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| 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 /sysdeps/ieee754 | |
| parent | ed225df3ad9cbac3c22ec3f0fbbed1f9c61d1c54 (diff) | |
| download | glibc-a04bb3306a9f9f17e5c588c903a438f1182ecd1a.zip glibc-a04bb3306a9f9f17e5c588c903a438f1182ecd1a.tar.gz glibc-a04bb3306a9f9f17e5c588c903a438f1182ecd1a.tar.bz2 | |
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.
Diffstat (limited to 'sysdeps/ieee754')
| -rw-r--r-- | sysdeps/ieee754/ldbl-128/s_expm1l.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/sysdeps/ieee754/ldbl-128/s_expm1l.c b/sysdeps/ieee754/ldbl-128/s_expm1l.c index f708af5..573d00b 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. */ |