This patch adds a new mode class to represent vectors of booleans.
GET_MODE_BITSIZE (m) / GET_MODE_NUNITS (m) determines the number
of bits that are used to represent each boolean; this can be 1
for a fully-packed representation or greater than 1 for an unpacked
representation.  In the latter case, the value of bits other than
the lowest is not significant.

These are used by the SVE port to represent predicates.

2018-01-03  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* mode-classes.def (MODE_VECTOR_BOOL): New mode class.
	* machmode.h (INTEGRAL_MODE_P, VECTOR_MODE_P): Return true
	for MODE_VECTOR_BOOL.
	* machmode.def (VECTOR_BOOL_MODE): Document.
	* genmodes.c (VECTOR_BOOL_MODE): New macro.
	(make_vector_bool_mode): New function.
	(complete_mode, emit_mode_wider, emit_mode_adjustments): Handle
	MODE_VECTOR_BOOL.
	* lto-streamer-in.c (lto_input_mode_table): Likewise.
	* rtx-vector-builder.c (rtx_vector_builder::find_cached_value):
	Likewise.
	* stor-layout.c (int_mode_for_mode): Likewise.
	* tree.c (build_vector_type_for_mode): Likewise.
	* varasm.c (output_constant_pool_2): Likewise.
	* emit-rtl.c (init_emit_once): Make sure that CONST1_RTX (BImode) and
	CONSTM1_RTX (BImode) are the same thing.  Initialize const_tiny_rtx
	for MODE_VECTOR_BOOL.
	* expr.c (expand_expr_real_1): Use VECTOR_MODE_P instead of a list
	of mode class checks.
	* tree-vect-generic.c (expand_vector_operation): Use VECTOR_MODE_P
	instead of a list of mode class checks.
	(expand_vector_scalar_condition): Likewise.
	(type_for_widest_vector_mode): Handle BImode as an inner mode.

gcc/c-family/
	* c-common.c (c_common_type_for_mode): Handle MODE_VECTOR_BOOL.

gcc/fortran/
	* trans-types.c (gfc_type_for_mode): Handle MODE_VECTOR_BOOL.

gcc/go/
	* go-lang.c (go_langhook_type_for_mode): Handle MODE_VECTOR_BOOL.

gcc/lto/
	* lto-lang.c (lto_type_for_mode): Handle MODE_VECTOR_BOOL.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r256202