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>

configure.ac

@@ -415,6 +415,20 @@ if test "x$GCC_ATOMIC_BUILTINS_SUPPORTED" = x1; then
 fi
 AM_CONDITIONAL([GCC_ATOMIC_BUILTINS_SUPPORTED], [test x$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,

src/util/Makefile.sources

@@ -43,6 +43,7 @@ MESA_UTIL_FILES := \
 	strtod.c \
 	strtod.h \
 	texcompress_rgtc_tmp.h \
+	u_atomic.c \
 	u_atomic.h \
 	u_endian.h \
 	u_queue.c \

src/util/u_atomic.c

@@ -0,0 +1,75 @@
+/*
+ * Copyright © 2017 Gražvydas Ignotas
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#if defined(MISSING_64BIT_ATOMICS) && defined(HAVE_PTHREAD)
+
+#include <stdint.h>
+#include <pthread.h>
+
+#if defined(HAVE_FUNC_ATTRIBUTE_WEAK) && !defined(__CYGWIN__)
+#define WEAK __attribute__((weak))
+#else
+#define WEAK
+#endif
+
+static pthread_mutex_t sync_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+WEAK uint64_t
+__sync_add_and_fetch_8(uint64_t *ptr, uint64_t val)
+{
+   uint64_t r;
+
+   pthread_mutex_lock(&sync_mutex);
+   *ptr += val;
+   r = *ptr;
+   pthread_mutex_unlock(&sync_mutex);
+
+   return r;
+}
+
+WEAK uint64_t
+__sync_sub_and_fetch_8(uint64_t *ptr, uint64_t val)
+{
+   uint64_t r;
+
+   pthread_mutex_lock(&sync_mutex);
+   *ptr -= val;
+   r = *ptr;
+   pthread_mutex_unlock(&sync_mutex);
+
+   return r;
+}
+
+WEAK uint64_t
+__atomic_fetch_add_8(uint64_t *ptr, uint64_t val, int memorder)
+{
+   return __sync_add_and_fetch(ptr, val);
+}
+
+WEAK uint64_t
+__atomic_fetch_sub_8(uint64_t *ptr, uint64_t val, int memorder)
+{
+   return __sync_sub_and_fetch(ptr, val);
+}
+
+#endif