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author | Szabolcs Nagy <nsz@port70.net> | 2013-09-05 16:57:46 +0000 |
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committer | Szabolcs Nagy <nsz@port70.net> | 2013-09-05 16:57:46 +0000 |
commit | f4d9bfb3a986f2c25ec023426b4fb222130af75f (patch) | |
tree | b2fd726519f60975ffd2fef8365014b6f98b1b99 /src/math/atanh.c | |
parent | afa2aaccea6e9f8c55809abb6471dc9aaa402711 (diff) | |
download | musl-f4d9bfb3a986f2c25ec023426b4fb222130af75f.tar.gz musl-f4d9bfb3a986f2c25ec023426b4fb222130af75f.tar.xz musl-f4d9bfb3a986f2c25ec023426b4fb222130af75f.zip |
math: fix atanh (overflow and underflow issues)
in atanh exception handling was left to the called log functions, but the argument to those functions could underflow or overflow. use double_t and float_t to avoid some useless stores on x86
Diffstat (limited to 'src/math/atanh.c')
-rw-r--r-- | src/math/atanh.c | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/src/math/atanh.c b/src/math/atanh.c index 84a84c69..63a035d7 100644 --- a/src/math/atanh.c +++ b/src/math/atanh.c @@ -6,16 +6,24 @@ double atanh(double x) union {double f; uint64_t i;} u = {.f = x}; unsigned e = u.i >> 52 & 0x7ff; unsigned s = u.i >> 63; + double_t y; /* |x| */ u.i &= (uint64_t)-1/2; - x = u.f; + y = u.f; if (e < 0x3ff - 1) { - /* |x| < 0.5, up to 1.7ulp error */ - x = 0.5*log1p(2*x + 2*x*x/(1-x)); + if (e < 0x3ff - 32) { + /* handle underflow */ + if (e == 0) + FORCE_EVAL((float)y); + } else { + /* |x| < 0.5, up to 1.7ulp error */ + y = 0.5*log1p(2*y + 2*y*y/(1-y)); + } } else { - x = 0.5*log1p(2*x/(1-x)); + /* avoid overflow */ + y = 0.5*log1p(2*(y/(1-y))); } - return s ? -x : x; + return s ? -y : y; } |