i965: don't require 64bit cmpxchg

There are still some distributions trying to support unfortunate people
with old or exotic CPUs that don't have 64bit atomic operations. The
only thing preventing compile of the Intel driver for them seems to be
initialization of a debug variable.

v2: use call_once() instead of unsafe code, as suggested by Matt Turner

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93089
Signed-off-by: Grazvydas Ignotas <[email protected]>

1 files changed, 11 insertions, 3 deletions

diff --git a/src/intel/common/gen_debug.c b/src/intel/common/gen_debug.c
index 858f04db432..96efdab65f7 100644
--- a/src/intel/common/gen_debug.c
+++ b/src/intel/common/gen_debug.c
@@ -33,8 +33,8 @@
 
 #include "common/gen_debug.h"
 #include "util/macros.h"
-#include "util/u_atomic.h" /* for p_atomic_cmpxchg */
 #include "util/debug.h"
+#include "c11/threads.h"
 
 uint64_t INTEL_DEBUG = 0;
 
@@ -101,9 +101,17 @@ intel_debug_flag_for_shader_stage(gl_shader_stage stage)
    return flags[stage];
 }
 
+static void
+brw_process_intel_debug_variable_once(void)
+{
+   INTEL_DEBUG = parse_debug_string(getenv("INTEL_DEBUG"), debug_control);
+}
+
 void
 brw_process_intel_debug_variable(void)
 {
-   uint64_t intel_debug = parse_debug_string(getenv("INTEL_DEBUG"), debug_control);
-   (void) p_atomic_cmpxchg(&INTEL_DEBUG, 0, intel_debug);
+   static once_flag process_intel_debug_variable_flag = ONCE_FLAG_INIT;
+
+   call_once(&process_intel_debug_variable_flag,
+             brw_process_intel_debug_variable_once);
 }