[PATCH v2 1/2] compiler-clang.h: Add CLANG_VERSION and __diag macros

[Nick Desaulniers <ndesaulniers@google.com>]

These are needed for doing proper version checks, though feature
detection via __has_attribute,  __has_builtin, and __has_feature should
be preferred, see:
https://clang.llvm.org/docs/LanguageExtensions.html#feature-checking-macros

Also adds __diag support, for generating compiler version specific
_Pragma()'s.

__diag support based on commit 8793bb7f4a9d ("kbuild: add macro for
controlling warnings to linux/compiler.h")

Cc: stable@vger.kernel.org # 4.17, 4.14, 4.9, 4.4
Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 include/linux/compiler-clang.h | 19 +++++++++++++++++++
 include/linux/compiler_types.h |  4 ++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index 7087446c24c8..9442e07a361e 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -7,6 +7,10 @@
  * for Clang compiler
  */
 
+#define CLANG_VERSION (__clang_major__ * 10000	\
+		       + __clang_minor__ * 100	\
+		       + __clang_patchlevel__)
+
 #ifdef uninitialized_var
 #undef uninitialized_var
 #define uninitialized_var(x) x = *(&(x))
@@ -46,3 +50,18 @@
     __has_builtin(__builtin_sub_overflow)
 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 #endif
+
+#define __diag_str1(s) #s
+#define __diag_str(s) __diag_str1(s)
+#define __diag(s) _Pragma(__diag_str(clang diagnostic s))
+#define __diag_CLANG_ignore ignored
+#define __diag_CLANG_warn warning
+#define __diag_CLANG_error error
+#define __diag_CLANG(version, severity, s) \
+	__diag_CLANG_ ## version(__diag_CLANG_ ## severity s)
+
+#if CLANG_VERSION >= 70000
+#define __diag_CLANG_7(s) __diag(s)
+#else
+#define __diag_CLANG_7(s)
+#endif
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index a8ba6b04152c..a04e6bd63476 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -279,6 +279,10 @@ struct ftrace_likely_data {
 #define __diag_GCC(version, severity, string)
 #endif
 
+#ifndef __diag_CLANG
+#define __diag_CLANG(version, severity, string)
+#endif
+
 #define __diag_push()	__diag(push)
 #define __diag_pop()	__diag(pop)
 
-- 
2.18.0.345.g5c9ce644c3-goog