[AArch64] Improve SVE constant moves

[AArch64] Improve SVE constant moves

If there's no SVE instruction to load a given constant directly, this
patch instead tries to use an Advanced SIMD constant move and then
duplicates the constant to fill an SVE vector.  The main use of this
is to support constants in which each byte is in { 0, 0xff }.

Also, the patch prefers a simple integer move followed by a duplicate
over a load from memory, like we already do for Advanced SIMD.  This is
a useful option to have and would be easy to turn off via a tuning
parameter if necessary.

The patch also extends the handling of wide LD1Rs to big endian,
whereas previously we punted to a full LD1RQ.

2019-08-13  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* machmode.h (opt_mode::else_mode): New function.
	(opt_mode::else_blk): Use it.
	* config/aarch64/aarch64-protos.h (aarch64_vq_mode): Declare.
	(aarch64_full_sve_mode, aarch64_sve_ld1rq_operand_p): Likewise.
	(aarch64_gen_stepped_int_parallel): Likewise.
	(aarch64_stepped_int_parallel_p): Likewise.
	(aarch64_expand_mov_immediate): Remove the optional gen_vec_duplicate
	argument.
	* config/aarch64/aarch64.c
	(aarch64_expand_sve_widened_duplicate): Delete.
	(aarch64_expand_sve_dupq, aarch64_expand_sve_ld1rq): New functions.
	(aarch64_expand_sve_const_vector): Rewrite to handle more cases.
	(aarch64_expand_mov_immediate): Remove the optional gen_vec_duplicate
	argument.  Use early returns in the !CONST_INT_P handling.
	Pass all SVE data vectors to aarch64_expand_sve_const_vector rather
	than handling some inline.
	(aarch64_full_sve_mode, aarch64_vq_mode): New functions, split out
	from...
	(aarch64_simd_container_mode): ...here.
	(aarch64_gen_stepped_int_parallel, aarch64_stepped_int_parallel_p)
	(aarch64_sve_ld1rq_operand_p): New functions.
	* config/aarch64/predicates.md (descending_int_parallel)
	(aarch64_sve_ld1rq_operand): New predicates.
	* config/aarch64/constraints.md (UtQ): New constraint.
	* config/aarch64/aarch64.md (UNSPEC_REINTERPRET): New unspec.
	* config/aarch64/aarch64-sve.md (mov<SVE_ALL:mode>): Remove the
	gen_vec_duplicate from call to aarch64_expand_mov_immediate.
	(@aarch64_sve_reinterpret<mode>): New expander.
	(*aarch64_sve_reinterpret<mode>): New pattern.
	(@aarch64_vec_duplicate_vq<mode>_le): New pattern.
	(@aarch64_vec_duplicate_vq<mode>_be): Likewise.
	(*sve_ld1rq<Vesize>): Replace with...
	(@aarch64_sve_ld1rq<mode>): ...this new pattern.

gcc/testsuite/
	* gcc.target/aarch64/sve/init_2.c: Expect ld1rd to be used
	instead of a full vector load.
	* gcc.target/aarch64/sve/init_4.c: Likewise.
	* gcc.target/aarch64/sve/ld1r_2.c: Remove constants that no longer
	need to be loaded from memory.
	* gcc.target/aarch64/sve/slp_2.c: Expect the same output for
	big and little endian.
	* gcc.target/aarch64/sve/slp_3.c: Likewise.  Expect 3 of the
	doubles to be moved via integer registers rather than loaded
	from memory.
	* gcc.target/aarch64/sve/slp_4.c: Likewise but for 4 doubles.
	* gcc.target/aarch64/sve/spill_4.c: Expect 16-bit constants to be
	loaded via an integer register rather than from memory.
	* gcc.target/aarch64/sve/const_1.c: New test.
	* gcc.target/aarch64/sve/const_2.c: Likewise.
	* gcc.target/aarch64/sve/const_3.c: Likewise.

From-SVN: r274375