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Fix e_logl (128ibm) spurious underflow

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This commit is contained in:
Adhemerval Zanella 2013-03-28 09:52:48 -03:00
parent 7a86be6e5f
commit fbbe2b9a1f
4 changed files with 26 additions and 4 deletions
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7
ChangeLog
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@ -1,3 +1,10 @@
2013-03-28 Adhemerval Zanella <azanella@linux.vnet.ibm.com>
[BZ #15214]
* sysdeps/ieee754/ldbl-128ibm/e_logl.c (__ieee754_logl): Fix spurious
underflow.
* sysdeps/powerpc/fpu/libm-test-ulps: Update.
2013-03-28 Siddhesh Poyarekar <siddhesh@redhat.com>
[BZ #15304]

4
NEWS
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@ -11,8 +11,8 @@ Version 2.18
11120, 11561, 12723, 13550, 13889, 13951, 14142, 14176, 14200, 14317,
14327, 14496, 14812, 14920, 14964, 14981, 14982, 14985, 14994, 14996,
15003, 15006, 15020, 15023, 15036, 15054, 15055, 15062, 15078, 15160,
15232, 15234, 15283, 15285, 15287, 15304, 15307.
15003, 15006, 15020, 15023, 15036, 15054, 15055, 15062, 15078, 15124,
15160, 15232, 15234, 15283, 15285, 15287, 15304, 15307.
* Add support for calling C++11 thread_local object destructors on thread
and program exit. This needs compiler support for offloading C++11

13
sysdeps/ieee754/ldbl-128ibm/e_logl.c
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@ -182,6 +182,9 @@ static const long double
ln2a = 6.93145751953125e-1L,
ln2b = 1.4286068203094172321214581765680755001344E-6L;
static const long double
ldbl_epsilon = 0x1p-106L;
long double
__ieee754_logl(long double x)
{
@ -258,7 +261,12 @@ __ieee754_logl(long double x)
}
/* Series expansion of log(1+z). */
w = z * z;
y = ((((((((((((l15 * z
/* Avoid spurious underflows. */
if (__glibc_unlikely(w <= ldbl_epsilon))
y = 0.0L;
else
{
y = ((((((((((((l15 * z
+ l14) * z
+ l13) * z
+ l12) * z
@ -271,7 +279,8 @@ __ieee754_logl(long double x)
+ l5) * z
+ l4) * z
+ l3) * z * w;
y -= 0.5 * w;
y -= 0.5 * w;
}
y += e * ln2b; /* Base 2 exponent offset times ln(2). */
y += z;
y += logtbl[k-26]; /* log(t) - (t-1) */

6
sysdeps/powerpc/fpu/libm-test-ulps
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@ -243,9 +243,11 @@ idouble: 1
Test "Real part of: cacos (-0.5 + +0 i) == 2.094395102393195492308428922186335256131 - 0 i":
double: 1
idouble: 1
ldouble: 1
Test "Real part of: cacos (-0.5 - 0 i) == 2.094395102393195492308428922186335256131 + +0 i":
double: 1
idouble: 1
ldouble: 1
Test "Imaginary part of: cacos (-1.5 + +0 i) == pi - 0.9624236501192068949955178268487368462704 i":
double: 1
float: 1
@ -265,6 +267,10 @@ double: 1
float: 1
idouble: 1
ifloat: 1
Test "Imaginary part of: cacos (0x1.fp1023 + 0x1.fp1023 i) == 7.853981633974483096156608458198757210493e-1 - 7.107906849659093345062145442726115449315e2 i":
ldouble: 1
Test "Imaginary part of: cacos (0x1.fp127 + 0x1.fp127 i) == 7.853981633974483096156608458198757210493e-1 - 8.973081118419833726837456344608533993585e1 i":
ldouble: 1
# cacosh
Test "Real part of: cacosh (+0 + 0.5 i) == 0.4812118250596034474977589134243684231352 + pi/2 i":