AArch64: Add LUTI ACLE for SVE2

AArch64: Add LUTI ACLE for SVE2

This patch introduces support for LUTI2/LUTI4 ACLE for SVE2.

LUTI instructions are used for efficient table lookups with 2-bit
or 4-bit indices. LUTI2 reads indexed 8-bit or 16-bit elements from
the low 128 bits of the table vector using packed 2-bit indices,
while LUTI4 can read from the low 128 or 256 bits of the table
vector or from two table vectors using packed 4-bit indices.
These instructions fill the destination vector by copying elements
indexed by segments of the source vector, selected by the vector
segment index.

The changes include the addition of a new AArch64 option
extension "lut", __ARM_FEATURE_LUT preprocessor macro, definitions
for the new LUTI instruction shapes, and implementations of the
svluti2 and svluti4 builtins.

gcc/ChangeLog:

	* config/aarch64/aarch64-c.cc
	(aarch64_update_cpp_builtins): Add new flag TARGET_LUT.
	* config/aarch64/aarch64-sve-builtins-shapes.cc
	(struct luti_base): Shape for lut intrinsics.
	(SHAPE): Specializations for lut shapes for luti2 and luti4..
	* config/aarch64/aarch64-sve-builtins-shapes.h: Declare lut
	intrinsics.
	* config/aarch64/aarch64-sve-builtins-sve2.cc
	(class svluti_lane_impl): Define expand for lut intrinsics.
	(FUNCTION): Define expand for lut intrinsics.
	* config/aarch64/aarch64-sve-builtins-sve2.def
	(REQUIRED_EXTENSIONS): Declare lut intrinsics behind lut flag.
	(svluti2_lane): Define intrinsic behind flag.
	(svluti4_lane): Define intrinsic behind flag.
	* config/aarch64/aarch64-sve-builtins-sve2.h: Declare lut
	intrinsics.
	* config/aarch64/aarch64-sve-builtins.cc
	(TYPES_bh_data): New type for byte and halfword.
	(bh_data): Type array for byte and halfword.
	(h_data): Type array for halfword.
	* config/aarch64/aarch64-sve2.md
	(@aarch64_sve_luti<LUTI_BITS><mode>): Instruction patterns for
	lut intrinsics.
	* config/aarch64/iterators.md: Iterators and attributes for lut
	intrinsics.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/sve/acle/asm/test_sve_acle.h: New test
	macro.
	* lib/target-supports.exp: Add lut flag to the for loop.
	* gcc.target/aarch64/sve/acle/general-c/lut_1.c: New test.
	* gcc.target/aarch64/sve/acle/general-c/lut_2.c: New test.
	* gcc.target/aarch64/sve/acle/general-c/lut_3.c: New test.
	* gcc.target/aarch64/sve/acle/general-c/lut_4.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti2_bf16.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti2_f16.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti2_s16.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti2_s8.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti2_u16.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti2_u8.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti4_bf16.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti4_bf16_x2.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti4_f16.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti4_f16_x2.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti4_s16.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti4_s16_x2.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti4_s8.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti4_u16.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti4_u16_x2.c: New test.
	* gcc.target/aarch64/sve2/acle/asm/luti4_u8.c: New test.