[Arm] Enable CLI for Armv8.6-a: armv8.6-a, i8mm and bf16.

[Arm] Enable CLI for Armv8.6-a: armv8.6-a, i8mm and bf16.

2020-01-02  Dennis Zhang  <dennis.zhang@arm.com>

	* config/arm/arm-c.c (arm_cpu_builtins): Define
	__ARM_FEATURE_MATMUL_INT8, __ARM_FEATURE_BF16_VECTOR_ARITHMETIC,
	__ARM_FEATURE_BF16_SCALAR_ARITHMETIC, and
	__ARM_BF16_FORMAT_ALTERNATIVE when enabled.
	* config/arm/arm-cpus.in (armv8_6, i8mm, bf16): New features.
	* config/arm/arm-tables.opt: Regenerated.
	* config/arm/arm.c (arm_option_reconfigure_globals): Initialize
	arm_arch_i8mm and arm_arch_bf16 when enabled.
	* config/arm/arm.h (TARGET_I8MM): New macro.
	(TARGET_BF16_FP, TARGET_BF16_SIMD): Likewise.
	* config/arm/t-aprofile: Add matching rules for -march=armv8.6-a.
	* config/arm/t-arm-elf (all_v8_archs): Add armv8.6-a.
	* config/arm/t-multilib: Add matching rules for -march=armv8.6-a.
	(v8_6_a_simd_variants): New.
	(v8_*_a_simd_variants): Add i8mm and bf16.
	* doc/invoke.texi (armv8.6-a, i8mm, bf16): Document new options.

2020-01-02  Dennis Zhang  <dennis.zhang@arm.com>

	* gcc.target/arm/multilib.exp: Add combination tests for armv8.6-a.

From-SVN: r279839