intel: Fallback to atomic-ops.h [libatomic-ops-dev]

Use the external implementation for atomic operations across a wide
range of architectures.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

2 files changed, 26 insertions, 1 deletions

diff --git a/configure.ac b/configure.ac
index fd6f696b..7efc4d4e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -163,15 +163,23 @@ if test "x$INTEL" != "xno"; then
     ], [],
 	      drm_cv_atomic_primitives="Intel"
 	      )
+
+	    if test "x$drm_cv_atomic_primitives" = "xnone"; then
+		    AC_CHECK_HEADER([atomic_ops.h], drm_cv_atomic_primitives="libatomic-ops")
+	    fi
+
     ])
     if test "x$drm_cv_atomic_primitives" = xIntel; then
 	    AC_DEFINE(HAVE_INTEL_ATOMIC_PRIMITIVES, 1,
 		      [Enable if your compiler supports the Intel __sync_* atomic primitives])
     fi
+    if test "x$drm_cv_atomic_primitives" = "xlibatomic-ops"; then
+	    AC_DEFINE(HAVE_LIB_ATOMIC_OPS, 1, [Enable if you have libatomic-ops-dev installed])
+    fi
 
     if test "x$drm_cv_atomic_primitives" = "xnone"; then
 	    if test "x$INTEL" != "xauto"; then
-		    AC_MSG_ERROR([libdrm_intel depends upon atomic operations, which were not found for your compiler/cpu. Try compiling with -march=native, or disable support for Intel GPUs by passing --disable-intel to ./configure])
+		    AC_MSG_ERROR([libdrm_intel depends upon atomic operations, which were not found for your compiler/cpu. Try compiling with -march=native, or install the libatomics-op-dev package, or, failing both of those, disable support for Intel GPUs by passing --disable-intel to ./configure])
 	   else
 		    INTEL=no
 	   fi
diff --git a/libdrm/intel/intel_atomic.h b/libdrm/intel/intel_atomic.h
index 9eb50a1e..e725c4a4 100644
--- a/libdrm/intel/intel_atomic.h
+++ b/libdrm/intel/intel_atomic.h
@@ -54,6 +54,23 @@ typedef struct {
 
 #endif
 
+#if HAVE_LIB_ATOMIC_OPS
+#include <atomic_ops.h>
+
+#define HAS_ATOMIC_OPS 1
+
+typedef struct {
+	AO_t atomic;
+} atomic_t;
+
+# define atomic_read(x) AO_load_full(&(x)->atomic)
+# define atomic_set(x, val) AO_store_full(&(x)->atomic, (val))
+# define atomic_inc(x) ((void) AO_fetch_and_add1_full(&(x)->atomic))
+# define atomic_dec_and_test(x) (AO_fetch_and_sub1_full(&(x)->atomic) == 1)
+# define atomic_cmpxchg(x, oldv, newv) AO_compare_and_swap_full(&(x)->atomic, oldv, newv)
+
+#endif
+
 #if ! HAS_ATOMIC_OPS
 #error libdrm-intel requires atomic operations, please define them for your CPU/compiler.
 #endif