The inclusion of <linux/kernel.h> was causing issue as the definition of __arch_hweight64 from arch/x86/include/asm/arch_hweight.h eventually gets included. The definition is problematic when compiled with -m16 (all code in arch/x86/boot/ is) as the "D" inline assembly constraint is rejected by both compilers when passed an argument of type long long (regardless of signedness, anything smaller is fine).
Because GCC performs inlining before semantic analysis, and __arch_hweight64 is dead in this translation unit, GCC does not report any issues at compile time. Clang does the semantic analysis in the front end, before inlining (run in the middle) can determine the code is dead. I consider this another case of PR33587, which I think we can do more work to solve. It turns out that arch/x86/boot/string.c doesn't actually need linux/kernel.h, simply linux/limits.h and linux/compiler.h. Include them, and sort the headers alphabetically. Link: https://bugs.llvm.org/show_bug.cgi?id=33587 Link: https://github.com/ClangBuiltLinux/linux/issues/347 Reviewed-by: Nathan Chancellor <natechancel...@gmail.com> Tested-by: Nathan Chancellor <natechancel...@gmail.com> Suggested-by: Stephen Rothwell <s...@canb.auug.org.au> Signed-off-by: Nick Desaulniers <ndesaulni...@google.com> --- Changes V1 -> V2: * Add Reviewed, Tested, Suggested tags. * Drop linux/types.h; it's included in linux/limits.h. My original intention was to unsort the headers (sorted in V1), but if we drop the out of place linux/types.h, then we can insert the two more specific headers in alphabetic order. arch/x86/boot/string.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c index 315a67b8896b..597589cafb45 100644 --- a/arch/x86/boot/string.c +++ b/arch/x86/boot/string.c @@ -12,9 +12,9 @@ * Very basic string functions */ -#include <linux/types.h> -#include <linux/kernel.h> +#include <linux/compiler.h> #include <linux/errno.h> +#include <linux/limits.h> #include <asm/asm.h> #include "ctype.h" #include "string.h" -- 2.21.0.352.gf09ad66450-goog
