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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
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.
-rw-r--r--ChangeLog6
-rw-r--r--NEWS4
-rw-r--r--math/auto-libm-test-in1
-rw-r--r--math/auto-libm-test-out25
-rw-r--r--sysdeps/ieee754/flt-32/s_atanf.c2
5 files changed, 35 insertions, 3 deletions
diff --git a/ChangeLog b/ChangeLog
index f6bf877..1179142 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
2015-05-14 Joseph Myers <joseph@codesourcery.com>
+ [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.
+
[BZ #16339]
* sysdeps/i386/fpu/s_log1p.S (dbl_min): New object.
(__log1p): Force underflow exception for results with small
diff --git a/NEWS b/NEWS
index a9b0138..c46ee35 100644
--- a/NEWS
+++ b/NEWS
@@ -16,8 +16,8 @@ Version 2.22
17964, 17965, 17967, 17969, 17978, 17987, 17991, 17996, 17998, 17999,
18007, 18019, 18020, 18029, 18030, 18032, 18036, 18038, 18039, 18042,
18043, 18046, 18047, 18068, 18080, 18093, 18100, 18104, 18110, 18111,
- 18125, 18128, 18138, 18185, 18197, 18206, 18210, 18211, 18247, 18287,
- 18319, 18333, 18346, 18397, 18409.
+ 18125, 18128, 18138, 18185, 18196, 18197, 18206, 18210, 18211, 18247,
+ 18287, 18319, 18333, 18346, 18397, 18409.
* Cache information can be queried via sysconf() function on s390 e.g. with
_SC_LEVEL1_ICACHE_SIZE as argument.
diff --git a/math/auto-libm-test-in b/math/auto-libm-test-in
index 7e5c7bb..1deb99a 100644
--- a/math/auto-libm-test-in
+++ b/math/auto-libm-test-in
@@ -239,6 +239,7 @@ atan 0x1p-5
atan 2.5
atan 10
atan 1e6
+atan 0x1p31
atan 0x1p-100
atan 0x1p-600
atan 0x1p-10000
diff --git a/math/auto-libm-test-out b/math/auto-libm-test-out
index 7c8a3fb..9f6bbbb 100644
--- a/math/auto-libm-test-out
+++ b/math/auto-libm-test-out
@@ -7796,6 +7796,31 @@ atan 1e6
= atan tonearest ldbl-128ibm 0xf.424p+16L : 0x1.921fa47d4b30ce822275563fcb8p+0L : inexact-ok
= atan towardzero ldbl-128ibm 0xf.424p+16L : 0x1.921fa47d4b30ce822275563fcb8p+0L : inexact-ok
= atan upward ldbl-128ibm 0xf.424p+16L : 0x1.921fa47d4b30ce822275563fccp+0L : inexact-ok
+atan 0x1p31
+= atan downward flt-32 0x8p+28f : 0x1.921fb4p+0f : inexact-ok
+= atan tonearest flt-32 0x8p+28f : 0x1.921fb6p+0f : inexact-ok
+= atan towardzero flt-32 0x8p+28f : 0x1.921fb4p+0f : inexact-ok
+= atan upward flt-32 0x8p+28f : 0x1.921fb6p+0f : inexact-ok
+= atan downward dbl-64 0x8p+28 : 0x1.921fb54242d18p+0 : inexact-ok
+= atan tonearest dbl-64 0x8p+28 : 0x1.921fb54242d18p+0 : inexact-ok
+= atan towardzero dbl-64 0x8p+28 : 0x1.921fb54242d18p+0 : inexact-ok
+= atan upward dbl-64 0x8p+28 : 0x1.921fb54242d19p+0 : inexact-ok
+= atan downward ldbl-96-intel 0x8p+28L : 0x1.921fb54242d18468p+0L : inexact-ok
+= atan tonearest ldbl-96-intel 0x8p+28L : 0x1.921fb54242d1846ap+0L : inexact-ok
+= atan towardzero ldbl-96-intel 0x8p+28L : 0x1.921fb54242d18468p+0L : inexact-ok
+= atan upward ldbl-96-intel 0x8p+28L : 0x1.921fb54242d1846ap+0L : inexact-ok
+= atan downward ldbl-96-m68k 0x8p+28L : 0x1.921fb54242d18468p+0L : inexact-ok
+= atan tonearest ldbl-96-m68k 0x8p+28L : 0x1.921fb54242d1846ap+0L : inexact-ok
+= atan towardzero ldbl-96-m68k 0x8p+28L : 0x1.921fb54242d18468p+0L : inexact-ok
+= atan upward ldbl-96-m68k 0x8p+28L : 0x1.921fb54242d1846ap+0L : inexact-ok
+= atan downward ldbl-128 0x8p+28L : 0x1.921fb54242d18469898cc519ac62p+0L : inexact-ok
+= atan tonearest ldbl-128 0x8p+28L : 0x1.921fb54242d18469898cc519ac63p+0L : inexact-ok
+= atan towardzero ldbl-128 0x8p+28L : 0x1.921fb54242d18469898cc519ac62p+0L : inexact-ok
+= atan upward ldbl-128 0x8p+28L : 0x1.921fb54242d18469898cc519ac63p+0L : inexact-ok
+= atan downward ldbl-128ibm 0x8p+28L : 0x1.921fb54242d18469898cc519acp+0L : inexact-ok
+= atan tonearest ldbl-128ibm 0x8p+28L : 0x1.921fb54242d18469898cc519ac8p+0L : inexact-ok
+= atan towardzero ldbl-128ibm 0x8p+28L : 0x1.921fb54242d18469898cc519acp+0L : inexact-ok
+= atan upward ldbl-128ibm 0x8p+28L : 0x1.921fb54242d18469898cc519ac8p+0L : inexact-ok
atan 0x1p-100
= atan downward flt-32 0x1p-100f : 0xf.fffffp-104f : inexact-ok
= atan tonearest flt-32 0x1p-100f : 0x1p-100f : inexact-ok
diff --git a/sysdeps/ieee754/flt-32/s_atanf.c b/sysdeps/ieee754/flt-32/s_atanf.c
index 1593918..be2addb 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];