Re: [PATCH] perf/x86/intel: Mark expected switch fall-throughs

[Joe Perches]

On Tue, 2019-06-25 at 11:15 -0700, Nick Desaulniers wrote:
> Unreleased versions of Clang built from source can; the latest release
> of Clang-8 doesn't have asm goto support required for
> CONFIG_JUMP_LABEL.  Things can get complicated based on which kernel
> tree/branch (mainline, -next, stable), arch, and configs, but I think
> we just have a few long tail bugs left.

At some point, when clang generically compiles the kernel,
I believe it'd be good to remove the various bits that
are unusual like CONFIG_CC_HAS_ASM_GOTO in Makefile
and the scripts/clang-version.sh and the like.

This could help when compiling a specific .config on
different systems.

Maybe add the equivalent compiler-gcc.h #define below
even before the removals

(whatever minor/patchlevel appropriate)
---
 include/linux/compiler-clang.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index 333a6695a918..b46aece0f9ca 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -5,6 +5,14 @@
 
 /* Compiler specific definitions for Clang compiler */
 
+#define CLANG_VERSION (__clang_major__ * 10000	\
+		       + __clang_minor__ * 100	\
+		       + __clang_patchlevel__)
+
+#if CLANG_VERSION < 90000
+# error Sorry, your compiler is too old - please upgrade it.
+#endif
+
 #define uninitialized_var(x) x = *(&(x))
 
 /* same as gcc, this was present in clang-2.6 so we can assume it works