[AArch64] Use UNSPEC_MERGE_PTRUE for comparisons

[AArch64] Use UNSPEC_MERGE_PTRUE for comparisons

This patch rewrites the SVE comparison handling so that it uses
UNSPEC_MERGE_PTRUE for comparisons that are known to be predicated
on a PTRUE, for consistency with other patterns.  Specific unspecs
are then only needed for truly predicated floating-point comparisons,
such as those used in the expansion of UNEQ for flag_trapping_math.

The patch also makes sure that the comparison expanders attach
a REG_EQUAL note to instructions that use UNSPEC_MERGE_PTRUE,
so passes can use that as an alternative to the unspec pattern.
(This happens automatically for optabs.  The problem was that
this code emits instruction patterns directly.)

No specific benefit on its own, but it lays the groundwork for
the next patch.

2018-05-08  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* config/aarch64/iterators.md (UNSPEC_COND_LO, UNSPEC_COND_LS)
	(UNSPEC_COND_HI, UNSPEC_COND_HS, UNSPEC_COND_UO): Delete.
	(SVE_INT_CMP, SVE_FP_CMP): New code iterators.
	(cmp_op, sve_imm_con): New code attributes.
	(SVE_COND_INT_CMP, imm_con): Delete.
	(cmp_op): Remove above unspecs from int attribute.
	* config/aarch64/aarch64-sve.md (*vec_cmp<cmp_op>_<mode>): Rename
	to...
	(*cmp<cmp_op><mode>): ...this.  Use UNSPEC_MERGE_PTRUE instead of
	comparison-specific unspecs.
	(*vec_cmp<cmp_op>_<mode>_ptest): Rename to...
	(*cmp<cmp_op><mode>_ptest): ...this and adjust likewise.
	(*vec_cmp<cmp_op>_<mode>_cc): Rename to...
	(*cmp<cmp_op><mode>_cc): ...this and adjust likewise.
	(*vec_fcm<cmp_op><mode>): Rename to...
	(*fcm<cmp_op><mode>): ...this and adjust likewise.
	(*vec_fcmuo<mode>): Rename to...
	(*fcmuo<mode>): ...this and adjust likewise.
	(*pred_fcm<cmp_op><mode>): New pattern.
	* config/aarch64/aarch64.c (aarch64_emit_unop, aarch64_emit_binop)
	(aarch64_emit_sve_ptrue_op, aarch64_emit_sve_ptrue_op_cc): New
	functions.
	(aarch64_unspec_cond_code): Remove handling of LTU, GTU, LEU, GEU
	and UNORDERED.
	(aarch64_gen_unspec_cond, aarch64_emit_unspec_cond): Delete.
	(aarch64_emit_sve_predicated_cond): New function.
	(aarch64_expand_sve_vec_cmp_int): Use aarch64_emit_sve_ptrue_op_cc.
	(aarch64_emit_unspec_cond_or): Replace with...
	(aarch64_emit_sve_or_conds): ...this new function.  Use
	aarch64_emit_sve_ptrue_op for the individual comparisons and
	aarch64_emit_binop to OR them together.
	(aarch64_emit_inverted_unspec_cond): Replace with...
	(aarch64_emit_sve_inverted_cond): ...this new function.  Use
	aarch64_emit_sve_ptrue_op for the comparison and
	aarch64_emit_unop to invert the result.
	(aarch64_expand_sve_vec_cmp_float): Update after the above
	changes.  Use aarch64_emit_sve_ptrue_op for native comparisons.

From-SVN: r260029