Joseph Myers ff069f024a Fix lgammaf spurious underflows (bug 18220). ...

The flt-32 implementation of lgammaf produces spurious underflow
exceptions for some large arguments, because of calculations involving
x^-2 multiplied by small constants.  This patch fixes this by
adjusting the threshold for a simpler computation to 2**26 (the error
in the simpler computation is on the order of 0.5 * log (x), for a
result on the order of x * log (x)).

Tested for x86_64 and x86.

	[BZ #18220]
	* sysdeps/ieee754/flt-32/e_lgammaf_r.c (__ieee754_lgammaf_r): Use
	2**26 not 2**58 as threshold for returning x * (log (x) - 1).
	* math/auto-libm-test-in: Add another test of lgamma.
	* math/auto-libm-test-out: Regenerated.

2015-05-15 17:21:08 +00:00

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