MIPS: Add some floating point instructions support for MIPSr6

MIPS: Add some floating point instructions support for MIPSr6

This patch adds some of the float point instructions from
MIPS32 Release 6(mips32r6) with their respective built-in
functions and tests:

    min_a_s, min_a_d
    max_a_s, max_a_d
    rint_s, rint_d
    class_s, class_d

gcc/ChangeLog:

	* config/mips/i6400.md (i6400_fpu_minmax): Include
	fclass type.
	(i6400_fpu_fadd): Include frint type.
	* config/mips/mips.cc (AVAIL_NON_MIPS16): Add an entry
	for __builtin_mipsr6_xxx.
	(MIPSR6_BUILTIN_PURE): Same as above.
	(CODE_FOR_mipsr6_min_a_s, CODE_FOR_mipsr6_min_a_d)
	(CODE_FOR_mipsr6_max_a_s, CODE_FOR_mipsr6_max_a_d)
	(CODE_FOR_mipsr6_class_s, CODE_FOR_mipsr6_class_d):
	New code_aliasing macros.
	(mips_builtins): Add mips32r6 min_a_s, min_a_d, max_a_s,
	max_a_d, class_s, class_d builtins.
	* config/mips/mips.h (ISA_HAS_FRINT): Define a new macro.
	(ISA_HAS_FCLASS): Same as above.
	* config/mips/mips.md (UNSPEC_FRINT): New unspec.
	(UNSPEC_FCLASS): Same as above.
	(type): Add frint and fclass.
	(fmin_a_<mode>): Generates MINA.fmt instructions.
	(fmax_a_<mode>): Generates MAXA.fmt instructions.
	(rint<mode>2): Generates RINT.fmt instructions.
	(fclass_<mode>): Generates CLASS.fmt instructions.
	* config/mips/p6600.md (p6600_fpu_fadd): Include
	frint type.
	(p6600_fpu_fabs): Include fclass type.

gcc/testsuite/ChangeLog:

	* gcc.target/mips/mips-class.c: New tests for MIPSr6
	* gcc.target/mips/mips-minamaxa.c: Same as above.
	* gcc.target/mips/mips-rint.c: Same as above.

Signed-off-by: Jie Mei <jie.mei@oss.cipunited.com>
Co-authored-by: Xi Ruoyao <xry111@xry111.site>