PR fortran/15326

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

/* Expression translation
   Copyright (C) 2002, 2003, 2004, 2005 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-expr.c-- generate GENERIC trees for gfc_expr.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tree.h"
#include "convert.h"
#include "ggc.h"
#include "toplev.h"
#include "real.h"
#include "tree-gimple.h"
#include "flags.h"
#include "gfortran.h"
#include "trans.h"
#include "trans-const.h"
#include "trans-types.h"
#include "trans-array.h"
/* Only for gfc_trans_assign and gfc_trans_pointer_assign.  */
#include "trans-stmt.h"

static tree gfc_trans_structure_assign (tree dest, gfc_expr * expr);

/* Copy the scalarization loop variables.  */

static void
gfc_copy_se_loopvars (gfc_se * dest, gfc_se * src)
{
  dest->ss = src->ss;
  dest->loop = src->loop;
}


/* Initialize a simple expression holder.

   Care must be taken when multiple se are created with the same parent.
   The child se must be kept in sync.  The easiest way is to delay creation
   of a child se until after after the previous se has been translated.  */

void
gfc_init_se (gfc_se * se, gfc_se * parent)
{
  memset (se, 0, sizeof (gfc_se));
  gfc_init_block (&se->pre);
  gfc_init_block (&se->post);

  se->parent = parent;

  if (parent)
    gfc_copy_se_loopvars (se, parent);
}


/* Advances to the next SS in the chain.  Use this rather than setting
   se->ss = se->ss->next because all the parents needs to be kept in sync.
   See gfc_init_se.  */

void
gfc_advance_se_ss_chain (gfc_se * se)
{
  gfc_se *p;

  gcc_assert (se != NULL && se->ss != NULL && se->ss != gfc_ss_terminator);

  p = se;
  /* Walk down the parent chain.  */
  while (p != NULL)
    {
      /* Simple consistency check.  */
      gcc_assert (p->parent == NULL || p->parent->ss == p->ss);

      p->ss = p->ss->next;

      p = p->parent;
    }
}


/* Ensures the result of the expression as either a temporary variable
   or a constant so that it can be used repeatedly.  */

void
gfc_make_safe_expr (gfc_se * se)
{
  tree var;

  if (CONSTANT_CLASS_P (se->expr))
    return;

  /* We need a temporary for this result.  */
  var = gfc_create_var (TREE_TYPE (se->expr), NULL);
  gfc_add_modify_expr (&se->pre, var, se->expr);
  se->expr = var;
}


/* Return an expression which determines if a dummy parameter is present.
   Also used for arguments to procedures with multiple entry points.  */

tree
gfc_conv_expr_present (gfc_symbol * sym)
{
  tree decl;

  gcc_assert (sym->attr.dummy);

  decl = gfc_get_symbol_decl (sym);
  if (TREE_CODE (decl) != PARM_DECL)
    {
      /* Array parameters use a temporary descriptor, we want the real
         parameter.  */
      gcc_assert (GFC_DESCRIPTOR_TYPE_P (TREE_TYPE (decl))
             || GFC_ARRAY_TYPE_P (TREE_TYPE (decl)));
      decl = GFC_DECL_SAVED_DESCRIPTOR (decl);
    }
  return build2 (NE_EXPR, boolean_type_node, decl,
                 fold_convert (TREE_TYPE (decl), null_pointer_node));
}


/* Get the character length of an expression, looking through gfc_refs
   if necessary.  */

tree
gfc_get_expr_charlen (gfc_expr *e)
{
  gfc_ref *r;
  tree length;

  gcc_assert (e->expr_type == EXPR_VARIABLE 
              && e->ts.type == BT_CHARACTER);
  
  length = NULL; /* To silence compiler warning.  */

  /* First candidate: if the variable is of type CHARACTER, the
     expression's length could be the length of the character
     variable.  */
  if (e->symtree->n.sym->ts.type == BT_CHARACTER)
    length = e->symtree->n.sym->ts.cl->backend_decl;

  /* Look through the reference chain for component references.  */
  for (r = e->ref; r; r = r->next)
    {
      switch (r->type)
        {
        case REF_COMPONENT:
          if (r->u.c.component->ts.type == BT_CHARACTER)
            length = r->u.c.component->ts.cl->backend_decl;
          break;

        case REF_ARRAY:
          /* Do nothing.  */
          break;

        default:
          /* We should never got substring references here.  These will be
             broken down by the scalarizer.  */
          gcc_unreachable ();
        }
    }

  gcc_assert (length != NULL);
  return length;
}

  

/* Generate code to initialize a string length variable. Returns the
   value.  */

void
gfc_trans_init_string_length (gfc_charlen * cl, stmtblock_t * pblock)
{
  gfc_se se;
  tree tmp;

  gfc_init_se (&se, NULL);
  gfc_conv_expr_type (&se, cl->length, gfc_charlen_type_node);
  gfc_add_block_to_block (pblock, &se.pre);

  tmp = cl->backend_decl;
  gfc_add_modify_expr (pblock, tmp, se.expr);
}


static void
gfc_conv_substring (gfc_se * se, gfc_ref * ref, int kind)
{
  tree tmp;
  tree type;
  tree var;
  gfc_se start;
  gfc_se end;

  type = gfc_get_character_type (kind, ref->u.ss.length);
  type = build_pointer_type (type);

  var = NULL_TREE;
  gfc_init_se (&start, se);
  gfc_conv_expr_type (&start, ref->u.ss.start, gfc_charlen_type_node);
  gfc_add_block_to_block (&se->pre, &start.pre);

  if (integer_onep (start.expr))
    gfc_conv_string_parameter (se);
  else
    {
      /* Change the start of the string.  */
      if (TYPE_STRING_FLAG (TREE_TYPE (se->expr)))
        tmp = se->expr;
      else
        tmp = gfc_build_indirect_ref (se->expr);
      tmp = gfc_build_array_ref (tmp, start.expr);
      se->expr = gfc_build_addr_expr (type, tmp);
    }

  /* Length = end + 1 - start.  */
  gfc_init_se (&end, se);
  if (ref->u.ss.end == NULL)
    end.expr = se->string_length;
  else
    {
      gfc_conv_expr_type (&end, ref->u.ss.end, gfc_charlen_type_node);
      gfc_add_block_to_block (&se->pre, &end.pre);
    }
  tmp =
    build2 (MINUS_EXPR, gfc_charlen_type_node,
            fold_convert (gfc_charlen_type_node, integer_one_node),
            start.expr);
  tmp = build2 (PLUS_EXPR, gfc_charlen_type_node, end.expr, tmp);
  se->string_length = fold (tmp);
}


/* Convert a derived type component reference.  */

static void
gfc_conv_component_ref (gfc_se * se, gfc_ref * ref)
{
  gfc_component *c;
  tree tmp;
  tree decl;
  tree field;

  c = ref->u.c.component;

  gcc_assert (c->backend_decl);

  field = c->backend_decl;
  gcc_assert (TREE_CODE (field) == FIELD_DECL);
  decl = se->expr;
  tmp = build3 (COMPONENT_REF, TREE_TYPE (field), decl, field, NULL_TREE);

  se->expr = tmp;

  if (c->ts.type == BT_CHARACTER)
    {
      tmp = c->ts.cl->backend_decl;
      /* Components must always be constant length.  */
      gcc_assert (tmp && INTEGER_CST_P (tmp));
      se->string_length = tmp;
    }

  if (c->pointer && c->dimension == 0 && c->ts.type != BT_CHARACTER)
    se->expr = gfc_build_indirect_ref (se->expr);
}


/* Return the contents of a variable. Also handles reference/pointer
   variables (all Fortran pointer references are implicit).  */

static void
gfc_conv_variable (gfc_se * se, gfc_expr * expr)
{
  gfc_ref *ref;
  gfc_symbol *sym;

  sym = expr->symtree->n.sym;
  if (se->ss != NULL)
    {
      /* Check that something hasn't gone horribly wrong.  */
      gcc_assert (se->ss != gfc_ss_terminator);
      gcc_assert (se->ss->expr == expr);

      /* A scalarized term.  We already know the descriptor.  */
      se->expr = se->ss->data.info.descriptor;
      se->string_length = se->ss->string_length;
      for (ref = se->ss->data.info.ref; ref; ref = ref->next)
        if (ref->type == REF_ARRAY && ref->u.ar.type != AR_ELEMENT)
          break;
    }
  else
    {
      tree se_expr = NULL_TREE;

      se->expr = gfc_get_symbol_decl (sym);

      /* Special case for assigning the return value of a function.
         Self recursive functions must have an explicit return value.  */
      if (se->expr == current_function_decl && sym->attr.function
          && (sym->result == sym))
        se_expr = gfc_get_fake_result_decl (sym);

      /* Similarly for alternate entry points.  */
      else if (sym->attr.function && sym->attr.entry
               && (sym->result == sym)
               && sym->ns->proc_name->backend_decl == current_function_decl)
        {
          gfc_entry_list *el = NULL;

          for (el = sym->ns->entries; el; el = el->next)
            if (sym == el->sym)
              {
                se_expr = gfc_get_fake_result_decl (sym);
                break;
              }
        }

      else if (sym->attr.result
               && sym->ns->proc_name->backend_decl == current_function_decl
               && sym->ns->proc_name->attr.entry_master
               && !gfc_return_by_reference (sym->ns->proc_name))
        se_expr = gfc_get_fake_result_decl (sym);

      if (se_expr)
        se->expr = se_expr;

      /* Procedure actual arguments.  */
      else if (sym->attr.flavor == FL_PROCEDURE
               && se->expr != current_function_decl)
        {
          gcc_assert (se->want_pointer);
          if (!sym->attr.dummy)
            {
              gcc_assert (TREE_CODE (se->expr) == FUNCTION_DECL);
              se->expr = gfc_build_addr_expr (NULL, se->expr);
            }
          return;
        }


      /* Dereference the expression, where needed. Since characters
         are entirely different from other types, they are treated 
         separately.  */
      if (sym->ts.type == BT_CHARACTER)
        {
          /* Dereference character pointer dummy arguments
             or results.  */
          if ((sym->attr.pointer || sym->attr.allocatable)
              && (sym->attr.dummy
                  || sym->attr.function
                  || sym->attr.result))
            se->expr = gfc_build_indirect_ref (se->expr);
        }
      else
        {
          /* Dereference non-character scalar dummy arguments.  */
          if (sym->attr.dummy && !sym->attr.dimension)
            se->expr = gfc_build_indirect_ref (se->expr);

          /* Dereference scalar hidden result.  */
          if (gfc_option.flag_f2c && sym->ts.type == BT_COMPLEX
              && (sym->attr.function || sym->attr.result)
              && !sym->attr.dimension && !sym->attr.pointer)
            se->expr = gfc_build_indirect_ref (se->expr);

