[AArch64] Simplify WHILERW and WHILEWR definition

[AArch64] Simplify WHILERW and WHILEWR definition

I'd made WHILERW and WHILEWR use separate patterns from the SVE
WHILE instructions, but they're similar enough that we can use
a single pattern.  This means that we also get the flag-related
patterns "for free".

2020-01-09  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/iterators.md (SVE_WHILE): Add UNSPEC_WHILERW
	and UNSPEC_WHILEWR.
	(while_optab_cmp): Handle them.
	* config/aarch64/aarch64-sve.md
	(*while_<while_optab_cmp><GPI:mode><PRED_ALL:mode>_ptest): Make public
	and add a "@" marker.
	* config/aarch64/aarch64-sve2.md (check_<raw_war>_ptrs<mode>): Use it
	instead of gen_aarch64_sve2_while_ptest.
	(@aarch64_sve2_while<cmp_op><GPI:mode><PRED_ALL:mode>_ptest): Delete.

From-SVN: r280054