[AArch64] Add support for SVE CLS and CLZ

[AArch64] Add support for SVE CLS and CLZ

This patch adds support for unpredicated SVE CLS and CLZ.  A later patch
will add support for predicated unary integer arithmetic.

2019-08-14  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/iterators.md (SVE_INT_UNARY): Add clrsb and clz.
	(optab, sve_int_op): Handle them.
	* config/aarch64/aarch64-sve.md: Expand comment.

gcc/testsuite/
	* gcc.target/aarch64/vect-clz.c: Force SVE off.
	* gcc.target/aarch64/sve/clrsb_1.c: New test.
	* gcc.target/aarch64/sve/clrsb_1_run.c: Likewise.
	* gcc.target/aarch64/sve/clz_1.c: Likewise.
	* gcc.target/aarch64/sve/clz_1_run.c: Likewise.

From-SVN: r274437