util/u_atomic: provide 64bit atomics where they're missing
There are still some distributions trying to support unfortunate people
with old or exotic CPUs that don't have 64bit atomic operations. When
compiling for such a machine, gcc conveniently inserts a library call to
a helper, but it's implementation is missing and we get a linker error.
This allows us to provide our own implementation, which is marked weak
to prefer a better implementation, should one exist.
v2: changed copyright, some style adjustments
v3: [mattst88] Print results with AC_MSG_CHECKING/AC_MSG_RESULT
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93089
Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
diff --git a/configure.ac b/configure.ac
index 016e38f..83cd5d1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -415,6 +415,20 @@
fi
AM_CONDITIONAL([GCC_ATOMIC_BUILTINS_SUPPORTED], [test x$GCC_ATOMIC_BUILTINS_SUPPORTED = x1])
+dnl Check if host supports 64-bit atomics
+dnl note that lack of support usually results in link (not compile) error
+AC_MSG_CHECKING(whether __sync_add_and_fetch_8 is supported)
+AC_LINK_IFELSE([AC_LANG_SOURCE([[
+#include <stdint.h>
+uint64_t v;
+int main() {
+ return __sync_add_and_fetch(&v, (uint64_t)1);
+}]])], GCC_64BIT_ATOMICS_SUPPORTED=yes, GCC_64BIT_ATOMICS_SUPPORTED=no)
+if test "x$GCC_64BIT_ATOMICS_SUPPORTED" != xyes; then
+ DEFINES="$DEFINES -DMISSING_64BIT_ATOMICS"
+fi
+AC_MSG_RESULT($GCC_64BIT_ATOMICS_SUPPORTED)
+
dnl Check for Endianness
AC_C_BIGENDIAN(
little_endian=no,