compiler: Introduce __always_unused

I wrote some code which is used as compile-time checker, and the
code should be elided after compile.

So I need to annotate the code as "always unused", compared to
"maybe unused".

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <4AEE2CEC.8040206@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index a3ed7cb8ca34..73dcf804bc94 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -79,6 +79,7 @@
 #define  noinline                       __attribute__((noinline))
 #define __attribute_const__             __attribute__((__const__))
 #define __maybe_unused                  __attribute__((unused))
+#define __always_unused                 __attribute__((unused))
 
 #define __gcc_header(x) #x
 #define _gcc_header(x) __gcc_header(linux/compiler-gcc##x.h)
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 04fb5135b4e1..7947f4f6fa51 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -213,6 +213,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 # define __maybe_unused         /* unimplemented */
 #endif
 
+#ifndef __always_unused
+# define __always_unused        /* unimplemented */
+#endif
+
 #ifndef noinline
 #define noinline
 #endif