gimplify.c

	     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.  */
	  cleared = true;
	else if (num_ctor_elements - num_nonzero_elements
		 > CLEAR_RATIO (optimize_function_for_speed_p (cfun))
		 && num_nonzero_elements < num_ctor_elements / 4)
	  /* If there are "lots" of zeros, it's more efficient to clear
	     the memory and then set the nonzero elements.  */
	  cleared = true;
	else
	  cleared = false;

	/* 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.  Also don't do this for small
	   all-zero initializers (which aren't big enough to merit
	   clearing), and don't try to make bitwise copies of
	   TREE_ADDRESSABLE types.  */
	if (valid_const_initializer
	    && !(cleared || num_nonzero_elements == 0)
	    && !TREE_ADDRESSABLE (type))
	  {
	    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);

	    /* Do a block move either if the size is so small as to make
	       each individual move a sub-unit move on average, or if it
	       is so large as to make individual moves inefficient.  */
	    if (size > 0
		&& num_nonzero_elements > 1
		&& (size < num_nonzero_elements
		    || !can_move_by_pieces (size, align)))
	      {
		if (notify_temp_creation)
		  return GS_ERROR;

		walk_tree (&ctor, force_labels_r, NULL, NULL);
		ctor = tree_output_constant_def (ctor);
		if (!useless_type_conversion_p (type, TREE_TYPE (ctor)))
		  ctor = build1 (VIEW_CONVERT_EXPR, type, ctor);
		TREE_OPERAND (*expr_p, 1) = ctor;

		/* 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 the target is volatile, we have non-zero elements and more than
	   one field to assign, initialize the target from a temporary.  */
	if (TREE_THIS_VOLATILE (object)
	    && !TREE_ADDRESSABLE (type)
	    && num_nonzero_elements > 0
	    && VEC_length (constructor_elt, elts) > 1)
	  {
	    tree temp = create_tmp_var (TYPE_MAIN_VARIANT (type), NULL);
	    TREE_OPERAND (*expr_p, 0) = temp;
	    *expr_p = build2 (COMPOUND_EXPR, TREE_TYPE (*expr_p),
			      *expr_p,
			      build2 (MODIFY_EXPR, void_type_node,
				      object, temp));
	    return GS_OK;
	  }

	if (notify_temp_creation)
	  return GS_OK;

	/* If there are nonzero elements and if needed, 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 && TREE_CODE (*expr_p) != INIT_EXPR)
	  {
	    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 = build_zero_cst (TREE_TYPE (type));
	    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_EACH_VEC_ELT (constructor_elt, elts, ix, ce)
	  {
	    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 ptype = TREE_TYPE (t), type = TREE_TYPE (ptype);
  tree sub = t;
  tree subtype;

  STRIP_NOPS (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
	  && TREE_CODE (TYPE_SIZE (TREE_TYPE (optype))) == INTEGER_CST
	  && 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);
	 if (TREE_CODE (min_val) == INTEGER_CST)
	   return build4 (ARRAY_REF, type, op, min_val, NULL_TREE, NULL_TREE);
       }
      /* *(foo *)&complexfoo => __real__ complexfoo */
      else if (TREE_CODE (optype) == COMPLEX_TYPE
               && useless_type_conversion_p (type, TREE_TYPE (optype)))
        return fold_build1 (REALPART_EXPR, type, op);
      /* *(foo *)&vectorfoo => BIT_FIELD_REF<vectorfoo,...> */
      else if (TREE_CODE (optype) == VECTOR_TYPE
               && useless_type_conversion_p (type, TREE_TYPE (optype)))
        {
          tree part_width = TYPE_SIZE (type);
          tree index = bitsize_int (0);
          return fold_build3 (BIT_FIELD_REF, type, op, part_width, index);
        }
    }

