arm: Add missing vec_cmp and vcond patterns

arm: Add missing vec_cmp and vcond patterns

This patch does several things at once:

(1) Add vector compare patterns (vec_cmp and vec_cmpu).

(2) Add vector selects between floating-point modes when the
    values being compared are integers (affects vcond and vcondu).

(3) Add vector selects between integer modes when the values being
    compared are floating-point (affects vcond).

(4) Add standalone vector select patterns (vcond_mask).

(5) Tweak the handling of compound comparisons with zeros.

Unfortunately it proved too difficult (for me) to separate this
out into a series of smaller patches, since everything is so
inter-related.  Defining only some of the new patterns does
not leave things in a happy state.

The handling of comparisons is mostly taken from the vcond patterns.
This means that it remains non-compliant with IEEE: “quiet” comparisons
use signalling instructions.  But that shouldn't matter for floats,
since we require -funsafe-math-optimizations to vectorize for them
anyway.

It remains the case that comparisons and selects aren't implemented
at all for HF vectors.  Implementing those feels like separate work.

gcc/
	PR target/96528
	PR target/97288
	* config/arm/arm-protos.h (arm_expand_vector_compare): Declare.
	(arm_expand_vcond): Likewise.
	* config/arm/arm.c (arm_expand_vector_compare): New function.
	(arm_expand_vcond): Likewise.
	* config/arm/neon.md (vec_cmp<VDQW:mode><v_cmp_result>): New pattern.
	(vec_cmpu<VDQW:mode><VDQW:mode>): Likewise.
	(vcond<VDQW:mode><VDQW:mode>): Require operand 5 to be a register
	or zero.  Use arm_expand_vcond.
	(vcond<V_cvtto><V32:mode>): New pattern.
	(vcondu<VDQIW:mode><VDQIW:mode>): Generalize to...
	(vcondu<VDQW:mode><v_cmp_result): ...this.  Require operand 5
	to be a register or zero.  Use arm_expand_vcond.
	(vcond_mask_<VDQW:mode><v_cmp_result>): New pattern.
	(neon_vc<cmp_op><mode>, neon_vc<cmp_op><mode>_insn): Add "@" marker.
	(neon_vbsl<mode>): Likewise.
	(neon_vc<cmp_op>u<mode>): Reexpress as...
	(@neon_vc<code><mode>): ...this.

gcc/testsuite/
	* lib/target-supports.exp (check_effective_target_vect_cond_mixed): Add
	arm neon targets.
	* gcc.target/arm/neon-compare-1.c: New test.
	* gcc.target/arm/neon-compare-2.c: Likewise.
	* gcc.target/arm/neon-compare-3.c: Likewise.
	* gcc.target/arm/neon-compare-4.c: Likewise.
	* gcc.target/arm/neon-compare-5.c: Likewise.
	* gcc.target/arm/neon-vcond-gt.c: Expect comparisons with zero.
	* gcc.target/arm/neon-vcond-ltgt.c: Likewise.
	* gcc.target/arm/neon-vcond-unordered.c: Likewise.