vect: Relax gather/scatter detection by swapping offset sign.

This patch adjusts vect_gather_scatter_fn_p to always check an offset
type with swapped signedness (vs. the original offset argument).
If the target supports the gather/scatter with the new offset type as
well as the conversion of the offset we now emit an explicit offset
conversion before the actual gather/scatter.

The relaxation is only done for the IFN path of gather/scatter and the
general idea roughly looks like:

  - vect_gather_scatter_fn_p builds a list of all offset vector types
  that the target supports for the current vectype.  Then it goes
  through that list, trying direct support first and sign-swapped
  offset types next, taking precision requirements into account.
  If successful it sets supported_offset_vectype to the type that actually
  worked while offset_vectype_out is the type that was requested.
  - vect_check_gather_scatter works as before but uses the relaxed
  vect_gather_scatter_fn_p.
  - get_load_store_type sets ls_data->supported_offset_vectype if the
  requested type wasn't supported but another one was.
  - check_load_store_for_partial_vectors uses the
  supported_offset_vectype in order to validate what get_load_store_type
  determined.
  - vectorizable_load/store emit a conversion if
  ls_data->supported_offset_vectype is nonzero and cost it.

The offset type is either of pointer size (if we started with a signed
offset) or twice the size of the original offset (when that one was
unsigned).

gcc/ChangeLog:

	* tree-vect-data-refs.cc (struct gather_scatter_config): New
	struct to hold gather/scatter configurations.
	(vect_gather_scatter_which_ifn): New function to determine which
	IFN to use.
	(vect_gather_scatter_get_configs): New function to enumerate all
	target-supported configs.
	(vect_gather_scatter_fn_p): Rework to use
	vect_gather_scatter_get_configs and try sign-swapped offset.
	(vect_check_gather_scatter): Use new supported offset vectype
	argument.
	* tree-vect-stmts.cc (check_load_store_for_partial_vectors):
	Ditto.
	(vect_truncate_gather_scatter_offset): Ditto.
	(vect_use_grouped_gather): Ditto.
	(get_load_store_type): Ditto.
	(vectorizable_store): Convert to sign-swapped offset type if
	needed.
	(vectorizable_load): Ditto.
	* tree-vectorizer.h (struct vect_load_store_data): Add
	supported_offset_vectype.
	(vect_gather_scatter_fn_p): Add argument.

0 files changed, 0 insertions, 0 deletions