          /* Dereference non-character pointer variables. 
             These must be dummies, results, or scalars.  */
          if ((sym->attr.pointer || sym->attr.allocatable)
              && (sym->attr.dummy
                  || sym->attr.function
                  || sym->attr.result
                  || !sym->attr.dimension))
            se->expr = gfc_build_indirect_ref (se->expr);
        }

      ref = expr->ref;
    }

  /* For character variables, also get the length.  */
  if (sym->ts.type == BT_CHARACTER)
    {
      se->string_length = sym->ts.cl->backend_decl;
      gcc_assert (se->string_length);
    }

  while (ref)
    {
      switch (ref->type)
        {
        case REF_ARRAY:
          /* Return the descriptor if that's what we want and this is an array
             section reference.  */
          if (se->descriptor_only && ref->u.ar.type != AR_ELEMENT)
            return;
/* TODO: Pointers to single elements of array sections, eg elemental subs.  */
          /* Return the descriptor for array pointers and allocations.  */
          if (se->want_pointer
              && ref->next == NULL && (se->descriptor_only))
            return;

          gfc_conv_array_ref (se, &ref->u.ar);
          /* Return a pointer to an element.  */
          break;

        case REF_COMPONENT:
          gfc_conv_component_ref (se, ref);
          break;

        case REF_SUBSTRING:
          gfc_conv_substring (se, ref, expr->ts.kind);
          break;

        default:
          gcc_unreachable ();
          break;
        }
      ref = ref->next;
    }
  /* Pointer assignment, allocation or pass by reference.  Arrays are handled
     separately.  */
  if (se->want_pointer)
    {
      if (expr->ts.type == BT_CHARACTER)
        gfc_conv_string_parameter (se);
      else 
        se->expr = gfc_build_addr_expr (NULL, se->expr);
    }
}


/* Unary ops are easy... Or they would be if ! was a valid op.  */

static void
gfc_conv_unary_op (enum tree_code code, gfc_se * se, gfc_expr * expr)
{
  gfc_se operand;
  tree type;

  gcc_assert (expr->ts.type != BT_CHARACTER);
  /* Initialize the operand.  */
  gfc_init_se (&operand, se);
  gfc_conv_expr_val (&operand, expr->value.op.op1);
  gfc_add_block_to_block (&se->pre, &operand.pre);

  type = gfc_typenode_for_spec (&expr->ts);

  /* TRUTH_NOT_EXPR is not a "true" unary operator in GCC.
     We must convert it to a compare to 0 (e.g. EQ_EXPR (op1, 0)).
     All other unary operators have an equivalent GIMPLE unary operator.  */
  if (code == TRUTH_NOT_EXPR)
    se->expr = build2 (EQ_EXPR, type, operand.expr,
                       convert (type, integer_zero_node));
  else
    se->expr = build1 (code, type, operand.expr);

}

/* Expand power operator to optimal multiplications when a value is raised
   to a constant integer n. See section 4.6.3, "Evaluation of Powers" of
   Donald E. Knuth, "Seminumerical Algorithms", Vol. 2, "The Art of Computer
   Programming", 3rd Edition, 1998.  */

/* This code is mostly duplicated from expand_powi in the backend.
   We establish the "optimal power tree" lookup table with the defined size.
   The items in the table are the exponents used to calculate the index
   exponents. Any integer n less than the value can get an "addition chain",
   with the first node being one.  */
#define POWI_TABLE_SIZE 256

/* The table is from builtins.c.  */
static const unsigned char powi_table[POWI_TABLE_SIZE] =
  {
      0,   1,   1,   2,   2,   3,   3,   4,  /*   0 -   7 */
      4,   6,   5,   6,   6,  10,   7,   9,  /*   8 -  15 */
      8,  16,   9,  16,  10,  12,  11,  13,  /*  16 -  23 */
     12,  17,  13,  18,  14,  24,  15,  26,  /*  24 -  31 */
     16,  17,  17,  19,  18,  33,  19,  26,  /*  32 -  39 */
     20,  25,  21,  40,  22,  27,  23,  44,  /*  40 -  47 */
     24,  32,  25,  34,  26,  29,  27,  44,  /*  48 -  55 */
     28,  31,  29,  34,  30,  60,  31,  36,  /*  56 -  63 */
     32,  64,  33,  34,  34,  46,  35,  37,  /*  64 -  71 */
     36,  65,  37,  50,  38,  48,  39,  69,  /*  72 -  79 */
     40,  49,  41,  43,  42,  51,  43,  58,  /*  80 -  87 */
     44,  64,  45,  47,  46,  59,  47,  76,  /*  88 -  95 */
     48,  65,  49,  66,  50,  67,  51,  66,  /*  96 - 103 */
     52,  70,  53,  74,  54, 104,  55,  74,  /* 104 - 111 */
     56,  64,  57,  69,  58,  78,  59,  68,  /* 112 - 119 */
     60,  61,  61,  80,  62,  75,  63,  68,  /* 120 - 127 */
     64,  65,  65, 128,  66, 129,  67,  90,  /* 128 - 135 */
     68,  73,  69, 131,  70,  94,  71,  88,  /* 136 - 143 */
     72, 128,  73,  98,  74, 132,  75, 121,  /* 144 - 151 */
     76, 102,  77, 124,  78, 132,  79, 106,  /* 152 - 159 */
     80,  97,  81, 160,  82,  99,  83, 134,  /* 160 - 167 */
     84,  86,  85,  95,  86, 160,  87, 100,  /* 168 - 175 */
     88, 113,  89,  98,  90, 107,  91, 122,  /* 176 - 183 */
     92, 111,  93, 102,  94, 126,  95, 150,  /* 184 - 191 */
     96, 128,  97, 130,  98, 133,  99, 195,  /* 192 - 199 */
    100, 128, 101, 123, 102, 164, 103, 138,  /* 200 - 207 */
    104, 145, 105, 146, 106, 109, 107, 149,  /* 208 - 215 */
    108, 200, 109, 146, 110, 170, 111, 157,  /* 216 - 223 */
    112, 128, 113, 130, 114, 182, 115, 132,  /* 224 - 231 */
    116, 200, 117, 132, 118, 158, 119, 206,  /* 232 - 239 */
    120, 240, 121, 162, 122, 147, 123, 152,  /* 240 - 247 */
    124, 166, 125, 214, 126, 138, 127, 153,  /* 248 - 255 */
  };

/* If n is larger than lookup table's max index, we use the "window 
   method".  */
#define POWI_WINDOW_SIZE 3

/* Recursive function to expand the power operator. The temporary 
   values are put in tmpvar. The function returns tmpvar[1] ** n.  */
static tree
gfc_conv_powi (gfc_se * se, int n, tree * tmpvar)
{
  tree op0;
  tree op1;
  tree tmp;
  int digit;

  if (n < POWI_TABLE_SIZE)
    {
      if (tmpvar[n])
        return tmpvar[n];

      op0 = gfc_conv_powi (se, n - powi_table[n], tmpvar);
      op1 = gfc_conv_powi (se, powi_table[n], tmpvar);
    }
  else if (n & 1)
    {
      digit = n & ((1 << POWI_WINDOW_SIZE) - 1);
      op0 = gfc_conv_powi (se, n - digit, tmpvar);
      op1 = gfc_conv_powi (se, digit, tmpvar);
    }
  else
    {
      op0 = gfc_conv_powi (se, n >> 1, tmpvar);
      op1 = op0;
    }

  tmp = fold_build2 (MULT_EXPR, TREE_TYPE (op0), op0, op1);
  tmp = gfc_evaluate_now (tmp, &se->pre);

  if (n < POWI_TABLE_SIZE)
    tmpvar[n] = tmp;

  return tmp;
}


/* Expand lhs ** rhs. rhs is a constant integer. If it expands successfully,
   return 1. Else return 0 and a call to runtime library functions
   will have to be built.  */
static int
gfc_conv_cst_int_power (gfc_se * se, tree lhs, tree rhs)
{
  tree cond;
  tree tmp;
  tree type;
  tree vartmp[POWI_TABLE_SIZE];
  int n;
  int sgn;

  type = TREE_TYPE (lhs);
  n = abs (TREE_INT_CST_LOW (rhs));
  sgn = tree_int_cst_sgn (rhs);

  if (((FLOAT_TYPE_P (type) && !flag_unsafe_math_optimizations) || optimize_size)
      && (n > 2 || n < -1))
    return 0;

  /* rhs == 0  */
  if (sgn == 0)
    {
      se->expr = gfc_build_const (type, integer_one_node);
      return 1;
    }
  /* If rhs < 0 and lhs is an integer, the result is -1, 0 or 1.  */
  if ((sgn == -1) && (TREE_CODE (type) == INTEGER_TYPE))
    {
      tmp = build2 (EQ_EXPR, boolean_type_node, lhs,
                    fold_convert (TREE_TYPE (lhs), integer_minus_one_node));
      cond = build2 (EQ_EXPR, boolean_type_node, lhs,
                     convert (TREE_TYPE (lhs), integer_one_node));

      /* If rhs is even,
         result = (lhs == 1 || lhs == -1) ? 1 : 0.  */
      if ((n & 1) == 0)
        {
          tmp = build2 (TRUTH_OR_EXPR, boolean_type_node, tmp, cond);
          se->expr = build3 (COND_EXPR, type, tmp,
                             convert (type, integer_one_node),
                             convert (type, integer_zero_node));
          return 1;
        }
      /* If rhs is odd,
         result = (lhs == 1) ? 1 : (lhs == -1) ? -1 : 0.  */
      tmp = build3 (COND_EXPR, type, tmp,
                    convert (type, integer_minus_one_node),
                    convert (type, integer_zero_node));
      se->expr = build3 (COND_EXPR, type, cond,
                         convert (type, integer_one_node),
                         tmp);
      return 1;
    }

  memset (vartmp, 0, sizeof (vartmp));
  vartmp[1] = lhs;
  if (sgn == -1)
    {
      tmp = gfc_build_const (type, integer_one_node);
      vartmp[1] = build2 (RDIV_EXPR, type, tmp, vartmp[1]);
    }

  se->expr = gfc_conv_powi (se, n, vartmp);

  return 1;
}


/* Power op (**).  Constant integer exponent has special handling.  */

static void
gfc_conv_power_op (gfc_se * se, gfc_expr * expr)
{
  tree gfc_int4_type_node;
  int kind;
  int ikind;
  gfc_se lse;
  gfc_se rse;
  tree fndecl;
  tree tmp;

  gfc_init_se (&lse, se);
  gfc_conv_expr_val (&lse, expr->value.op.op1);
  lse.expr = gfc_evaluate_now (lse.expr, &lse.pre);
  gfc_add_block_to_block (&se->pre, &lse.pre);

  gfc_init_se (&rse, se);
  gfc_conv_expr_val (&rse, expr->value.op.op2);
  gfc_add_block_to_block (&se->pre, &rse.pre);

  if (expr->value.op.op2->ts.type == BT_INTEGER
         && expr->value.op.op2->expr_type == EXPR_CONSTANT)
    if (gfc_conv_cst_int_power (se, lse.expr, rse.expr))
      return;        

  gfc_int4_type_node = gfc_get_int_type (4);

  kind = expr->value.op.op1->ts.kind;
  switch (expr->value.op.op2->ts.type)
    {
    case BT_INTEGER:
      ikind = expr->value.op.op2->ts.kind;
      switch (ikind)
        {
        case 1:
        case 2:
          rse.expr = convert (gfc_int4_type_node, rse.expr);
          /* Fall through.  */

        case 4:
          ikind = 0;
          break;
          
        case 8:
          ikind = 1;
          break;

        default:
          gcc_unreachable ();
        }
      switch (kind)
        {
        case 1:
        case 2:
          if (expr->value.op.op1->ts.type == BT_INTEGER)
            lse.expr = convert (gfc_int4_type_node, lse.expr);
          else
            gcc_unreachable ();
          /* Fall through.  */

        case 4:
          kind = 0;
          break;
          
        case 8:
          kind = 1;
          break;

        default:
          gcc_unreachable ();
        }
      
      switch (expr->value.op.op1->ts.type)
        {
        case BT_INTEGER:
          fndecl = gfor_fndecl_math_powi[kind][ikind].integer;
          break;

        case BT_REAL:
          fndecl = gfor_fndecl_math_powi[kind][ikind].real;
          break;

        case BT_COMPLEX:
          fndecl = gfor_fndecl_math_powi[kind][ikind].cmplx;
          break;

        default:
          gcc_unreachable ();
        }
      break;

    case BT_REAL:
      switch (kind)
        {
        case 4:
          fndecl = built_in_decls[BUILT_IN_POWF];
          break;
        case 8:
          fndecl = built_in_decls[BUILT_IN_POW];
          break;
        default:
          gcc_unreachable ();
        }
      break;

    case BT_COMPLEX:
      switch (kind)
        {
        case 4:
          fndecl = gfor_fndecl_math_cpowf;
          break;
        case 8:
          fndecl = gfor_fndecl_math_cpow;
          break;
        default:
          gcc_unreachable ();
        }
      break;

    default:
      gcc_unreachable ();
      break;
    }

  tmp = gfc_chainon_list (NULL_TREE, lse.expr);
  tmp = gfc_chainon_list (tmp, rse.expr);
  se->expr = fold (gfc_build_function_call (fndecl, tmp));
}


