[Mesa-dev] [PATCH 1/2] Clang doesn't have 64bit __atomic* builtins on i386

[Jan Beich]

glsl/.libs/libstandalone.a(libmesautil_la-disk_cache.o): In function `disk_cache_remove':
disk_cache.c:(.text+0x763): undefined reference to `__atomic_fetch_add_8'
glsl/.libs/libstandalone.a(libmesautil_la-disk_cache.o): In function `cache_put':
disk_cache.c:(.text+0xabc): undefined reference to `__atomic_fetch_add_8'
disk_cache.c:(.text+0xec1): undefined reference to `__atomic_fetch_add_8'
c++: error: linker command failed with exit code 1 (use -v to see invocation)

Signed-off-by: Jan Beich <jbeich at FreeBSD.org>
---
 configure.ac        | 13 ++++++++++++-
 src/util/u_atomic.c |  4 ++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index ce5301f3e4..08d8879986 100644
--- a/configure.ac
+++ b/configure.ac
@@ -415,13 +415,24 @@ AM_CONDITIONAL([GCC_ATOMIC_BUILTINS_SUPPORTED], [test x$GCC_ATOMIC_BUILTINS_SUPP
 
 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)
+save_CFLAGS=$CFLAGS
+if test "x$GCC_ATOMIC_BUILTINS_SUPPORTED" = x1; then
+    CFLAGS="$CFLAGS -DUSE_GCC_ATOMIC_BUILTINS"
+    AC_MSG_CHECKING(whether __atomic_fetch_add_8 is supported)
+else
+    AC_MSG_CHECKING(whether __sync_add_and_fetch_8 is supported)
+fi
 AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #include <stdint.h>
 uint64_t v;
 int main() {
+#ifdef USE_GCC_ATOMIC_BUILTINS
+    return __atomic_add_fetch(&v, 1, __ATOMIC_ACQ_REL);
+#else
     return __sync_add_and_fetch(&v, (uint64_t)1);
+#endif
 }]])], GCC_64BIT_ATOMICS_SUPPORTED=yes, GCC_64BIT_ATOMICS_SUPPORTED=no)
+CFLAGS=$save_CFLAGS
 if test "x$GCC_64BIT_ATOMICS_SUPPORTED" != xyes; then
     DEFINES="$DEFINES -DMISSING_64BIT_ATOMICS"
 fi
diff --git a/src/util/u_atomic.c b/src/util/u_atomic.c
index 44b75fb0c0..691c34cf30 100644
--- a/src/util/u_atomic.c
+++ b/src/util/u_atomic.c
@@ -34,6 +34,7 @@
 
 static pthread_mutex_t sync_mutex = PTHREAD_MUTEX_INITIALIZER;
 
+#ifndef USE_GCC_ATOMIC_BUILTINS
 WEAK uint64_t
 __sync_add_and_fetch_8(uint64_t *ptr, uint64_t val)
 {
@@ -60,6 +61,8 @@ __sync_sub_and_fetch_8(uint64_t *ptr, uint64_t val)
    return r;
 }
 
+#else
+
 WEAK uint64_t
 __atomic_fetch_add_8(uint64_t *ptr, uint64_t val, int memorder)
 {
@@ -71,5 +74,6 @@ __atomic_fetch_sub_8(uint64_t *ptr, uint64_t val, int memorder)
 {
    return __sync_sub_and_fetch(ptr, val);
 }
+#endif /* !USE_GCC_ATOMIC_BUILTINS */
 
 #endif