  /* *(p + CST) -> ...  */
  if (TREE_CODE (sub) == POINTER_PLUS_EXPR
      && TREE_CODE (TREE_OPERAND (sub, 1)) == INTEGER_CST)
    {
      tree addr = TREE_OPERAND (sub, 0);
      tree off = TREE_OPERAND (sub, 1);
      tree addrtype;

      STRIP_NOPS (addr);
      addrtype = TREE_TYPE (addr);

      /* ((foo*)&vectorfoo)[1] -> BIT_FIELD_REF<vectorfoo,...> */
      if (TREE_CODE (addr) == ADDR_EXPR
	  && TREE_CODE (TREE_TYPE (addrtype)) == VECTOR_TYPE
	  && useless_type_conversion_p (type, TREE_TYPE (TREE_TYPE (addrtype)))
	  && host_integerp (off, 1))
	{
          unsigned HOST_WIDE_INT offset = tree_low_cst (off, 1);
          tree part_width = TYPE_SIZE (type);
          unsigned HOST_WIDE_INT part_widthi
            = tree_low_cst (part_width, 0) / BITS_PER_UNIT;
          unsigned HOST_WIDE_INT indexi = offset * BITS_PER_UNIT;
          tree index = bitsize_int (indexi);
          if (offset / part_widthi
              <= TYPE_VECTOR_SUBPARTS (TREE_TYPE (addrtype)))
            return fold_build3 (BIT_FIELD_REF, type, TREE_OPERAND (addr, 0),
                                part_width, index);
	}

      /* ((foo*)&complexfoo)[1] -> __imag__ complexfoo */
      if (TREE_CODE (addr) == ADDR_EXPR
	  && TREE_CODE (TREE_TYPE (addrtype)) == COMPLEX_TYPE
	  && useless_type_conversion_p (type, TREE_TYPE (TREE_TYPE (addrtype))))
        {
          tree size = TYPE_SIZE_UNIT (type);
          if (tree_int_cst_equal (size, off))
            return fold_build1 (IMAGPART_EXPR, type, TREE_OPERAND (addr, 0));
        }

      /* *(p + CST) -> MEM_REF <p, CST>.  */
      if (TREE_CODE (addr) != ADDR_EXPR
	  || DECL_P (TREE_OPERAND (addr, 0)))
	return fold_build2 (MEM_REF, type,
			    addr,
			    build_int_cst_wide (ptype,
						TREE_INT_CST_LOW (off),
						TREE_INT_CST_HIGH (off)));
    }

  /* *(foo *)fooarrptr => (*fooarrptr)[0] */
  if (TREE_CODE (TREE_TYPE (subtype)) == ARRAY_TYPE
      && TREE_CODE (TYPE_SIZE (TREE_TYPE (TREE_TYPE (subtype)))) == INTEGER_CST
      && 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);
      if (TREE_CODE (min_val) == INTEGER_CST)
	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_UNHANDLED;
  bool changed;

  do
    {
      changed = false;
      switch (TREE_CODE (*from_p))
	{
	case VAR_DECL:
	  /* If we're assigning from a read-only variable initialized with
	     a constructor, do the direct assignment from the constructor,
	     but only if neither source nor target are volatile since this
	     latter assignment might end up being done on a per-field basis.  */
	  if (DECL_INITIAL (*from_p)
	      && TREE_READONLY (*from_p)
	      && !TREE_THIS_VOLATILE (*from_p)
	      && !TREE_THIS_VOLATILE (*to_p)
	      && TREE_CODE (DECL_INITIAL (*from_p)) == CONSTRUCTOR)
	    {
	      tree old_from = *from_p;
	      enum gimplify_status subret;

