE (type, n), tmp);
              gfc_add_modify_expr (&block, stride, tmp);
            }
        }
    }

  /* Set the offset.  */
  if (TREE_CODE (GFC_TYPE_ARRAY_OFFSET (type)) == VAR_DECL)
    gfc_add_modify_expr (&block, GFC_TYPE_ARRAY_OFFSET (type), offset);

  gfc_trans_vla_type_sizes (sym, &block);

  stmt = gfc_finish_block (&block);

  gfc_start_block (&block);

  /* Only do the entry/initialization code if the arg is present.  */
  dumdesc = GFC_DECL_SAVED_DESCRIPTOR (tmpdesc);
  optional_arg = (sym->attr.optional
                  || (sym->ns->proc_name->attr.entry_master
                      && sym->attr.dummy));
  if (optional_arg)
    {
      tmp = gfc_conv_expr_present (sym);
      stmt = build3_v (COND_EXPR, tmp, stmt, build_empty_stmt ());
    }
  gfc_add_expr_to_block (&block, stmt);

  /* Add the main function body.  */
  gfc_add_expr_to_block (&block, body);

  /* Cleanup code.  */
  if (!no_repack)
    {
      gfc_start_block (&cleanup);
      
      if (sym->attr.intent != INTENT_IN)
        {
          /* Copy the data back.  */
          tmp = gfc_chainon_list (NULL_TREE, dumdesc);
          tmp = gfc_chainon_list (tmp, tmpdesc);
          tmp = build_function_call_expr (gfor_fndecl_in_unpack, tmp);
          gfc_add_expr_to_block (&cleanup, tmp);
        }

      /* Free the temporary.  */
      tmp = gfc_chainon_list (NULL_TREE, tmpdesc);
      tmp = build_function_call_expr (gfor_fndecl_internal_free, tmp);
      gfc_add_expr_to_block (&cleanup, tmp);

      stmt = gfc_finish_block (&cleanup);
        
      /* Only do the cleanup if the array was repacked.  */
      tmp = build_fold_indirect_ref (dumdesc);
      tmp = gfc_conv_descriptor_data_get (tmp);
      tmp = build2 (NE_EXPR, boolean_type_node, tmp, tmpdesc);
      stmt = build3_v (COND_EXPR, tmp, stmt, build_empty_stmt ());

      if (optional_arg)
        {
          tmp = gfc_conv_expr_present (sym);
          stmt = build3_v (COND_EXPR, tmp, stmt, build_empty_stmt ());
        }
      gfc_add_expr_to_block (&block, stmt);
    }
  /* We don't need to free any memory allocated by internal_pack as it will
     be freed at the end of the function by pop_context.  */
  return gfc_finish_block (&block);
}


/* Convert an array for passing as an actual argument.  Expressions and
   vector subscripts are evaluated and stored in a temporary, which is then
   passed.  For whole arrays the descriptor is passed.  For array sections
   a modified copy of the descriptor is passed, but using the original data.

   This function is also used for array pointer assignments, and there
   are three cases:

     - want_pointer && !se->direct_byref
         EXPR is an actual argument.  On exit, se->expr contains a
         pointer to the array descriptor.

     - !want_pointer && !se->direct_byref
         EXPR is an actual argument to an intrinsic function or the
         left-hand side of a pointer assignment.  On exit, se->expr
         contains the descriptor for EXPR.

     - !want_pointer && se->direct_byref
         EXPR is the right-hand side of a pointer assignment and
         se->expr is the descriptor for the previously-evaluated
         left-hand side.  The function creates an assignment from
         EXPR to se->expr.  */

void
gfc_conv_expr_descriptor (gfc_se * se, gfc_expr * expr, gfc_ss * ss)
{
  gfc_loopinfo loop;
  gfc_ss *secss;
  gfc_ss_info *info;
  int need_tmp;
  int n;
  tree tmp;
  tree desc;
  stmtblock_t block;
  tree start;
  tree offset;
  int full;
  gfc_ref *ref;

  gcc_assert (ss != gfc_ss_terminator);

  /* TODO: Pass constant array constructors without a temporary.  */
  /* Special case things we know we can pass easily.  */
  switch (expr->expr_type)
    {
    case EXPR_VARIABLE:
      /* If we have a linear array section, we can pass it directly.
         Otherwise we need to copy it into a temporary.  */

