Commit Graph

2 Commits

Author SHA1 Message Date
Paul Walmsley c32fa99f0b bitops: Fix signedness of compile-time hweight implementations
Enabling '-Wsign-compare' compiler warnings on code that includes
include/linux/bitops.h can generate the following warning:

  In file included from include/linux/kernel.h:10:0,
                    from <random filename>:48:
  include/linux/bitops.h: In function 'hweight_long':
  include/linux/bitops.h:77:26: error: signed and unsigned type in conditional expression [-Werror=sign-compare]

(converted to an error with -Werror)

This is due to the use of the logical negation operator '!' in the
__const_hweight8 macro in include/asm-generic/bitops/const_hweight.h.
The use of that operator here results in a signed value.

Fix by explicitly casting the __const_hweight8 macro expansion to
'unsigned int'.  While here, clean up several checkpatch.pl warnings.

Signed-off-by: Paul Walmsley <pwalmsley@nvidia.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1312180459580.30198@tamien
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2014-02-09 13:39:26 +01:00
Peter Zijlstra 1527bc8b92 bitops: Optimize hweight() by making use of compile-time evaluation
Rename the extisting runtime hweight() implementations to
__arch_hweight(), rename the compile-time versions to __const_hweight()
and then have hweight() pick between them.

Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100318111929.GB11152@aftab>
Acked-by: H. Peter Anvin <hpa@zytor.com>
LKML-Reference: <1265028224.24455.154.camel@laptop>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2010-04-06 15:52:11 -07:00