	      /* 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.  */
	      subret = gimplify_init_constructor (expr_p, NULL, NULL,
						  false, true);
	      if (subret == GS_ERROR)
		{
		  /* If so, revert the change.  */
		  *from_p = old_from;
		}
	      else
		{
		  ret = GS_OK;
		  changed = true;
		}
	    }
	  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.  */
	    bool volatile_p = TREE_THIS_VOLATILE (*from_p);
	    tree t = gimple_fold_indirect_ref_rhs (TREE_OPERAND (*from_p, 0));
	    if (t)
	      {
		if (TREE_THIS_VOLATILE (t) != volatile_p)
		  {
		    if (TREE_CODE_CLASS (TREE_CODE (t)) == tcc_declaration)
		      t = build_simple_mem_ref_loc (EXPR_LOCATION (*from_p),
						    build_fold_addr_expr (t));
		    if (REFERENCE_CLASS_P (t))
		      TREE_THIS_VOLATILE (t) = volatile_p;
		  }
		*from_p = t;
		ret = GS_OK;
		changed = true;
	      }
	    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;
		changed = true;
	      }
	  }
	  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;
	  changed = true;
	  break;

	case CONSTRUCTOR:
	  /* If we already made some changes, let the front end have a
	     crack at this before we break it down.  */
	  if (ret != GS_UNHANDLED)
	    break;
	  /* 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),
			    TREE_OPERAND (cond, 2));

	      TREE_TYPE (cond) = void_type_node;
	      recalculate_side_effects (cond);

	      if (want_value)
		{
		  gimplify_and_add (cond, pre_p);
		  *expr_p = unshare_expr (result);
		}
	      else
		*expr_p = cond;
	      return ret;
	    }
	  break;

	case CALL_EXPR:
	  /* For calls that return in memory, give *to_p as the CALL_EXPR's
	     return slot so that we don't generate a temporary.  */
	  if (!CALL_EXPR_RETURN_SLOT_OPT (*from_p)
	      && aggregate_value_p (*from_p, *from_p))
	    {
	      bool use_target;

	      if (!(rhs_predicate_for (*to_p))(*from_p))
		/* If we need a temporary, *to_p isn't accurate.  */
		use_target = false;
	      /* It's OK to use the return slot directly unless it's an NRV. */
	      else if (TREE_CODE (*to_p) == RESULT_DECL
		       && DECL_NAME (*to_p) == NULL_TREE
		       && needs_to_live_in_memory (*to_p))
		use_target = true;
	      else if (is_gimple_reg_type (TREE_TYPE (*to_p))
		       || (DECL_P (*to_p) && DECL_REGISTER (*to_p)))
		/* Don't force regs into memory.  */
		use_target = false;
	      else if (TREE_CODE (*expr_p) == INIT_EXPR)
		/* It's OK to use the target directly if it's being
		   initialized. */
		use_target = true;
	      else if (variably_modified_type_p (TREE_TYPE (*to_p), NULL_TREE))
		/* Always use the target and thus RSO for variable-sized types.
		   GIMPLE cannot deal with a variable-sized assignment
		   embedded in a call statement.  */
		use_target = true;
	      else if (TREE_CODE (*to_p) != SSA_NAME
		      && (!is_gimple_variable (*to_p)
			  || needs_to_live_in_memory (*to_p)))
		/* Don't use the original target if it's already addressable;
		   if its address escapes, and the called function uses the
		   NRV optimization, a conforming program could see *to_p
		   change before the called function returns; see c++/19317.
		   When optimizing, the return_slot pass marks more functions
		   as safe after we have escape info.  */
		use_target = false;
	      else
		use_target = true;

	      if (use_target)
		{
		  CALL_EXPR_RETURN_SLOT_OPT (*from_p) = 1;
		  mark_addressable (*to_p);
		}
	    }
	  break;

	case WITH_SIZE_EXPR:
	  /* Likewise for calls that return an aggregate of non-constant size,
	     since we would not be able to generate a temporary at all.  */
	  if (TREE_CODE (TREE_OPERAND (*from_p, 0)) == CALL_EXPR)
	    {
	      *from_p = TREE_OPERAND (*from_p, 0);
	      /* We don't change ret in this case because the
		 WITH_SIZE_EXPR might have been added in
		 gimplify_modify_expr, so returning GS_OK would lead to an
		 infinite loop.  */
	      changed = true;
	    }
	  break;