      /* Find the SS for the array section.  */
      secss = ss;
      while (secss != gfc_ss_terminator && secss->type != GFC_SS_SECTION)
        secss = secss->next;

      gcc_assert (secss != gfc_ss_terminator);
      info = &secss->data.info;

      /* Get the descriptor for the array.  */
      gfc_conv_ss_descriptor (&se->pre, secss, 0);
      desc = info->descriptor;

      need_tmp = gfc_ref_needs_temporary_p (expr->ref);
      if (need_tmp)
        full = 0;
      else if (GFC_ARRAY_TYPE_P (TREE_TYPE (desc)))
        {
          /* Create a new descriptor if the array doesn't have one.  */
          full = 0;
        }
      else if (info->ref->u.ar.type == AR_FULL)
        full = 1;
      else if (se->direct_byref)
        full = 0;
      else
        {
          ref = info->ref;
          gcc_assert (ref->u.ar.type == AR_SECTION);

          full = 1;
          for (n = 0; n < ref->u.ar.dimen; n++)
            {
              /* Detect passing the full array as a section.  This could do
                 even more checking, but it doesn't seem worth it.  */
              if (ref->u.ar.start[n]
                  || ref->u.ar.end[n]
                  || (ref->u.ar.stride[n]
                      && !gfc_expr_is_one (ref->u.ar.stride[n], 0)))
                {
                  full = 0;
                  break;
                }
            }
        }

      if (full)
        {
          if (se->direct_byref)
            {
              /* Copy the descriptor for pointer assignments.  */
              gfc_add_modify_expr (&se->pre, se->expr, desc);
            }
          else if (se->want_pointer)
            {
              /* We pass full arrays directly.  This means that pointers and
                 allocatable arrays should also work.  */
              se->expr = build_fold_addr_expr (desc);
            }
          else
            {
              se->expr = desc;
            }

          if (expr->ts.type == BT_CHARACTER)
            se->string_length = gfc_get_expr_charlen (expr);

          return;
        }
      break;
      
    case EXPR_FUNCTION:
      /* A transformational function return value will be a temporary
         array descriptor.  We still need to go through the scalarizer
         to create the descriptor.  Elemental functions ar handled as
         arbitrary expressions, i.e. copy to a temporary.  */
      secss = ss;
      /* Look for the SS for this function.  */
      while (secss != gfc_ss_terminator
             && (secss->type != GFC_SS_FUNCTION || secss->expr != expr))
        secss = secss->next;

      if (se->direct_byref)
        {
          gcc_assert (secss != gfc_ss_terminator);

          /* For pointer assignments pass the descriptor directly.  */
          se->ss = secss;
          se->expr = build_fold_addr_expr (se->expr);
          gfc_conv_expr (se, expr);
          return;
        }

      if (secss == gfc_ss_terminator)
        {
          /* Elemental function.  */
          need_tmp = 1;
          info = NULL;
        }
      else
        {
          /* Transformational function.  */
          info = &secss->data.info;
          need_tmp = 0;
        }
      break;

    default:
      /* Something complicated.  Copy it into a temporary.  */
      need_tmp = 1;
      secss = NULL;
      info = NULL;
      break;
    }


  gfc_init_loopinfo (&loop);

  /* Associate the SS with the loop.  */
  gfc_add_ss_to_loop (&loop, ss);

  /* Tell the scalarizer not to bother creating loop variables, etc.  */
  if (!need_tmp)
    loop.array_parameter = 1;
  else
    /* The right-hand side of a pointer assignment mustn't use a temporary.  */
    gcc_assert (!se->direct_byref);

  /* Setup the scalarizing loops and bounds.  */
  gfc_conv_ss_startstride (&loop);

  if (need_tmp)
    {
      /* Tell the scalarizer to make a temporary.  */
      loop.temp_ss = gfc_get_ss ();
      loop.temp_ss->type = GFC_SS_TEMP;
      loop.temp_ss->next = gfc_ss_terminator;
      if (expr->ts.type == BT_CHARACTER)
        {
          gcc_assert (expr->ts.cl && expr->ts.cl->length
                      && expr->ts.cl->length->expr_type == EXPR_CONSTANT);
          loop.temp_ss->string_length = gfc_conv_mpz_to_tree
                        (expr->ts.cl->length->value.integer,
                         expr->ts.cl->length->ts.kind);
          expr->ts.cl->backend_decl = loop.temp_ss->string_length;
        }
        loop.temp_ss->data.temp.type = gfc_typenode_for_spec (&expr->ts);

