gimplify.c

	  /* For if (...) { code; } else {} or
	     if (...) { code; } else goto label; or
	     if (...) { code; return; } else { ... }
	     label_cont isn't needed.  */
	  if (!have_else_clause_p
	      && TREE_OPERAND (expr, 2) != NULL_TREE
	      && gimple_seq_may_fallthru (seq))
	    {
	      gimple g;
	      label_cont = create_artificial_label ();

	      g = gimple_build_goto (label_cont);

	      /* GIMPLE_COND's are very low level; they have embedded
		 gotos.  This particular embedded goto should not be marked
		 with the location of the original COND_EXPR, as it would
		 correspond to the COND_EXPR's condition, not the ELSE or the
		 THEN arms.  To avoid marking it with the wrong location, flag
		 it as "no location".  */
	      gimple_set_do_not_emit_location (g);

	      gimplify_seq_add_stmt (&seq, g);
	    }
	}
    }
  if (!have_else_clause_p)
    {
      gimplify_seq_add_stmt (&seq, gimple_build_label (label_false));
      have_else_clause_p = gimplify_stmt (&TREE_OPERAND (expr, 2), &seq);
    }
  if (label_cont)
    gimplify_seq_add_stmt (&seq, gimple_build_label (label_cont));

  gimple_pop_condition (pre_p);
  gimple_seq_add_seq (pre_p, seq);

  if (ret == GS_ERROR)
    ; /* Do nothing.  */
  else if (have_then_clause_p || have_else_clause_p)
    ret = GS_ALL_DONE;
  else
    {
      /* Both arms are empty; replace the COND_EXPR with its predicate.  */
      expr = TREE_OPERAND (expr, 0);
      gimplify_stmt (&expr, pre_p);
    }

  *expr_p = NULL;
  return ret;
}

/* A subroutine of gimplify_modify_expr.  Replace a MODIFY_EXPR with
   a call to __builtin_memcpy.  */

static enum gimplify_status
gimplify_modify_expr_to_memcpy (tree *expr_p, tree size, bool want_value,
    				gimple_seq *seq_p)
{
  tree t, to, to_ptr, from, from_ptr;
  gimple gs;

  to = TREE_OPERAND (*expr_p, 0);
  from = TREE_OPERAND (*expr_p, 1);

  from_ptr = build_fold_addr_expr (from);
  gimplify_arg (&from_ptr, seq_p, EXPR_LOCATION (*expr_p));

  to_ptr = build_fold_addr_expr (to);
  gimplify_arg (&to_ptr, seq_p, EXPR_LOCATION (*expr_p));

  t = implicit_built_in_decls[BUILT_IN_MEMCPY];

  gs = gimple_build_call (t, 3, to_ptr, from_ptr, size);

  if (want_value)
    {
      /* tmp = memcpy() */
      t = create_tmp_var (TREE_TYPE (to_ptr), NULL);
      gimple_call_set_lhs (gs, t);
      gimplify_seq_add_stmt (seq_p, gs);

      *expr_p = build1 (INDIRECT_REF, TREE_TYPE (to), t);
      return GS_ALL_DONE;
    }

  gimplify_seq_add_stmt (seq_p, gs);
  *expr_p = NULL;
  return GS_ALL_DONE;
}

/* A subroutine of gimplify_modify_expr.  Replace a MODIFY_EXPR with
   a call to __builtin_memset.  In this case we know that the RHS is
   a CONSTRUCTOR with an empty element list.  */

static enum gimplify_status
gimplify_modify_expr_to_memset (tree *expr_p, tree size, bool want_value,
    				gimple_seq *seq_p)
{
  tree t, from, to, to_ptr;
  gimple gs;

  /* Assert our assumptions, to abort instead of producing wrong code
     silently if they are not met.  Beware that the RHS CONSTRUCTOR might
     not be immediately exposed.  */
  from = TREE_OPERAND (*expr_p, 1);  
  if (TREE_CODE (from) == WITH_SIZE_EXPR)
    from = TREE_OPERAND (from, 0);

  gcc_assert (TREE_CODE (from) == CONSTRUCTOR
	      && VEC_empty (constructor_elt, CONSTRUCTOR_ELTS (from)));

  /* Now proceed.  */
  to = TREE_OPERAND (*expr_p, 0);

  to_ptr = build_fold_addr_expr (to);
  gimplify_arg (&to_ptr, seq_p, EXPR_LOCATION (*expr_p));
  t = implicit_built_in_decls[BUILT_IN_MEMSET];

  gs = gimple_build_call (t, 3, to_ptr, integer_zero_node, size);

  if (want_value)
    {
      /* tmp = memset() */
      t = create_tmp_var (TREE_TYPE (to_ptr), NULL);
      gimple_call_set_lhs (gs, t);
      gimplify_seq_add_stmt (seq_p, gs);

