Re: [PATCH][ARM][cleanup] Use IN_RANGE more often

[Jakub Jelinek <jakub@redhat.com>]

On Mon, Apr 20, 2015 at 12:03:11PM +0100, Kyrill Tkachov wrote:
> The definition and comment on IN_RANGE in system.h is:
> /* A macro to determine whether a VALUE lies inclusively within a
>    certain range without evaluating the VALUE more than once.  This
>    macro won't warn if the VALUE is unsigned and the LOWER bound is
>    zero, as it would e.g. with "VALUE >= 0 && ...".  Note the LOWER
>    bound *is* evaluated twice, and LOWER must not be greater than
>    UPPER.  However the bounds themselves can be either positive or
>    negative.  */
> #define IN_RANGE(VALUE, LOWER, UPPER) \
>   ((unsigned HOST_WIDE_INT) (VALUE) - (unsigned HOST_WIDE_INT) (LOWER) \
>    <= (unsigned HOST_WIDE_INT) (UPPER) - (unsigned HOST_WIDE_INT) (LOWER))
> 
> Since it works on positive or negative bounds, I'd think it would work on
> signed numbers, wouldn't it?

Of course it does, as long as the types of VALUE, LOWER and UPPER aren't
wider integer types than {,un}signed HOST_WIDE_INT.  As HWI is always 64-bit
now, that just means it wouldn't work for 128-bit integral types that aren't
used anywhere in GCC.  So, just don't use IN_RANGE for floating point
values, that might have surprising effects, otherwise it is safe to use it.

	Jakub