fix: properly detect 'cmpxchg' on x86-32

[userspace-rcu.git] / include / urcu / arch.h

diff --git a/include/urcu/arch.h b/include/urcu/arch.h
index 620743c0f68fb33dd004d3266bcf900e2a96b898..2bffdbe97d8e20339d1d06ea6ccb66e79b4d366c 100644 (file)
--- a/include/urcu/arch.h
+++ b/include/urcu/arch.h
@@ -64,15 +64,25 @@
 #define URCU_ARCH_AMD64 1
 #include <urcu/arch/x86.h>
 
-#elif (defined(__i486__) || defined(__i586__) || defined(__i686__))
+#elif (defined(__i386__) || defined(__i386) || defined(__i486__) || defined(__i586__) || defined(__i686__))
 
 #define URCU_ARCH_X86 1
-#include <urcu/arch/x86.h>
-
-#elif (defined(__i386__) || defined(__i386))
 
-#define URCU_ARCH_X86 1
+/*
+ * URCU_ARCH_X86_NO_CAS enables a compat layer that will detect the presence of
+ * the cmpxchg instructions at runtime and provide a compat mode based on a
+ * pthread mutex when it isn't.
+ *
+ * __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 was introduced in GCC 4.3 and Clang 3.3,
+ * building with older compilers will result in the compat layer always being
+ * used on x86-32.
+ */
+#ifndef __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4
+#define URCU_ARCH_X86_NO_CAS 1
+/* For backwards compat */
 #define URCU_ARCH_I386 1
+#endif
+
 #include <urcu/arch/x86.h>
 
 #elif (defined(__powerpc64__) || defined(__ppc64__))