[17/n] PR85694: AArch64 support for AVG_FLOOR/CEIL

[17/n] PR85694: AArch64 support for AVG_FLOOR/CEIL

This patch adds AArch64 patterns for the new AVG_FLOOR/CEIL operations.
AVG_FLOOR is [SU]HADD and AVG_CEIL is [SU]RHADD.

2018-07-03  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	PR tree-optimization/85694
	* config/aarch64/iterators.md (HADD, RHADD): New int iterators.
	(u): Handle UNSPEC_SHADD, UNSPEC_UHADD, UNSPEC_SRHADD and
	UNSPEC_URHADD.
	* config/aarch64/aarch64-simd.md (<u>avg<mode>3_floor)
	(<u>avg<mode>3_ceil): New patterns.

gcc/testsuite/
	PR tree-optimization/85694
	* lib/target-supports.exp (check_effective_target_vect_avg_qi):
	Return true for AArch64 without SVE.
	* gcc.target/aarch64/vect_hadd_1.h: New file.
	* gcc.target/aarch64/vect_shadd_1.c: New test.
	* gcc.target/aarch64/vect_srhadd_1.c: Likewise.
	* gcc.target/aarch64/vect_uhadd_1.c: Likewise.
	* gcc.target/aarch64/vect_urhadd_1.c: Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@262347 138bc75d-0d04-0410-961f-82ee72b054a4