aarch64: Add support for fp8 convert and scale

aarch64: Add support for fp8 convert and scale

The AArch64 FEAT_FP8 extension introduces instructions for conversion
and scaling.

This patch introduces the following intrinsics:
1. vcvt{1|2}_{bf16|high_bf16|low_bf16}_mf8_fpm.
2. vcvt{q}_mf8_f16_fpm.
3. vcvt_{high}_mf8_f32_fpm.
4. vscale{q}_{f16|f32|f64}.

We introduced two aarch64_builtin_signatures enum variants, unary and
ternary, and added support for these variants in the functions
aarch64_fntype and aarch64_expand_pragma_builtin.

We added new simd_types for integers (s32, s32q, and s64q) and for
floating points (f8 and f8q).

Because we added support for fp8 intrinsics here, we modified the check
in acle/fp8.c that was checking that __ARM_FEATURE_FP8 macro is not
defined.

gcc/ChangeLog:

	* config/aarch64/aarch64-builtins.cc
	(FLAG_USES_FPMR, FLAG_FP8): New flags.
	(ENTRY): Modified to support ternary operations.
	(enum class): New variants to support new signatures.
	(struct aarch64_pragma_builtins_data): Extend types to 4 elements.
	(aarch64_fntype): Handle new signatures.
	(aarch64_get_low_unspec): New function.
	(aarch64_convert_to_v64): New function, split out from...
	(aarch64_expand_pragma_builtin): ...here.  Handle new signatures.
	* config/aarch64/aarch64-c.cc
	(aarch64_update_cpp_builtins): New flag for FP8.
	* config/aarch64/aarch64-simd-pragma-builtins.def: Define new fp8
	intrinsics.
	(ENTRY_BINARY, ENTRY_BINARY_LANE): Update for new ENTRY interface.
	(ENTRY_UNARY, ENTRY_TERNARY, ENTRY_UNARY_FPM): New macros.
	(ENTRY_BINARY_VHSDF_SIGNED): Likewise.
	* config/aarch64/aarch64-simd.md
	(@aarch64_<fpm_uns_op><mode>): New pattern.
	(@aarch64_<fpm_uns_op><mode>_high): Likewise.
	(@aarch64_<fpm_uns_op><mode>_high_be): Likewise.
	(@aarch64_<fpm_uns_op><mode>_high_le): Likewise.
	* config/aarch64/iterators.md (V4SF_ONLY, VQ_BHF): New mode iterators.
	(UNSPEC_FCVTN_FP8, UNSPEC_FCVTN2_FP8, UNSPEC_F1CVTL_FP8)
	(UNSPEC_F1CVTL2_FP8, UNSPEC_F2CVTL_FP8, UNSPEC_F2CVTL2_FP8)
	(UNSPEC_FSCALE): New unspecs.
	(VPACKB, VPACKBtype): New mode attributes.
	(b): Add support for V[48][BH]F.
	(FPM_UNARY_UNS, FPM_BINARY_UNS, SCALE_UNS): New int iterators.
	(insn): New int attribute.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/acle/fp8.c: Remove check that fp8 feature
	macro doesn't exist and...
	* gcc.target/aarch64/pragma_cpp_predefs_4.c: ...test that it does here.
	* gcc.target/aarch64/simd/scale_fpm.c: New test.
	* gcc.target/aarch64/simd/vcvt_fpm.c: New test.

Co-authored-by: Richard Sandiford <richard.sandiford@arm.com>