--- webkitgtk-2.0.0/configure.ac.orig	2013-04-12 08:25:14.896829422 +0200
+++ webkitgtk-2.0.0/configure.ac	2013-04-12 08:27:21.244776999 +0200
@@ -32,6 +32,18 @@
 AM_INIT_AUTOMAKE([foreign subdir-objects dist-xz no-dist-gzip tar-ustar])
 m4_include([Source/autotools/SetupAutomake.m4])
 
+dnl Check whether the target supports 64-bit __sync_*_compare_and_swap.
+AC_TRY_LINK([#include <stdint.h>],
+    [uint64_t foo, bar;
+     bar = __sync_val_compare_and_swap(&foo, 0, 1);],
+     wtf_cv_have_64bit_sync_builtins=yes,
+     wtf_cv_have_64bit_sync_builtins=no)
+
+if test $wtf_cv_have_64bit_sync_builtins = yes; then
+    AC_DEFINE(HAVE_64BIT_SYNC_BUILTINS, 1,
+              [Define to 1 if the target supports 64-bit __sync_*_compare_and_swap])
+fi
+
 ######################################################################################
 # Processing of configuration files
 ######################################################################################
--- webkitgtk-2.0.0/Source/WTF/wtf/Atomics.h~	2013-04-12 08:05:55.951740895 +0200
+++ webkitgtk-2.0.0/Source/WTF/wtf/Atomics.h	2013-04-12 08:22:46.701992338 +0200
@@ -70,6 +70,9 @@
 #elif OS(ANDROID)
 #include <sys/atomics.h>
 #endif
+#ifndef HAVE_64BIT_SYNC_BUILTINS
+#include <pthread.h>
+#endif
 
 namespace WTF {
 
@@ -113,8 +113,15 @@
 inline int atomicIncrement(int volatile* addend) { return __sync_add_and_fetch(addend, 1); }
 inline int atomicDecrement(int volatile* addend) { return __sync_sub_and_fetch(addend, 1); }
 
+#ifdef HAVE_64BIT_SYNC_BUILTINS
 inline int64_t atomicIncrement(int64_t volatile* addend) { return __sync_add_and_fetch(addend, 1); }
 inline int64_t atomicDecrement(int64_t volatile* addend) { return __sync_sub_and_fetch(addend, 1); }
+#else
+static pthread_mutex_t global_wtf_lock = PTHREAD_MUTEX_INITIALIZER;
+
+inline int64_t atomicIncrement(int64_t volatile* addend) { pthread_mutex_lock(&global_wtf_lock); int64_t v = (*addend)++; pthread_mutex_unlock(&global_wtf_lock); return v; }
+inline int64_t atomicDecrement(int64_t volatile* addend) { pthread_mutex_lock(&global_wtf_lock); int64_t v = (*addend)--; pthread_mutex_unlock(&global_wtf_lock); return v; }
+#endif
 
 #endif