      /* ... which can hold our string, if present.  */
      if (expr->ts.type == BT_CHARACTER)
        {
          loop.temp_ss->string_length = TYPE_SIZE_UNIT (loop.temp_ss->data.temp.type);
          se->string_length = loop.temp_ss->string_length;
        }
      else
        loop.temp_ss->string_length = NULL;
      loop.temp_ss->data.temp.dimen = loop.dimen;
      gfc_add_ss_to_loop (&loop, loop.temp_ss);
    }

  gfc_conv_loop_setup (&loop);

  if (need_tmp)
    {
      /* Copy into a temporary and pass that.  We don't need to copy the data
         back because expressions and vector subscripts must be INTENT_IN.  */
      /* TODO: Optimize passing function return values.  */
      gfc_se lse;
      gfc_se rse;

      /* Start the copying loops.  */
      gfc_mark_ss_chain_used (loop.temp_ss, 1);
      gfc_mark_ss_chain_used (ss, 1);
      gfc_start_scalarized_body (&loop, &block);

      /* Copy each data element.  */
      gfc_init_se (&lse, NULL);
      gfc_copy_loopinfo_to_se (&lse, &loop);
      gfc_init_se (&rse, NULL);
      gfc_copy_loopinfo_to_se (&rse, &loop);

      lse.ss = loop.temp_ss;
      rse.ss = ss;

      gfc_conv_scalarized_array_ref (&lse, NULL);
      if (expr->ts.type == BT_CHARACTER)
        {
          gfc_conv_expr (&rse, expr);
          rse.expr = build_fold_indirect_ref (rse.expr);
        }
      else
        gfc_conv_expr_val (&rse, expr);

      gfc_add_block_to_block (&block, &rse.pre);
      gfc_add_block_to_block (&block, &lse.pre);

      gfc_add_modify_expr (&block, lse.expr, rse.expr);

      /* Finish the copying loops.  */
      gfc_trans_scalarizing_loops (&loop, &block);

      /* Set the first stride component to zero to indicate a temporary.  */
      desc = loop.temp_ss->data.info.descriptor;
      tmp = gfc_conv_descriptor_stride (desc, gfc_rank_cst[0]);
      gfc_add_modify_expr (&loop.pre, tmp, gfc_index_zero_node);

      gcc_assert (is_gimple_lvalue (desc));
    }
  else if (expr->expr_type == EXPR_FUNCTION)
    {
      desc = info->descriptor;
      se->string_length = ss->string_length;
    }
  else
    {
      /* We pass sections without copying to a temporary.  Make a new
         descriptor and point it at the section we want.  The loop variable
         limits will be the limits of the section.
         A function may decide to repack the array to speed up access, but
         we're not bothered about that here.  */
      int dim;
      tree parm;
      tree parmtype;
      tree stride;
      tree from;
      tree to;
      tree base;

      /* Set the string_length for a character array.  */
      if (expr->ts.type == BT_CHARACTER)
        se->string_length =  gfc_get_expr_charlen (expr);

      desc = info->descriptor;
      gcc_assert (secss && secss != gfc_ss_terminator);
      if (se->direct_byref)
        {
          /* For pointer assignments we fill in the destination.  */
          parm = se->expr;
          parmtype = TREE_TYPE (parm);
        }
      else
        {
          /* Otherwise make a new one.  */
          parmtype = gfc_get_element_type (TREE_TYPE (desc));
          parmtype = gfc_get_array_type_bounds (parmtype, loop.dimen,
                                                loop.from, loop.to, 0);
          parm = gfc_create_var (parmtype, "parm");
        }

      offset = gfc_index_zero_node;
      dim = 0;

      /* The following can be somewhat confusing.  We have two
         descriptors, a new one and the original array.
         {parm, parmtype, dim} refer to the new one.
         {desc, type, n, secss, loop} refer to the original, which maybe
         a descriptorless array.
         The bounds of the scalarization are the bounds of the section.
         We don't have to worry about numeric overflows when calculating
         the offsets because all elements are within the array data.  */

      /* Set the dtype.  */
      tmp = gfc_conv_descriptor_dtype (parm);
      gfc_add_modify_expr (&loop.pre, tmp, gfc_get_dtype (parmtype));

      if (se->direct_byref)
        base = gfc_index_zero_node;
      else
        base = NULL_TREE;

      for (n = 0; n < info->ref->u.ar.dimen; n++)
        {
          stride = gfc_conv_array_stride (desc, n);

