Joseph Myers 1d9ab20c14 Fix ldbl-128/ldbl-128ibm acosl inaccuracy (bug 18038, bug 18039). ...

The ldbl-128 and ldbl-128ibm implementations of acosl have similar
bugs, using a threshold of 0x1p-57L to determine when they just return
pi/2.  Since the result pi/2 - asinl (x) is roughly pi/2 - x for small
x, the relevant cut-off is actually x being < 0.5ulp of 1.  This patch
fixes the implementations to use that cut-off and adds tests of small
acos arguments.

Tested for powerpc and mips64.  Also tested for x86_64 and x86; no
ulps updates needed.

	[BZ #18038]
	[BZ #18039]
	* sysdeps/ieee754/ldbl-128/e_acosl.c (__ieee754_acosl): Only
	return pi/2 for arguments below 0x1p-113L.
	* sysdeps/ieee754/ldbl-128ibm/e_acosl.c (__ieee754_acosl): Only
	return pi/2 for arguments below 0x1p-106L.
	* math/auto-libm-test-in: Add more tests of acos.
	* math/auto-libm-test-out: Regenerated.

2015-02-26 21:06:34 +00:00

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