re PR middle-end/83623 (ICE: in convert_move, at expr.c:248 with -march=knl and 16bit vector bswap/rotate)

	PR middle-end/83623
	* expmed.c (expand_shift_1): For 2-byte rotates by BITS_PER_UNIT,
	check for bswap in mode rather than HImode and use that in expand_unop
	too.

	* gcc.dg/pr83623.c: New test.

From-SVN: r256051