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SubjectRe: [PATCH] remove abs64()
On Tue, 12 Apr 2011 14:07:26 -0700
Randy Dunlap <rdunlap@xenotime.net> wrote:

> > --- 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?

I think so.

It's a bit concerning that it changes the return type of abs().


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