          /* Work out the offset.  */
          if (info->ref->u.ar.dimen_type[n] == DIMEN_ELEMENT)
            {
              gcc_assert (info->subscript[n]
                      && info->subscript[n]->type == GFC_SS_SCALAR);
              start = info->subscript[n]->data.scalar.expr;
            }
          else
            {
              /* Check we haven't somehow got out of sync.  */
              gcc_assert (info->dim[dim] == n);

              /* Evaluate and remember the start of the section.  */
              start = info->start[dim];
              stride = gfc_evaluate_now (stride, &loop.pre);
            }

          tmp = gfc_conv_array_lbound (desc, n);
          tmp = fold_build2 (MINUS_EXPR, TREE_TYPE (tmp), start, tmp);

          tmp = fold_build2 (MULT_EXPR, TREE_TYPE (tmp), tmp, stride);
          offset = fold_build2 (PLUS_EXPR, TREE_TYPE (tmp), offset, tmp);

          if (info->ref->u.ar.dimen_type[n] == DIMEN_ELEMENT)
            {
              /* For elemental dimensions, we only need the offset.  */
              continue;
            }

          /* Vector subscripts need copying and are handled elsewhere.  */
          gcc_assert (info->ref->u.ar.dimen_type[n] == DIMEN_RANGE);

          /* Set the new lower bound.  */
          from = loop.from[dim];
          to = loop.to[dim];

          /* If we have an array section or are assigning to a pointer,
             make sure that the lower bound is 1.  References to the full
             array should otherwise keep the original bounds.  */
          if ((info->ref->u.ar.type != AR_FULL || se->direct_byref)
              && !integer_onep (from))
            {
              tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type,
                                 gfc_index_one_node, from);
              to = fold_build2 (PLUS_EXPR, gfc_array_index_type, to, tmp);
              from = gfc_index_one_node;
            }
          tmp = gfc_conv_descriptor_lbound (parm, gfc_rank_cst[dim]);
          gfc_add_modify_expr (&loop.pre, tmp, from);

          /* Set the new upper bound.  */
          tmp = gfc_conv_descriptor_ubound (parm, gfc_rank_cst[dim]);
          gfc_add_modify_expr (&loop.pre, tmp, to);

          /* Multiply the stride by the section stride to get the
             total stride.  */
          stride = fold_build2 (MULT_EXPR, gfc_array_index_type,
                                stride, info->stride[dim]);

          if (se->direct_byref)
            base = fold_build2 (MINUS_EXPR, TREE_TYPE (base),
                                base, stride);

          /* Store the new stride.  */
          tmp = gfc_conv_descriptor_stride (parm, gfc_rank_cst[dim]);
          gfc_add_modify_expr (&loop.pre, tmp, stride);

          dim++;
        }

      if (se->data_not_needed)
        gfc_conv_descriptor_data_set (&loop.pre, parm, gfc_index_zero_node);
      else
        {
          /* Point the data pointer at the first element in the section.  */
          tmp = gfc_conv_array_data (desc);
          tmp = build_fold_indirect_ref (tmp);
          tmp = gfc_build_array_ref (tmp, offset);
          offset = gfc_build_addr_expr (gfc_array_dataptr_type (desc), tmp);
          gfc_conv_descriptor_data_set (&loop.pre, parm, offset);
        }

      if (se->direct_byref && !se->data_not_needed)
        {
          /* Set the offset.  */
          tmp = gfc_conv_descriptor_offset (parm);
          gfc_add_modify_expr (&loop.pre, tmp, base);
        }
      else
        {
          /* Only the callee knows what the correct offset it, so just set
             it to zero here.  */
          tmp = gfc_conv_descriptor_offset (parm);
          gfc_add_modify_expr (&loop.pre, tmp, gfc_index_zero_node);
        }
      desc = parm;
    }

  if (!se->direct_byref)
    {
      /* Get a pointer to the new descriptor.  */
      if (se->want_pointer)
        se->expr = build_fold_addr_expr (desc);
      else
        se->expr = desc;
    }

  gfc_add_block_to_block (&se->pre, &loop.pre);
  gfc_add_block_to_block (&se->post, &loop.post);

