diff options
| author | Joseph Myers <joseph@codesourcery.com> | 2015-07-01 22:27:49 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-07-01 22:27:49 +0000 |
| commit | a04bb3306a9f9f17e5c588c903a438f1182ecd1a (patch) | |
| tree | 41ea8bb67309f76a21a4269fd384518fee2cf000 | |
| parent | ed225df3ad9cbac3c22ec3f0fbbed1f9c61d1c54 (diff) | |
| download | glibc-a04bb3306a9f9f17e5c588c903a438f1182ecd1a.tar.gz glibc-a04bb3306a9f9f17e5c588c903a438f1182ecd1a.tar.xz glibc-a04bb3306a9f9f17e5c588c903a438f1182ecd1a.zip | |
Fix ldbl-128 expm1l (-min_subnorm) result sign (bug 18619).
In the ldbl-128 implementation of expm1l, when expm1l's result should underflow to 0 (argument minus the least subnormal, in some rounding modes), it can be a zero of the wrong sign. This patch fixes this in the same way previously used for the x86 / x86_64 versions. Tested for mips64. [BZ #18619] * sysdeps/ieee754/ldbl-128/s_expm1l.c (__expm1l): Force underflow and return argument in case of subnormal argument.
| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | NEWS | 2 | ||||
| -rw-r--r-- | sysdeps/ieee754/ldbl-128/s_expm1l.c | 15 |
3 files changed, 19 insertions, 4 deletions
diff --git a/ChangeLog b/ChangeLog index a2fd213951..7d501d5491 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2015-07-01 Joseph Myers <joseph@codesourcery.com> + + [BZ #18619] + * sysdeps/ieee754/ldbl-128/s_expm1l.c (__expm1l): Force underflow + and return argument in case of subnormal argument. + 2015-07-01 Martin Sebor <msebor@redhat.com> [BZ #18435] diff --git a/NEWS b/NEWS index 91320dd429..eecc9a1cc6 100644 --- a/NEWS +++ b/NEWS @@ -25,7 +25,7 @@ Version 2.22 18496, 18497, 18498, 18502, 18507, 18512, 18513, 18519, 18520, 18522, 18527, 18528, 18529, 18530, 18532, 18533, 18534, 18536, 18539, 18540, 18542, 18544, 18545, 18546, 18547, 18549, 18553, 18558, 18569, 18583, - 18585, 18586, 18593, 18594, 18602, 18612, 18613. + 18585, 18586, 18593, 18594, 18602, 18612, 18613, 18619. * Cache information can be queried via sysconf() function on s390 e.g. with _SC_LEVEL1_ICACHE_SIZE as argument. diff --git a/sysdeps/ieee754/ldbl-128/s_expm1l.c b/sysdeps/ieee754/ldbl-128/s_expm1l.c index f708af504c..573d00be57 100644 --- a/sysdeps/ieee754/ldbl-128/s_expm1l.c +++ b/sysdeps/ieee754/ldbl-128/s_expm1l.c @@ -137,9 +137,18 @@ __expm1l (long double x) if (x < minarg) return (4.0/big - 1.0L); - /* Avoid internal underflow when result does not underflow. */ - if (fabsl (x) < 0x1p-113L && fabsl (x) >= LDBL_MIN) - return x; + /* Avoid internal underflow when result does not underflow, while + ensuring underflow (without returning a zero of the wrong sign) + when the result does underflow. */ + if (fabsl (x) < 0x1p-113L) + { + if (fabsl (x) < LDBL_MIN) + { + long double force_underflow = x * x; + math_force_eval (force_underflow); + } + return x; + } /* Express x = ln 2 (k + remainder), remainder not exceeding 1/2. */ xx = C1 + C2; /* ln 2. */ |