re PR target/49687 ([avr] Missed optimization for widening MUL)

re PR target/49687 ([avr] Missed optimization for widening MUL)

	PR target/49687
	* config/avr/avr.md (smulqi3_highpart): New insn.
	(umulqi3_highpart): New insn.
	(*subqi3.ashiftrt7): New insn.
	(smulhi3_highpart): New expander.
	(umulhi3_highpart): Nex expander.
	(*smulhi3_highpart_call): New insn.
	(*umulhi3_highpart_call): New insn.
	(extend_u): New code attribute.
	(extend_prefix): Rename code attribute to extend_su.
	* config/avr/avr.c (avr_rtx_costs): Report costs of highpart of
	widening QI/HI multiply.

From-SVN: r177648