linux/bitmap.h: improve BITMAP_{LAST,FIRST}_WORD_MASK
linux/bitmap.h: improve BITMAP_{LAST,FIRST}_WORD_MASK

The macro BITMAP_LAST_WORD_MASK can be implemented without a conditional,
which will generally lead to slightly better generated code (221 bytes
saved for allmodconfig-GCOV_KERNEL, ~2k with GCOV_KERNEL).  As a small
bonus, this also ensures that the nbits parameter is expanded exactly
once.

In BITMAP_FIRST_WORD_MASK, if start is signed gcc is technically allowed
to assume it is positive (or divisible by BITS_PER_LONG), and hence just
do the simple mask.  It doesn't seem to use this, and even on an
architecture like x86 where the shift only depends on the lower 5 or 6
bits, and these bits are not affected by the signedness of the expression,
gcc still generates code to compute the C99 mandated value of start %
BITS_PER_LONG.  So just use a mask explicitly, also for consistency with
BITMAP_LAST_WORD_MASK.

Signed-off-by: Rasmus Villemoes <ba324ca7b1c77fc20bb970d5aff6eea9377918a5@rasmusvillemoes.dk>
Cc: Tejun Heo <546b05909706652891a87f7bfe385ae147f61f91@kernel.org>
Reviewed-by: George Spelvin <ba324ca7b1c77fc20bb970d5aff6eea9377918a5@horizon.com>
Cc: Yury Norov <d4c98dcfb8a2d1a780b73ae0523ba1408042900b@gmail.com>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs