[PATCH] libm round - fix for 16-bit CPU

[Craig Howland]

On 06/20/2018 12:04 PM, Jon Beniston wrote:
> Hi,
>
> The following is a patch for round on 16-bit CPUs to avoid a shift being out
> of range:
>
> libm/common/s_round.c (round): Make constant long so shift isn't out of
> range on 16-bit CPUs
>
> ---
>   newlib/libm/common/s_round.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/newlib/libm/common/s_round.c b/newlib/libm/common/s_round.c
> index 047574a84..f0926d85f 100644
> --- a/newlib/libm/common/s_round.c
> +++ b/newlib/libm/common/s_round.c
> @@ -68,7 +68,7 @@ SEEALSO
>             msw &= 0x80000000;
>             if (exponent_less_1023 == -1)
>               /* Result is +1.0 or -1.0. */
> -            msw |= (1023 << 20);
> +            msw |= (1023L << 20);
>             lsw = 0;
>           }
>         else
Might it be slightly better to use a cast with the type of msw? While it would 
probably make no difference on any 16-bit target, it could prevent an 
intermediate change to 64 bits instead of 32 on some targets.  So

+            msw |= (((__int32_t)1023 << 20);
  
(Or, better for maintenance, but not as portable with a GCC extension:

+            msw |= (((typeof(msw))1023 << 20);
(There do seem to be multiple uses of typeof already, although the first few I checked are all gated with validity checks.  So probably not appropriate as shown here.))

Craig