[PATCH 4/4] include/qemu/atomic128: Avoid __sync_val_compare_and_swap_16

[Richard Henderson]

Merge the CONFIG_ATOMIC128 and CONFIG_CMPXCHG128 cases
with respect to atomic16_cmpxchg and use
__atomic_compare_exchange_nomic (via qatomic_cmpxchg)
instead of the "legacy" __sync_val_compare_and_swap_16.

Update the meson has_cmpxchg128 test to match.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/qemu/atomic128.h | 8 +-------
 meson.build              | 3 ++-
 2 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/include/qemu/atomic128.h b/include/qemu/atomic128.h
index adb9a1a260..ec45754515 100644
--- a/include/qemu/atomic128.h
+++ b/include/qemu/atomic128.h
@@ -41,18 +41,12 @@
  * Therefore, special case each platform.
  */
 
-#if defined(CONFIG_ATOMIC128)
+#if defined(CONFIG_ATOMIC128) || defined(CONFIG_CMPXCHG128)
 static inline Int128 atomic16_cmpxchg(Int128 *ptr, Int128 cmp, Int128 new)
 {
     return qatomic_cmpxchg__nocheck(ptr, cmp, new);
 }
 # define HAVE_CMPXCHG128 1
-#elif defined(CONFIG_CMPXCHG128)
-static inline Int128 atomic16_cmpxchg(Int128 *ptr, Int128 cmp, Int128 new)
-{
-    return __sync_val_compare_and_swap_16(ptr, cmp, new);
-}
-# define HAVE_CMPXCHG128 1
 #elif defined(__aarch64__)
 /* Through gcc 8, aarch64 has no support for 128-bit at all.  */
 static inline Int128 atomic16_cmpxchg(Int128 *ptr, Int128 cmp, Int128 new)
diff --git a/meson.build b/meson.build
index 1ec3f72edc..d8c4e76e7b 100644
--- a/meson.build
+++ b/meson.build
@@ -2224,7 +2224,8 @@ if has_int128
       int main(void)
       {
         unsigned __int128 x = 0, y = 0;
-        __sync_val_compare_and_swap_16(&x, y, x);
+        __atomic_compare_exchange_n(&x, &y, x, 0,
+            __ATOMIC_RELAXED, __ATOMIC_RELAXED);
         return 0;
       }
     ''')
-- 
2.34.1