nvptx: Add support for subword compare-and-swap

This adds support for __sync_val_compare_and_swap and
__sync_bool_compare_and_swap for 1-byte and 2-byte long
values, which are not natively supported on nvptx.

Build and reg-tested on nvptx.
Build and reg-tested libgomp on x86_64 with nvptx accelerator.

2020-07-16  Kwok Cheung Yeung  <kcy@codesourcery.com>

	libgcc/
	* config/nvptx/atomic.c: New.
	* config/nvptx/t-nvptx (LIB2ADD): Add atomic.c.

	gcc/testsuite/
	* gcc.target/nvptx/ia64-sync-5.c: New.

	libgomp/
	* testsuite/libgomp.c-c++-common/reduction-16.c: New.

1 files changed, 53 insertions, 0 deletions

diff --git a/libgomp/testsuite/libgomp.c-c++-common/reduction-16.c b/libgomp/testsuite/libgomp.c-c++-common/reduction-16.c
new file mode 100644
index 0000000..d0e82b0
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c-c++-common/reduction-16.c
@@ -0,0 +1,53 @@
+/* { dg-do run } */
+
+#include <stdlib.h>
+
+#define N 512
+
+#define GENERATE_TEST(T)	\
+int test_##T (void)		\
+{				\
+  T a[N], res = 0;		\
+				\
+  for (int i = 0; i < N; ++i)	\
+    a[i] = i & 1;		\
+				\
+_Pragma("omp target teams distribute reduction(||:res) defaultmap(tofrom:scalar)") \
+  for (int i = 0; i < N; ++i)	\
+    res = res || a[i];		\
+				\
+  /* res should be non-zero.  */\
+  if (!res)			\
+    return 1;			\
+				\
+_Pragma("omp target teams distribute reduction(&&:res) defaultmap(tofrom:scalar)") \
+  for (int i = 0; i < N; ++i)	\
+    res = res && a[i];		\
+				\
+  /* res should be zero.  */	\
+  return res;			\
+}
+
+GENERATE_TEST(char)
+GENERATE_TEST(short)
+GENERATE_TEST(int)
+GENERATE_TEST(long)
+#ifdef __SIZEOF_INT128__
+GENERATE_TEST(__int128)
+#endif
+
+int main(void)
+{
+  if (test_char ())
+    abort ();
+  if (test_short ())
+    abort ();
+  if (test_int ())
+    abort ();
+  if (test_long ())
+    abort ();
+#ifdef __SIZEOF_INT128__
+  if (test___int128 ())
+    abort ();
+#endif
+}