/* Generate code to allocate a string temporary.  */

tree
gfc_conv_string_tmp (gfc_se * se, tree type, tree len)
{
  tree var;
  tree tmp;
  tree args;

  gcc_assert (TREE_TYPE (len) == gfc_charlen_type_node);

  if (gfc_can_put_var_on_stack (len))
    {
      /* Create a temporary variable to hold the result.  */
      tmp = fold_build2 (MINUS_EXPR, gfc_charlen_type_node, len,
                         convert (gfc_charlen_type_node, integer_one_node));
      tmp = build_range_type (gfc_array_index_type, gfc_index_zero_node, tmp);
      tmp = build_array_type (gfc_character1_type_node, tmp);
      var = gfc_create_var (tmp, "str");
      var = gfc_build_addr_expr (type, var);
    }
  else
    {
      /* Allocate a temporary to hold the result.  */
      var = gfc_create_var (type, "pstr");
      args = gfc_chainon_list (NULL_TREE, len);
      tmp = gfc_build_function_call (gfor_fndecl_internal_malloc, args);
      tmp = convert (type, tmp);
      gfc_add_modify_expr (&se->pre, var, tmp);

      /* Free the temporary afterwards.  */
      tmp = convert (pvoid_type_node, var);
      args = gfc_chainon_list (NULL_TREE, tmp);
      tmp = gfc_build_function_call (gfor_fndecl_internal_free, args);
      gfc_add_expr_to_block (&se->post, tmp);
    }

  return var;
}


/* Handle a string concatenation operation.  A temporary will be allocated to
   hold the result.  */

static void
gfc_conv_concat_op (gfc_se * se, gfc_expr * expr)
{
  gfc_se lse;
  gfc_se rse;
  tree len;
  tree type;
  tree var;
  tree args;
  tree tmp;

  gcc_assert (expr->value.op.op1->ts.type == BT_CHARACTER
          && expr->value.op.op2->ts.type == BT_CHARACTER);

  gfc_init_se (&lse, se);
  gfc_conv_expr (&lse, expr->value.op.op1);
  gfc_conv_string_parameter (&lse);
  gfc_init_se (&rse, se);
  gfc_conv_expr (&rse, expr->value.op.op2);
  gfc_conv_string_parameter (&rse);

  gfc_add_block_to_block (&se->pre, &lse.pre);
  gfc_add_block_to_block (&se->pre, &rse.pre);

  type = gfc_get_character_type (expr->ts.kind, expr->ts.cl);
  len = TYPE_MAX_VALUE (TYPE_DOMAIN (type));
  if (len == NULL_TREE)
    {
      len = fold_build2 (PLUS_EXPR, TREE_TYPE (lse.string_length),
                         lse.string_length, rse.string_length);
    }

  type = build_pointer_type (type);

  var = gfc_conv_string_tmp (se, type, len);

  /* Do the actual concatenation.  */
  args = NULL_TREE;
  args = gfc_chainon_list (args, len);
  args = gfc_chainon_list (args, var);
  args = gfc_chainon_list (args, lse.string_length);
  args = gfc_chainon_list (args, lse.expr);
  args = gfc_chainon_list (args, rse.string_length);
  args = gfc_chainon_list (args, rse.expr);
  tmp = gfc_build_function_call (gfor_fndecl_concat_string, args);
  gfc_add_expr_to_block (&se->pre, tmp);

  /* Add the cleanup for the operands.  */
  gfc_add_block_to_block (&se->pre, &rse.post);
  gfc_add_block_to_block (&se->pre, &lse.post);

  se->expr = var;
  se->string_length = len;
}


/* Translates an op expression. Common (binary) cases are handled by this
   function, others are passed on. Recursion is used in either case.
   We use the fact that (op1.ts == op2.ts) (except for the power
   operator **).
   Operators need no special handling for scalarized expressions as long as
   they call gfc_conv_simple_val to get their operands.
   Character strings get special handling.  */

static void
gfc_conv_expr_op (gfc_se * se, gfc_expr * expr)
{
  enum tree_code code;
  gfc_se lse;
  gfc_se rse;
  tree type;
  tree tmp;
  int lop;
  int checkstring;

  checkstring = 0;
  lop = 0;
  switch (expr->value.op.operator)
    {
    case INTRINSIC_UPLUS:
      gfc_conv_expr (se, expr->value.op.op1);
      return;

    case INTRINSIC_UMINUS:
      gfc_conv_unary_op (NEGATE_EXPR, se, expr);
      return;

    case INTRINSIC_NOT:
      gfc_conv_unary_op (TRUTH_NOT_EXPR, se, expr);
      return;

    case INTRINSIC_PLUS:
      code = PLUS_EXPR;
      break;

    case INTRINSIC_MINUS:
      code = MINUS_EXPR;
      break;

    case INTRINSIC_TIMES:
      code = MULT_EXPR;
      break;

    case INTRINSIC_DIVIDE:
      /* If expr is a real or complex expr, use an RDIV_EXPR. If op1 is
         an integer, we must round towards zero, so we use a
         TRUNC_DIV_EXPR.  */
      if (expr->ts.type == BT_INTEGER)
        code = TRUNC_DIV_EXPR;
      else
        code = RDIV_EXPR;
      break;

    case INTRINSIC_POWER:
      gfc_conv_power_op (se, expr);
      return;

    case INTRINSIC_CONCAT:
      gfc_conv_concat_op (se, expr);
      return;

    case INTRINSIC_AND:
      code = TRUTH_ANDIF_EXPR;
      lop = 1;
      break;

    case INTRINSIC_OR:
      code = TRUTH_ORIF_EXPR;
      lop = 1;
      break;

      /* EQV and NEQV only work on logicals, but since we represent them
         as integers, we can use EQ_EXPR and NE_EXPR for them in GIMPLE.  */
    case INTRINSIC_EQ:
    case INTRINSIC_EQV:
      code = EQ_EXPR;
      checkstring = 1;
      lop = 1;
      break;

    case INTRINSIC_NE:
    case INTRINSIC_NEQV:
      code = NE_EXPR;
      checkstring = 1;
      lop = 1;
      break;

    case INTRINSIC_GT:
      code = GT_EXPR;
      checkstring = 1;
      lop = 1;
      break;

    case INTRINSIC_GE:
      code = GE_EXPR;
      checkstring = 1;
      lop = 1;
      break;

    case INTRINSIC_LT:
      code = LT_EXPR;
      checkstring = 1;
      lop = 1;
      break;

    case INTRINSIC_LE:
      code = LE_EXPR;
      checkstring = 1;
      lop = 1;
      break;

    case INTRINSIC_USER:
    case INTRINSIC_ASSIGN:
      /* These should be converted into function calls by the frontend.  */
      gcc_unreachable ();

    default:
      fatal_error ("Unknown intrinsic op");
      return;
    }

  /* The only exception to this is **, which is handled separately anyway.  */
  gcc_assert (expr->value.op.op1->ts.type == expr->value.op.op2->ts.type);

  if (checkstring && expr->value.op.op1->ts.type != BT_CHARACTER)
    checkstring = 0;

  /* lhs */
  gfc_init_se (&lse, se);
  gfc_conv_expr (&lse, expr->value.op.op1);
  gfc_add_block_to_block (&se->pre, &lse.pre);

  /* rhs */
  gfc_init_se (&rse, se);
  gfc_conv_expr (&rse, expr->value.op.op2);
  gfc_add_block_to_block (&se->pre, &rse.pre);

  /* For string comparisons we generate a library call, and compare the return
     value with 0.  */
  if (checkstring)
    {
      gfc_conv_string_parameter (&lse);
      gfc_conv_string_parameter (&rse);
      tmp = NULL_TREE;
      tmp = gfc_chainon_list (tmp, lse.string_length);
      tmp = gfc_chainon_list (tmp, lse.expr);
      tmp = gfc_chainon_list (tmp, rse.string_length);
      tmp = gfc_chainon_list (tmp, rse.expr);

      /* Build a call for the comparison.  */
      lse.expr = gfc_build_function_call (gfor_fndecl_compare_string, tmp);
      gfc_add_block_to_block (&lse.post, &rse.post);

      rse.expr = integer_zero_node;
    }

  type = gfc_typenode_for_spec (&expr->ts);

  if (lop)
    {
      /* The result of logical ops is always boolean_type_node.  */
      tmp = fold_build2 (code, type, lse.expr, rse.expr);
      se->expr = convert (type, tmp);
    }
  else
    se->expr = fold_build2 (code, type, lse.expr, rse.expr);

  /* Add the post blocks.  */
  gfc_add_block_to_block (&se->post, &rse.post);
  gfc_add_block_to_block (&se->post, &lse.post);
}


static void
gfc_conv_function_val (gfc_se * se, gfc_symbol * sym)
{
  tree tmp;

  if (sym->attr.dummy)
    {
      tmp = gfc_get_symbol_decl (sym);
      gcc_assert (TREE_CODE (TREE_TYPE (tmp)) == POINTER_TYPE
              && TREE_CODE (TREE_TYPE (TREE_TYPE (tmp))) == FUNCTION_TYPE);
    }
  else
    {
      if (!sym->backend_decl)
        sym->backend_decl = gfc_get_extern_function_decl (sym);

      tmp = sym->backend_decl;
      if (!POINTER_TYPE_P (TREE_TYPE (tmp)))
        {
          gcc_assert (TREE_CODE (tmp) == FUNCTION_DECL);
          tmp = gfc_build_addr_expr (NULL, tmp);
        }
    }
  se->expr = tmp;
}


/* This group of functions allows a caller to evaluate an expression from
   the callee's interface.  It establishes a mapping between the interface's
   dummy arguments and the caller's actual arguments, then applies that
   mapping to a given gfc_expr.

