[gomp4] Rationalise thread-local variables in libgomp OpenACC support

Hi,

This patch rationalises TLS support by moving all thread-local
variables into a single structure. Because this meant interfering with
how per-thread/per-device initialisation was done, I took the
opportunity to tidy up a couple of other bits along the way. Highlights
are:

- TLS support is now optional, with the possibility of falling back to
  pthread primitives (pthread_{get,set}specific). All thread-specific
  data is now stored in a "goacc_thread" structure, and any additional
  data needed by a backend is now pointed to from that structure also.
  New hooks have been added to create and destroy such target-specific
  per-thread data.

- Support for multiple offload devices of the same type has been moved
  into the generic part of libgomp, and can now (in principle) be
  reused by OpenMP also. Because of this, the splay tree mapping host
  memory addresses to addresses on the target device is now stored in
  the same place for OpenMP and OpenACC, whereas beforehand the
  map for the latter was stored in an off-side associative list, which
  was a bit of an ugly niggle.

- The explicit lists of "contexts" (in oacc-init.c) and PTX device info
  (in the NVPTX plugin) have been removed, in favour of linking the
  associated data directly with the entity that it concerns: as
  mentioned above, the memory map is part of the device descriptor
  (since there is now one of those per device instance), and the extra
  info needed for a PTX device over a generic device is simply linked
  by a pointer from the latter.

Additionally, headers have been rearranged a little so that plugins no
longer need to include "oacc-int.h" (and in fact cannot do so), and some
code which is now dead has been removed.

No regressions on a build from the gomp4 branch that has been
additionally patched to support the PTX backend.

OK to apply?