  /* Cleanup the scalarizer.  */
  gfc_cleanup_loop (&loop);
}


/* Convert an array for passing as an actual parameter.  */
/* TODO: Optimize passing g77 arrays.  */

void
gfc_conv_array_parameter (gfc_se * se, gfc_expr * expr, gfc_ss * ss, int g77)
{
  tree ptr;
  tree desc;
  tree tmp;
  tree stmt;
  gfc_symbol *sym;
  stmtblock_t block;

  /* Passing address of the array if it is not pointer or assumed-shape.  */
  if (expr->expr_type == EXPR_VARIABLE
       && expr->ref->u.ar.type == AR_FULL && g77)
    {
      sym = expr->symtree->n.sym;
      tmp = gfc_get_symbol_decl (sym);

      if (sym->ts.type == BT_CHARACTER)
        se->string_length = sym->ts.cl->backend_decl;
      if (!sym->attr.pointer && sym->as->type != AS_ASSUMED_SHAPE 
          && !sym->attr.allocatable)
        {
          /* Some variables are declared directly, others are declared as
             pointers and allocated on the heap.  */
          if (sym->attr.dummy || POINTER_TYPE_P (TREE_TYPE (tmp)))
            se->expr = tmp;
          else
            se->expr = build_fold_addr_expr (tmp);
          return;
        }
      if (sym->attr.allocatable)
        {
          se->expr = gfc_conv_array_data (tmp);
          return;
        }
    }

  se->want_pointer = 1;
  gfc_conv_expr_descriptor (se, expr, ss);

  if (g77)
    {
      desc = se->expr;
      /* Repack the array.  */
      tmp = gfc_chainon_list (NULL_TREE, desc);
      ptr = build_function_call_expr (gfor_fndecl_in_pack, tmp);
      ptr = gfc_evaluate_now (ptr, &se->pre);
      se->expr = ptr;

      gfc_start_block (&block);

      /* Copy the data back.  */
      tmp = gfc_chainon_list (NULL_TREE, desc);
      tmp = gfc_chainon_list (tmp, ptr);
      tmp = build_function_call_expr (gfor_fndecl_in_unpack, tmp);
      gfc_add_expr_to_block (&block, tmp);

      /* Free the temporary.  */
      tmp = convert (pvoid_type_node, ptr);
      tmp = gfc_chainon_list (NULL_TREE, tmp);
      tmp = build_function_call_expr (gfor_fndecl_internal_free, tmp);
      gfc_add_expr_to_block (&block, tmp);

      stmt = gfc_finish_block (&block);

      gfc_init_block (&block);
      /* Only if it was repacked.  This code needs to be executed before the
         loop cleanup code.  */
      tmp = build_fold_indirect_ref (desc);
      tmp = gfc_conv_array_data (tmp);
      tmp = build2 (NE_EXPR, boolean_type_node, ptr, tmp);
      tmp = build3_v (COND_EXPR, tmp, stmt, build_empty_stmt ());

      gfc_add_expr_to_block (&block, tmp);
      gfc_add_block_to_block (&block, &se->post);

      gfc_init_block (&se->post);
      gfc_add_block_to_block (&se->post, &block);
    }
}


/* Generate code to deallocate the symbol 'sym', if it is allocated.  */

tree
gfc_trans_dealloc_allocated (gfc_symbol * sym)
{ 
  tree tmp;
  tree descriptor;
  tree deallocate;
  stmtblock_t block;

  gcc_assert (sym->attr.allocatable);

  gfc_start_block (&block);
  descriptor = sym->backend_decl;
  deallocate = gfc_array_deallocate (descriptor, null_pointer_node);

  tmp = gfc_conv_descriptor_data_get (descriptor);
  tmp = build2 (NE_EXPR, boolean_type_node, tmp,
                build_int_cst (TREE_TYPE (tmp), 0));
  tmp = build3_v (COND_EXPR, tmp, deallocate, build_empty_stmt ());
  gfc_add_expr_to_block (&block, tmp);

  tmp = gfc_finish_block (&block);

  return tmp;
}


/* NULLIFY an allocatable/pointer array on function entry, free it on exit.  */

tree
gfc_trans_deferred_array (gfc_symbol * sym, tree body)
{
  tree type;
  tree tmp;
  tree descriptor;
  stmtblock_t fnblock;
  locus loc;

