Add nvptx support to libatomic.

Given that atomic_test_and_set is not implemented for nvptx (PR96964), the
compiler translates __atomic_test_and_set falling back onto the "Failing all
else, assume a single threaded environment and simply perform the operation"
case in expand_atomic_test_and_set, so it doesn't map onto an actual atomic
operation.

Still, that counts as supported for the configure test of libatomic, so we
end up with HAVE_ATOMIC_TAS_1/2/4/8/16 == 1, and the corresponding
__atomic_test_and_set_1/2/4/8/16 in libatomic all using that non-atomic
implementation.

Fix this by adding an atomic_test_and_set expansion for nvptx, that uses
libatomics __atomic_test_and_set_1.

This again makes the configure tests for HAVE_ATOMIC_TAS_1/2/4/8/16 fail, so
instead we use this case in tas_n.c:
...
/* If this type is smaller than word-sized, fall back to a word-sized
   compare-and-swap loop.  */
bool
SIZE(libat_test_and_set) (UTYPE *mptr, int smodel)
...
which for __atomic_test_and_set_8 uses INVERT_MASK_8.

Add INVERT_MASK_8 in libatomic_i.h, as well as MASK_8.

Tested libatomic testsuite on nvptx.

gcc/ChangeLog:

	PR target/96964
	* config/nvptx/nvptx.md (define_expand "atomic_test_and_set"): New
	expansion.

libatomic/ChangeLog:

	PR target/96898
	* configure.tgt: Add nvptx.
	* libatomic_i.h (MASK_8, INVERT_MASK_8): New macro definition.
	* config/nvptx/host-config.h: New file.
	* config/nvptx/lock.c: New file.

From-SVN: r279813

From-SVN: r267494

From-SVN: r256169

2017-12-04  Steve Ellcey  <sellcey@cavium.com>

	* Makefile.am (ARCH_AARCH64_LINUX): Add IFUNC_OPTIONS and
	libatomic_la_LIBADD.
	* config/linux/aarch64/host-config.h: New file.
	* configure.ac (IFUNC_RESOLVER_ARGS): Define.
	(ARCH_AARCH64_LINUX): New conditional for IFUNC builds.
	* configure.tgt (aarch64): Set ARCH and try_ifunc.
	(aarch64*-*-linux*) Update config_path.
	(aarch64*-*-linux*) Set IFUNC_RESOLVER_ARGS.
	* libatomic_i.h (GEN_SELECTOR): Add IFUNC_RESOLVER_ARGS argument.
	* Makefile.in: Regenerate.
	* auto-config.h.in: Regenerate.
	* configure: Regenerate.

From-SVN: r255399

libatomic/ChangeLog:
2017-10-02  Martin Sebor  <msebor@redhat.com>

	PR c/81854
	* acinclude.m4 (LIBAT_CHECK_IFUNC): Have ifunc resolver return
	a function pointer rather than void* to avoid GCC 8 warnings.
	* configure: Regenerate.
	* libatomic_i.h: Declare ifunc resolvers to return function
	pointers rather than void*.

From-SVN: r253372

From-SVN: r243994

From-SVN: r232055

From-SVN: r219188

From-SVN: r206291

From-SVN: r195164

From-SVN: r187018