Merge pull request #614 from Tilka/branch_prediction

[RFC] Common: add macros for assisting branch prediction

Source/Core/Common/Common.h

@@ -15,7 +15,7 @@
 #define __has_feature(x) 0
 #endif
 
-// SVN version number
+// Git version number
 extern const char *scm_desc_str;
 extern const char *scm_branch_str;
 extern const char *scm_rev_str;
@@ -37,6 +37,28 @@ extern const char *netplay_dolphin_ver;
 #define UNUSED
 #endif
 
+#if defined(__GNUC__) || __clang__
+	#define EXPECT(x, y) __builtin_expect(x, y)
+	#define LIKELY(x)    __builtin_expect(!!(x), 1)
+	#define UNLIKELY(x)  __builtin_expect(!!(x), 0)
+	// Careful, wrong assumptions result in undefined behavior!
+	#define UNREACHABLE  __builtin_unreachable()
+	// Careful, wrong assumptions result in undefined behavior!
+	#define ASSUME(x)    do { if (!x) __builtin_unreachable(); } while (0)
+#else
+	#define EXPECT(x, y) (x)
+	#define LIKELY(x)    (x)
+	#define UNLIKELY(x)  (x)
+	// Careful, wrong assumptions result in undefined behavior!
+	#define UNREACHABLE  ASSUME(0)
+	#if defined(_MSC_VER)
+		// Careful, wrong assumptions result in undefined behavior!
+		#define ASSUME(x) __assume(x)
+	#else
+		#define ASSUME(x) do { void(x); } while (0)
+	#endif
+#endif
+
 #define STACKALIGN
 
 #if __cplusplus >= 201103 || defined(_MSC_VER) || defined(__GXX_EXPERIMENTAL_CXX0X__)