  /* Make sure the frontend gets these right.  */
  if (!(sym->attr.pointer || sym->attr.allocatable))
    fatal_error
      ("Possible frontend bug: Deferred array size without pointer or allocatable attribute.");

  gfc_init_block (&fnblock);

  gcc_assert (TREE_CODE (sym->backend_decl) == VAR_DECL
                || TREE_CODE (sym->backend_decl) == PARM_DECL);

  if (sym->ts.type == BT_CHARACTER
      && !INTEGER_CST_P (sym->ts.cl->backend_decl))
    {
      gfc_trans_init_string_length (sym->ts.cl, &fnblock);
      gfc_trans_vla_type_sizes (sym, &fnblock);
    }

  /* Dummy and use associated variables don't need anything special.  */
  if (sym->attr.dummy || sym->attr.use_assoc)
    {
      gfc_add_expr_to_block (&fnblock, body);

      return gfc_finish_block (&fnblock);
    }

  gfc_get_backend_locus (&loc);
  gfc_set_backend_locus (&sym->declared_at);
  descriptor = sym->backend_decl;

  if (TREE_STATIC (descriptor))
    {
      /* SAVEd variables are not freed on exit.  */
      gfc_trans_static_array_pointer (sym);
      return body;
    }

  /* Get the descriptor type.  */
  type = TREE_TYPE (sym->backend_decl);
  gcc_assert (GFC_DESCRIPTOR_TYPE_P (type));

  /* NULLIFY the data pointer.  */
  gfc_conv_descriptor_data_set (&fnblock, descriptor, null_pointer_node);

  gfc_add_expr_to_block (&fnblock, body);

  gfc_set_backend_locus (&loc);
  /* Allocatable arrays need to be freed when they go out of scope.  */
  if (sym->attr.allocatable)
    {
      tmp = gfc_trans_dealloc_allocated (sym);
      gfc_add_expr_to_block (&fnblock, tmp);
    }

  return gfc_finish_block (&fnblock);
}

/************ Expression Walking Functions ******************/

/* Walk a variable reference.

   Possible extension - multiple component subscripts.
    x(:,:) = foo%a(:)%b(:)
   Transforms to
    forall (i=..., j=...)
      x(i,j) = foo%a(j)%b(i)
    end forall
   This adds a fair amout of complexity because you need to deal with more
   than one ref.  Maybe handle in a similar manner to vector subscripts.
   Maybe not worth the effort.  */


static gfc_ss *
gfc_walk_variable_expr (gfc_ss * ss, gfc_expr * expr)
{
  gfc_ref *ref;
  gfc_array_ref *ar;
  gfc_ss *newss;
  gfc_ss *head;
  int n;

  for (ref = expr->ref; ref; ref = ref->next)
    if (ref->type == REF_ARRAY && ref->u.ar.type != AR_ELEMENT)
      break;

  for (; ref; ref = ref->next)
    {
      if (ref->type == REF_SUBSTRING)
        {
          newss = gfc_get_ss ();
          newss->type = GFC_SS_SCALAR;
          newss->expr = ref->u.ss.start;
          newss->next = ss;
          ss = newss;

          newss = gfc_get_ss ();
          newss->type = GFC_SS_SCALAR;
          newss->expr = ref->u.ss.end;
          newss->next = ss;
          ss = newss;
        }

      /* We're only interested in array sections from now on.  */
      if (ref->type != REF_ARRAY)
        continue;

      ar = &ref->u.ar;
      switch (ar->type)
        {
        case AR_ELEMENT:
          for (n = 0; n < ar->dimen; n++)
            {
              newss = gfc_get_ss ();
              newss->type = GFC_SS_SCALAR;
              newss->expr = ar->start[n];
              newss->next = ss;
              ss = newss;
            }
          break;

        case AR_FULL:
          newss = gfc_get_ss ();
          newss->type = GFC_SS_SECTION;
          newss->expr = expr;
          newss->next = ss;
          newss->data.info.dimen = ar->as->rank;
          newss->data.info.ref = ref;

          /* Make sure array is the same as array(:,:), this way
             we don't need to special case all the time.  */
          ar->dimen = ar->as->rank;
          for (n = 0; n < ar->dimen; n++)
            {
              newss->data.info.dim[n] = n;
              ar->dimen_type[n] = DIMEN_RANGE;

              gcc_assert (ar->start[n] == NULL);
              gcc_assert (ar->end[n] == NULL);
              gcc_assert (ar->stride[n] == NULL);
            }
          ss = newss;
          break;

        case AR_SECTION:
          newss = gfc_get_ss ();
          newss->type = GFC_SS_SECTION;
          newss->expr = expr;
          newss->next = ss;
          newss->data.info.dimen = 0;
          newss->data.info.ref = ref;

          head = newss;

