build_same_sized_truth_vector_type was confusingly named, since for
SVE and AVX512 the returned vector isn't the same byte size (although
it does have the same number of elements).  What it really returns
is the "truth" vector type for a given data vector type.

The more general truth_type_for provides the same thing when passed
a vector and IMO has a more descriptive name, so this patch replaces
all uses of build_same_sized_truth_vector_type with that.  It does
the same for a call to build_truth_vector_type, leaving truth_type_for
itself as the only remaining caller.

It's then more natural to pass build_truth_vector_type the original
vector type rather than its size and nunits, especially since the
given size isn't the size of the returned vector.  This in turn allows
a future patch to simplify the interface of get_mask_mode.  Doing this
also fixes a bug in which truth_type_for would pass a size of zero for
BLKmode vector types.

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

gcc/
	* tree.h (build_truth_vector_type): Delete.
	(build_same_sized_truth_vector_type): Likewise.
	* tree.c (build_truth_vector_type): Rename to...
	(build_truth_vector_type_for): ...this.  Make static and take
	a vector type as argument.
	(truth_type_for): Update accordingly.
	(build_same_sized_truth_vector_type): Delete.
	* tree-vect-generic.c (expand_vector_divmod): Use truth_type_for
	instead of build_same_sized_truth_vector_type.
	* tree-vect-loop.c (vect_create_epilog_for_reduction): Likewise.
	(vect_record_loop_mask, vect_get_loop_mask): Likewise.
	* tree-vect-patterns.c (build_mask_conversion): Likeise.
	* tree-vect-slp.c (vect_get_constant_vectors): Likewise.
	* tree-vect-stmts.c (vect_get_vec_def_for_operand): Likewise.
	(vect_build_gather_load_calls, vectorizable_call): Likewise.
	(scan_store_can_perm_p, vectorizable_scan_store): Likewise.
	(vectorizable_store, vectorizable_condition): Likewise.
	(get_mask_type_for_scalar_type, get_same_sized_vectype): Likewise.
	(vect_get_mask_type_for_stmt): Use truth_type_for instead of
	build_truth_vector_type.
	* config/aarch64/aarch64-sve-builtins.cc (gimple_folder::convert_pred):
	Use truth_type_for instead of build_same_sized_truth_vector_type.
	* config/rs6000/rs6000-call.c (fold_build_vec_cmp): Likewise.

gcc/c/
	* c-typeck.c (build_conditional_expr): Use truth_type_for instead
	of build_same_sized_truth_vector_type.
	(build_vec_cmp): Likewise.

gcc/cp/
	* call.c (build_conditional_expr_1): Use truth_type_for instead
	of build_same_sized_truth_vector_type.
	* typeck.c (build_vec_cmp): Likewise.

gcc/d/
	* d-codegen.cc (build_boolop): Use truth_type_for instead of
	build_same_sized_truth_vector_type.

From-SVN: r278232