toolchain: Introduce likely() and unlikely() macros

The likely() and unlikely() macros may be used as hints to the compiler to
indicate whether a branch is likely or unlikely to be taken so that it may
generate code accordingly.

Signed-off-by: Peter Mitsis <peter.mitsis@gmail.com>

Author: PeterMitsis

code/globalincs/toolchain/clang.h

@@ -61,3 +61,6 @@
 #define PTRDIFF_T_ARG "%zd"
 
 #define NOEXCEPT  noexcept
+
+#define likely(x)    __builtin_expect((long) !!(x), 1L)
+#define unlikely(x)  __builtin_expect((long) !!(x), 0L)

code/globalincs/toolchain/gcc.h

@@ -60,3 +60,6 @@
 #define PTRDIFF_T_ARG "%zd"
 
 #define NOEXCEPT  noexcept
+
+#define likely(x)    __builtin_expect((long) !!(x), 1L)
+#define unlikely(x)  __builtin_expect((long) !!(x), 0L)

code/globalincs/toolchain/mingw.h

@@ -55,3 +55,6 @@
 #define PTRDIFF_T_ARG "%zd"
 
 #define NOEXCEPT  noexcept
+
+#define likely(x)    __builtin_expect((long) !!(x), 1L)
+#define unlikely(x)  __builtin_expect((long) !!(x), 0L)

code/globalincs/toolchain/msvc.h

@@ -79,3 +79,6 @@
 #else
 #	define NOEXCEPT  noexcept
 #endif
+
+#define likely(x)
+#define unlikely(x)