[atomic] Fallback to libatomic-ops-dev

Use libatomic-ops-dev in preference to mutex-based atomics, if we do not
have the builtin atomic intrinsics available.

build/aclocal.cairo.m4

@@ -172,11 +172,21 @@ int atomic_cmpxchg(int i, int j, int k) { return __sync_val_compare_and_swap (&i
 ], [],
 		  cairo_cv_atomic_primitives="Intel"
 		  )
+
+		if test "x$cairo_cv_atomic_primitives" = "xnone"; then
+			AC_CHECK_HEADER([atomic_ops.h],
+					cairo_cv_atomic_primitives="libatomic-ops")
+		fi
 	])
 	if test "x$cairo_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$cairo_cv_atomic_primitives" = "xlibatomic-ops"; then
+		AC_DEFINE(HAVE_LIB_ATOMIC_OPS, 1,
+			  [Enable if you have libatomic-ops-dev installed])
+	fi
 ])
 
 dnl Usage:

src/cairo-atomic-private.h

@@ -57,6 +57,9 @@ CAIRO_BEGIN_DECLS
 
 typedef int cairo_atomic_int_t;
 
+# define _cairo_atomic_int_get(x) (*x)
+# define _cairo_atomic_int_set(x, value) ((*x) = value)
+
 # define _cairo_atomic_int_inc(x) ((void) __sync_fetch_and_add(x, 1))
 # define _cairo_atomic_int_dec_and_test(x) (__sync_fetch_and_add(x, -1) == 1)
 # define _cairo_atomic_int_cmpxchg(x, oldv, newv) __sync_val_compare_and_swap (x, oldv, newv)
@@ -76,6 +79,35 @@ typedef long long cairo_atomic_intptr_t;
 
 #endif
 
+#if HAVE_LIB_ATOMIC_OPS
+#include <atomic_ops.h>
+
+#define HAS_ATOMIC_OPS 1
+
+typedef  AO_t cairo_atomic_int_t;
+
+# define _cairo_atomic_int_get(x) (AO_load_full (x))
+# define _cairo_atomic_int_set(x, value) (AO_store_full (x))
+
+# define _cairo_atomic_int_inc(x) ((void) AO_fetch_and_add1_full(x))
+# define _cairo_atomic_int_dec_and_test(x) (AO_fetch_and_sub1_full(x) == 1)
+# define _cairo_atomic_int_cmpxchg(x, oldv, newv) ((cairo_atomic_int_t) AO_compare_and_swap_full(x, oldv, newv))
+
+#if SIZEOF_VOID_P==SIZEOF_INT
+typedef unsigned int cairo_atomic_intptr_t;
+#elif SIZEOF_VOID_P==SIZEOF_LONG
+typedef unsigned long cairo_atomic_intptr_t;
+#elif SIZEOF_VOID_P==SIZEOF_LONG_LONG
+typedef unsigned long long cairo_atomic_intptr_t;
+#else
+#error No matching integer pointer type
+#endif
+
+# define _cairo_atomic_ptr_cmpxchg(x, oldv, newv) \
+    (void*) (cairo_atomic_intptr_t) _cairo_atomic_int_cmpxchg ((cairo_atomic_intptr_t*)(x), (cairo_atomic_intptr_t)oldv, (cairo_atomic_intptr_t)newv)
+
+#endif
+
 
 #ifndef HAS_ATOMIC_OPS
 
@@ -93,9 +125,6 @@ _cairo_atomic_int_cmpxchg (int *x, int oldv, int newv);
 cairo_private void *
 _cairo_atomic_ptr_cmpxchg (void **x, void *oldv, void *newv);
 
-#endif
-
-
 #ifdef ATOMIC_OP_NEEDS_MEMORY_BARRIER
 
 # include "cairo-compiler-private.h"
@@ -113,14 +142,16 @@ _cairo_atomic_int_set (int *x, int value);
 
 #endif
 
+#endif
+
 #define _cairo_atomic_uint_get(x) _cairo_atomic_int_get(x)
 #define _cairo_atomic_uint_cmpxchg(x, oldv, newv) \
-    _cairo_atomic_int_cmpxchg((int *)x, oldv, newv)
+    _cairo_atomic_int_cmpxchg((cairo_atomic_int_t *)x, oldv, newv)
 
