re PR target/66112 (__builtin_mul_overflow for int16_t emits poor code)

re PR target/66112 (__builtin_mul_overflow for int16_t emits poor code)

	PR target/66112
	* config/i386/i386.md (mulv<mode>4, umulv<mode>4, *umulv<mode>4):
	Use SWI248 iterator instead of SWI.
	(*mulv<mode>4_1): Use SWI48 instead of SWI.  Simplify output template.
	Use eq_attr "alternative" "0" instead of match_test in
	length_immediate attribute computation.
	(*mulvhi4, *mulvhi4_1): New define_insns.

	* gcc.target/i386/pr66112-2.c: New test.

From-SVN: r223116