	  /* If we're initializing from a container, push the initialization
	     inside it.  */
	case CLEANUP_POINT_EXPR:
	case BIND_EXPR:
	case STATEMENT_LIST:
	  {
	    tree wrap = *from_p;
	    tree t;

	    ret = gimplify_expr (to_p, pre_p, post_p, is_gimple_min_lval,
				 fb_lvalue);
	    if (ret != GS_ERROR)
	      ret = GS_OK;

	    t = voidify_wrapper_expr (wrap, *expr_p);
	    gcc_assert (t == *expr_p);

	    if (want_value)
	      {
		gimplify_and_add (wrap, pre_p);
		*expr_p = unshare_expr (*to_p);
	      }
	    else
	      *expr_p = wrap;
	    return GS_OK;
	  }

	case COMPOUND_LITERAL_EXPR:
	  {
	    tree complit = TREE_OPERAND (*expr_p, 1);
	    tree decl_s = COMPOUND_LITERAL_EXPR_DECL_EXPR (complit);
	    tree decl = DECL_EXPR_DECL (decl_s);
	    tree init = DECL_INITIAL (decl);

	    /* struct T x = (struct T) { 0, 1, 2 } can be optimized
	       into struct T x = { 0, 1, 2 } if the address of the
	       compound literal has never been taken.  */
	    if (!TREE_ADDRESSABLE (complit)
		&& !TREE_ADDRESSABLE (decl)
		&& init)
	      {
		*expr_p = copy_node (*expr_p);
		TREE_OPERAND (*expr_p, 1) = init;
		return GS_OK;
	      }
	  }

	default:
	  break;
	}
    }
  while (changed);

  return ret;
}


/* Return true if T looks like a valid GIMPLE statement.  */

static bool
is_gimple_stmt (tree t)
{
  const enum tree_code code = TREE_CODE (t);

  switch (code)
    {
    case NOP_EXPR:
      /* The only valid NOP_EXPR is the empty statement.  */
      return IS_EMPTY_STMT (t);

    case BIND_EXPR:
    case COND_EXPR:
      /* These are only valid if they're void.  */
      return TREE_TYPE (t) == NULL || VOID_TYPE_P (TREE_TYPE (t));

    case SWITCH_EXPR:
    case GOTO_EXPR:
    case RETURN_EXPR:
    case LABEL_EXPR:
    case CASE_LABEL_EXPR:
    case TRY_CATCH_EXPR:
    case TRY_FINALLY_EXPR:
    case EH_FILTER_EXPR:
    case CATCH_EXPR:
    case ASM_EXPR:
    case STATEMENT_LIST:
    case OMP_PARALLEL:
    case OMP_FOR:
    case OMP_SECTIONS:
    case OMP_SECTION:
    case OMP_SINGLE:
    case OMP_MASTER:
    case OMP_ORDERED:
    case OMP_CRITICAL:
    case OMP_TASK:
      /* These are always void.  */
      return true;

    case CALL_EXPR:
    case MODIFY_EXPR:
    case PREDICT_EXPR:
      /* These are valid regardless of their type.  */
      return true;

    default:
      return false;
    }
}


/* Promote partial stores to COMPLEX variables to total stores.  *EXPR_P is
   a MODIFY_EXPR with a lhs of a REAL/IMAGPART_EXPR of a variable with
   DECL_GIMPLE_REG_P set.