          /* We add SS chains for all the subscripts in the section.  */
          for (n = 0; n < ar->dimen; n++)
            {
              gfc_ss *indexss;

              switch (ar->dimen_type[n])
                {
                case DIMEN_ELEMENT:
                  /* Add SS for elemental (scalar) subscripts.  */
                  gcc_assert (ar->start[n]);
                  indexss = gfc_get_ss ();
                  indexss->type = GFC_SS_SCALAR;
                  indexss->expr = ar->start[n];
                  indexss->next = gfc_ss_terminator;
                  indexss->loop_chain = gfc_ss_terminator;
                  newss->data.info.subscript[n] = indexss;
                  break;

                case DIMEN_RANGE:
                  /* We don't add anything for sections, just remember this
                     dimension for later.  */
                  newss->data.info.dim[newss->data.info.dimen] = n;
                  newss->data.info.dimen++;
                  break;

                case DIMEN_VECTOR:
                  /* Create a GFC_SS_VECTOR index in which we can store
                     the vector's descriptor.  */
                  indexss = gfc_get_ss ();
                  indexss->type = GFC_SS_VECTOR;
                  indexss->expr = ar->start[n];
                  indexss->next = gfc_ss_terminator;
                  indexss->loop_chain = gfc_ss_terminator;
                  newss->data.info.subscript[n] = indexss;
                  newss->data.info.dim[newss->data.info.dimen] = n;
                  newss->data.info.dimen++;
                  break;

                default:
                  /* We should know what sort of section it is by now.  */
                  gcc_unreachable ();
                }
            }
          /* We should have at least one non-elemental dimension.  */
          gcc_assert (newss->data.info.dimen > 0);
          ss = newss;
          break;

        default:
          /* We should know what sort of section it is by now.  */
          gcc_unreachable ();
        }

    }
  return ss;
}


/* Walk an expression operator. If only one operand of a binary expression is
   scalar, we must also add the scalar term to the SS chain.  */

static gfc_ss *
gfc_walk_op_expr (gfc_ss * ss, gfc_expr * expr)
{
  gfc_ss *head;
  gfc_ss *head2;
  gfc_ss *newss;

  head = gfc_walk_subexpr (ss, expr->value.op.op1);
  if (expr->value.op.op2 == NULL)
    head2 = head;
  else
    head2 = gfc_walk_subexpr (head, expr->value.op.op2);

  /* All operands are scalar.  Pass back and let the caller deal with it.  */
  if (head2 == ss)
    return head2;

  /* All operands require scalarization.  */
  if (head != ss && (expr->value.op.op2 == NULL || head2 != head))
    return head2;

  /* One of the operands needs scalarization, the other is scalar.
     Create a gfc_ss for the scalar expression.  */
  newss = gfc_get_ss ();
  newss->type = GFC_SS_SCALAR;
  if (head == ss)
    {
      /* First operand is scalar.  We build the chain in reverse order, so
         add the scarar SS after the second operand.  */
      head = head2;
      while (head && head->next != ss)
        head = head->next;
      /* Check we haven't somehow broken the chain.  */
      gcc_assert (head);
      newss->next = ss;
      head->next = newss;
      newss->expr = expr->value.op.op1;
    }
  else                          /* head2 == head */
    {
      gcc_assert (head2 == head);
      /* Second operand is scalar.  */
      newss->next = head2;
      head2 = newss;
      newss->expr = expr->value.op.op2;
    }

  return head2;
}


/* Reverse a SS chain.  */

gfc_ss *
gfc_reverse_ss (gfc_ss * ss)
{
  gfc_ss *next;
  gfc_ss *head;

  gcc_assert (ss != NULL);

  head = gfc_ss_terminator;
  while (ss != gfc_ss_terminator)
    {
      next = ss->next;
      /* Check we didn't somehow break the chain.  */
      gcc_assert (next != NULL);
      ss->next = head;
      head = ss;
      ss = next;
    }

  return (head);
}


/* Walk the arguments of an elemental function.  */

gfc_ss *
gfc_walk_elemental_function_args (gfc_ss * ss, gfc_actual_arglist *arg,
                                  gfc_ss_type type)
{
  int scalar;
  gfc_ss *head;
  gfc_ss *tail;
  gfc_ss *newss;