   You can initialize a mapping structure like so:

       gfc_interface_mapping mapping;
       ...
       gfc_init_interface_mapping (&mapping);

   You should then evaluate each actual argument into a temporary
   gfc_se structure, here called "se", and map the result to the
   dummy argument's symbol, here called "sym":

       gfc_add_interface_mapping (&mapping, sym, &se);

   After adding all mappings, you should call:

       gfc_finish_interface_mapping (&mapping, pre, post);

   where "pre" and "post" are statement blocks for initialization
   and finalization code respectively.  You can then evaluate an
   interface expression "expr" as follows:

       gfc_apply_interface_mapping (&mapping, se, expr);

   Once you've evaluated all expressions, you should free
   the mapping structure with:

       gfc_free_interface_mapping (&mapping); */


/* This structure represents a mapping from OLD to NEW, where OLD is a
   dummy argument symbol and NEW is a symbol that represents the value
   of an actual argument.  Mappings are linked together using NEXT
   (in no particular order).  */
typedef struct gfc_interface_sym_mapping
{
  struct gfc_interface_sym_mapping *next;
  gfc_symbol *old;
  gfc_symtree *new;
}
gfc_interface_sym_mapping;


/* This structure is used by callers to evaluate an expression from
   a callee's interface.  */
typedef struct gfc_interface_mapping
{
  /* Maps the interface's dummy arguments to the values that the caller
     is passing.  The whole list is owned by this gfc_interface_mapping.  */
  gfc_interface_sym_mapping *syms;

  /* A list of gfc_charlens that were needed when creating copies of
     expressions.  The whole list is owned by this gfc_interface_mapping.  */
  gfc_charlen *charlens;
}
gfc_interface_mapping;


static void gfc_apply_interface_mapping_to_expr (gfc_interface_mapping *,
                                                 gfc_expr *);

/* Initialize MAPPING.  */

static void
gfc_init_interface_mapping (gfc_interface_mapping * mapping)
{
  mapping->syms = NULL;
  mapping->charlens = NULL;
}


/* Free all memory held by MAPPING (but not MAPPING itself).  */

static void
gfc_free_interface_mapping (gfc_interface_mapping * mapping)
{
  gfc_interface_sym_mapping *sym;
  gfc_interface_sym_mapping *nextsym;
  gfc_charlen *cl;
  gfc_charlen *nextcl;

  for (sym = mapping->syms; sym; sym = nextsym)
    {
      nextsym = sym->next;
      gfc_free_symbol (sym->new->n.sym);
      gfc_free (sym->new);
      gfc_free (sym);
    }
  for (cl = mapping->charlens; cl; cl = nextcl)
    {
      nextcl = cl->next;
      gfc_free_expr (cl->length);
      gfc_free (cl);
    }
}


/* Return a copy of gfc_charlen CL.  Add the returned structure to
   MAPPING so that it will be freed by gfc_free_interface_mapping.  */

static gfc_charlen *
gfc_get_interface_mapping_charlen (gfc_interface_mapping * mapping,
                                   gfc_charlen * cl)
{
  gfc_charlen *new;

  new = gfc_get_charlen ();
  new->next = mapping->charlens;
  new->length = gfc_copy_expr (cl->length);

  mapping->charlens = new;
  return new;
}


/* A subroutine of gfc_add_interface_mapping.  Return a descriptorless
   array variable that can be used as the actual argument for dummy
   argument SYM.  Add any initialization code to BLOCK.  PACKED is as
   for gfc_get_nodesc_array_type and DATA points to the first element
   in the passed array.  */

static tree
gfc_get_interface_mapping_array (stmtblock_t * block, gfc_symbol * sym,
                                 int packed, tree data)
{
  tree type;
  tree var;

  type = gfc_typenode_for_spec (&sym->ts);
  type = gfc_get_nodesc_array_type (type, sym->as, packed);

  var = gfc_create_var (type, "parm");
  gfc_add_modify_expr (block, var, fold_convert (type, data));

  return var;
}


/* A subroutine of gfc_add_interface_mapping.  Set the stride, upper bounds
   and offset of descriptorless array type TYPE given that it has the same
   size as DESC.  Add any set-up code to BLOCK.  */

static void
gfc_set_interface_mapping_bounds (stmtblock_t * block, tree type, tree desc)
{
  int n;
  tree dim;
  tree offset;
  tree tmp;

  offset = gfc_index_zero_node;
  for (n = 0; n < GFC_TYPE_ARRAY_RANK (type); n++)
    {
      GFC_TYPE_ARRAY_STRIDE (type, n) = gfc_conv_array_stride (desc, n);
      if (GFC_TYPE_ARRAY_UBOUND (type, n) == NULL_TREE)
        {
          dim = gfc_rank_cst[n];
          tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type,
                             gfc_conv_descriptor_ubound (desc, dim),
                             gfc_conv_descriptor_lbound (desc, dim));
          tmp = fold_build2 (PLUS_EXPR, gfc_array_index_type,
                             GFC_TYPE_ARRAY_LBOUND (type, n),
                             tmp);
          tmp = gfc_evaluate_now (tmp, block);
          GFC_TYPE_ARRAY_UBOUND (type, n) = tmp;
        }
      tmp = fold_build2 (MULT_EXPR, gfc_array_index_type,
                         GFC_TYPE_ARRAY_LBOUND (type, n),
                         GFC_TYPE_ARRAY_STRIDE (type, n));
      offset = fold_build2 (MINUS_EXPR, gfc_array_index_type, offset, tmp);
    }
  offset = gfc_evaluate_now (offset, block);
  GFC_TYPE_ARRAY_OFFSET (type) = offset;
}


/* Extend MAPPING so that it maps dummy argument SYM to the value stored
   in SE.  The caller may still use se->expr and se->string_length after
   calling this function.  */

static void
gfc_add_interface_mapping (gfc_interface_mapping * mapping,
                           gfc_symbol * sym, gfc_se * se)
{
  gfc_interface_sym_mapping *sm;
  tree desc;
  tree tmp;
  tree value;
  gfc_symbol *new_sym;
  gfc_symtree *root;
  gfc_symtree *new_symtree;

  /* Create a new symbol to represent the actual argument.  */
  new_sym = gfc_new_symbol (sym->name, NULL);
  new_sym->ts = sym->ts;
  new_sym->attr.referenced = 1;
  new_sym->attr.dimension = sym->attr.dimension;
  new_sym->attr.pointer = sym->attr.pointer;
  new_sym->attr.flavor = sym->attr.flavor;

  /* Create a fake symtree for it.  */
  root = NULL;
  new_symtree = gfc_new_symtree (&root, sym->name);
  new_symtree->n.sym = new_sym;
  gcc_assert (new_symtree == root);

  /* Create a dummy->actual mapping.  */
  sm = gfc_getmem (sizeof (*sm));
  sm->next = mapping->syms;
  sm->old = sym;
  sm->new = new_symtree;
  mapping->syms = sm;

  /* Stabilize the argument's value.  */
  se->expr = gfc_evaluate_now (se->expr, &se->pre);

  if (sym->ts.type == BT_CHARACTER)
    {
      /* Create a copy of the dummy argument's length.  */
      new_sym->ts.cl = gfc_get_interface_mapping_charlen (mapping, sym->ts.cl);

      /* If the length is specified as "*", record the length that
         the caller is passing.  We should use the callee's length
         in all other cases.  */
      if (!new_sym->ts.cl->length)
        {
          se->string_length = gfc_evaluate_now (se->string_length, &se->pre);
          new_sym->ts.cl->backend_decl = se->string_length;
        }
    }

  /* Use the passed value as-is if the argument is a function.  */
  if (sym->attr.flavor == FL_PROCEDURE)
    value = se->expr;

  /* If the argument is either a string or a pointer to a string,
     convert it to a boundless character type.  */
  else if (!sym->attr.dimension && sym->ts.type == BT_CHARACTER)
    {
      tmp = gfc_get_character_type_len (sym->ts.kind, NULL);
      tmp = build_pointer_type (tmp);
      if (sym->attr.pointer)
        tmp = build_pointer_type (tmp);

      value = fold_convert (tmp, se->expr);
      if (sym->attr.pointer)
        value = gfc_build_indirect_ref (value);
    }

  /* If the argument is a scalar or a pointer to an array, dereference it.  */
  else if (!sym->attr.dimension || sym->attr.pointer)
    value = gfc_build_indirect_ref (se->expr);

  /* If the argument is an array descriptor, use it to determine
     information about the actual argument's shape.  */
  else if (POINTER_TYPE_P (TREE_TYPE (se->expr))
           && GFC_DESCRIPTOR_TYPE_P (TREE_TYPE (TREE_TYPE (se->expr))))
    {
      /* Get the actual argument's descriptor.  */
      desc = gfc_build_indirect_ref (se->expr);

      /* Create the replacement variable.  */
      tmp = gfc_conv_descriptor_data_get (desc);
      value = gfc_get_interface_mapping_array (&se->pre, sym, 0, tmp);

      /* Use DESC to work out the upper bounds, strides and offset.  */
      gfc_set_interface_mapping_bounds (&se->pre, TREE_TYPE (value), desc);
    }
  else
    /* Otherwise we have a packed array.  */
    value = gfc_get_interface_mapping_array (&se->pre, sym, 2, se->expr);

  new_sym->backend_decl = value;
}


/* Called once all dummy argument mappings have been added to MAPPING,
   but before the mapping is used to evaluate expressions.  Pre-evaluate
   the length of each argument, adding any initialization code to PRE and
   any finalization code to POST.  */

static void
gfc_finish_interface_mapping (gfc_interface_mapping * mapping,
                              stmtblock_t * pre, stmtblock_t * post)
{
  gfc_interface_sym_mapping *sym;
  gfc_expr *expr;
  gfc_se se;

  for (sym = mapping->syms; sym; sym = sym->next)
    if (sym->new->n.sym->ts.type == BT_CHARACTER
        && !sym->new->n.sym->ts.cl->backend_decl)
      {
        expr = sym->new->n.sym->ts.cl->length;
        gfc_apply_interface_mapping_to_expr (mapping, expr);
        gfc_init_se (&se, NULL);
        gfc_conv_expr (&se, expr);

        se.expr = gfc_evaluate_now (se.expr, &se.pre);
        gfc_add_block_to_block (pre, &se.pre);
        gfc_add_block_to_block (post, &se.post);

        sym->new->n.sym->ts.cl->backend_decl = se.expr;
      }
}


/* Like gfc_apply_interface_mapping_to_expr, but applied to
   constructor C.  */

static void
gfc_apply_interface_mapping_to_cons (gfc_interface_mapping * mapping,
                                     gfc_constructor * c)
{
  for (; c; c = c->next)
    {
      gfc_apply_interface_mapping_to_expr (mapping, c->expr);
      if (c->iterator)
        {
          gfc_apply_interface_mapping_to_expr (mapping, c->iterator->start);
          gfc_apply_interface_mapping_to_expr (mapping, c->iterator->end);
          gfc_apply_interface_mapping_to_expr (mapping, c->iterator->step);
        }
    }
}


