re PR target/78090 ([x86_64]: GCC allows integer register for inter unit conversion...

re PR target/78090 ([x86_64]: GCC allows integer register for inter unit conversion under -mtune-ctrl=^inter_unit_conversions .)

	PR target/78090
	* config/i386/constraints.md (Yc): New register constraint.
	* config/i386/i386.md (*float<SWI48:mode><MODEF:mode>2_mixed):
	Use Yc constraint for alternative 2 of operand 0.  Remove
	preferred_for_speed attribute.

testsuite/ChangeLog:

	PR target/78090
	* gcc.target/i386/conversion-2.c: Remove obsolete test.

From-SVN: r247036