   IMPORTANT NOTE: This promotion is performed by introducing a load of the
   other, unmodified part of the complex object just before the total store.
   As a consequence, if the object is still uninitialized, an undefined value
   will be loaded into a register, which may result in a spurious exception
   if the register is floating-point and the value happens to be a signaling
   NaN for example.  Then the fully-fledged complex operations lowering pass
   followed by a DCE pass are necessary in order to fix things up.  */

static enum gimplify_status
gimplify_modify_expr_complex_part (tree *expr_p, gimple_seq *pre_p,
                                   bool want_value)
{
  enum tree_code code, ocode;
  tree lhs, rhs, new_rhs, other, realpart, imagpart;

  lhs = TREE_OPERAND (*expr_p, 0);
  rhs = TREE_OPERAND (*expr_p, 1);
  code = TREE_CODE (lhs);
  lhs = TREE_OPERAND (lhs, 0);

  ocode = code == REALPART_EXPR ? IMAGPART_EXPR : REALPART_EXPR;
  other = build1 (ocode, TREE_TYPE (rhs), lhs);
  TREE_NO_WARNING (other) = 1;
  other = get_formal_tmp_var (other, pre_p);

  realpart = code == REALPART_EXPR ? rhs : other;
  imagpart = code == REALPART_EXPR ? other : rhs;

  if (TREE_CONSTANT (realpart) && TREE_CONSTANT (imagpart))
    new_rhs = build_complex (TREE_TYPE (lhs), realpart, imagpart);
  else
    new_rhs = build2 (COMPLEX_EXPR, TREE_TYPE (lhs), realpart, imagpart);

  gimplify_seq_add_stmt (pre_p, gimple_build_assign (lhs, new_rhs));
  *expr_p = (want_value) ? rhs : NULL_TREE;

  return GS_ALL_DONE;
}

/* Gimplify the MODIFY_EXPR node pointed to by EXPR_P.

      modify_expr
	      : varname '=' rhs
	      | '*' ID '=' rhs

    PRE_P points to the list where side effects that must happen before
	*EXPR_P should be stored.

    POST_P points to the list where side effects that must happen after
	*EXPR_P should be stored.

    WANT_VALUE is nonzero iff we want to use the value of this expression
	in another expression.  */

static enum gimplify_status
gimplify_modify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
		      bool want_value)
{
  tree *from_p = &TREE_OPERAND (*expr_p, 1);
  tree *to_p = &TREE_OPERAND (*expr_p, 0);
  enum gimplify_status ret = GS_UNHANDLED;
  gimple assign;
  location_t loc = EXPR_LOCATION (*expr_p);
  gimple_stmt_iterator gsi;

  gcc_assert (TREE_CODE (*expr_p) == MODIFY_EXPR
	      || TREE_CODE (*expr_p) == INIT_EXPR);

  /* Trying to simplify a clobber using normal logic doesn't work,
     so handle it here.  */
  if (TREE_CLOBBER_P (*from_p))
    {
      gcc_assert (!want_value && TREE_CODE (*to_p) == VAR_DECL);
      gimplify_seq_add_stmt (pre_p, gimple_build_assign (*to_p, *from_p));
      *expr_p = NULL;
      return GS_ALL_DONE;
    }

  /* Insert pointer conversions required by the middle-end that are not
     required by the frontend.  This fixes middle-end type checking for
     for example gcc.dg/redecl-6.c.  */
  if (POINTER_TYPE_P (TREE_TYPE (*to_p)))
    {
      STRIP_USELESS_TYPE_CONVERSION (*from_p);
      if (!useless_type_conversion_p (TREE_TYPE (*to_p), TREE_TYPE (*from_p)))
	*from_p = fold_convert_loc (loc, TREE_TYPE (*to_p), *from_p);
    }

  /* See if any simplifications can be done based on what the RHS is.  */
  ret = gimplify_modify_expr_rhs (expr_p, from_p, to_p, pre_p, post_p,
				  want_value);
  if (ret != GS_UNHANDLED)
    return ret;

  /* For zero sized types only gimplify the left hand side and right hand
     side as statements and throw away the assignment.  Do this after
     gimplify_modify_expr_rhs so we handle TARGET_EXPRs of addressable
     types properly.  */
  if (zero_sized_type (TREE_TYPE (*from_p)) && !want_value)
    {
      gimplify_stmt (from_p, pre_p);
      gimplify_stmt (to_p, pre_p);
      *expr_p = NULL_TREE;
      return GS_ALL_DONE;
    }

