md.texi: Document vec_shl_<mode> pattern.

md.texi: Document vec_shl_<mode> pattern.

	* doc/md.texi: Document vec_shl_<mode> pattern.
	* optabs.def (vec_shl_optab): New optab.
	* optabs.c (shift_amt_for_vec_perm_mask): Add shift_optab
	argument, if == vec_shl_optab, check for left whole vector shift
	pattern rather than right shift.
	(expand_vec_perm_const): Add vec_shl_optab support.
	* optabs-query.c (can_vec_perm_var_p): Mention also vec_shl optab
	in the comment.
	* tree-vect-generic.c (lower_vec_perm): Support permutations which
	can be handled by vec_shl_optab.
	* tree-vect-stmts.c (scan_store_can_perm_p): New function.
	(check_scan_store): Use it.
	(vectorizable_scan_store): If target can't do normal permutations,
	try to use whole vector left shifts and if needed a VEC_COND_EXPR
	after it.
	* config/i386/sse.md (vec_shl_<mode>): New expander.

	* gcc.dg/vect/vect-simd-8.c: If main is defined, don't include
	tree-vect.h nor call check_vect.
	* gcc.dg/vect/vect-simd-9.c: Likewise.
	* gcc.dg/vect/vect-simd-10.c: New test.
	* gcc.target/i386/sse2-vect-simd-8.c: New test.
	* gcc.target/i386/sse2-vect-simd-9.c: New test.
	* gcc.target/i386/sse2-vect-simd-10.c: New test.
	* gcc.target/i386/avx2-vect-simd-8.c: New test.
	* gcc.target/i386/avx2-vect-simd-9.c: New test.
	* gcc.target/i386/avx2-vect-simd-10.c: New test.
	* gcc.target/i386/avx512f-vect-simd-8.c: New test.
	* gcc.target/i386/avx512f-vect-simd-9.c: New test.
	* gcc.target/i386/avx512f-vect-simd-10.c: New test.

From-SVN: r272472