      *expr_p = build1 (INDIRECT_REF, TREE_TYPE (to), t);
      return GS_ALL_DONE;
    }

  gimplify_seq_add_stmt (seq_p, gs);
  *expr_p = NULL;
  return GS_ALL_DONE;
}

/* A subroutine of gimplify_init_ctor_preeval.  Called via walk_tree,
   determine, cautiously, if a CONSTRUCTOR overlaps the lhs of an
   assignment.  Returns non-null if we detect a potential overlap.  */

struct gimplify_init_ctor_preeval_data
{
  /* The base decl of the lhs object.  May be NULL, in which case we
     have to assume the lhs is indirect.  */
  tree lhs_base_decl;

  /* The alias set of the lhs object.  */
  alias_set_type lhs_alias_set;
};

static tree
gimplify_init_ctor_preeval_1 (tree *tp, int *walk_subtrees, void *xdata)
{
  struct gimplify_init_ctor_preeval_data *data
    = (struct gimplify_init_ctor_preeval_data *) xdata;
  tree t = *tp;

  /* If we find the base object, obviously we have overlap.  */
  if (data->lhs_base_decl == t)
    return t;

  /* If the constructor component is indirect, determine if we have a
     potential overlap with the lhs.  The only bits of information we
     have to go on at this point are addressability and alias sets.  */
  if (TREE_CODE (t) == INDIRECT_REF
      && (!data->lhs_base_decl || TREE_ADDRESSABLE (data->lhs_base_decl))
      && alias_sets_conflict_p (data->lhs_alias_set, get_alias_set (t)))
    return t;

  /* If the constructor component is a call, determine if it can hide a
     potential overlap with the lhs through an INDIRECT_REF like above.  */
  if (TREE_CODE (t) == CALL_EXPR)
    {
      tree type, fntype = TREE_TYPE (TREE_TYPE (CALL_EXPR_FN (t)));

      for (type = TYPE_ARG_TYPES (fntype); type; type = TREE_CHAIN (type))
	if (POINTER_TYPE_P (TREE_VALUE (type))
	    && (!data->lhs_base_decl || TREE_ADDRESSABLE (data->lhs_base_decl))
	    && alias_sets_conflict_p (data->lhs_alias_set,
				      get_alias_set
				        (TREE_TYPE (TREE_VALUE (type)))))
	  return t;
    }

  if (IS_TYPE_OR_DECL_P (t))
    *walk_subtrees = 0;
  return NULL;
}

/* A subroutine of gimplify_init_constructor.  Pre-evaluate EXPR,
   force values that overlap with the lhs (as described by *DATA)
   into temporaries.  */

static void
gimplify_init_ctor_preeval (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
			    struct gimplify_init_ctor_preeval_data *data)
{
  enum gimplify_status one;

  /* If the value is constant, then there's nothing to pre-evaluate.  */
  if (TREE_CONSTANT (*expr_p))
    {
      /* Ensure it does not have side effects, it might contain a reference to
	 the object we're initializing.  */
      gcc_assert (!TREE_SIDE_EFFECTS (*expr_p));
      return;
    }

  /* If the type has non-trivial constructors, we can't pre-evaluate.  */
  if (TREE_ADDRESSABLE (TREE_TYPE (*expr_p)))
    return;

  /* Recurse for nested constructors.  */
  if (TREE_CODE (*expr_p) == CONSTRUCTOR)
    {
      unsigned HOST_WIDE_INT ix;
      constructor_elt *ce;
      VEC(constructor_elt,gc) *v = CONSTRUCTOR_ELTS (*expr_p);

      for (ix = 0; VEC_iterate (constructor_elt, v, ix, ce); ix++)
	gimplify_init_ctor_preeval (&ce->value, pre_p, post_p, data);

      return;
    }

  /* If this is a variable sized type, we must remember the size.  */
  maybe_with_size_expr (expr_p);

  /* Gimplify the constructor element to something appropriate for the rhs
     of a MODIFY_EXPR.  Given that we know the LHS is an aggregate, we know
     the gimplifier will consider this a store to memory.  Doing this
     gimplification now means that we won't have to deal with complicated
     language-specific trees, nor trees like SAVE_EXPR that can induce
     exponential search behavior.  */
  one = gimplify_expr (expr_p, pre_p, post_p, is_gimple_mem_rhs, fb_rvalue);
  if (one == GS_ERROR)
    {
      *expr_p = NULL;
      return;
    }