/* Like gfc_apply_interface_mapping_to_expr, but applied to
   reference REF.  */

static void
gfc_apply_interface_mapping_to_ref (gfc_interface_mapping * mapping,
                                    gfc_ref * ref)
{
  int n;

  for (; ref; ref = ref->next)
    switch (ref->type)
      {
      case REF_ARRAY:
        for (n = 0; n < ref->u.ar.dimen; n++)
          {
            gfc_apply_interface_mapping_to_expr (mapping, ref->u.ar.start[n]);
            gfc_apply_interface_mapping_to_expr (mapping, ref->u.ar.end[n]);
            gfc_apply_interface_mapping_to_expr (mapping, ref->u.ar.stride[n]);
          }
        gfc_apply_interface_mapping_to_expr (mapping, ref->u.ar.offset);
        break;

      case REF_COMPONENT:
        break;

      case REF_SUBSTRING:
        gfc_apply_interface_mapping_to_expr (mapping, ref->u.ss.start);
        gfc_apply_interface_mapping_to_expr (mapping, ref->u.ss.end);
        break;
      }
}


/* EXPR is a copy of an expression that appeared in the interface
   associated with MAPPING.  Walk it recursively looking for references to
   dummy arguments that MAPPING maps to actual arguments.  Replace each such
   reference with a reference to the associated actual argument.  */

static void
gfc_apply_interface_mapping_to_expr (gfc_interface_mapping * mapping,
                                     gfc_expr * expr)
{
  gfc_interface_sym_mapping *sym;
  gfc_actual_arglist *actual;

  if (!expr)
    return;

  /* Copying an expression does not copy its length, so do that here.  */
  if (expr->ts.type == BT_CHARACTER && expr->ts.cl)
    {
      expr->ts.cl = gfc_get_interface_mapping_charlen (mapping, expr->ts.cl);
      gfc_apply_interface_mapping_to_expr (mapping, expr->ts.cl->length);
    }

  /* Apply the mapping to any references.  */
  gfc_apply_interface_mapping_to_ref (mapping, expr->ref);

  /* ...and to the expression's symbol, if it has one.  */
  if (expr->symtree)
    for (sym = mapping->syms; sym; sym = sym->next)
      if (sym->old == expr->symtree->n.sym)
        expr->symtree = sym->new;

  /* ...and to subexpressions in expr->value.  */
  switch (expr->expr_type)
    {
    case EXPR_VARIABLE:
    case EXPR_CONSTANT:
    case EXPR_NULL:
    case EXPR_SUBSTRING:
      break;

    case EXPR_OP:
      gfc_apply_interface_mapping_to_expr (mapping, expr->value.op.op1);
      gfc_apply_interface_mapping_to_expr (mapping, expr->value.op.op2);
      break;

    case EXPR_FUNCTION:
      for (sym = mapping->syms; sym; sym = sym->next)
        if (sym->old == expr->value.function.esym)
          expr->value.function.esym = sym->new->n.sym;

      for (actual = expr->value.function.actual; actual; actual = actual->next)
        gfc_apply_interface_mapping_to_expr (mapping, actual->expr);
      break;

    case EXPR_ARRAY:
    case EXPR_STRUCTURE:
      gfc_apply_interface_mapping_to_cons (mapping, expr->value.constructor);
      break;
    }
}


/* Evaluate interface expression EXPR using MAPPING.  Store the result
   in SE.  */

static void
gfc_apply_interface_mapping (gfc_interface_mapping * mapping,
                             gfc_se * se, gfc_expr * expr)
{
  expr = gfc_copy_expr (expr);
  gfc_apply_interface_mapping_to_expr (mapping, expr);
  gfc_conv_expr (se, expr);
  se->expr = gfc_evaluate_now (se->expr, &se->pre);
  gfc_free_expr (expr);
}


/* Generate code for a procedure call.  Note can return se->post != NULL.
   If se->direct_byref is set then se->expr contains the return parameter.
   Return nonzero, if the call has alternate specifiers.  */

int
gfc_conv_function_call (gfc_se * se, gfc_symbol * sym,
                        gfc_actual_arglist * arg)
{
  gfc_interface_mapping mapping;
  tree arglist;
  tree retargs;
  tree tmp;
  tree fntype;
  gfc_se parmse;
  gfc_ss *argss;
  gfc_ss_info *info;
  int byref;
  tree type;
  tree var;
  tree len;
  tree stringargs;
  gfc_formal_arglist *formal;
  int has_alternate_specifier = 0;
  bool need_interface_mapping;
  gfc_typespec ts;
  gfc_charlen cl;

  arglist = NULL_TREE;
  retargs = NULL_TREE;
  stringargs = NULL_TREE;
  var = NULL_TREE;
  len = NULL_TREE;

  if (se->ss != NULL)
    {
      if (!sym->attr.elemental)
        {
          gcc_assert (se->ss->type == GFC_SS_FUNCTION);
          if (se->ss->useflags)
            {
              gcc_assert (gfc_return_by_reference (sym)
                      && sym->result->attr.dimension);
              gcc_assert (se->loop != NULL);

              /* Access the previously obtained result.  */
              gfc_conv_tmp_array_ref (se);
              gfc_advance_se_ss_chain (se);
              return 0;
            }
        }
      info = &se->ss->data.info;
    }
  else
    info = NULL;

  gfc_init_interface_mapping (&mapping);
  need_interface_mapping = (sym->ts.type == BT_CHARACTER
                            && sym->ts.cl->length->expr_type != EXPR_CONSTANT);
  formal = sym->formal;
  /* Evaluate the arguments.  */
  for (; arg != NULL; arg = arg->next, formal = formal ? formal->next : NULL)
    {
      if (arg->expr == NULL)
        {

          if (se->ignore_optional)
            {
              /* Some intrinsics have already been resolved to the correct
                 parameters.  */
              continue;
            }
          else if (arg->label)
            {
              has_alternate_specifier = 1;
              continue;
            }
          else
            {
              /* Pass a NULL pointer for an absent arg.  */
              gfc_init_se (&parmse, NULL);
              parmse.expr = null_pointer_node;
              if (arg->missing_arg_type == BT_CHARACTER)
                parmse.string_length = convert (gfc_charlen_type_node,
                                                integer_zero_node);
            }
        }
      else if (se->ss && se->ss->useflags)
        {
          /* An elemental function inside a scalarized loop.  */
          gfc_init_se (&parmse, se);
          gfc_conv_expr_reference (&parmse, arg->expr);
        }
      else
        {
          /* A scalar or transformational function.  */
          gfc_init_se (&parmse, NULL);
          argss = gfc_walk_expr (arg->expr);

          if (argss == gfc_ss_terminator)
            {
              gfc_conv_expr_reference (&parmse, arg->expr);
              if (formal && formal->sym->attr.pointer
                  && arg->expr->expr_type != EXPR_NULL)
                {
                  /* Scalar pointer dummy args require an extra level of
                  indirection. The null pointer already contains
                  this level of indirection.  */
                  parmse.expr = gfc_build_addr_expr (NULL, parmse.expr);
                }
            }
          else
            {
              /* If the procedure requires an explicit interface, the
                 actual argument is passed according to the
                 corresponding formal argument.  If the corresponding
                 formal argument is a POINTER or assumed shape, we do
                 not use g77's calling convention, and pass the
                 address of the array descriptor instead. Otherwise we
                 use g77's calling convention.  */
              int f;
              f = (formal != NULL)
                  && !formal->sym->attr.pointer
                  && formal->sym->as->type != AS_ASSUMED_SHAPE;
              f = f || !sym->attr.always_explicit;
              gfc_conv_array_parameter (&parmse, arg->expr, argss, f);
            } 
        }

      if (formal && need_interface_mapping)
        gfc_add_interface_mapping (&mapping, formal->sym, &parmse);

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

      /* Character strings are passed as two parameters, a length and a
         pointer.  */
      if (parmse.string_length != NULL_TREE)
        stringargs = gfc_chainon_list (stringargs, parmse.string_length);

      arglist = gfc_chainon_list (arglist, parmse.expr);
    }
  gfc_finish_interface_mapping (&mapping, &se->pre, &se->post);

  ts = sym->ts;
  if (ts.type == BT_CHARACTER)
    {
      /* Calculate the length of the returned string.  */
      gfc_init_se (&parmse, NULL);
      if (need_interface_mapping)
        gfc_apply_interface_mapping (&mapping, &parmse, sym->ts.cl->length);
      else
        gfc_conv_expr (&parmse, sym->ts.cl->length);
      gfc_add_block_to_block (&se->pre, &parmse.pre);
      gfc_add_block_to_block (&se->post, &parmse.post);

      /* Set up a charlen structure for it.  */
      cl.next = NULL;
      cl.length = NULL;
      cl.backend_decl = fold_convert (gfc_charlen_type_node, parmse.expr);
      ts.cl = &cl;

      len = cl.backend_decl;
    }
  gfc_free_interface_mapping (&mapping);

  byref = gfc_return_by_reference (sym);
  if (byref)
    {
      if (se->direct_byref)
        retargs = gfc_chainon_list (retargs, se->expr);
      else if (sym->result->attr.dimension)
        {
          gcc_assert (se->loop && info);

          /* Set the type of the array.  */
          tmp = gfc_typenode_for_spec (&ts);
          info->dimen = se->loop->dimen;

          /* Allocate a temporary to store the result.  */
          gfc_trans_allocate_temp_array (se->loop, info, tmp);

          /* Zero the first stride to indicate a temporary.  */
          tmp = gfc_conv_descriptor_stride (info->descriptor, gfc_rank_cst[0]);
          gfc_add_modify_expr (&se->pre, tmp,
                               convert (TREE_TYPE (tmp), integer_zero_node));

          /* Pass the temporary as the first argument.  */
          tmp = info->descriptor;
          tmp = gfc_build_addr_expr (NULL, tmp);
          retargs = gfc_chainon_list (retargs, tmp);
        }
      else if (ts.type == BT_CHARACTER)
        {
          /* Pass the string length.  */
          type = gfc_get_character_type (ts.kind, ts.cl);
          type = build_pointer_type (type);

          /* Return an address to a char[0:len-1]* temporary for
             character pointers.  */
          if (sym->attr.pointer || sym->attr.allocatable)
            {
              /* Build char[0:len-1] * pstr.  */
              tmp = fold_build2 (MINUS_EXPR, gfc_charlen_type_node, len,
                                 build_int_cst (gfc_charlen_type_node, 1));
              tmp = build_range_type (gfc_array_index_type,
                                      gfc_index_zero_node, tmp);
              tmp = build_array_type (gfc_character1_type_node, tmp);
              var = gfc_create_var (build_pointer_type (tmp), "pstr");

              /* Provide an address expression for the function arguments.  */
              var = gfc_build_addr_expr (NULL, var);
            }
          else
            var = gfc_conv_string_tmp (se, type, len);

          retargs = gfc_chainon_list (retargs, var);
        }
      else
        {
          gcc_assert (gfc_option.flag_f2c && ts.type == BT_COMPLEX);

          type = gfc_get_complex_type (ts.kind);
          var = gfc_build_addr_expr (NULL, gfc_create_var (type, "cmplx"));
          retargs = gfc_chainon_list (retargs, var);
        }

      /* Add the string length to the argument list.  */
      if (ts.type == BT_CHARACTER)
        retargs = gfc_chainon_list (retargs, len);
    }

  /* Add the return arguments.  */
  arglist = chainon (retargs, arglist);

  /* Add the hidden string length parameters to the arguments.  */
  arglist = chainon (arglist, stringargs);

