Fix x86/x86_64 expm1 inaccuracy near 0 in directed rounding modes (bug 16293)

[Andreas Jaeger]

On 12/19/2013 02:14 AM, Joseph S. Myers wrote:
> Bug 16293 is inaccuracy of x86/x86_64 versions of expm1, near 0 in
> directed rounding modes, that arises from frndint rounding the
> exponent to 1 or -1 instead of 0, resulting in large cancellation
> error.  This inaccuracy in turn affects other functions such as sinh
> that use expm1.  This patch fixes the problem by setting
> round-to-nearest mode temporarily around the affected calls to
> frndint.  I don't think this is needed for other uses of frndint, such
> as in exp itself, as only for expm1 is the cancellation error
> significant.

ok, thanks,

Andreas
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