Add support for SVE gather loads

Add support for SVE gather loads

This patch adds support for SVE gather loads.  It uses the basically
the same analysis code as the AVX gather support, but after that
there are two major differences:

- It uses new internal functions rather than target built-ins.
  The interface is:

     IFN_GATHER_LOAD (base, offsets scale)
     IFN_MASK_GATHER_LOAD (base, offsets scale, mask)

  which should be reasonably generic.  One of the advantages of
  using internal functions is that other passes can understand what
  the functions do, but a more immediate advantage is that we can
  query the underlying target pattern to see which scales it supports.

- It uses pattern recognition to convert the offset to the right width,
  if it was originally narrower than that.  This avoids having to do
  a widening operation as part of the gather expansion itself.

2018-01-13  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* doc/md.texi (gather_load@var{m}): Document.
	(mask_gather_load@var{m}): Likewise.
	* genopinit.c (main): Add supports_vec_gather_load and
	supports_vec_gather_load_cached to target_optabs.
	* optabs-tree.c (init_tree_optimization_optabs): Use
	ggc_cleared_alloc to allocate target_optabs.
	* optabs.def (gather_load_optab, mask_gather_laod_optab): New optabs.
	* internal-fn.def (GATHER_LOAD, MASK_GATHER_LOAD): New internal
	functions.
	* internal-fn.h (internal_load_fn_p): Declare.
	(internal_gather_scatter_fn_p): Likewise.
	(internal_fn_mask_index): Likewise.
	(internal_gather_scatter_fn_supported_p): Likewise.
	* internal-fn.c (gather_load_direct): New macro.
	(expand_gather_load_optab_fn): New function.
	(direct_gather_load_optab_supported_p): New macro.
	(direct_internal_fn_optab): New function.
	(internal_load_fn_p): Likewise.
	(internal_gather_scatter_fn_p): Likewise.
	(internal_fn_mask_index): Likewise.
	(internal_gather_scatter_fn_supported_p): Likewise.
	* optabs-query.c (supports_at_least_one_mode_p): New function.
	(supports_vec_gather_load_p): Likewise.
	* optabs-query.h (supports_vec_gather_load_p): Declare.
	* tree-vectorizer.h (gather_scatter_info): Add ifn, element_type
	and memory_type field.
	(NUM_PATTERNS): Bump to 15.
	* tree-vect-data-refs.c: Include internal-fn.h.
	(vect_gather_scatter_fn_p): New function.
	(vect_describe_gather_scatter_call): Likewise.
	(vect_check_gather_scatter): Try using internal functions for
	gather loads.  Recognize existing calls to a gather load function.
	(vect_analyze_data_refs): Consider using gather loads if
	supports_vec_gather_load_p.
	* tree-vect-patterns.c (vect_get_load_store_mask): New function.
	(vect_get_gather_scatter_offset_type): Likewise.
	(vect_convert_mask_for_vectype): Likewise.
	(vect_add_conversion_to_patterm): Likewise.
	(vect_try_gather_scatter_pattern): Likewise.
	(vect_recog_gather_scatter_pattern): New pattern recognizer.
	(vect_vect_recog_func_ptrs): Add it.
	* tree-vect-stmts.c (exist_non_indexing_operands_for_use_p): Use
	internal_fn_mask_index and internal_gather_scatter_fn_p.
	(check_load_store_masking): Take the gather_scatter_info as an
	argument and handle gather loads.
	(vect_get_gather_scatter_ops): New function.
	(vectorizable_call): Check internal_load_fn_p.
	(vectorizable_load): Likewise.  Handle gather load internal
	functions.
	(vectorizable_store): Update call to check_load_store_masking.
	* config/aarch64/aarch64.md (UNSPEC_LD1_GATHER): New unspec.
	* config/aarch64/iterators.md (SVE_S, SVE_D): New mode iterators.
	* config/aarch64/predicates.md (aarch64_gather_scale_operand_w)
	(aarch64_gather_scale_operand_d): New predicates.
	* config/aarch64/aarch64-sve.md (gather_load<mode>): New expander.
	(mask_gather_load<mode>): New insns.

gcc/testsuite/
	* gcc.target/aarch64/sve/gather_load_1.c: New test.
	* gcc.target/aarch64/sve/gather_load_2.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_3.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_4.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_5.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_6.c: Likewise.
	* gcc.target/aarch64/sve/gather_load_7.c: Likewise.
	* gcc.target/aarch64/sve/mask_gather_load_1.c: Likewise.
	* gcc.target/aarch64/sve/mask_gather_load_2.c: Likewise.
	* gcc.target/aarch64/sve/mask_gather_load_3.c: Likewise.
	* gcc.target/aarch64/sve/mask_gather_load_4.c: Likewise.
	* gcc.target/aarch64/sve/mask_gather_load_5.c: Likewise.
	* gcc.target/aarch64/sve/mask_gather_load_6.c: Likewise.
	* gcc.target/aarch64/sve/mask_gather_load_7.c: Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@256640 138bc75d-0d04-0410-961f-82ee72b054a4