 #define _cairo_status_set_error(status, err) do { \
     /* hide compiler warnings about cairo_status_t != int (gcc treats its as \
      * an unsigned integer instead, and about ignoring the return value. */  \
-    int ret__ = _cairo_atomic_int_cmpxchg ((int *) status, CAIRO_STATUS_SUCCESS, err); \
+    int ret__ = _cairo_atomic_int_cmpxchg ((cairo_atomic_int_t *) status, CAIRO_STATUS_SUCCESS, err); \
     (void) ret__; \
 } while (0)
 

src/cairo-surface.c

@@ -193,14 +193,14 @@ slim_hidden_def (cairo_surface_status);
 static unsigned int
 _cairo_surface_allocate_unique_id (void)
 {
-    static unsigned int unique_id;
+    static cairo_atomic_int_t unique_id;
 
 #if CAIRO_NO_MUTEX
     if (++unique_id == 0)
 	unique_id = 1;
     return unique_id;
 #else
-    unsigned int old, id;
+    cairo_atomic_int_t old, id;
 
     do {
 	old = _cairo_atomic_uint_get (&unique_id);

src/cairo-xlib-private.h

@@ -85,7 +85,7 @@ struct _cairo_xlib_screen {
     cairo_font_options_t font_options;
 
     GC gc[4];
-    int gc_depths; /* 4 x uint8_t */
+    cairo_atomic_int_t gc_depths; /* 4 x uint8_t */
 
     cairo_array_t visuals;
 };

src/cairo-xlib-screen.c

@@ -269,7 +269,8 @@ _cairo_xlib_screen_close_display (cairo_xlib_screen_t *info)
 {
     cairo_xlib_visual_info_t **visuals;
     Display *dpy;
-    int i, old;
+    cairo_atomic_int_t old;
+    int i;
 
     CAIRO_MUTEX_LOCK (info->mutex);
 
@@ -277,7 +278,7 @@ _cairo_xlib_screen_close_display (cairo_xlib_screen_t *info)
 
 #if HAS_ATOMIC_OPS
     do {
-	old = info->gc_depths;
+	old = _cairo_atomic_int_get (&info->gc_depths);
     } while (_cairo_atomic_int_cmpxchg (&info->gc_depths, old, 0) != old);
 #else
     old = info->gc_depths;
@@ -384,7 +385,8 @@ _cairo_xlib_screen_get_gc (cairo_xlib_screen_t *info,
 			   Drawable drawable)
 {
     XGCValues gcv;
-    int i, new, old;
+    cairo_atomic_int_t old, new;
+    int i;
     GC gc;
 
     do {
@@ -393,13 +395,13 @@ _cairo_xlib_screen_get_gc (cairo_xlib_screen_t *info,
 	if (old == 0)
 	    break;
 
-	if (((old >> 0) & 0xff) == depth)
+	if (((old >> 0) & 0xff) == (unsigned) depth)
 	    i = 0;
-	else if (((old >> 8) & 0xff) == depth)
+	else if (((old >> 8) & 0xff) == (unsigned) depth)
 	    i = 1;
-	else if (((old >> 16) & 0xff) == depth)
+	else if (((old >> 16) & 0xff) == (unsigned) depth)
 	    i = 2;
-	else if (((old >> 24) & 0xff) == depth)
+	else if (((old >> 24) & 0xff) == (unsigned) depth)
 	    i = 3;
 	else
 	    break;

src/cairo.c

@@ -124,16 +124,16 @@ _cairo_set_error (cairo_t *cr, cairo_status_t status)
 #define CAIRO_STASH_SIZE 4
 static struct {
     cairo_t pool[CAIRO_STASH_SIZE];
-    int occupied;
+    cairo_atomic_int_t occupied;
 } _context_stash;
 
 static cairo_t *
 _context_get (void)
 {
-    int avail, old, new;
+    cairo_atomic_int_t avail, old, new;
 
     do {
-	old = _context_stash.occupied;
+	old = _cairo_atomic_int_get (&_context_stash.occupied);
 	avail = ffs (~old) - 1;
 	if (avail >= CAIRO_STASH_SIZE)
 	    return malloc (sizeof (cairo_t));
@@ -147,7 +147,7 @@ _context_get (void)
 static void
 _context_put (cairo_t *cr)
 {
-    int old, new, avail;
+    cairo_atomic_int_t old, new, avail;
 
     if (cr < &_context_stash.pool[0] ||
 	cr >= &_context_stash.pool[CAIRO_STASH_SIZE])
@@ -158,7 +158,7 @@ _context_put (cairo_t *cr)
 
     avail = ~(1 << (cr - &_context_stash.pool[0]));
     do {
-	old = _context_stash.occupied;
+	old = _cairo_atomic_int_get (&_context_stash.occupied);
 	new = old & avail;
     } while (_cairo_atomic_int_cmpxchg (&_context_stash.occupied, old, new) != old);
 }