[AArch64] Add support for SVE F{MAX,MIN}NM immediate

[AArch64] Add support for SVE F{MAX,MIN}NM immediate

This patch uses the immediate forms of FMAXNM and FMINNM for
unconditional arithmetic.

The same rules apply to FMAX and FMIN, but we only generate those
via the ACLE.

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

gcc/
	* config/aarch64/predicates.md (aarch64_sve_float_maxmin_immediate)
	(aarch64_sve_float_maxmin_operand): New predicates.
	* config/aarch64/constraints.md (vsB): New constraint.
	(vsM): Fix typo.
	* config/aarch64/iterators.md (sve_pred_fp_rhs2_operand): Use
	aarch64_sve_float_maxmin_operand for UNSPEC_COND_FMAXNM and
	UNSPEC_COND_FMINNM.
	* config/aarch64/aarch64-sve.md (<maxmin_uns><SVE_F:mode>3):
	Use aarch64_sve_float_maxmin_operand for operand 2.
	(*<SVE_COND_FP_MAXMIN_PUBLIC:optab><SVE_F:mode>3): Likewise.
	Add alternatives for the constant forms.

gcc/testsuite/
	* gcc.target/aarch64/sve/fmaxnm_1.c: New test.
	* gcc.target/aarch64/sve/fminnm_1.c: Likewise.

From-SVN: r274440