This is another patch in the series to remove the assumption that
all modes involved in vectorisation have to be the same size.
Rather than have the target provide a list of vector sizes,
it makes the target provide a list of vector "approaches",
with each approach represented by a mode.

A later patch will pass this mode to targetm.vectorize.related_mode
to get the vector mode for a given element mode.  Until then, the modes
simply act as an alternative way of specifying the vector size.

2019-11-14  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* target.h (vector_sizes, auto_vector_sizes): Delete.
	(vector_modes, auto_vector_modes): New typedefs.
	* target.def (autovectorize_vector_sizes): Replace with...
	(autovectorize_vector_modes): ...this new hook.
	* doc/tm.texi.in (TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_SIZES):
	Replace with...
	(TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_MODES): ...this new hook.
	* doc/tm.texi: Regenerate.
	* targhooks.h (default_autovectorize_vector_sizes): Delete.
	(default_autovectorize_vector_modes): New function.
	* targhooks.c (default_autovectorize_vector_sizes): Delete.
	(default_autovectorize_vector_modes): New function.
	* omp-general.c (omp_max_vf): Use autovectorize_vector_modes instead
	of autovectorize_vector_sizes.  Use the number of units in the mode
	to calculate the maximum VF.
	* omp-low.c (omp_clause_aligned_alignment): Use
	autovectorize_vector_modes instead of autovectorize_vector_sizes.
	Use a loop based on related_mode to iterate through all supported
	vector modes for a given scalar mode.
	* optabs-query.c (can_vec_mask_load_store_p): Use
	autovectorize_vector_modes instead of autovectorize_vector_sizes.
	* tree-vect-loop.c (vect_analyze_loop, vect_transform_loop): Likewise.
	* tree-vect-slp.c (vect_slp_bb_region): Likewise.
	* config/aarch64/aarch64.c (aarch64_autovectorize_vector_sizes):
	Replace with...
	(aarch64_autovectorize_vector_modes): ...this new function.
	(TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_SIZES): Delete.
	(TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_MODES): Define.
	* config/arc/arc.c (arc_autovectorize_vector_sizes): Replace with...
	(arc_autovectorize_vector_modes): ...this new function.
	(TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_SIZES): Delete.
	(TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_MODES): Define.
	* config/arm/arm.c (arm_autovectorize_vector_sizes): Replace with...
	(arm_autovectorize_vector_modes): ...this new function.
	(TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_SIZES): Delete.
	(TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_MODES): Define.
	* config/i386/i386.c (ix86_autovectorize_vector_sizes): Replace with...
	(ix86_autovectorize_vector_modes): ...this new function.
	(TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_SIZES): Delete.
	(TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_MODES): Define.
	* config/mips/mips.c (mips_autovectorize_vector_sizes): Replace with...
	(mips_autovectorize_vector_modes): ...this new function.
	(TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_SIZES): Delete.
	(TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_MODES): Define.

From-SVN: r278236