  /* Generate the actual call.  */
  gfc_conv_function_val (se, sym);
  /* If there are alternate return labels, function type should be
     integer.  Can't modify the type in place though, since it can be shared
     with other functions.  */
  if (has_alternate_specifier
      && TREE_TYPE (TREE_TYPE (TREE_TYPE (se->expr))) != integer_type_node)
    {
      gcc_assert (! sym->attr.dummy);
      TREE_TYPE (sym->backend_decl)
        = build_function_type (integer_type_node,
                               TYPE_ARG_TYPES (TREE_TYPE (sym->backend_decl)));
      se->expr = gfc_build_addr_expr (NULL, sym->backend_decl);
    }

  fntype = TREE_TYPE (TREE_TYPE (se->expr));
  se->expr = build3 (CALL_EXPR, TREE_TYPE (fntype), se->expr,
                     arglist, NULL_TREE);

  /* If we have a pointer function, but we don't want a pointer, e.g.
     something like
        x = f()
     where f is pointer valued, we have to dereference the result.  */
  if (!se->want_pointer && !byref && sym->attr.pointer)
    se->expr = gfc_build_indirect_ref (se->expr);

  /* f2c calling conventions require a scalar default real function to
     return a double precision result.  Convert this back to default
     real.  We only care about the cases that can happen in Fortran 77.
  */
  if (gfc_option.flag_f2c && sym->ts.type == BT_REAL
      && sym->ts.kind == gfc_default_real_kind
      && !sym->attr.always_explicit)
    se->expr = fold_convert (gfc_get_real_type (sym->ts.kind), se->expr);

  /* A pure function may still have side-effects - it may modify its
     parameters.  */
  TREE_SIDE_EFFECTS (se->expr) = 1;
#if 0
  if (!sym->attr.pure)
    TREE_SIDE_EFFECTS (se->expr) = 1;
#endif

  if (byref)
    {
      /* Add the function call to the pre chain.  There is no expression.  */
      gfc_add_expr_to_block (&se->pre, se->expr);
      se->expr = NULL_TREE;

      if (!se->direct_byref)
        {
          if (sym->attr.dimension)
            {
              if (flag_bounds_check)
                {
                  /* Check the data pointer hasn't been modified.  This would
                     happen in a function returning a pointer.  */
                  tmp = gfc_conv_descriptor_data_get (info->descriptor);
                  tmp = build2 (NE_EXPR, boolean_type_node, tmp, info->data);
                  gfc_trans_runtime_check (tmp, gfc_strconst_fault, &se->pre);
                }
              se->expr = info->descriptor;
              /* Bundle in the string length.  */
              se->string_length = len;
            }
          else if (sym->ts.type == BT_CHARACTER)
            {
              /* Dereference for character pointer results.  */
              if (sym->attr.pointer || sym->attr.allocatable)
                se->expr = gfc_build_indirect_ref (var);
              else
                se->expr = var;

              se->string_length = len;
            }
          else
            {
              gcc_assert (sym->ts.type == BT_COMPLEX && gfc_option.flag_f2c);
              se->expr = gfc_build_indirect_ref (var);
            }
        }
    }

  return has_alternate_specifier;
}


/* Generate code to copy a string.  */

static void
gfc_trans_string_copy (stmtblock_t * block, tree dlen, tree dest,
                       tree slen, tree src)
{
  tree tmp;

  tmp = NULL_TREE;
  tmp = gfc_chainon_list (tmp, dlen);
  tmp = gfc_chainon_list (tmp, dest);
  tmp = gfc_chainon_list (tmp, slen);
  tmp = gfc_chainon_list (tmp, src);
  tmp = gfc_build_function_call (gfor_fndecl_copy_string, tmp);
  gfc_add_expr_to_block (block, tmp);
}


/* Translate a statement function.
   The value of a statement function reference is obtained by evaluating the
   expression using the values of the actual arguments for the values of the
   corresponding dummy arguments.  */

static void
gfc_conv_statement_function (gfc_se * se, gfc_expr * expr)
{
  gfc_symbol *sym;
  gfc_symbol *fsym;
  gfc_formal_arglist *fargs;
  gfc_actual_arglist *args;
  gfc_se lse;
  gfc_se rse;
  gfc_saved_var *saved_vars;
  tree *temp_vars;
  tree type;
  tree tmp;
  int n;

  sym = expr->symtree->n.sym;
  args = expr->value.function.actual;
  gfc_init_se (&lse, NULL);
  gfc_init_se (&rse, NULL);

  n = 0;
  for (fargs = sym->formal; fargs; fargs = fargs->next)
    n++;
  saved_vars = (gfc_saved_var *)gfc_getmem (n * sizeof (gfc_saved_var));
  temp_vars = (tree *)gfc_getmem (n * sizeof (tree));

  for (fargs = sym->formal, n = 0; fargs; fargs = fargs->next, n++)
    {
      /* Each dummy shall be specified, explicitly or implicitly, to be
         scalar.  */
      gcc_assert (fargs->sym->attr.dimension == 0);
      fsym = fargs->sym;

      /* Create a temporary to hold the value.  */
      type = gfc_typenode_for_spec (&fsym->ts);
      temp_vars[n] = gfc_create_var (type, fsym->name);

      if (fsym->ts.type == BT_CHARACTER)
        {
          /* Copy string arguments.  */
          tree arglen;

          gcc_assert (fsym->ts.cl && fsym->ts.cl->length
                  && fsym->ts.cl->length->expr_type == EXPR_CONSTANT);

          arglen = TYPE_MAX_VALUE (TYPE_DOMAIN (type));
          tmp = gfc_build_addr_expr (build_pointer_type (type),
                                     temp_vars[n]);

          gfc_conv_expr (&rse, args->expr);
          gfc_conv_string_parameter (&rse);
          gfc_add_block_to_block (&se->pre, &lse.pre);
          gfc_add_block_to_block (&se->pre, &rse.pre);

          gfc_trans_string_copy (&se->pre, arglen, tmp, rse.string_length,
                                 rse.expr);
          gfc_add_block_to_block (&se->pre, &lse.post);
          gfc_add_block_to_block (&se->pre, &rse.post);
        }
      else
        {
          /* For everything else, just evaluate the expression.  */
          gfc_conv_expr (&lse, args->expr);

          gfc_add_block_to_block (&se->pre, &lse.pre);
          gfc_add_modify_expr (&se->pre, temp_vars[n], lse.expr);
          gfc_add_block_to_block (&se->pre, &lse.post);
        }

      args = args->next;
    }

  /* Use the temporary variables in place of the real ones.  */
  for (fargs = sym->formal, n = 0; fargs; fargs = fargs->next, n++)
    gfc_shadow_sym (fargs->sym, temp_vars[n], &saved_vars[n]);

  gfc_conv_expr (se, sym->value);

  if (sym->ts.type == BT_CHARACTER)
    {
      gfc_conv_const_charlen (sym->ts.cl);

      /* Force the expression to the correct length.  */
      if (!INTEGER_CST_P (se->string_length)
          || tree_int_cst_lt (se->string_length,
                              sym->ts.cl->backend_decl))
        {
          type = gfc_get_character_type (sym->ts.kind, sym->ts.cl);
          tmp = gfc_create_var (type, sym->name);
          tmp = gfc_build_addr_expr (build_pointer_type (type), tmp);
          gfc_trans_string_copy (&se->pre, sym->ts.cl->backend_decl, tmp,
                                 se->string_length, se->expr);
          se->expr = tmp;
        }
      se->string_length = sym->ts.cl->backend_decl;
    }

  /* Restore the original variables.  */
  for (fargs = sym->formal, n = 0; fargs; fargs = fargs->next, n++)
    gfc_restore_sym (fargs->sym, &saved_vars[n]);
  gfc_free (saved_vars);
}


/* Translate a function expression.  */

static void
gfc_conv_function_expr (gfc_se * se, gfc_expr * expr)
{
  gfc_symbol *sym;

  if (expr->value.function.isym)
    {
      gfc_conv_intrinsic_function (se, expr);
      return;
    }

  /* We distinguish statement functions from general functions to improve
     runtime performance.  */
  if (expr->symtree->n.sym->attr.proc == PROC_ST_FUNCTION)
    {
      gfc_conv_statement_function (se, expr);
      return;
    }

  /* expr.value.function.esym is the resolved (specific) function symbol for
     most functions.  However this isn't set for dummy procedures.  */
  sym = expr->value.function.esym;
  if (!sym)
    sym = expr->symtree->n.sym;
  gfc_conv_function_call (se, sym, expr->value.function.actual);
}


static void
gfc_conv_array_constructor_expr (gfc_se * se, gfc_expr * expr)
{
  gcc_assert (se->ss != NULL && se->ss != gfc_ss_terminator);
  gcc_assert (se->ss->expr == expr && se->ss->type == GFC_SS_CONSTRUCTOR);

  gfc_conv_tmp_array_ref (se);
  gfc_advance_se_ss_chain (se);
}


/* Build a static initializer.  EXPR is the expression for the initial value.
   The other parameters describe the variable of the component being 
   initialized. EXPR may be null.  */

tree
gfc_conv_initializer (gfc_expr * expr, gfc_typespec * ts, tree type,
                      bool array, bool pointer)
{
  gfc_se se;

  if (!(expr || pointer))
    return NULL_TREE;

  if (array)
    {
      /* Arrays need special handling.  */
      if (pointer)
        return gfc_build_null_descriptor (type);
      else
        return gfc_conv_array_initializer (type, expr);
    }
  else if (pointer)
    return fold_convert (type, null_pointer_node);
  else
    {
      switch (ts->type)
        {
        case BT_DERIVED:
          gfc_init_se (&se, NULL);
          gfc_conv_structure (&se, expr, 1);
          return se.expr;

        case BT_CHARACTER:
          return gfc_conv_string_init (ts->cl->backend_decl,expr);

        default:
          gfc_init_se (&se, NULL);
          gfc_conv_constant (&se, expr);
          return se.expr;
        }
    }
}
  
static tree
gfc_trans_subarray_assign (tree dest, gfc_component * cm, gfc_expr * expr)
{
  gfc_se rse;
  gfc_se lse;
  gfc_ss *rss;
  gfc_ss *lss;
  stmtblock_t body;
  stmtblock_t block;
  gfc_loopinfo loop;
  int n;
  tree tmp;

  gfc_start_block (&block);

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

  gfc_init_se (&lse, NULL);
  gfc_init_se (&rse, NULL);

  /* Walk the rhs.  */
  rss = gfc_walk_expr (expr);
  if (rss == gfc_ss_terminator)
    {
      /* The rhs is scalar.  Add a ss for the expression.  */
      rss = gfc_get_ss ();
      rss->next = gfc_ss_terminator;
      rss->type = GFC_SS_SCALAR;
      rss->expr = expr;
    }

  /* Create a SS for the destination.  */
  lss = gfc_get_ss ();
  lss->type = GFC_SS_COMPONENT;
  lss->expr = NULL;
  lss->shape = gfc_get_shape (cm->as->rank);
  lss->next = gfc_ss_terminator;
  lss->data.info.dimen = cm->as->rank;
  lss->data.info.descriptor = dest;
  lss->data.info.data = gfc_conv_array_data (dest);
  lss->data.info.offset = gfc_conv_array_offset (dest);
  for (n = 0; n < cm->as->rank; n++)
    {
      lss->data.info.dim[n] = n;
      lss->data.info.start[n] = gfc_conv_array_lbound (dest, n);
      lss->data.info.stride[n] = gfc_index_one_node;

      mpz_init (lss->shape[n]);
      mpz_sub (lss->shape[n], cm->as->upper[n]->value.integer,
               cm->as->lower[n]->value.integer);
      mpz_add_ui (lss->shape[n], lss->shape[n], 1);
    }
  