  /* If we gimplified to a bare decl, we can be sure that it doesn't overlap
     with the lhs, since "a = { .x=a }" doesn't make sense.  This will
     always be true for all scalars, since is_gimple_mem_rhs insists on a
     temporary variable for them.  */
  if (DECL_P (*expr_p))
    return;

  /* If this is of variable size, we have no choice but to assume it doesn't
     overlap since we can't make a temporary for it.  */
  if (TREE_CODE (TYPE_SIZE (TREE_TYPE (*expr_p))) != INTEGER_CST)
    return;

  /* Otherwise, we must search for overlap ...  */
  if (!walk_tree (expr_p, gimplify_init_ctor_preeval_1, data, NULL))
    return;

  /* ... and if found, force the value into a temporary.  */
  *expr_p = get_formal_tmp_var (*expr_p, pre_p);
}

/* A subroutine of gimplify_init_ctor_eval.  Create a loop for
   a RANGE_EXPR in a CONSTRUCTOR for an array.

      var = lower;
    loop_entry:
      object[var] = value;
      if (var == upper)
	goto loop_exit;
      var = var + 1;
      goto loop_entry;
    loop_exit:

   We increment var _after_ the loop exit check because we might otherwise
   fail if upper == TYPE_MAX_VALUE (type for upper).

   Note that we never have to deal with SAVE_EXPRs here, because this has
   already been taken care of for us, in gimplify_init_ctor_preeval().  */

static void gimplify_init_ctor_eval (tree, VEC(constructor_elt,gc) *,
				     gimple_seq *, bool);

static void
gimplify_init_ctor_eval_range (tree object, tree lower, tree upper,
			       tree value, tree array_elt_type,
			       gimple_seq *pre_p, bool cleared)
{
  tree loop_entry_label, loop_exit_label, fall_thru_label;
  tree var, var_type, cref, tmp;

  loop_entry_label = create_artificial_label ();
  loop_exit_label = create_artificial_label ();
  fall_thru_label = create_artificial_label ();

  /* Create and initialize the index variable.  */
  var_type = TREE_TYPE (upper);
  var = create_tmp_var (var_type, NULL);
  gimplify_seq_add_stmt (pre_p, gimple_build_assign (var, lower));

  /* Add the loop entry label.  */
  gimplify_seq_add_stmt (pre_p, gimple_build_label (loop_entry_label));

  /* Build the reference.  */
  cref = build4 (ARRAY_REF, array_elt_type, unshare_expr (object),
		 var, NULL_TREE, NULL_TREE);

  /* If we are a constructor, just call gimplify_init_ctor_eval to do
     the store.  Otherwise just assign value to the reference.  */

  if (TREE_CODE (value) == CONSTRUCTOR)
    /* NB we might have to call ourself recursively through
       gimplify_init_ctor_eval if the value is a constructor.  */
    gimplify_init_ctor_eval (cref, CONSTRUCTOR_ELTS (value),
			     pre_p, cleared);
  else
    gimplify_seq_add_stmt (pre_p, gimple_build_assign (cref, value));

  /* We exit the loop when the index var is equal to the upper bound.  */
  gimplify_seq_add_stmt (pre_p,
			 gimple_build_cond (EQ_EXPR, var, upper,
					    loop_exit_label, fall_thru_label));

  gimplify_seq_add_stmt (pre_p, gimple_build_label (fall_thru_label));

  /* Otherwise, increment the index var...  */
  tmp = build2 (PLUS_EXPR, var_type, var,
		fold_convert (var_type, integer_one_node));
  gimplify_seq_add_stmt (pre_p, gimple_build_assign (var, tmp));

  /* ...and jump back to the loop entry.  */
  gimplify_seq_add_stmt (pre_p, gimple_build_goto (loop_entry_label));

  /* Add the loop exit label.  */
  gimplify_seq_add_stmt (pre_p, gimple_build_label (loop_exit_label));
}

/* Return true if FDECL is accessing a field that is zero sized.  */
   
static bool
zero_sized_field_decl (const_tree fdecl)
{
  if (TREE_CODE (fdecl) == FIELD_DECL && DECL_SIZE (fdecl) 
      && integer_zerop (DECL_SIZE (fdecl)))
    return true;
  return false;
}

/* Return true if TYPE is zero sized.  */
   
static bool
zero_sized_type (const_tree type)
{
  if (AGGREGATE_TYPE_P (type) && TYPE_SIZE (type)
      && integer_zerop (TYPE_SIZE (type)))
    return true;
  return false;
}

