aarch64: Add support for SME_F16F16

aarch64: Add support for SME_F16F16

This patch adds support for the SME_F16F16 extension.  The extension
adds two new instructions to convert from a single vector of f16s
to two vectors of f32s.  It also adds f16 variants of existing SME
ZA instructions.

gcc/
	* config/aarch64/aarch64-option-extensions.def
	(sme-f16f16): New extension.
	* doc/invoke.texi: Document it.  Also document that sme-i16i64 and
	sme-f64f64 enable SME.
	* config/aarch64/aarch64.h (TARGET_STREAMING_SME_F16F16): New macro.
	* config/aarch64/aarch64-c.cc (aarch64_update_cpp_builtins):
	Conditionally define __ARM_FEATURE_SME_F16F16.
	* config/aarch64/aarch64-sve-builtins-sve2.def (svcvt, svcvtl): Add
	new SME_F16F16 intrinsics.
	* config/aarch64/aarch64-sve-builtins-sme.def: Add SME_F16F16 forms
	of existing intrinsics.
	* config/aarch64/aarch64-sve-builtins.cc (TYPES_h_float)
	(TYPES_cvt_f32_f16, TYPES_za_h_float): New type macros.
	* config/aarch64/aarch64-sve-builtins-base.cc
	(svcvt_impl::expand): Add sext_optab as another possibility.
	* config/aarch64/aarch64-sve-builtins-sve2.h (svcvtl): Declare.
	* config/aarch64/aarch64-sve-builtins-sve2.cc (svcvtl_impl): New class.
	(svcvtl): New function.
	* config/aarch64/iterators.md (VNx8SF_ONLY): New mode iterator.
	(SME_ZA_SDFx24): Replace with...
	(SME_ZA_HSDFx24): ...this.
	(SME_MOP_SDF): Replace with...
	(SME_MOP_HSDF): ...this.
	(SME_BINARY_SLICE_SDF): Replace with...
	(SME_BINARY_SLICE_HSDF): ...this.
	* config/aarch64/aarch64-sve2.md (extendvnx8hfvnx8sf2)
	(@aarch64_sve_cvtl<mode>): New patterns.
	* config/aarch64/aarch64-sme.md
	(@aarch64_sme_<SME_BINARY_SLICE_SDF:optab><mode>): Extend to...
	(@aarch64_sme_<SME_BINARY_SLICE_HSDF:optab><mode>): ...this.
	(*aarch64_sme_<SME_BINARY_SLICE_SDF:optab><mode>_plus): Extend to...
	(*aarch64_sme_<SME_BINARY_SLICE_HSDF:optab><mode>_plus): ...this.
	(@aarch64_sme_<SME_FP_TERNARY_SLICE:optab><mode><mode>): Extend to
	HF modes.
	(*aarch64_sme_<SME_FP_TERNARY_SLICE:optab><mode><mode>_plus)
	(@aarch64_sme_single_<SME_FP_TERNARY_SLICE:optab><mode><mode>)
	(*aarch64_sme_single_<SME_FP_TERNARY_SLICE:optab><mode><mode>_plus)
	(@aarch64_sme_lane_<SME_FP_TERNARY_SLICE:optab><mode><mode>)
	(*aarch64_sme_lane_<SME_FP_TERNARY_SLICE:optab><mode><mode>)
	(@aarch64_sme_<SME_FP_MOP:optab><mode><mode>): Likewise.

gcc/testsuite/
	* lib/target-supports.exp: Test the assembler for sve-f16f16 support.
	* gcc.target/aarch64/pragma_cpp_predefs_4.c: Add tests for
	__ARM_FEATURE_SME_F16F16.  Also extend the existing SME tests.
	* gcc.target/aarch64/sve/acle/asm/test_sve_acle.h
	(TEST_X2_WIDE): New macro
	* gcc.target/aarch64/sme2/acle-asm/add_za16_f16_vg1x2.c: New test.
	* gcc.target/aarch64/sme2/acle-asm/add_za16_f16_vg1x4.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/cvt_f32_f16_x2.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/cvtl_f32_f16_x2.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/mla_lane_za16_f16_vg1x2.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/mla_lane_za16_f16_vg1x4.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/mla_za16_f16_vg1x2.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/mla_za16_f16_vg1x4.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/mls_lane_za16_f16_vg1x2.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/mls_lane_za16_f16_vg1x4.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/mls_za16_f16_vg1x2.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/mls_za16_f16_vg1x4.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/mopa_za16_f16.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/mops_za16_f16.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/sub_za16_f16_vg1x2.c: Likewise.
	* gcc.target/aarch64/sme2/acle-asm/sub_za16_f16_vg1x4.c: Likewise.