The SLP unrolling factor is calculated by finding the smallest
scalar type for each SLP statement and taking the number of required
lanes from the vector versions of those scalar types.  E.g. for an
int32->int64 conversion, it's the vector of int32s rather than the
vector of int64s that determines the unroll factor.

We rely on tree-vect-patterns.c to replace boolean operations like:

   bool a, b, c;
   a = b & c;

with integer operations of whatever the best size is in context.
E.g. if b and c are fed by comparisons of ints, a, b and c will become
the appropriate size for an int comparison.  For most targets this means
that a, b and c will end up as int-sized themselves, but on targets like
SVE and AVX512 with packed vector booleans, they'll instead become a
small bitfield like :1, padded to a byte for memory purposes.
The SLP code would then take these scalar types and try to calculate
the vector type for them, causing the unroll factor to be much higher
than necessary.

This patch tries to make the SLP code use the same approach as the
loop vectorizer, by splitting out the code that calculates the
statement vector type and the vector type that should be used for
the number of units.

2018-05-16  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* tree-vectorizer.h (vect_get_vector_types_for_stmt): Declare.
	(vect_get_mask_type_for_stmt): Likewise.
	* tree-vect-slp.c (vect_two_operations_perm_ok_p): New function,
	split out from...
	(vect_build_slp_tree_1): ...here.  Use vect_get_vector_types_for_stmt
	to determine the statement's vector type and the vector type that
	should be used for calculating nunits.  Deal with cases in which
	the type has to be deferred.
	(vect_slp_analyze_node_operations): Use vect_get_vector_types_for_stmt
	and vect_get_mask_type_for_stmt to calculate STMT_VINFO_VECTYPE.
	* tree-vect-loop.c (vect_determine_vf_for_stmt_1)
	(vect_determine_vf_for_stmt): New functions, split out from...
	(vect_determine_vectorization_factor): ...here.
	* tree-vect-stmts.c (vect_get_vector_types_for_stmt)
	(vect_get_mask_type_for_stmt): New functions, split out from
	vect_determine_vectorization_factor.

gcc/testsuite/
	* gcc.target/aarch64/sve/vcond_10.c: New test.
	* gcc.target/aarch64/sve/vcond_10_run.c: Likewise.
	* gcc.target/aarch64/sve/vcond_11.c: Likewise.
	* gcc.target/aarch64/sve/vcond_11_run.c: Likewise.

From-SVN: r260287