  /* Associate the SS with the loop.  */
  gfc_add_ss_to_loop (&loop, lss);
  gfc_add_ss_to_loop (&loop, rss);

  /* Calculate the bounds of the scalarization.  */
  gfc_conv_ss_startstride (&loop);

  /* Setup the scalarizing loops.  */
  gfc_conv_loop_setup (&loop);

  /* Setup the gfc_se structures.  */
  gfc_copy_loopinfo_to_se (&lse, &loop);
  gfc_copy_loopinfo_to_se (&rse, &loop);

  rse.ss = rss;
  gfc_mark_ss_chain_used (rss, 1);
  lse.ss = lss;
  gfc_mark_ss_chain_used (lss, 1);

  /* Start the scalarized loop body.  */
  gfc_start_scalarized_body (&loop, &body);

  gfc_conv_tmp_array_ref (&lse);
  if (cm->ts.type == BT_CHARACTER)
    lse.string_length = cm->ts.cl->backend_decl;

  gfc_conv_expr (&rse, expr);

  tmp = gfc_trans_scalar_assign (&lse, &rse, cm->ts.type);
  gfc_add_expr_to_block (&body, tmp);

  gcc_assert (rse.ss == gfc_ss_terminator);

  /* Generate the copying loops.  */
  gfc_trans_scalarizing_loops (&loop, &body);

  /* Wrap the whole thing up.  */
  gfc_add_block_to_block (&block, &loop.pre);
  gfc_add_block_to_block (&block, &loop.post);

  for (n = 0; n < cm->as->rank; n++)
    mpz_clear (lss->shape[n]);
  gfc_free (lss->shape);

  gfc_cleanup_loop (&loop);

  return gfc_finish_block (&block);
}

/* Assign a single component of a derived type constructor.  */

static tree
gfc_trans_subcomponent_assign (tree dest, gfc_component * cm, gfc_expr * expr)
{
  gfc_se se;
  gfc_ss *rss;
  stmtblock_t block;
  tree tmp;

  gfc_start_block (&block);
  if (cm->pointer)
    {
      gfc_init_se (&se, NULL);
      /* Pointer component.  */
      if (cm->dimension)
        {
          /* Array pointer.  */
          if (expr->expr_type == EXPR_NULL)
            gfc_conv_descriptor_data_set (&block, dest, null_pointer_node);
          else
            {
              rss = gfc_walk_expr (expr);
              se.direct_byref = 1;
              se.expr = dest;
              gfc_conv_expr_descriptor (&se, expr, rss);
              gfc_add_block_to_block (&block, &se.pre);
              gfc_add_block_to_block (&block, &se.post);
            }
        }
      else
        {
          /* Scalar pointers.  */
          se.want_pointer = 1;
          gfc_conv_expr (&se, expr);
          gfc_add_block_to_block (&block, &se.pre);
          gfc_add_modify_expr (&block, dest,
                               fold_convert (TREE_TYPE (dest), se.expr));
          gfc_add_block_to_block (&block, &se.post);
        }
    }
  else if (cm->dimension)
    {
      tmp = gfc_trans_subarray_assign (dest, cm, expr);
      gfc_add_expr_to_block (&block, tmp);
    }
  else if (expr->ts.type == BT_DERIVED)
    {
      /* Nested derived type.  */
      tmp = gfc_trans_structure_assign (dest, expr);
      gfc_add_expr_to_block (&block, tmp);
    }
  else
    {
      /* Scalar component.  */
      gfc_se lse;

      gfc_init_se (&se, NULL);
      gfc_init_se (&lse, NULL);

      gfc_conv_expr (&se, expr);
      if (cm->ts.type == BT_CHARACTER)
        lse.string_length = cm->ts.cl->backend_decl;
      lse.expr = dest;
      tmp = gfc_trans_scalar_assign (&lse, &se, cm->ts.type);
      gfc_add_expr_to_block (&block, tmp);
    }
  return gfc_finish_block (&block);
}

/* Assign a derived type constructor to a variable.  */

static tree
gfc_trans_structure_assign (tree dest, gfc_expr * expr)
{
  gfc_constructor *c;
  gfc_component *cm;
  stmtblock_t block;
  tree field;
  tree tmp;

  gfc_start_block (&block);
  cm = expr->ts.derived->components;
  for (c = expr->value.constructor; c; c = c->next, cm = cm->next)
    {
      /* Skip absent members in default initializers.  */
      if (!c->expr)
        continue;

      field = cm->backend_decl;
      tmp = build3 (COMPONENT_REF, TREE_TYPE (field), dest, field, NULL_TREE);
      tmp = gfc_trans_subcomponent_assign (tmp, cm, c->expr);
      gfc_add_expr_to_block (&block, tmp);
    }
  return gfc_finish_block (&block);
}

/* Build an expression for a constructor. If init is nonzero then
   this is part of a static variable initializer.  */

void
gfc_conv_structure (gfc_se * se, gfc_expr * expr, int init)
{
  gfc_constructor *c;
  gfc_component *cm;
  tree val;
  tree type;
  tree tmp;
  VEC(constructor_elt,gc) *v = NULL;

  gcc_assert (se->ss == NULL);
  gcc_assert (expr->expr_type == EXPR_STRUCTURE);
  type = gfc_typenode_for_spec (&expr->ts);

  if (!init)
    {
      /* Create a temporary variable and fill it in.  */
      se->expr = gfc_create_var (type, expr->ts.derived->name);
      tmp = gfc_trans_structure_assign (se->expr, expr);
      gfc_add_expr_to_block (&se->pre, tmp);
      return;
    }

  cm = expr->ts.derived->components;
  for (c = expr->value.constructor; c; c = c->next, cm = cm->next)
    {
      /* Skip absent members in default initializers.  */
      if (!c->expr)
        continue;

      val = gfc_conv_initializer (c->expr, &cm->ts,
          TREE_TYPE (cm->backend_decl), cm->dimension, cm->pointer);

      /* Append it to the constructor list.  */
      CONSTRUCTOR_APPEND_ELT (v, cm->backend_decl, val);
    }
  se->expr = build_constructor (type, v);
}


/* Translate a substring expression.  */

static void
gfc_conv_substring_expr (gfc_se * se, gfc_expr * expr)
{
  gfc_ref *ref;

  ref = expr->ref;

  gcc_assert (ref->type == REF_SUBSTRING);

  se->expr = gfc_build_string_const(expr->value.character.length,
                                    expr->value.character.string);
  se->string_length = TYPE_MAX_VALUE (TYPE_DOMAIN (TREE_TYPE (se->expr)));
  TYPE_STRING_FLAG (TREE_TYPE (se->expr))=1;

  gfc_conv_substring(se,ref,expr->ts.kind);
}


/* Entry point for expression translation.  Evaluates a scalar quantity.
   EXPR is the expression to be translated, and SE is the state structure if
   called from within the scalarized.  */

void
gfc_conv_expr (gfc_se * se, gfc_expr * expr)
{
  if (se->ss && se->ss->expr == expr
      && (se->ss->type == GFC_SS_SCALAR || se->ss->type == GFC_SS_REFERENCE))
    {
      /* Substitute a scalar expression evaluated outside the scalarization
         loop.  */
      se->expr = se->ss->data.scalar.expr;
      se->string_length = se->ss->string_length;
      gfc_advance_se_ss_chain (se);
      return;
    }

  switch (expr->expr_type)
    {
    case EXPR_OP:
      gfc_conv_expr_op (se, expr);
      break;

    case EXPR_FUNCTION:
      gfc_conv_function_expr (se, expr);
      break;

    case EXPR_CONSTANT:
      gfc_conv_constant (se, expr);
      break;

    case EXPR_VARIABLE:
      gfc_conv_variable (se, expr);
      break;

    case EXPR_NULL:
      se->expr = null_pointer_node;
      break;

    case EXPR_SUBSTRING:
      gfc_conv_substring_expr (se, expr);
      break;

    case EXPR_STRUCTURE:
      gfc_conv_structure (se, expr, 0);
      break;

    case EXPR_ARRAY:
      gfc_conv_array_constructor_expr (se, expr);
      break;

    default:
      gcc_unreachable ();
      break;
    }
}

/* Like gfc_conv_expr_val, but the value is also suitable for use in the lhs
   of an assignment.  */
void
gfc_conv_expr_lhs (gfc_se * se, gfc_expr * expr)
{
  gfc_conv_expr (se, expr);
  /* All numeric lvalues should have empty post chains.  If not we need to
     figure out a way of rewriting an lvalue so that it has no post chain.  */
  gcc_assert (expr->ts.type == BT_CHARACTER || !se->post.head);
}

/* Like gfc_conv_expr, but the POST block is guaranteed to be empty for
   numeric expressions.  Used for scalar values whee inserting cleanup code
   is inconvenient.  */
void
gfc_conv_expr_val (gfc_se * se, gfc_expr * expr)
{
  tree val;

  gcc_assert (expr->ts.type != BT_CHARACTER);
  gfc_conv_expr (se, expr);
  if (se->post.head)
    {
      val = gfc_create_var (TREE_TYPE (se->expr), NULL);
      gfc_add_modify_expr (&se->pre, val, se->expr);
      se->expr = val;
      gfc_add_block_to_block (&se->pre, &se->post);
    }
}

/* Helper to translate and expression and convert it to a particular type.  */
void
gfc_conv_expr_type (gfc_se * se, gfc_expr * expr, tree type)
{
  gfc_conv_expr_val (se, expr);
  se->expr = convert (type, se->expr);
}


/* Converts an expression so that it can be passed by reference.  Scalar
   values only.  */

void
gfc_conv_expr_reference (gfc_se * se, gfc_expr * expr)
{
  tree var;

  if (se->ss && se->ss->expr == expr
      && se->ss->type == GFC_SS_REFERENCE)
    {
      se->expr = se->ss->data.scalar.expr;
      se->string_length = se->ss->string_length;
      gfc_advance_se_ss_chain (se);
      return;
    }

  if (expr->ts.type == BT_CHARACTER)
    {
      gfc_conv_expr (se, expr);
      gfc_conv_string_parameter (se);
      return;
    }

  if (expr->expr_type == EXPR_VARIABLE)
    {
      se->want_pointer = 1;
      gfc_conv_expr (se, expr);
      if (se->post.head)
        {
          var = gfc_create_var (TREE_TYPE (se->expr), NULL);
          gfc_add_modify_expr (&se->pre, var, se->expr);
          gfc_add_block_to_block (&se->pre, &se->post);
          se->expr = var;
        }
      return;
    }

  gfc_conv_expr (se, expr);

  /* Create a temporary var to hold the value.  */
  if (TREE_CONSTANT (se->expr))
    {
      var = build_decl (CONST_DECL, NULL, TREE_TYPE (se->expr));
      DECL_INITIAL (var) = se->expr;
      pushdecl (var);
    }
  else
    {
      var = gfc_create_var (TREE_TYPE (se->expr), NULL);
      gfc_add_modify_expr (&se->pre, var, se->expr);
    }
  gfc_add_block_to_block (&se->pre, &se->post);