/* A subroutine of gimplify_init_constructor.  Generate individual
   MODIFY_EXPRs for a CONSTRUCTOR.  OBJECT is the LHS against which the
   assignments should happen.  ELTS is the CONSTRUCTOR_ELTS of the
   CONSTRUCTOR.  CLEARED is true if the entire LHS object has been
   zeroed first.  */

static void
gimplify_init_ctor_eval (tree object, VEC(constructor_elt,gc) *elts,
			 gimple_seq *pre_p, bool cleared)
{
  tree array_elt_type = NULL;
  unsigned HOST_WIDE_INT ix;
  tree purpose, value;

  if (TREE_CODE (TREE_TYPE (object)) == ARRAY_TYPE)
    array_elt_type = TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (object)));

  FOR_EACH_CONSTRUCTOR_ELT (elts, ix, purpose, value)
    {
      tree cref;

      /* NULL values are created above for gimplification errors.  */
      if (value == NULL)
	continue;

      if (cleared && initializer_zerop (value))
	continue;

      /* ??? Here's to hoping the front end fills in all of the indices,
	 so we don't have to figure out what's missing ourselves.  */
      gcc_assert (purpose);

      /* Skip zero-sized fields, unless value has side-effects.  This can
	 happen with calls to functions returning a zero-sized type, which
	 we shouldn't discard.  As a number of downstream passes don't
	 expect sets of zero-sized fields, we rely on the gimplification of
	 the MODIFY_EXPR we make below to drop the assignment statement.  */
      if (! TREE_SIDE_EFFECTS (value) && zero_sized_field_decl (purpose))
	continue;

      /* If we have a RANGE_EXPR, we have to build a loop to assign the
	 whole range.  */
      if (TREE_CODE (purpose) == RANGE_EXPR)
	{
	  tree lower = TREE_OPERAND (purpose, 0);
	  tree upper = TREE_OPERAND (purpose, 1);

	  /* If the lower bound is equal to upper, just treat it as if
	     upper was the index.  */
	  if (simple_cst_equal (lower, upper))
	    purpose = upper;
	  else
	    {
	      gimplify_init_ctor_eval_range (object, lower, upper, value,
					     array_elt_type, pre_p, cleared);
	      continue;
	    }
	}

      if (array_elt_type)
	{
	  /* Do not use bitsizetype for ARRAY_REF indices.  */
	  if (TYPE_DOMAIN (TREE_TYPE (object)))
	    purpose = fold_convert (TREE_TYPE (TYPE_DOMAIN (TREE_TYPE (object))),
				    purpose);
	  cref = build4 (ARRAY_REF, array_elt_type, unshare_expr (object),
			 purpose, NULL_TREE, NULL_TREE);
	}
      else
	{
	  gcc_assert (TREE_CODE (purpose) == FIELD_DECL);
	  cref = build3 (COMPONENT_REF, TREE_TYPE (purpose),
			 unshare_expr (object), purpose, NULL_TREE);
	}

      if (TREE_CODE (value) == CONSTRUCTOR
	  && TREE_CODE (TREE_TYPE (value)) != VECTOR_TYPE)
	gimplify_init_ctor_eval (cref, CONSTRUCTOR_ELTS (value),
				 pre_p, cleared);
      else
	{
	  tree init = build2 (INIT_EXPR, TREE_TYPE (cref), cref, value);
	  gimplify_and_add (init, pre_p);
	  ggc_free (init);
	}
    }
}


/* Returns the appropriate RHS predicate for this LHS.  */

gimple_predicate
rhs_predicate_for (tree lhs)
{
  if (is_gimple_formal_tmp_var (lhs))
    return is_gimple_formal_tmp_or_call_rhs;
  else if (is_gimple_reg (lhs))
    return is_gimple_reg_or_call_rhs;
  else
    return is_gimple_mem_or_call_rhs;
}


/* A subroutine of gimplify_modify_expr.  Break out elements of a
   CONSTRUCTOR used as an initializer into separate MODIFY_EXPRs.

   Note that we still need to clear any elements that don't have explicit
   initializers, so if not all elements are initialized we keep the
   original MODIFY_EXPR, we just remove all of the constructor elements.

   If NOTIFY_TEMP_CREATION is true, do not gimplify, just return
   GS_ERROR if we would have to create a temporary when gimplifying
   this constructor.  Otherwise, return GS_OK.