Thanks,

Julian

ChangeLog

    libgomp/
    * env.c (oacc-int.h): Include.
    * libgomp-plugin.h (GOMP_PLUGIN_async_unmap_vars): Don't declare
    here.
    * libgomp.map (PLUGIN_1.0): Add GOMP_PLUGIN_acc_thread symbol.
    * oacc-async.c (oacc-int.h): Include.
    (acc_async_test, acc_async_test_all, acc_wait, acc_wait_async)
    (acc_wait_all, acc_wait_all_async): Use base_dev not ACC_dev.
    * oacc-cuda.c (oacc-int.h): Include.
    (acc_get_current_cuda_device, acc_get_current_cuda_context)
    (acc_get_cuda_stream): Use base_dev not ACC_dev.
    (acc_set_cuda_stream): Call ACC_lazy_initialize, use base_dev not
    ACC_dev.
    * oacc-host.c (oacc-plugin.h, oacc-int.h): Include one or the
    other, depending on HOST_NONSHM_PLUGIN setting.
    (openacc_create_thread_data, openacc_destroy_thread_data): New.
    (host_dispatch): Initialize create_thread_data_func,
    destroy_thread_data_func hooks.
    * oacc-init.c (oacc-int.h): Include.
    (acc_device_lock): Make static.
    (ACC_dev, ACC_handle, handle_num, struct ACC_context, ACC_contexts)
    (_ACC_contexts): Remove.
    (base_dev, goacc_threads, goacc_thread_lock, goacc_cleanup_key):
    Add.
    (goacc_tls_data, goacc_tls_key): Define one or the other, depending
    on HAVE_TLS setting.
    (dispatchers): Add comment.
    (ACC_register): Only register 0th device.
    (close_handle): Remove.
    (_acc_init): Add comment. Don't use ACC_dev.
    (goacc_new_thread, goacc_destroy_thread): New.
    (lazy_open): Update comment. Remove code relating to contexts and
    memory maps. Create thread-specific data if necessary.
    (acc_init): Use base_dev not ACC_dev.
    (_acc_shutdown): Don't call close_handle. Use base_dev not ACC_dev.
    Free target-specific TLS data and close devices that are open at
    the time of shutdown.
    (lazy_init): Add comment. Use base_dev not ACC_dev.
    (lazy_init_and_open): Add comment. Use base_dev not ACC_dev.
    (acc_get_num_devices, acc_get_device_type, acc_get_device_num): Use
    base_dev not ACC_dev.
    (acc_set_device_num): Likewise. If switching device number,
    de-associate previous device number from the current thread, but do
    not close the device.
    (acc_on_device): Check type for device for current thread, not
    ACC_dev.
    (ACC_runtime_initialize): Initialize goacc_tls_key,
    goacc_cleanup_key, base_dev, goacc_threads, goacc_thread_lock. Don't
    initialize ACC_contexts.
    (saved_bound_dev): Remove.
    (ACC_save_and_set_bind, ACC_restore_bind): Use goacc_thread.
    (ACC_lazy_initialize): Use base_dev, goacc_thread instead of
    ACC_dev, ACC_memmap.
    * oacc-int.h (struct ACC_dispatch_t): Don't declare here.
    (struct goacc_thread): New.
    (goacc_tls_data): Define for HAVE_TLS.
    (goacc_tls_key): Define for !HAVE_TLS.
    (goacc_thread): New (versions with and without HAVE_TLS).
    (ACC_mem_open, ACC_mem_close, ACC_resolve_device, ACC_dev)
    (ACC_handle, struct memmap_t, ACC_memmap): Remove.
    (base_dev): Add extern declaration.
    * oacc-mem.c (oacc-int.h, assert.h): Include.
    (ACC_memmap, ACC_mem_open, ACC_mem_close): Remove.
    (lookup_host): Change memmap_t argument to struct
    gomp_memory_mapping.
    (lookup_dev): Change memmap_t argument to struct target_mem_desc.
    Use list_count not refcount for iterating over mapped elements.
    (acc_malloc): Use base_dev not ACC_dev.
    (acc_free): Update call to lookup_dev. Use base_dev not ACC_dev.
    (acc_memcpy_to_device, acc_memcpy_from_device): Use base_dev not
    ACC_dev.
    (acc_deviceptr, acc_is_present): Update call to lookup_host.
    (acc_hostptr): Update call to lookup_dev.
    (acc_map_data): Look up thread device instead of using ACC_dev,
    update calls to lookup_host, lookup_dev. Use data environment in
    device descriptor.
    (acc_unmap_data): Update call to lookup_host. Remove mapped data
    from data environment not ACC_memmap.
    (present_create_copy): Update call to lookup_host. Use data
    environment instead of list in ACC_memmap.
    (delete_copyout): Update call to lookup_host. Look up device in
    current thread info instead of using ACC_dev.
    (update_dev_host): Look up device in current thread info instead of
    using ACC_dev.
    * oacc-parallel.c (oacc-int.h): Include.
    (struct devgeom, devgeom, dump_devaddrs): Remove.
    (select_acc_device): Call ACC_lazy_initialize earlier.
    (GOACC_parallel): Use device for current thread instead of ACC_dev.
    Use memory map from current device.
    (GOACC_data_start): Likewise. Use thread info block for mapped data.
    (GOACC_data_end): Use thread info block for mapped data.
    (goacc_wait): Use device for current thread instead of ACC_dev.
    (GOACC_update): Likewise. Formatting fixes.
    * oacc-plugin.c (ACC_plugin_register): Remove.
    (oacc-int.h): Include.
    (GOMP_PLUGIN_acc_thread): New.
    * oacc-plugin.h (target.h): Don't include.
    (ACC_plugin_register): Remove.
    (GOMP_PLUGIN_async_unmap_vars, GOMP_PLUGIN_acc_thread): Add extern
    declarations.
    * plugin-nvptx.c (oacc-plugin.h): Include.
    (current_stream, PTX_dev, PTX_devices): Remove.
    (struct nvptx_thread): New.
    (nvptx_thread): New function.
    (select_stream_for_async): Locate ptx_dev in device-specific TLS
    data instead of using TLS PTX_dev variable.
    (PTX_init): Don't initialize PTX_devices.
    (PTX_open_device): Remove PTX_devices list handling. Tweak context
    initialization.
    (PTX_close_device): Remove PTX_devices list handling. Find PTX
    device info via function argument instead of global TLS variable.
    (PTX_get_num_devices): Make callable when backend has not been
    initialized.
    (event_gc): Find PTX device info, current stream via nvptx_thread.
    (event_add, PTX_exec, PTX_host2dev, PTX_dev2host)
    (PTX_async_test_all, PTX_wait_all, PTX_wait_all_async)
    (PTX_get_current_cuda_device, PTX_get_current_cuda_context)
    (PTX_get_cuda_stream, PTX_set_cuda_stream, openacc_close_device)
    (openacc_set_device_num, openacc_register_async_cleanup)
    (openacc_async_set_async): Likewise.
    (openacc_create_thread_data, openacc_destroy_thread_data): New.
    * target.c (oacc-int.h): Include.
    (gomp_fini_device): Split out memory-map freeing into...
    (gomp_free_memmap): ...this new function.
    (gomp_load_plugin_for_device): Initialize
    openacc.create_thread_data_func, openacc.destroy_thread_data_func
    hooks.
    (gomp_find_available_plugins): Initialize one target_device_descr
    per physical device.
    * target.h (oacc-int.h): Don't include.
    (ACC_dispatch_t): Declare here. Add data_environ, ord fields.
    Update comment for mem_map field.
    (gomp_free_memmap): Add prototype.

[gomp4] Rationalise thread-local variables in libgomp OpenACC support

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