This patch changes the type of stack_var::size from HOST_WIDE_INT
to poly_uint64.  The difference in signedness is because the
field was set by:

  v->size = tree_to_uhwi (size);

2017-12-21  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* cfgexpand.c (stack_var::size): Change from a HOST_WIDE_INT
	to a poly_uint64.
	(add_stack_var, stack_var_cmp, partition_stack_vars)
	(dump_stack_var_partition): Update accordingly.
	(alloc_stack_frame_space): Take the size as a poly_int64 rather
	than a HOST_WIDE_INT.
	(expand_stack_vars, expand_one_stack_var_1): Handle polynomial sizes.
	(defer_stack_allocation, estimated_stack_frame_size): Likewise.
	(account_stack_vars, expand_one_var): Likewise.  Return a poly_uint64
	rather than a HOST_WIDE_INT.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r255922