[PATCH][BZ #16823] S390: Fix log1pl returning wrong infinity sign

[Ondřej Bílka]

On Wed, Apr 09, 2014 at 03:24:21PM +0200, Stefan Liebler wrote:
> Hi,
> 
> on S390 test-double fails for log1pl(-1) with infinity has wrong
> sign in rounding mode FE_DOWNWARD. See Bug 16823.
> In this rounding mode, (x-x) = -0.
> In all other rounding modes, (x-x) = +0.
> A division with divisor -0 leads to +inf, while +0 results in -inf
> as expected. This patch changes the divisor to a const +0.
> Tested on s390/s390x.
> 
> Is this okay?
>
Looks ok.

Perhaps we could add constants for infinity and nan would to write
return value directly.