re PR middle-end/55438 (tmpdir-gcc.dg-struct-layout-1/t001 - t028,  gcc.c-torture/execute/991118-1.c, gcc.c-torture/execute/bf64-1.c, ICE)

gcc/
	PR middle-end/55438
	* expmed.c (simple_mem_bitfield_p): New function, extracted from
	store_bit_field_1 and extract_bit_field_1.  Use GET_MODE_ALIGNMENT
	rather than bitsize when checking the alignment.
	(store_bit_field_1, extract_bit_field_1): Call it.
	* stor-layout.c (bit_field_mode_iterator::bit_field_mode_iterator):
	Don't limit ALIGN_.  Assume that memory is mapped in chunks of at
	least word size, regardless of BIGGEST_ALIGNMENT.
	(bit_field_mode_iterator::get_mode): Use GET_MODE_ALIGNMENT rather
	than unit when checking the alignment.
	(get_best_mode): Use GET_MODE_ALIGNMENT.

From-SVN: r193905