   If NOTIFY_TEMP_CREATION is false, just do the gimplification.  */

static enum gimplify_status
gimplify_init_constructor (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
			   bool want_value, bool notify_temp_creation)
{
  tree object;
  tree ctor = TREE_OPERAND (*expr_p, 1);
  tree type = TREE_TYPE (ctor);
  enum gimplify_status ret;
  VEC(constructor_elt,gc) *elts;

  if (TREE_CODE (ctor) != CONSTRUCTOR)
    return GS_UNHANDLED;

  if (!notify_temp_creation)
    {
      ret = gimplify_expr (&TREE_OPERAND (*expr_p, 0), pre_p, post_p,
			   is_gimple_lvalue, fb_lvalue);
      if (ret == GS_ERROR)
	return ret;
    }

  object = TREE_OPERAND (*expr_p, 0);
  elts = CONSTRUCTOR_ELTS (ctor);
  ret = GS_ALL_DONE;

  switch (TREE_CODE (type))
    {
    case RECORD_TYPE:
    case UNION_TYPE:
    case QUAL_UNION_TYPE:
    case ARRAY_TYPE:
      {
	struct gimplify_init_ctor_preeval_data preeval_data;
	HOST_WIDE_INT num_type_elements, num_ctor_elements;
	HOST_WIDE_INT num_nonzero_elements;
	bool cleared, valid_const_initializer;

	/* Aggregate types must lower constructors to initialization of
	   individual elements.  The exception is that a CONSTRUCTOR node
	   with no elements indicates zero-initialization of the whole.  */
	if (VEC_empty (constructor_elt, elts))
	  {
	    if (notify_temp_creation)
	      return GS_OK;
	    break;
	  }
 
	/* Fetch information about the constructor to direct later processing.
	   We might want to make static versions of it in various cases, and
	   can only do so if it known to be a valid constant initializer.  */
	valid_const_initializer
	  = categorize_ctor_elements (ctor, &num_nonzero_elements,
				      &num_ctor_elements, &cleared);

	/* If a const aggregate variable is being initialized, then it
	   should never be a lose to promote the variable to be static.  */
	if (valid_const_initializer
	    && num_nonzero_elements > 1
	    && TREE_READONLY (object)
	    && TREE_CODE (object) == VAR_DECL)
	  {
	    if (notify_temp_creation)
	      return GS_ERROR;
	    DECL_INITIAL (object) = ctor;
	    TREE_STATIC (object) = 1;
	    if (!DECL_NAME (object))
	      DECL_NAME (object) = create_tmp_var_name ("C");
	    walk_tree (&DECL_INITIAL (object), force_labels_r, NULL, NULL);

	    /* ??? C++ doesn't automatically append a .<number> to the
	       assembler name, and even when it does, it looks a FE private
	       data structures to figure out what that number should be,
	       which are not set for this variable.  I suppose this is
	       important for local statics for inline functions, which aren't
	       "local" in the object file sense.  So in order to get a unique
	       TU-local symbol, we must invoke the lhd version now.  */
	    lhd_set_decl_assembler_name (object);

	    *expr_p = NULL_TREE;
	    break;
	  }

	/* If there are "lots" of initialized elements, even discounting
	   those that are not address constants (and thus *must* be
	   computed at runtime), then partition the constructor into
	   constant and non-constant parts.  Block copy the constant
	   parts in, then generate code for the non-constant parts.  */
	/* TODO.  There's code in cp/typeck.c to do this.  */

	num_type_elements = count_type_elements (type, true);

	/* If count_type_elements could not determine number of type elements
	   for a constant-sized object, assume clearing is needed.
	   Don't do this for variable-sized objects, as store_constructor
	   will ignore the clearing of variable-sized objects.  */
	if (num_type_elements < 0 && int_size_in_bytes (type) >= 0)
	  cleared = true;
	/* If there are "lots" of zeros, then block clear the object first.  */
	else if (num_type_elements - num_nonzero_elements
		 > CLEAR_RATIO (optimize_function_for_speed_p (cfun))
		 && num_nonzero_elements < num_type_elements/4)
	  cleared = true;
	/* ??? This bit ought not be needed.  For any element not present
	   in the initializer, we should simply set them to zero.  Except
	   we'd need to *find* the elements that are not present, and that
	   requires trickery to avoid quadratic compile-time behavior in
	   large cases or excessive memory use in small cases.  */
	else if (num_ctor_elements < num_type_elements)
	  cleared = true;

	/* If there are "lots" of initialized elements, and all of them
	   are valid address constants, then the entire initializer can
	   be dropped to memory, and then memcpy'd out.  Don't do this
	   for sparse arrays, though, as it's more efficient to follow
	   the standard CONSTRUCTOR behavior of memset followed by
	   individual element initialization.  */
	if (valid_const_initializer && !cleared)
	  {
	    HOST_WIDE_INT size = int_size_in_bytes (type);
	    unsigned int align;

	    /* ??? We can still get unbounded array types, at least
	       from the C++ front end.  This seems wrong, but attempt
	       to work around it for now.  */
	    if (size < 0)
	      {
		size = int_size_in_bytes (TREE_TYPE (object));
		if (size >= 0)
		  TREE_TYPE (ctor) = type = TREE_TYPE (object);
	      }