  /* If the value being copied is of variable width, compute the length
     of the copy into a WITH_SIZE_EXPR.   Note that we need to do this
     before gimplifying any of the operands so that we can resolve any
     PLACEHOLDER_EXPRs in the size.  Also note that the RTL expander uses
     the size of the expression to be copied, not of the destination, so
     that is what we must do here.  */
  maybe_with_size_expr (from_p);

  ret = gimplify_expr (to_p, pre_p, post_p, is_gimple_lvalue, fb_lvalue);
  if (ret == GS_ERROR)
    return ret;

  /* As a special case, we have to temporarily allow for assignments
     with a CALL_EXPR on the RHS.  Since in GIMPLE a function call is
     a toplevel statement, when gimplifying the GENERIC expression
     MODIFY_EXPR <a, CALL_EXPR <foo>>, we cannot create the tuple
     GIMPLE_ASSIGN <a, GIMPLE_CALL <foo>>.

     Instead, we need to create the tuple GIMPLE_CALL <a, foo>.  To
     prevent gimplify_expr from trying to create a new temporary for
     foo's LHS, we tell it that it should only gimplify until it
     reaches the CALL_EXPR.  On return from gimplify_expr, the newly
     created GIMPLE_CALL <foo> will be the last statement in *PRE_P
     and all we need to do here is set 'a' to be its LHS.  */
  ret = gimplify_expr (from_p, pre_p, post_p, rhs_predicate_for (*to_p),
		       fb_rvalue);
  if (ret == GS_ERROR)
    return ret;

  /* Now see if the above changed *from_p to something we handle specially.  */
  ret = gimplify_modify_expr_rhs (expr_p, from_p, to_p, pre_p, post_p,
				  want_value);
  if (ret != GS_UNHANDLED)
    return ret;

  /* If we've got a variable sized assignment between two lvalues (i.e. does
     not involve a call), then we can make things a bit more straightforward
     by converting the assignment to memcpy or memset.  */
  if (TREE_CODE (*from_p) == WITH_SIZE_EXPR)
    {
      tree from = TREE_OPERAND (*from_p, 0);
      tree size = TREE_OPERAND (*from_p, 1);

      if (TREE_CODE (from) == CONSTRUCTOR)
	return gimplify_modify_expr_to_memset (expr_p, size, want_value, pre_p);

      if (is_gimple_addressable (from))
	{
	  *from_p = from;
	  return gimplify_modify_expr_to_memcpy (expr_p, size, want_value,
	      					 pre_p);
	}
    }

  /* Transform partial stores to non-addressable complex variables into
     total stores.  This allows us to use real instead of virtual operands
     for these variables, which improves optimization.  */
  if ((TREE_CODE (*to_p) == REALPART_EXPR
       || TREE_CODE (*to_p) == IMAGPART_EXPR)
      && is_gimple_reg (TREE_OPERAND (*to_p, 0)))
    return gimplify_modify_expr_complex_part (expr_p, pre_p, want_value);

  /* Try to alleviate the effects of the gimplification creating artificial
     temporaries (see for example is_gimple_reg_rhs) on the debug info.  */
  if (!gimplify_ctxp->into_ssa
      && TREE_CODE (*from_p) == VAR_DECL
      && DECL_IGNORED_P (*from_p)
      && DECL_P (*to_p)
      && !DECL_IGNORED_P (*to_p))
    {
      if (!DECL_NAME (*from_p) && DECL_NAME (*to_p))
	DECL_NAME (*from_p)
	  = create_tmp_var_name (IDENTIFIER_POINTER (DECL_NAME (*to_p)));
      DECL_DEBUG_EXPR_IS_FROM (*from_p) = 1;
      SET_DECL_DEBUG_EXPR (*from_p, *to_p);
   }

  if (want_value && TREE_THIS_VOLATILE (*to_p))
    *from_p = get_initialized_tmp_var (*from_p, pre_p, post_p);

