Mesa (main): util/u_atomic: fix build on clang archs without 64-bit atomics

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Module: Mesa
Branch: main
Commit: f12c107b030b0aacc0c8b11c99fdce13f38bc98f
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=f12c107b030b0aacc0c8b11c99fdce13f38bc98f

Author: Jonathan Gray <jsg at jsg.id.au>
Date:   Mon Jun 15 14:40:06 2020 +1000

util/u_atomic: fix build on clang archs without 64-bit atomics

Make this build on clang architectures that don't have 64-bit atomic
instructions.  Clang doesn't allow redeclaration (and therefore
redefinition) of the __sync_* builtins.  Use #pragma redefine_extname
to work around that restriction.  Clang also turns __sync_add_and_fetch
into __sync_fetch_and_add (and __sync_sub_and_fetch into
__sync_fetch_and_sub) in certain cases, so provide these functions as
well.

Fixes: a6a38a038bd ("util/u_atomic: provide 64bit atomics where they're missing")
patch from Mark Kettenis

Signed-off-by: Jonathan Gray <jsg at jsg.id.au>
Reviewed-by: Ilia Mirkin <imirkin at alum.mit.edu>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6511>

---

 src/util/u_atomic.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/src/util/u_atomic.c b/src/util/u_atomic.c
index e4bffa8534e..5a5eab411c4 100644
--- a/src/util/u_atomic.c
+++ b/src/util/u_atomic.c
@@ -34,6 +34,21 @@
 
 static pthread_mutex_t sync_mutex = PTHREAD_MUTEX_INITIALIZER;
 
+#ifdef __clang__
+#pragma clang diagnostic ignored "-Wmissing-prototypes"
+#pragma redefine_extname __sync_add_and_fetch_8_c __sync_add_and_fetch_8
+#pragma redefine_extname __sync_sub_and_fetch_8_c __sync_sub_and_fetch_8
+#pragma redefine_extname __sync_fetch_and_add_8_c __sync_fetch_and_add_8
+#pragma redefine_extname __sync_fetch_and_sub_8_c __sync_fetch_and_sub_8
+#pragma redefine_extname __sync_val_compare_and_swap_8_c \
+    __sync_val_compare_and_swap_8
+#define __sync_add_and_fetch_8 __sync_add_and_fetch_8_c
+#define __sync_sub_and_fetch_8 __sync_sub_and_fetch_8_c
+#define __sync_fetch_and_add_8 __sync_fetch_and_add_8_c
+#define __sync_fetch_and_sub_8 __sync_fetch_and_sub_8_c
+#define __sync_val_compare_and_swap_8 __sync_val_compare_and_swap_8_c
+#endif
+
 WEAK uint64_t
 __sync_add_and_fetch_8(uint64_t *ptr, uint64_t val)
 {
@@ -60,6 +75,32 @@ __sync_sub_and_fetch_8(uint64_t *ptr, uint64_t val)
    return r;
 }
 
+WEAK uint64_t
+__sync_fetch_and_add_8(uint64_t *ptr, uint64_t val)
+{
+   uint64_t r;
+
+   pthread_mutex_lock(&sync_mutex);
+   r = *ptr;
+   *ptr += val;
+   pthread_mutex_unlock(&sync_mutex);
+
+   return r;
+}
+
+WEAK uint64_t
+__sync_fetch_and_sub_8(uint64_t *ptr, uint64_t val)
+{
+   uint64_t r;
+
+   pthread_mutex_lock(&sync_mutex);
+   r = *ptr;
+   *ptr -= val;
+   pthread_mutex_unlock(&sync_mutex);
+
+   return r;
+}
+
 WEAK uint64_t
 __sync_val_compare_and_swap_8(uint64_t *ptr, uint64_t oldval, uint64_t newval)
 {