[AArch64] Use SVE MOV /M of scalars

[AArch64] Use SVE MOV /M of scalars

This patch uses MOV /M to optimise selects between a duplicated
scalar variable and a vector.

2019-08-14  Richard Sandiford  <richard.sandiford@arm.com>
	    Kugan Vivekanandarajah  <kugan.vivekanandarajah@linaro.org>

gcc/
	* config/aarch64/aarch64-sve.md (*aarch64_sel_dup<mode>): New pattern.

gcc/testsuite/
	* g++.target/aarch64/sve/dup_sel_1.C: New test.
	* g++.target/aarch64/sve/dup_sel_2.C: Likewise.
	* g++.target/aarch64/sve/dup_sel_3.C: Likewise.
	* g++.target/aarch64/sve/dup_sel_4.C: Likewise.
	* g++.target/aarch64/sve/dup_sel_5.C: Likewise.
	* g++.target/aarch64/sve/dup_sel_6.C: Likewise.

Co-Authored-By: Kugan Vivekanandarajah <kuganv@linaro.org>
From-SVN: r274442