vect: inbranch SIMD clones

vect: inbranch SIMD clones

There has been support for generating "inbranch" SIMD clones for a long time,
but nothing actually uses them (as far as I can see).

This patch add supports for a sub-set of possible cases (those using
mask_mode == VOIDmode).  The other cases fail to vectorize, just as before,
so there should be no regressions.

The sub-set of support should cover all cases needed by amdgcn, at present.

gcc/ChangeLog:

	* internal-fn.cc (expand_MASK_CALL): New.
	* internal-fn.def (MASK_CALL): New.
	* internal-fn.h (expand_MASK_CALL): New prototype.
	* omp-simd-clone.cc (simd_clone_adjust_argument_types): Set vector_type
	for mask arguments also.
	* tree-if-conv.cc: Include cgraph.h.
	(if_convertible_stmt_p): Do if conversions for calls to SIMD calls.
	(predicate_statements): Convert functions to IFN_MASK_CALL.
	* tree-vect-loop.cc (vect_get_datarefs_in_loop): Recognise
	IFN_MASK_CALL as a SIMD function call.
	* tree-vect-stmts.cc (vectorizable_simd_clone_call): Handle
	IFN_MASK_CALL as an inbranch SIMD function call.
	Generate the mask vector arguments.

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/vect-simd-clone-16.c: New test.
	* gcc.dg/vect/vect-simd-clone-16b.c: New test.
	* gcc.dg/vect/vect-simd-clone-16c.c: New test.
	* gcc.dg/vect/vect-simd-clone-16d.c: New test.
	* gcc.dg/vect/vect-simd-clone-16e.c: New test.
	* gcc.dg/vect/vect-simd-clone-16f.c: New test.
	* gcc.dg/vect/vect-simd-clone-17.c: New test.
	* gcc.dg/vect/vect-simd-clone-17b.c: New test.
	* gcc.dg/vect/vect-simd-clone-17c.c: New test.
	* gcc.dg/vect/vect-simd-clone-17d.c: New test.
	* gcc.dg/vect/vect-simd-clone-17e.c: New test.
	* gcc.dg/vect/vect-simd-clone-17f.c: New test.
	* gcc.dg/vect/vect-simd-clone-18.c: New test.
	* gcc.dg/vect/vect-simd-clone-18b.c: New test.
	* gcc.dg/vect/vect-simd-clone-18c.c: New test.
	* gcc.dg/vect/vect-simd-clone-18d.c: New test.
	* gcc.dg/vect/vect-simd-clone-18e.c: New test.
	* gcc.dg/vect/vect-simd-clone-18f.c: New test.