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    SubjectRe: [PATCH] remove abs64()
    On Wed, 13 Apr 2011 00:00:45 +0300 Alexey Dobriyan wrote:

    > We don't need no stinking abs64() given some GCC extensions
    > (especially __builtin_choose_expr()).
    >
    > One abs() implementation is better than two abs() implementations.

    questionable.

    > New abs() doesn't expand type needlessly.
    >
    > Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
    > ---
    >
    > drivers/gpu/drm/drm_irq.c | 4 ++--
    > include/linux/kernel.h | 43 +++++++++++++++++++++----------------------
    > lib/div64.c | 2 +-
    > 3 files changed, 24 insertions(+), 25 deletions(-)


    > --- a/include/linux/kernel.h
    > +++ b/include/linux/kernel.h
    > @@ -143,28 +143,27 @@ extern int _cond_resched(void);
    >
    > #define might_sleep_if(cond) do { if (cond) might_sleep(); } while (0)
    >
    > -/*
    > - * abs() handles unsigned and signed longs, ints, shorts and chars. For all
    > - * input types abs() returns a signed long.
    > - * abs() should not be used for 64-bit types (s64, u64, long long) - use abs64()
    > - * for those.
    > - */
    > -#define abs(x) ({ \
    > - long ret; \
    > - if (sizeof(x) == sizeof(long)) { \
    > - long __x = (x); \
    > - ret = (__x < 0) ? -__x : __x; \
    > - } else { \
    > - int __x = (x); \
    > - ret = (__x < 0) ? -__x : __x; \
    > - } \
    > - ret; \
    > - })
    > -
    > -#define abs64(x) ({ \
    > - s64 __x = (x); \
    > - (__x < 0) ? -__x : __x; \
    > - })
    > +#define abs(x) \
    > +({ \
    > + typeof(x) _x = (x); \
    > + \
    > + __builtin_choose_expr( \
    > + __builtin_types_compatible_p(typeof(_x), signed char), \
    > + (unsigned char)({ _x < 0 ? -_x : _x; }), \
    > + __builtin_choose_expr( \
    > + __builtin_types_compatible_p(typeof(_x), short), \
    > + (unsigned short)({ _x < 0 ? -_x : _x; }), \
    > + __builtin_choose_expr( \
    > + __builtin_types_compatible_p(typeof(_x), int), \
    > + (unsigned int)({ _x < 0 ? -_x : _x; }), \
    > + __builtin_choose_expr( \
    > + __builtin_types_compatible_p(typeof(_x), long), \
    > + (unsigned long)({ _x < 0 ? -_x : _x; }), \
    > + __builtin_choose_expr( \
    > + __builtin_types_compatible_p(typeof(_x), long long), \
    > + (unsigned long long)({ _x < 0 ? -_x : _x; }), \
    > + _x))))); \
    > +})

    that is better?

    ---
    ~Randy


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