[nvptx] Add support for a per-worker broadcast buffer and barrier

[nvptx] Add support for a per-worker broadcast buffer and barrier

Add support for a per-worker broadcast buffer and barrier, to be used for
openacc vector_length larger than warp-size.

2019-01-07  Tom de Vries  <tdevries@suse.de>

	* config/nvptx/nvptx.c (oacc_bcast_partition): Declare.
	(nvptx_option_override): Init oacc_bcast_partition.
	(nvptx_init_oacc_workers): New function.
	(nvptx_declare_function_name): Call nvptx_init_oacc_workers.
	(nvptx_needs_shared_bcast): New function.
	(nvptx_find_par): Generalize to enable vectors to use shared-memory
	to propagate state.
	(nvptx_shared_propagate): Initialize vector bcast partition and
	synchronization state.
	(nvptx_single):  Generalize to enable vectors to use shared-memory
	to propagate state.
	(nvptx_process_pars): Likewise.
	(nvptx_set_current_function): Initialize oacc_broadcast_partition.
	* config/nvptx/nvptx.h (struct machine_function): Add
	bcast_partition and sync_bar members.

From-SVN: r267629