diff mbox series

[4.19,136/206] include/linux/bitops.h: avoid clang shift-count-overflow warnings

Message ID 20200623195323.676418958@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg KH June 23, 2020, 7:57 p.m. UTC 
From: Arnd Bergmann <arnd@arndb.de>


[ Upstream commit bd93f003b7462ae39a43c531abca37fe7073b866 ]

Clang normally does not warn about certain issues in inline functions when
it only happens in an eliminated code path. However if something else
goes wrong, it does tend to complain about the definition of hweight_long()
on 32-bit targets:

  include/linux/bitops.h:75:41: error: shift count >= width of type [-Werror,-Wshift-count-overflow]
          return sizeof(w) == 4 ? hweight32(w) : hweight64(w);
                                                 ^~~~~~~~~~~~
  include/asm-generic/bitops/const_hweight.h:29:49: note: expanded from macro 'hweight64'
   define hweight64(w) (__builtin_constant_p(w) ? __const_hweight64(w) : __arch_hweight64(w))
                                                  ^~~~~~~~~~~~~~~~~~~~
  include/asm-generic/bitops/const_hweight.h:21:76: note: expanded from macro '__const_hweight64'
   define __const_hweight64(w) (__const_hweight32(w) + __const_hweight32((w) >> 32))
                                                                             ^  ~~
  include/asm-generic/bitops/const_hweight.h:20:49: note: expanded from macro '__const_hweight32'
   define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((w) >> 16))
                                                  ^
  include/asm-generic/bitops/const_hweight.h:19:72: note: expanded from macro '__const_hweight16'
   define __const_hweight16(w) (__const_hweight8(w)  + __const_hweight8((w)  >> 8 ))
                                                                         ^
  include/asm-generic/bitops/const_hweight.h:12:9: note: expanded from macro '__const_hweight8'
            (!!((w) & (1ULL << 2))) +     \

Adding an explicit cast to __u64 avoids that warning and makes it easier
to read other output.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Acked-by: Christian Brauner <christian.brauner@ubuntu.com>

Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Link: http://lkml.kernel.org/r/20200505135513.65265-1-arnd@arndb.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: Sasha Levin <sashal@kernel.org>

---
 include/linux/bitops.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.25.1
diff mbox series

Patch

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index e02cbca3cfaf0..5c1522ed2d7c7 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -50,7 +50,7 @@  static inline int get_bitmask_order(unsigned int count)
 
 static __always_inline unsigned long hweight_long(unsigned long w)
 {
-	return sizeof(w) == 4 ? hweight32(w) : hweight64(w);
+	return sizeof(w) == 4 ? hweight32(w) : hweight64((__u64)w);
 }
 
 /**