* omp-low.c (lower_rec_input_clauses): If OMP_CLAUSE_IF
	has non-constant expression, force sctx.lane and use two
	argument IFN_GOMP_SIMD_LANE instead of single argument.
	* tree-ssa-dce.c (eliminate_unnecessary_stmts): Don't DCE
	two argument IFN_GOMP_SIMD_LANE without lhs.
	* tree-vectorizer.h (struct _loop_vec_info): Add simd_if_cond
	member.
	(LOOP_VINFO_SIMD_IF_COND, LOOP_REQUIRES_VERSIONING_FOR_SIMD_IF_COND):
	Define.
	(LOOP_REQUIRES_VERSIONING): Or in
	LOOP_REQUIRES_VERSIONING_FOR_SIMD_IF_COND.
	* tree-vect-loop.c (_loop_vec_info::_loop_vec_info): Initialize
	simd_if_cond.
	(vect_analyze_loop_2): Punt if LOOP_VINFO_SIMD_IF_COND is constant 0.
	* tree-vect-loop-manip.c (vect_loop_versioning): Add runtime check
	from simd if clause if needed.

	* gcc.dg/vect/vect-simd-1.c: New test.
	* gcc.dg/vect/vect-simd-2.c: New test.
	* gcc.dg/vect/vect-simd-3.c: New test.
	* gcc.dg/vect/vect-simd-4.c: New test.

From-SVN: r271298