OpenMP: Support reverse offload (middle end part)

OpenMP: Support reverse offload (middle end part)

gcc/ChangeLog:

	* internal-fn.cc (expand_GOMP_TARGET_REV): New.
	* internal-fn.def (GOMP_TARGET_REV): New.
	* lto-cgraph.cc (lto_output_node, verify_node_partition): Mark
	'omp target device_ancestor_host' as in_other_partition and don't
	error if absent.
	* omp-low.cc (create_omp_child_function): Mark as 'noclone'.
	* omp-expand.cc (expand_omp_target): For reverse offload, remove
	sorry, use device = GOMP_DEVICE_HOST_FALLBACK and create
	empty-body nohost function.
	* omp-offload.cc (execute_omp_device_lower): Handle
	IFN_GOMP_TARGET_REV.
	(pass_omp_target_link::execute): For ACCEL_COMPILER, don't
	nullify fn argument for reverse offload

libgomp/ChangeLog:

	* libgomp.texi (OpenMP 5.0): Mark 'ancestor' as implemented but
	refer to 'requires'.
	* testsuite/libgomp.c-c++-common/reverse-offload-1-aux.c: New test.
	* testsuite/libgomp.c-c++-common/reverse-offload-1.c: New test.
	* testsuite/libgomp.fortran/reverse-offload-1-aux.f90: New test.
	* testsuite/libgomp.fortran/reverse-offload-1.f90: New test.

gcc/testsuite/ChangeLog:

	* c-c++-common/gomp/reverse-offload-1.c: Remove dg-sorry.
	* c-c++-common/gomp/target-device-ancestor-4.c: Likewise.
	* gfortran.dg/gomp/target-device-ancestor-4.f90: Likewise.
	* gfortran.dg/gomp/target-device-ancestor-5.f90: Likewise.
	* c-c++-common/goacc/classify-kernels-parloops.c: Add 'noclone' to
	scan-tree-dump-times.
	* c-c++-common/goacc/classify-kernels-unparallelized-parloops.c:
	Likewise.
	* c-c++-common/goacc/classify-kernels-unparallelized.c: Likewise.
	* c-c++-common/goacc/classify-kernels.c: Likewise.
	* c-c++-common/goacc/classify-parallel.c: Likewise.
	* c-c++-common/goacc/classify-serial.c: Likewise.
	* c-c++-common/goacc/kernels-counter-vars-function-scope.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.
	* gfortran.dg/goacc/classify-kernels-parloops.f95: Likewise.
	* gfortran.dg/goacc/classify-kernels-unparallelized-parloops.f95:
	Likewise.
	* gfortran.dg/goacc/classify-kernels-unparallelized.f95: Likewise.
	* gfortran.dg/goacc/classify-kernels.f95: Likewise.
	* gfortran.dg/goacc/classify-parallel.f95: Likewise.
	* gfortran.dg/goacc/classify-serial.f95: Likewise.
	* gfortran.dg/goacc/kernels-loop-2.f95: Likewise.
	* gfortran.dg/goacc/kernels-loop-data-2.f95: Likewise.
	* gfortran.dg/goacc/kernels-loop-data-enter-exit-2.f95: Likewise.
	* gfortran.dg/goacc/kernels-loop-data-enter-exit.f95: Likewise.
	* gfortran.dg/goacc/kernels-loop-data-update.f95: Likewise.
	* gfortran.dg/goacc/kernels-loop-data.f95: Likewise.
	* gfortran.dg/goacc/kernels-loop-n.f95: Likewise.
	* gfortran.dg/goacc/kernels-loop.f95: Likewise.
	* gfortran.dg/goacc/kernels-parallel-loop-data-enter-exit.f95: Likewise.