* cfgloop.h (struct loop): Add simdlen member.
	* cfgloopmanip.c (copy_loop_info): Copy simdlen as well.
	* omp-expand.c (expand_omp_simd): Set it if simdlen clause is present.
	* tree-vect-loop.c (vect_analyze_loop): Pass loop->simdlen != 0
	as new argument to autovectorize_vector_sizes target hook.  If
	loop->simdlen, pick up vector size where the vectorization factor
	is equal to loop->simd, and if there is none, fall back to the first
	successful one.
	(vect_transform_loop): Adjust autovectorize_vector_sizes target hook
	caller.
	* omp-low.c (omp_clause_aligned_alignment): Likewise.
	* omp-general.c (omp_max_vf): Likewise.
	* optabs-query.c (can_vec_mask_load_store_p): Likewise.
	* tree-vect-slp.c (vect_slp_bb): Likewise.
	* target.def (autovectorize_vector_sizes): Add ALL argument and
	document it.
	* doc/tm.texi: Adjust documentation.
	* targhooks.c (default_autovectorize_vector_sizes): Add bool argument.
	* targhooks.h (default_autovectorize_vector_sizes): Likewise.
	* config/aarch64/aarch64.c (aarch64_autovectorize_vector_sizes): Add
	bool argument.
	* config/arc/arc.c (arc_autovectorize_vector_sizes): Likewise.
	* config/arm/arm.c (arm_autovectorize_vector_sizes): Likewise.
	* config/mips/mips.c (mips_autovectorize_vector_sizes): Likewise.
	* config/i386/i386.c (ix86_autovectorize_vector_sizes): Likewise.  If
	true and TARGET_AVX512F or TARGET_AVX, push 3 or 2 sizes even if
	preferred vector size is not 512-bit or 256-bit, just put those
	unpreferred ones last.

	* gcc.target/i386/avx512f-simd-1.c: New test.

From-SVN: r271403