[Mesa-dev] [PATCH 3/3] configure.ac: Test for __atomic_add_fetch in atomic checks

[Matt Turner]

From: Andrew Galante <spock128 at gmail.com>

Some platforms have 64-bit __atomic_load_n but not 64-bit
__atomic_add_fetch, so test for both of them.

Bug: https://bugs.gentoo.org/655616
Reviewed-by: Matt Turner <mattst88 at gmail.com>
---
 configure.ac | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index 704b67fd834..98fd4375b01 100644
--- a/configure.ac
+++ b/configure.ac
@@ -442,7 +442,8 @@ int main() {
     struct {
         uint64_t *v;
     } x;
-    return (int)__atomic_load_n(x.v, __ATOMIC_ACQUIRE);
+    return (int)__atomic_load_n(x.v, __ATOMIC_ACQUIRE) &
+           (int)__atomic_add_fetch(x.v, (uint64_t)1, __ATOMIC_ACQ_REL);
 }]])], GCC_ATOMIC_BUILTINS_SUPPORTED=yes, GCC_ATOMIC_BUILTINS_SUPPORTED=no)
 
 dnl If that didn't work, we try linking with -latomic, which is needed on some
@@ -456,7 +457,8 @@ if test "x$GCC_ATOMIC_BUILTINS_SUPPORTED" != xyes; then
         struct {
             uint64_t *v;
         } x;
-        return (int)__atomic_load_n(x.v, __ATOMIC_ACQUIRE);
+        return (int)__atomic_load_n(x.v, __ATOMIC_ACQUIRE) &
+               (int)__atomic_add_fetch(x.v, (uint64_t)1, __ATOMIC_ACQ_REL);
    }]])], GCC_ATOMIC_BUILTINS_SUPPORTED=yes LIBATOMIC_LIBS="-latomic",
           GCC_ATOMIC_BUILTINS_SUPPORTED=no)
    LDFLAGS=$save_LDFLAGS
-- 
2.16.1