  head = gfc_ss_terminator;
  tail = NULL;
  scalar = 1;
  for (; arg; arg = arg->next)
    {
      if (!arg->expr)
        continue;

      newss = gfc_walk_subexpr (head, arg->expr);
      if (newss == head)
        {
          /* Scalar argument.  */
          newss = gfc_get_ss ();
          newss->type = type;
          newss->expr = arg->expr;
          newss->next = head;
        }
      else
        scalar = 0;

      head = newss;
      if (!tail)
        {
          tail = head;
          while (tail->next != gfc_ss_terminator)
            tail = tail->next;
        }
    }

  if (scalar)
    {
      /* If all the arguments are scalar we don't need the argument SS.  */
      gfc_free_ss_chain (head);
      /* Pass it back.  */
      return ss;
    }

  /* Add it onto the existing chain.  */
  tail->next = ss;
  return head;
}


/* Walk a function call.  Scalar functions are passed back, and taken out of
   scalarization loops.  For elemental functions we walk their arguments.
   The result of functions returning arrays is stored in a temporary outside
   the loop, so that the function is only called once.  Hence we do not need
   to walk their arguments.  */

static gfc_ss *
gfc_walk_function_expr (gfc_ss * ss, gfc_expr * expr)
{
  gfc_ss *newss;
  gfc_intrinsic_sym *isym;
  gfc_symbol *sym;

  isym = expr->value.function.isym;

  /* Handle intrinsic functions separately.  */
  if (isym)
    return gfc_walk_intrinsic_function (ss, expr, isym);

  sym = expr->value.function.esym;
  if (!sym)
      sym = expr->symtree->n.sym;

  /* A function that returns arrays.  */
  if (gfc_return_by_reference (sym) && sym->result->attr.dimension)
    {
      newss = gfc_get_ss ();
      newss->type = GFC_SS_FUNCTION;
      newss->expr = expr;
      newss->next = ss;
      newss->data.info.dimen = expr->rank;
      return newss;
    }

  /* Walk the parameters of an elemental function.  For now we always pass
     by reference.  */
  if (sym->attr.elemental)
    return gfc_walk_elemental_function_args (ss, expr->value.function.actual,
                                             GFC_SS_REFERENCE);

  /* Scalar functions are OK as these are evaluated outside the scalarization
     loop.  Pass back and let the caller deal with it.  */
  return ss;
}


/* An array temporary is constructed for array constructors.  */

static gfc_ss *
gfc_walk_array_constructor (gfc_ss * ss, gfc_expr * expr)
{
  gfc_ss *newss;
  int n;

  newss = gfc_get_ss ();
  newss->type = GFC_SS_CONSTRUCTOR;
  newss->expr = expr;
  newss->next = ss;
  newss->data.info.dimen = expr->rank;
  for (n = 0; n < expr->rank; n++)
    newss->data.info.dim[n] = n;

  return newss;
}


/* Walk an expression.  Add walked expressions to the head of the SS chain.
   A wholly scalar expression will not be added.  */

static gfc_ss *
gfc_walk_subexpr (gfc_ss * ss, gfc_expr * expr)
{
  gfc_ss *head;

  switch (expr->expr_type)
    {
    case EXPR_VARIABLE:
      head = gfc_walk_variable_expr (ss, expr);
      return head;

    case EXPR_OP:
      head = gfc_walk_op_expr (ss, expr);
      return head;

    case EXPR_FUNCTION:
      head = gfc_walk_function_expr (ss, expr);
      return head;

    case EXPR_CONSTANT:
    case EXPR_NULL:
    case EXPR_STRUCTURE:
      /* Pass back and let the caller deal with it.  */
      break;

    case EXPR_ARRAY:
      head = gfc_walk_array_constructor (ss, expr);
      return head;

    case EXPR_SUBSTRING:
      /* Pass back and let the caller deal with it.  */
      break;

    default:
      internal_error ("bad expression type during walk (%d)",
                      expr->expr_type);
    }
  return ss;
}


/* Entry point for expression walking.
   A return value equal to the passed chain means this is
   a scalar expression.  It is up to the caller to take whatever action is
   necessary to translate these.  */

gfc_ss *
gfc_walk_expr (gfc_expr * expr)
{
  gfc_ss *res;

  res = gfc_walk_subexpr (gfc_ss_terminator, expr);
  return gfc_reverse_ss (res);
}