[ARC] Avoid use of hard registers before reg-alloc.

[ARC] Avoid use of hard registers before reg-alloc.

gcc/
2017-06-01  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.md (mulsi3): Avoid use of hard registers before
	reg-alloc when having mul64 or mul32x16 instructions.
	(mulsidi3): Likewise.
	(umulsidi3): Likewise.
	(mulsi32x16): New pattern.
	(mulsi64): Likewise.
	(mulsidi64): Likewise.
	(umulsidi64): Likewise.
	(MUL32x16_REG): Define.
	(mul64_600): Use MUL32x16_REG.
	(mac64_600): Likewise.
	(umul64_600): Likewise.
	(umac64_600): Likewise.

From-SVN: r248777