  /* Take the address of that value.  */
  se->expr = gfc_build_addr_expr (NULL, var);
}


tree
gfc_trans_pointer_assign (gfc_code * code)
{
  return gfc_trans_pointer_assignment (code->expr, code->expr2);
}


/* Generate code for a pointer assignment.  */

tree
gfc_trans_pointer_assignment (gfc_expr * expr1, gfc_expr * expr2)
{
  gfc_se lse;
  gfc_se rse;
  gfc_ss *lss;
  gfc_ss *rss;
  stmtblock_t block;
  tree desc;
  tree tmp;

  gfc_start_block (&block);

  gfc_init_se (&lse, NULL);

  lss = gfc_walk_expr (expr1);
  rss = gfc_walk_expr (expr2);
  if (lss == gfc_ss_terminator)
    {
      /* Scalar pointers.  */
      lse.want_pointer = 1;
      gfc_conv_expr (&lse, expr1);
      gcc_assert (rss == gfc_ss_terminator);
      gfc_init_se (&rse, NULL);
      rse.want_pointer = 1;
      gfc_conv_expr (&rse, expr2);
      gfc_add_block_to_block (&block, &lse.pre);
      gfc_add_block_to_block (&block, &rse.pre);
      gfc_add_modify_expr (&block, lse.expr,
                           fold_convert (TREE_TYPE (lse.expr), rse.expr));
      gfc_add_block_to_block (&block, &rse.post);
      gfc_add_block_to_block (&block, &lse.post);
    }
  else
    {
      /* Array pointer.  */
      gfc_conv_expr_descriptor (&lse, expr1, lss);
      switch (expr2->expr_type)
        {
        case EXPR_NULL:
          /* Just set the data pointer to null.  */
          gfc_conv_descriptor_data_set (&block, lse.expr, null_pointer_node);
          break;

        case EXPR_VARIABLE:
          /* Assign directly to the pointer's descriptor.  */
          lse.direct_byref = 1;
          gfc_conv_expr_descriptor (&lse, expr2, rss);
          break;

        default:
          /* Assign to a temporary descriptor and then copy that
             temporary to the pointer.  */
          desc = lse.expr;
          tmp = gfc_create_var (TREE_TYPE (desc), "ptrtemp");

          lse.expr = tmp;
          lse.direct_byref = 1;
          gfc_conv_expr_descriptor (&lse, expr2, rss);
          gfc_add_modify_expr (&lse.pre, desc, tmp);
          break;
        }
      gfc_add_block_to_block (&block, &lse.pre);
      gfc_add_block_to_block (&block, &lse.post);
    }
  return gfc_finish_block (&block);
}


/* Makes sure se is suitable for passing as a function string parameter.  */
/* TODO: Need to check all callers fo this function.  It may be abused.  */

void
gfc_conv_string_parameter (gfc_se * se)
{
  tree type;

  if (TREE_CODE (se->expr) == STRING_CST)
    {
      se->expr = gfc_build_addr_expr (pchar_type_node, se->expr);
      return;
    }

  type = TREE_TYPE (se->expr);
  if (TYPE_STRING_FLAG (type))
    {
      gcc_assert (TREE_CODE (se->expr) != INDIRECT_REF);
      se->expr = gfc_build_addr_expr (pchar_type_node, se->expr);
    }

  gcc_assert (POINTER_TYPE_P (TREE_TYPE (se->expr)));
  gcc_assert (se->string_length
          && TREE_CODE (TREE_TYPE (se->string_length)) == INTEGER_TYPE);
}


/* Generate code for assignment of scalar variables.  Includes character
   strings.  */

tree
gfc_trans_scalar_assign (gfc_se * lse, gfc_se * rse, bt type)
{
  stmtblock_t block;

  gfc_init_block (&block);

  if (type == BT_CHARACTER)
    {
      gcc_assert (lse->string_length != NULL_TREE
              && rse->string_length != NULL_TREE);

      gfc_conv_string_parameter (lse);
      gfc_conv_string_parameter (rse);

      gfc_add_block_to_block (&block, &lse->pre);
      gfc_add_block_to_block (&block, &rse->pre);

      gfc_trans_string_copy (&block, lse->string_length, lse->expr,
                             rse->string_length, rse->expr);
    }
  else
    {
      gfc_add_block_to_block (&block, &lse->pre);
      gfc_add_block_to_block (&block, &rse->pre);

      gfc_add_modify_expr (&block, lse->expr,
                           fold_convert (TREE_TYPE (lse->expr), rse->expr));
    }

  gfc_add_block_to_block (&block, &lse->post);
  gfc_add_block_to_block (&block, &rse->post);

  return gfc_finish_block (&block);
}


/* Try to translate array(:) = func (...), where func is a transformational
   array function, without using a temporary.  Returns NULL is this isn't the
   case.  */

static tree
gfc_trans_arrayfunc_assign (gfc_expr * expr1, gfc_expr * expr2)
{
  gfc_se se;
  gfc_ss *ss;

  /* The caller has already checked rank>0 and expr_type == EXPR_FUNCTION.  */
  if (expr2->value.function.isym && !gfc_is_intrinsic_libcall (expr2))
    return NULL;

  /* Elemental functions don't need a temporary anyway.  */
  if (expr2->symtree->n.sym->attr.elemental)
    return NULL;

  /* Check for a dependency.  */
  if (gfc_check_fncall_dependency (expr1, expr2))
    return NULL;

  /* The frontend doesn't seem to bother filling in expr->symtree for intrinsic
     functions.  */
  gcc_assert (expr2->value.function.isym
              || (gfc_return_by_reference (expr2->value.function.esym)
              && expr2->value.function.esym->result->attr.dimension));

  ss = gfc_walk_expr (expr1);
  gcc_assert (ss != gfc_ss_terminator);
  gfc_init_se (&se, NULL);
  gfc_start_block (&se.pre);
  se.want_pointer = 1;

  gfc_conv_array_parameter (&se, expr1, ss, 0);

  se.direct_byref = 1;
  se.ss = gfc_walk_expr (expr2);
  gcc_assert (se.ss != gfc_ss_terminator);
  gfc_conv_function_expr (&se, expr2);
  gfc_add_block_to_block (&se.pre, &se.post);

  return gfc_finish_block (&se.pre);
}


/* Translate an assignment.  Most of the code is concerned with
   setting up the scalarizer.  */

tree
gfc_trans_assignment (gfc_expr * expr1, gfc_expr * expr2)
{
  gfc_se lse;
  gfc_se rse;
  gfc_ss *lss;
  gfc_ss *lss_section;
  gfc_ss *rss;
  gfc_loopinfo loop;
  tree tmp;
  stmtblock_t block;
  stmtblock_t body;

  /* Special case a single function returning an array.  */
  if (expr2->expr_type == EXPR_FUNCTION && expr2->rank > 0)
    {
      tmp = gfc_trans_arrayfunc_assign (expr1, expr2);
      if (tmp)
        return tmp;
    }

  /* Assignment of the form lhs = rhs.  */
  gfc_start_block (&block);

  gfc_init_se (&lse, NULL);
  gfc_init_se (&rse, NULL);

  /* Walk the lhs.  */
  lss = gfc_walk_expr (expr1);
  rss = NULL;
  if (lss != gfc_ss_terminator)
    {
      /* The assignment needs scalarization.  */
      lss_section = lss;

      /* Find a non-scalar SS from the lhs.  */
      while (lss_section != gfc_ss_terminator
             && lss_section->type != GFC_SS_SECTION)
        lss_section = lss_section->next;

      gcc_assert (lss_section != gfc_ss_terminator);

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

      /* Walk the rhs.  */
      rss = gfc_walk_expr (expr2);
      if (rss == gfc_ss_terminator)
        {
          /* The rhs is scalar.  Add a ss for the expression.  */
          rss = gfc_get_ss ();
          rss->next = gfc_ss_terminator;
          rss->type = GFC_SS_SCALAR;
          rss->expr = expr2;
        }
      /* Associate the SS with the loop.  */
      gfc_add_ss_to_loop (&loop, lss);
      gfc_add_ss_to_loop (&loop, rss);

      /* Calculate the bounds of the scalarization.  */
      gfc_conv_ss_startstride (&loop);
      /* Resolve any data dependencies in the statement.  */
      gfc_conv_resolve_dependencies (&loop, lss_section, rss);
      /* Setup the scalarizing loops.  */
      gfc_conv_loop_setup (&loop);

      /* Setup the gfc_se structures.  */
      gfc_copy_loopinfo_to_se (&lse, &loop);
      gfc_copy_loopinfo_to_se (&rse, &loop);

      rse.ss = rss;
      gfc_mark_ss_chain_used (rss, 1);
      if (loop.temp_ss == NULL)
        {
          lse.ss = lss;
          gfc_mark_ss_chain_used (lss, 1);
        }
      else
        {
          lse.ss = loop.temp_ss;
          gfc_mark_ss_chain_used (lss, 3);
          gfc_mark_ss_chain_used (loop.temp_ss, 3);
        }

      /* Start the scalarized loop body.  */
      gfc_start_scalarized_body (&loop, &body);
    }
  else
    gfc_init_block (&body);

  /* Translate the expression.  */
  gfc_conv_expr (&rse, expr2);

  if (lss != gfc_ss_terminator && loop.temp_ss != NULL)
    {
      gfc_conv_tmp_array_ref (&lse);
      gfc_advance_se_ss_chain (&lse);
    }
  else
    gfc_conv_expr (&lse, expr1);

  tmp = gfc_trans_scalar_assign (&lse, &rse, expr1->ts.type);
  gfc_add_expr_to_block (&body, tmp);

  if (lss == gfc_ss_terminator)
    {
      /* Use the scalar assignment as is.  */
      gfc_add_block_to_block (&block, &body);
    }
  else
    {
      gcc_assert (lse.ss == gfc_ss_terminator
                  && rse.ss == gfc_ss_terminator);

      if (loop.temp_ss != NULL)
        {
          gfc_trans_scalarized_loop_boundary (&loop, &body);

          /* We need to copy the temporary to the actual lhs.  */
          gfc_init_se (&lse, NULL);
          gfc_init_se (&rse, NULL);
          gfc_copy_loopinfo_to_se (&lse, &loop);
          gfc_copy_loopinfo_to_se (&rse, &loop);

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

          gfc_conv_tmp_array_ref (&rse);
          gfc_advance_se_ss_chain (&rse);
          gfc_conv_expr (&lse, expr1);

          gcc_assert (lse.ss == gfc_ss_terminator
                      && rse.ss == gfc_ss_terminator);

          tmp = gfc_trans_scalar_assign (&lse, &rse, expr1->ts.type);
          gfc_add_expr_to_block (&body, tmp);
        }
      /* Generate the copying loops.  */
      gfc_trans_scalarizing_loops (&loop, &body);

      /* Wrap the whole thing up.  */
      gfc_add_block_to_block (&block, &loop.pre);
      gfc_add_block_to_block (&block, &loop.post);

      gfc_cleanup_loop (&loop);
    }

  return gfc_finish_block (&block);
}

tree
gfc_trans_assign (gfc_code * code)
{
  return gfc_trans_assignment (code->expr, code->expr2);
}