PR middle-end/17112
	* stor-layout.c (compute_record_mode): For records with a single
	field, only use the field's mode if its size matches what we'd
	have choosen for the record ourselves.  This forces the use of
	BLKmode for packed records that don't completely fill a mode.

	* gcc.dg/pr17112-1.c: New test case.

Co-Authored-By: Giovanni Bajo <giovannibajo@gcc.gnu.org>

From-SVN: r88130