  if (TREE_CODE (*from_p) == CALL_EXPR)
    {
      /* Since the RHS is a CALL_EXPR, we need to create a GIMPLE_CALL
	 instead of a GIMPLE_ASSIGN.  */
      tree fnptrtype = TREE_TYPE (CALL_EXPR_FN (*from_p));
      CALL_EXPR_FN (*from_p) = TREE_OPERAND (CALL_EXPR_FN (*from_p), 0);
      STRIP_USELESS_TYPE_CONVERSION (CALL_EXPR_FN (*from_p));
      assign = gimple_build_call_from_tree (*from_p);
      gimple_call_set_fntype (assign, TREE_TYPE (fnptrtype));
      if (!gimple_call_noreturn_p (assign))
	gimple_call_set_lhs (assign, *to_p);
    }
  else
    {
      assign = gimple_build_assign (*to_p, *from_p);
      gimple_set_location (assign, EXPR_LOCATION (*expr_p));
    }

  if (gimplify_ctxp->into_ssa && is_gimple_reg (*to_p))
    {
      /* If we've somehow already got an SSA_NAME on the LHS, then
	 we've probably modified it twice.  Not good.  */
      gcc_assert (TREE_CODE (*to_p) != SSA_NAME);
      *to_p = make_ssa_name (*to_p, assign);
      gimple_set_lhs (assign, *to_p);
    }

  gimplify_seq_add_stmt (pre_p, assign);
  gsi = gsi_last (*pre_p);
  fold_stmt (&gsi);

  if (want_value)
    {
      *expr_p = TREE_THIS_VOLATILE (*to_p) ? *from_p : unshare_expr (*to_p);
      return GS_OK;
    }
  else
    *expr_p = NULL;

  return GS_ALL_DONE;
}

/* Gimplify a comparison between two variable-sized objects.  Do this
   with a call to BUILT_IN_MEMCMP.  */

static enum gimplify_status
gimplify_variable_sized_compare (tree *expr_p)
{
  location_t loc = EXPR_LOCATION (*expr_p);
  tree op0 = TREE_OPERAND (*expr_p, 0);
  tree op1 = TREE_OPERAND (*expr_p, 1);
  tree t, arg, dest, src, expr;

  arg = TYPE_SIZE_UNIT (TREE_TYPE (op0));
  arg = unshare_expr (arg);
  arg = SUBSTITUTE_PLACEHOLDER_IN_EXPR (arg, op0);
  src = build_fold_addr_expr_loc (loc, op1);
  dest = build_fold_addr_expr_loc (loc, op0);
  t = builtin_decl_implicit (BUILT_IN_MEMCMP);
  t = build_call_expr_loc (loc, t, 3, dest, src, arg);

  expr
    = build2 (TREE_CODE (*expr_p), TREE_TYPE (*expr_p), t, integer_zero_node);
  SET_EXPR_LOCATION (expr, loc);
  *expr_p = expr;

  return GS_OK;
}

/* Gimplify a comparison between two aggregate objects of integral scalar
   mode as a comparison between the bitwise equivalent scalar values.  */

static enum gimplify_status
gimplify_scalar_mode_aggregate_compare (tree *expr_p)
{
  location_t loc = EXPR_LOCATION (*expr_p);
  tree op0 = TREE_OPERAND (*expr_p, 0);
  tree op1 = TREE_OPERAND (*expr_p, 1);

  tree type = TREE_TYPE (op0);
  tree scalar_type = lang_hooks.types.type_for_mode (TYPE_MODE (type), 1);

  op0 = fold_build1_loc (loc, VIEW_CONVERT_EXPR, scalar_type, op0);
  op1 = fold_build1_loc (loc, VIEW_CONVERT_EXPR, scalar_type, op1);

  *expr_p
    = fold_build2_loc (loc, TREE_CODE (*expr_p), TREE_TYPE (*expr_p), op0, op1);

  return GS_OK;
}