[libatomic] Add nvptx support

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.

2 files changed, 112 insertions, 0 deletions

diff --git a/libatomic/config/nvptx/host-config.h b/libatomic/config/nvptx/host-config.h
new file mode 100644
index 0000000..eb9de81
--- /dev/null
+++ b/libatomic/config/nvptx/host-config.h
@@ -0,0 +1,56 @@
+/* Copyright (C) 2020 Free Software Foundation, Inc.
+
+   This file is part of the GNU Atomic Library (libatomic).
+
+   Libatomic is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+   more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Copied from libatomic/config/posix/host-config.h.  */
+
+/* Included after all more target-specific host-config.h.  */
+
+
+#ifndef protect_start_end
+# ifdef HAVE_ATTRIBUTE_VISIBILITY
+#  pragma GCC visibility push(hidden)
+# endif
+
+void libat_lock_1 (void *ptr);
+void libat_unlock_1 (void *ptr);
+
+static inline UWORD
+protect_start (void *ptr)
+{
+  libat_lock_1 (ptr);
+  return 0;
+}
+
+static inline void
+protect_end (void *ptr, UWORD dummy UNUSED)
+{
+  libat_unlock_1 (ptr);
+}
+
+# define protect_start_end 1
+# ifdef HAVE_ATTRIBUTE_VISIBILITY
+#  pragma GCC visibility pop
+# endif
+#endif /* protect_start_end */
+
+#include_next <host-config.h>
diff --git a/libatomic/config/nvptx/lock.c b/libatomic/config/nvptx/lock.c
new file mode 100644
index 0000000..dea85a3
--- /dev/null
+++ b/libatomic/config/nvptx/lock.c
@@ -0,0 +1,56 @@
+/* Copyright (C) 2020 Free Software Foundation, Inc.
+
+   This file is part of the GNU Atomic Library (libatomic).
+
+   Libatomic is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+   more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Functions libat_lock_n/libat_unlock_n based on GOMP_atomic_start/end in
+   libgomp/atomic.c.  */
+
+#include "libatomic_i.h"
+
+static int atomic_lock;
+
+void
+libat_lock_n (void *ptr __attribute__((unused)),
+	      size_t n __attribute__((unused)))
+{
+  while (__sync_lock_test_and_set (&atomic_lock, 1))
+    ;  /* Spin.  */
+}
+
+void
+libat_unlock_n (void *ptr __attribute__((unused)),
+		size_t n __attribute__((unused)))
+{
+  __sync_lock_release (&atomic_lock);
+}
+
+void
+libat_lock_1 (void *ptr)
+{
+  libat_lock_n (ptr, 1);
+}
+
+void
+libat_unlock_1 (void *ptr)
+{
+  libat_unlock_n (ptr, 1);
+}