add COMPILETIME_ASSERT, LIKELY and UNLIKELY to util.h

[r8719]

diff --git a/ir/adt/util.h b/ir/adt/util.h
index d382540..c8acb56 100644 (file)
--- a/ir/adt/util.h
+++ b/ir/adt/util.h
@@ -39,4 +39,32 @@
 #define array_size(arr) \
   (sizeof(arr) / sizeof((arr)[0]))
 
+/**
+ * Asserts that the constant expression x is not zero at compiletime. name has
+ * to be a unique identifier.
+ *
+ * @note This uses the fact, that double case labels are not allowed.
+ */
+#define COMPILETIME_ASSERT(x, name) \
+    static __attribute__((unused)) void compiletime_assert_##name (int h) { \
+        switch(h) { case 0: case (x): ; } \
+    }
+
+#ifdef __GNUC__
+/**
+ * Indicates to the compiler that the value of x is very likely 1
+ * @note Only use this in speed critical code and when you are sure x is often 1
+ */
+#define LIKELY(x)   __builtin_expect((x), 1)
+
+/**
+ * Indicates to the compiler that it's very likely that x is 0
+ * @note Only use this in speed critical code and when you are sure x is often 0
+ */
+#define UNLIKELY(x) __builtin_expect((x), 0)
+#else
+#define LIKELY(x)   x
+#define UNLIKELY(x) x
+#endif
+
 #endif /* _UTIL_H */