	    /* Find the maximum alignment we can assume for the object.  */
	    /* ??? Make use of DECL_OFFSET_ALIGN.  */
	    if (DECL_P (object))
	      align = DECL_ALIGN (object);
	    else
	      align = TYPE_ALIGN (type);

	    if (size > 0 && !can_move_by_pieces (size, align))
	      {
		tree new_tree;

		if (notify_temp_creation)
		  return GS_ERROR;

		new_tree = create_tmp_var_raw (type, "C");

		gimple_add_tmp_var (new_tree);
		TREE_STATIC (new_tree) = 1;
		TREE_READONLY (new_tree) = 1;
		DECL_INITIAL (new_tree) = ctor;
		if (align > DECL_ALIGN (new_tree))
		  {
		    DECL_ALIGN (new_tree) = align;
		    DECL_USER_ALIGN (new_tree) = 1;
		  }
	        walk_tree (&DECL_INITIAL (new_tree), force_labels_r, NULL, NULL);

		TREE_OPERAND (*expr_p, 1) = new_tree;

		/* This is no longer an assignment of a CONSTRUCTOR, but
		   we still may have processing to do on the LHS.  So
		   pretend we didn't do anything here to let that happen.  */
		return GS_UNHANDLED;
	      }
	  }

	if (notify_temp_creation)
	  return GS_OK;

	/* If there are nonzero elements, pre-evaluate to capture elements
	   overlapping with the lhs into temporaries.  We must do this before
	   clearing to fetch the values before they are zeroed-out.  */
	if (num_nonzero_elements > 0)
	  {
	    preeval_data.lhs_base_decl = get_base_address (object);
	    if (!DECL_P (preeval_data.lhs_base_decl))
	      preeval_data.lhs_base_decl = NULL;
	    preeval_data.lhs_alias_set = get_alias_set (object);

	    gimplify_init_ctor_preeval (&TREE_OPERAND (*expr_p, 1),
					pre_p, post_p, &preeval_data);
	  }

	if (cleared)
	  {
	    /* Zap the CONSTRUCTOR element list, which simplifies this case.
	       Note that we still have to gimplify, in order to handle the
	       case of variable sized types.  Avoid shared tree structures.  */
	    CONSTRUCTOR_ELTS (ctor) = NULL;
	    TREE_SIDE_EFFECTS (ctor) = 0;
	    object = unshare_expr (object);
	    gimplify_stmt (expr_p, pre_p);
	  }

	/* If we have not block cleared the object, or if there are nonzero
	   elements in the constructor, add assignments to the individual
	   scalar fields of the object.  */
	if (!cleared || num_nonzero_elements > 0)
	  gimplify_init_ctor_eval (object, elts, pre_p, cleared);

	*expr_p = NULL_TREE;
      }
      break;

    case COMPLEX_TYPE:
      {
	tree r, i;

	if (notify_temp_creation)
	  return GS_OK;

	/* Extract the real and imaginary parts out of the ctor.  */
	gcc_assert (VEC_length (constructor_elt, elts) == 2);
	r = VEC_index (constructor_elt, elts, 0)->value;
	i = VEC_index (constructor_elt, elts, 1)->value;
	if (r == NULL || i == NULL)
	  {
	    tree zero = fold_convert (TREE_TYPE (type), integer_zero_node);
	    if (r == NULL)
	      r = zero;
	    if (i == NULL)
	      i = zero;
	  }

	/* Complex types have either COMPLEX_CST or COMPLEX_EXPR to
	   represent creation of a complex value.  */
	if (TREE_CONSTANT (r) && TREE_CONSTANT (i))
	  {
	    ctor = build_complex (type, r, i);
	    TREE_OPERAND (*expr_p, 1) = ctor;
	  }
	else
	  {
	    ctor = build2 (COMPLEX_EXPR, type, r, i);
	    TREE_OPERAND (*expr_p, 1) = ctor;
	    ret = gimplify_expr (&TREE_OPERAND (*expr_p, 1),
				 pre_p,
				 post_p,
				 rhs_predicate_for (TREE_OPERAND (*expr_p, 0)),
				 fb_rvalue);
	  }
      }
      break;

    case VECTOR_TYPE:
      {
	unsigned HOST_WIDE_INT ix;
	constructor_elt *ce;

	if (notify_temp_creation)
	  return GS_OK;

	/* Go ahead and simplify constant constructors to VECTOR_CST.  */
	if (TREE_CONSTANT (ctor))
	  {
	    bool constant_p = true;
	    tree value;

	    /* Even when ctor is constant, it might contain non-*_CST
	       elements, such as addresses or trapping values like
	       1.0/0.0 - 1.0/0.0.  Such expressions don't belong
	       in VECTOR_CST nodes.  */
	    FOR_EACH_CONSTRUCTOR_VALUE (elts, ix, value)
	      if (!CONSTANT_CLASS_P (value))
		{
		  constant_p = false;
		  break;
		}

	    if (constant_p)
	      {
		TREE_OPERAND (*expr_p, 1) = build_vector_from_ctor (type, elts);
		break;
	      }

