Kernels loops annotation: C and C++.

Kernels loops annotation: C and C++.

This patch detects loops in kernels regions that are candidates for
parallelization, and adds "#pragma acc loop auto" annotations to them.
This annotation is controlled by the -fopenacc-kernels-annotate-loops
option, which is enabled by default.  -Wopenacc-kernels-annotate-loops
can be used to produce diagnostics about loops that cannot be annotated.

2020-03-27  Sandra Loosemore  <sandra@codesourcery.com>

	Kernels loops annotation: C and C++.

	gcc/c-family/
	* c-common.h (c_oacc_annotate_loops_in_kernels_regions): Declare.
	* c-omp.c: Include tree-iterator.h
	(enum annotation_state): New.
	(struct annotation_info): New.
	(do_not_annotate_loop): New.
	(do_not_annotate_loop_nest): New.
	(annotation_error): New.
	(c_finish_omp_for_internal): Split from c_finish_omp_for.  Use
	annotation_error function.  Code refactoring to avoid destructive
	changes that cannot be undone in case of error.
	(is_local_var): New.
	(lang_specific_unwrap_initializer): New.
	(annotate_for_loop): New.
	(check_and_annotate_for_loop): New.
	(annotate_loops_in_kernels_regions): New.
	(c_oacc_annotate_loops_in_kernels_regions): New.
	* c.opt (Wopenacc-kernels-annotate-loops): New.
	(fopenacc-kernels-annotate-loops): New.

	gcc/c/
	* c-decl.c (c_unwrap_for_init): New.
	(finish_function): Call c_oacc_annotate_loops_in_kernels_regions.

	gcc/cp/
	* decl.c (cp_unwrap_for_init): New.
	(finish_function): Call c_oacc_annotate_loops_in_kernels_regions.

	gcc/
	* doc/invoke.texi (Option Summary): Add entries for
	-Wopenacc-kernels-annotate-loops and
	-fno-openacc-kernels-annotate-loops.
	(Warning Options): Document -Wopenacc-kernels-annotate-loops.
	(Optimization Options): Document -fno-openacc-kernels-annotate-loops.

	gcc/testsuite/
	* c-c++-common/goacc/classify-kernels-unparallelized.c: Add
	-fno-openacc-kernels-annotate-loops option.
	* c-c++-common/goacc/classify-kernels.c: Likewise.
	* c-c++-common/goacc/kernels-counter-var-redundant-load.c: Likewise.
	* c-c++-common/goacc/kernels-counter-vars-function-scope.c: Likewise.
	* c-c++-common/goacc/kernels-double-reduction-n.c: Likewise.
	* c-c++-common/goacc/kernels-double-reduction.c: Likewise.
	* c-c++-common/goacc/kernels-loop-2.c: Likewise.
	* c-c++-common/goacc/kernels-loop-3.c: Likewise.
	* c-c++-common/goacc/kernels-loop-data-2.c: Likewise.
	* c-c++-common/goacc/kernels-loop-data-enter-exit-2.c: Likewise.
	* c-c++-common/goacc/kernels-loop-data-enter-exit.c: Likewise.
	* c-c++-common/goacc/kernels-loop-data-update.c: Likewise.
	* c-c++-common/goacc/kernels-loop-data.c: Likewise.
	* c-c++-common/goacc/kernels-loop-g.c: Likewise.
	* c-c++-common/goacc/kernels-loop-mod-not-zero.c: Likewise.
	* c-c++-common/goacc/kernels-loop-n.c: Likewise.
	* c-c++-common/goacc/kernels-loop-nest.c: Likewise.
	* c-c++-common/goacc/kernels-loop.c: Likewise.
	* c-c++-common/goacc/kernels-one-counter-var.c: Likewise.
	* c-c++-common/goacc/kernels-parallel-loop-data-enter-exit.c:
	Likewise.
	* c-c++-common/goacc/kernels-reduction.c: Likewise.
	* c-c++-common/goacc/kernels-loop-annotation-1.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-2.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-3.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-4.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-5.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-6.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-7.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-8.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-9.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-10.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-11.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-12.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-13.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-14.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-15.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-16.c: New.
	* c-c++-common/goacc/kernels-loop-annotation-17.c: New.