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authorJoseph Myers <joseph@codesourcery.com>2015-05-14 23:51:09 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-05-14 23:51:09 +0000
commit9a71f1fcf53615c00b5f9e5da4bba92bccb0efb4 (patch)
tree803585f46a9049a90164009e560b8f25e262faa0 /sysdeps/ieee754/flt-32
parent0b7a5f920163d03806d7c5d9d1c83b16942c9496 (diff)
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Fix atanf spurious underflows (bug 18196).
The sysdeps/ieee754/flt-32 version of atanf produces spurious
underflow exceptions for some large arguments, because of computations
that compute x^-4.  This patch fixes this by adjusting the threshold
for large arguments (for which +/- pi/2 can just be returned, the
correct result being roughly +/- pi/2 - 1/x) from 2^34 to 2^25.

Tested for x86_64 and x86.

	[BZ #18196]
	* sysdeps/ieee754/flt-32/s_atanf.c (__atanf): Use 2^25 not 2^34 as
	threshold for large arguments.
	* math/auto-libm-test-in: Add another test of atan.
	* math/auto-libm-test-out: Regenerated.
Diffstat (limited to 'sysdeps/ieee754/flt-32')
-rw-r--r--sysdeps/ieee754/flt-32/s_atanf.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/sysdeps/ieee754/flt-32/s_atanf.c b/sysdeps/ieee754/flt-32/s_atanf.c
index 159391894f..be2addbdff 100644
--- a/sysdeps/ieee754/flt-32/s_atanf.c
+++ b/sysdeps/ieee754/flt-32/s_atanf.c
@@ -60,7 +60,7 @@ float __atanf(float x)
 
 	GET_FLOAT_WORD(hx,x);
 	ix = hx&0x7fffffff;
-	if(ix>=0x50800000) {	/* if |x| >= 2^34 */
+	if(ix>=0x4c000000) {	/* if |x| >= 2^25 */
 	    if(ix>0x7f800000)
 		return x+x;		/* NaN */
 	    if(hx>0) return  atanhi[3]+atanlo[3];