	    /* Don't reduce an initializer constant even if we can't
	       make a VECTOR_CST.  It won't do anything for us, and it'll
	       prevent us from representing it as a single constant.  */
	    if (initializer_constant_valid_p (ctor, type))
	      break;

	    TREE_CONSTANT (ctor) = 0;
	  }

	/* Vector types use CONSTRUCTOR all the way through gimple
	  compilation as a general initializer.  */
	for (ix = 0; VEC_iterate (constructor_elt, elts, ix, ce); ix++)
	  {
	    enum gimplify_status tret;
	    tret = gimplify_expr (&ce->value, pre_p, post_p, is_gimple_val,
				  fb_rvalue);
	    if (tret == GS_ERROR)
	      ret = GS_ERROR;
	  }
	if (!is_gimple_reg (TREE_OPERAND (*expr_p, 0)))
	  TREE_OPERAND (*expr_p, 1) = get_formal_tmp_var (ctor, pre_p);
      }
      break;

    default:
      /* So how did we get a CONSTRUCTOR for a scalar type?  */
      gcc_unreachable ();
    }

  if (ret == GS_ERROR)
    return GS_ERROR;
  else if (want_value)
    {
      *expr_p = object;
      return GS_OK;
    }
  else
    {
      /* If we have gimplified both sides of the initializer but have
	 not emitted an assignment, do so now.  */
      if (*expr_p)
	{
	  tree lhs = TREE_OPERAND (*expr_p, 0);
	  tree rhs = TREE_OPERAND (*expr_p, 1);
	  gimple init = gimple_build_assign (lhs, rhs);
	  gimplify_seq_add_stmt (pre_p, init);
	  *expr_p = NULL;
	}

      return GS_ALL_DONE;
    }
}

/* Given a pointer value OP0, return a simplified version of an
   indirection through OP0, or NULL_TREE if no simplification is
   possible.  Note that the resulting type may be different from
   the type pointed to in the sense that it is still compatible
   from the langhooks point of view. */

tree
gimple_fold_indirect_ref (tree t)
{
  tree type = TREE_TYPE (TREE_TYPE (t));
  tree sub = t;
  tree subtype;

  STRIP_USELESS_TYPE_CONVERSION (sub);
  subtype = TREE_TYPE (sub);
  if (!POINTER_TYPE_P (subtype))
    return NULL_TREE;

  if (TREE_CODE (sub) == ADDR_EXPR)
    {
      tree op = TREE_OPERAND (sub, 0);
      tree optype = TREE_TYPE (op);
      /* *&p => p */
      if (useless_type_conversion_p (type, optype))
        return op;

      /* *(foo *)&fooarray => fooarray[0] */
      if (TREE_CODE (optype) == ARRAY_TYPE
	  && useless_type_conversion_p (type, TREE_TYPE (optype)))
       {
         tree type_domain = TYPE_DOMAIN (optype);
         tree min_val = size_zero_node;
         if (type_domain && TYPE_MIN_VALUE (type_domain))
           min_val = TYPE_MIN_VALUE (type_domain);
         return build4 (ARRAY_REF, type, op, min_val, NULL_TREE, NULL_TREE);
       }
    }

  /* *(foo *)fooarrptr => (*fooarrptr)[0] */
  if (TREE_CODE (TREE_TYPE (subtype)) == ARRAY_TYPE
      && useless_type_conversion_p (type, TREE_TYPE (TREE_TYPE (subtype))))
    {
      tree type_domain;
      tree min_val = size_zero_node;
      tree osub = sub;
      sub = gimple_fold_indirect_ref (sub);
      if (! sub)
	sub = build1 (INDIRECT_REF, TREE_TYPE (subtype), osub);
      type_domain = TYPE_DOMAIN (TREE_TYPE (sub));
      if (type_domain && TYPE_MIN_VALUE (type_domain))
        min_val = TYPE_MIN_VALUE (type_domain);
      return build4 (ARRAY_REF, type, sub, min_val, NULL_TREE, NULL_TREE);
    }

  return NULL_TREE;
}

/* Given a pointer value OP0, return a simplified version of an
   indirection through OP0, or NULL_TREE if no simplification is
   possible.  This may only be applied to a rhs of an expression.
   Note that the resulting type may be different from the type pointed
   to in the sense that it is still compatible from the langhooks
   point of view. */

static tree
gimple_fold_indirect_ref_rhs (tree t)
{
  return gimple_fold_indirect_ref (t);
}

