ruby.h: ASSUME

* include/ruby/ruby.h (ASSUME): hint for optimization, the
  expression is assumed to be true always.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51342 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

include/ruby/ruby.h

@@ -41,8 +41,15 @@ extern "C" {
 #ifndef NOINLINE
 # define NOINLINE(x) x
 #endif
+#ifndef ASSUME
+# ifdef UNREACHABLE
+#   define ASSUME(x) (LIKELY(!!(x)) ? (void)0 : UNREACHABLE)
+# else
+#   define ASSUME(x) ((void)0)
+# endif
+#endif
 #ifndef UNREACHABLE
-# define UNREACHABLE		/* unreachable */
+# define UNREACHABLE ((void)0)	/* unreachable */
 #endif
 
 #ifdef __GNUC__

win32/Makefile.sub

@@ -587,6 +587,7 @@ $(CONFIG_H): $(MKFILES) $(srcdir)/win32/Makefile.sub $(win_srcdir)/Makefile.sub
 #define NOINLINE(x) __declspec(noinline) x
 !endif
 #define UNREACHABLE __assume(0)
+#define ASSUME(x) __assume(!!(x))
 #define FUNC_STDCALL(x) __stdcall x
 #define FUNC_CDECL(x) __cdecl x
 #define FUNC_FASTCALL(x) __fastcall x