GCN back-end code

GCN back-end code

This patch contains the major part of the GCN back-end.  The machine
description has been broken out to avoid the mailing list size limit.

The back-end contains various bits that support OpenACC and OpenMP, but the
middle-end and libgomp patches are missing, as is mkoffload.  I include them
here because they're harmless and carving up the files seems like unnecessary
effort.  The remaining offload support will be posted at a later date.

The gcn-run.c is a separate tool that can run a GCN program on a GPU using
the ROCm drivers and HSA runtime libraries.

2019-01-17  Andrew Stubbs  <ams@codesourcery.com>
	    Kwok Cheung Yeung  <kcy@codesourcery.com>
	    Julian Brown  <julian@codesourcery.com>
	    Tom de Vries  <tom@codesourcery.com>
	    Jan Hubicka  <hubicka@ucw.cz>
	    Martin Jambor  <mjambor@suse.cz>

	gcc/
	* common/config/gcn/gcn-common.c: New file.
	* config/gcn/driver-gcn.c: New file.
	* config/gcn/gcn-builtins.def: New file.
	* config/gcn/gcn-hsa.h: New file.
	* config/gcn/gcn-modes.def: New file.
	* config/gcn/gcn-opts.h: New file.
	* config/gcn/gcn-passes.def: New file.
	* config/gcn/gcn-protos.h: New file.
	* config/gcn/gcn-run.c: New file.
	* config/gcn/gcn-tree.c: New file.
	* config/gcn/gcn.c: New file.
	* config/gcn/gcn.h: New file.
	* config/gcn/gcn.opt: New file.
	* config/gcn/t-gcn-hsa: New file.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@268023 138bc75d-0d04-0410-961f-82ee72b054a4