target.def (goacc.dim_limit): New hook.

	* target.def (goacc.dim_limit): New hook.
	* targhooks.h (default_goacc_dim_limit): Declare.
	* doc/tm.texi.in (TARGET_GOACC_DIM_LIMIT): Add.
	* doc/tm.texi: Rebuilt.
	* omp-low.h (get_oacc_fn_dim_size, get_oacc_ifn_dim_arg): Declare.
	* omp-low.c (get_oacc_fn_dim_size, get_oacc_ifn_dim_arg): New.
	(default_goacc_dim_limit): New.
	* config/nvptx/nvptx.c (PTX_VECTOR_LENGTH, PTX_WORKER_LENGTH): New.
	(nvptx_goacc_dim_limit) New.
	(TARGET_GOACC_DIM_LIMIT): Override.
	* tree-vrp.c: Include omp-low.h, target.h.
	(extract_range_basic): Add handling for IFN_GOACC_DIM_SIZE &
	IFN_GOACC_DIM_POS.

From-SVN: r229809