/* Subroutine of gimplify_modify_expr to do simplifications of
   MODIFY_EXPRs based on the code of the RHS.  We loop for as long as
   something changes.  */

static enum gimplify_status
gimplify_modify_expr_rhs (tree *expr_p, tree *from_p, tree *to_p,
			  gimple_seq *pre_p, gimple_seq *post_p,
			  bool want_value)
{
  enum gimplify_status ret = GS_OK;

  while (ret != GS_UNHANDLED)
    switch (TREE_CODE (*from_p))
      {
      case VAR_DECL:
	/* If we're assigning from a constant constructor, move the
	   constructor expression to the RHS of the MODIFY_EXPR.  */
	if (DECL_INITIAL (*from_p)
	    && TREE_READONLY (*from_p)
	    && !TREE_THIS_VOLATILE (*from_p)
	    && TREE_CODE (DECL_INITIAL (*from_p)) == CONSTRUCTOR)
	  {
	    tree old_from = *from_p;

	    /* Move the constructor into the RHS.  */
	    *from_p = unshare_expr (DECL_INITIAL (*from_p));

	    /* Let's see if gimplify_init_constructor will need to put
	       it in memory.  If so, revert the change.  */
	    ret = gimplify_init_constructor (expr_p, NULL, NULL, false, true);
	    if (ret == GS_ERROR)
	      {
		*from_p = old_from;
		/* Fall through.  */
	      }
	    else
	      {
		ret = GS_OK;
		break;
	      }
	  }
	ret = GS_UNHANDLED;
	break;
      case INDIRECT_REF:
	{
	  /* If we have code like 

	        *(const A*)(A*)&x

	     where the type of "x" is a (possibly cv-qualified variant
	     of "A"), treat the entire expression as identical to "x".
	     This kind of code arises in C++ when an object is bound
	     to a const reference, and if "x" is a TARGET_EXPR we want
	     to take advantage of the optimization below.  */
	  tree t = gimple_fold_indirect_ref_rhs (TREE_OPERAND (*from_p, 0));
	  if (t)
	    {
	      *from_p = t;
	      ret = GS_OK;
	    }
	  else
	    ret = GS_UNHANDLED;
	  break;
	}

      case TARGET_EXPR:
	{
	  /* If we are initializing something from a TARGET_EXPR, strip the
	     TARGET_EXPR and initialize it directly, if possible.  This can't
	     be done if the initializer is void, since that implies that the
	     temporary is set in some non-trivial way.

	     ??? What about code that pulls out the temp and uses it
	     elsewhere? I think that such code never uses the TARGET_EXPR as
	     an initializer.  If I'm wrong, we'll die because the temp won't
	     have any RTL.  In that case, I guess we'll need to replace
	     references somehow.  */
	  tree init = TARGET_EXPR_INITIAL (*from_p);

	  if (init
	      && !VOID_TYPE_P (TREE_TYPE (init)))
	    {
	      *from_p = init;
	      ret = GS_OK;
	    }
	  else
	    ret = GS_UNHANDLED;
	}
	break;

      case COMPOUND_EXPR:
	/* Remove any COMPOUND_EXPR in the RHS so the following cases will be
	   caught.  */
	gimplify_compound_expr (from_p, pre_p, true);
	ret = GS_OK;
	break;

      case CONSTRUCTOR:
	/* If we're initializing from a CONSTRUCTOR, break this into
	   individual MODIFY_EXPRs.  */
	return gimplify_init_constructor (expr_p, pre_p, post_p, want_value,
					  false);

      case COND_EXPR:
	/* If we're assigning to a non-register type, push the assignment
	   down into the branches.  This is mandatory for ADDRESSABLE types,
	   since we cannot generate temporaries for such, but it saves a
	   copy in other cases as well.  */
	if (!is_gimple_reg_type (TREE_TYPE (*from_p)))
	  {
	    /* This code should mirror the code in gimplify_cond_expr. */
	    enum tree_code code = TREE_CODE (*expr_p);
	    tree cond = *from_p;
	    tree result = *to_p;

	    ret = gimplify_expr (&result, pre_p, post_p,
				 is_gimple_lvalue, fb_lvalue);
	    if (ret != GS_ERROR)
	      ret = GS_OK;

	    if (TREE_TYPE (TREE_OPERAND (cond, 1)) != void_type_node)
	      TREE_OPERAND (cond, 1)
		= build2 (code, void_type_node, result,
			  TREE_OPERAND (cond, 1));
	    if (TREE_TYPE (TREE_OPERAND (cond, 2)) != void_type_node)
	      TREE_OPERAND (cond, 2)
		= build2 (code, void_type_node, unshare_expr (result),