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| author | Joseph Myers <joseph@codesourcery.com> | 2015-08-13 16:40:39 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-08-13 16:40:39 +0000 |
| commit | 37d83a089ddf7649ea0a97d4121883381e23f999 (patch) | |
| tree | e5cbd0a6885b4c122099090852c5f5cdd72ae409 /sysdeps/ieee754/dbl-64 | |
| parent | a5cf909b8f25f8240eabc5f1ff96b4be0472d8e1 (diff) | |
| download | glibc-37d83a089ddf7649ea0a97d4121883381e23f999.tar.gz glibc-37d83a089ddf7649ea0a97d4121883381e23f999.tar.xz glibc-37d83a089ddf7649ea0a97d4121883381e23f999.zip | |
Fix tanh missing underflows (bug 16520).
Similar to various other bugs in this area, some tanh implementations do not raise the underflow exception for subnormal arguments, when the result is tiny and inexact. This patch forces the exception in a similar way to previous fixes. Tested for x86_64, x86, mips64 and powerpc. [BZ #16520] * sysdeps/ieee754/dbl-64/s_tanh.c: Include <float.h>. (__tanh): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/flt-32/s_tanhf.c: Include <float.h>. (__tanhf): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/ldbl-128/s_tanhl.c: Include <float.h>. (__tanhl): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/ldbl-128ibm/s_tanhl.c: Include <float.h>. (__tanhl): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/ldbl-96/s_tanhl.c: Include <float.h>. (__tanhl): Force underflow exception for arguments with small absolute value. * math/auto-libm-test-in: Add more tests of tanh. * math/auto-libm-test-out: Regenerated. * sysdeps/i386/fpu/libm-test-ulps: Update.
Diffstat (limited to 'sysdeps/ieee754/dbl-64')
| -rw-r--r-- | sysdeps/ieee754/dbl-64/s_tanh.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/sysdeps/ieee754/dbl-64/s_tanh.c b/sysdeps/ieee754/dbl-64/s_tanh.c index 23cfcdead5..4f9fcfd2bd 100644 --- a/sysdeps/ieee754/dbl-64/s_tanh.c +++ b/sysdeps/ieee754/dbl-64/s_tanh.c @@ -38,6 +38,7 @@ static char rcsid[] = "$NetBSD: s_tanh.c,v 1.7 1995/05/10 20:48:22 jtc Exp $"; * only tanh(0)=0 is exact for finite argument. */ +#include <float.h> #include <math.h> #include <math_private.h> @@ -68,7 +69,14 @@ __tanh (double x) if ((ix | lx) == 0) return x; /* x == +-0 */ if (ix < 0x3c800000) /* |x|<2**-55 */ - return x * (one + x); /* tanh(small) = small */ + { + if (fabs (x) < DBL_MIN) + { + double force_underflow = x * x; + math_force_eval (force_underflow); + } + return x * (one + x); /* tanh(small) = small */ + } if (ix >= 0x3ff00000) /* |x|>=1 */ { t = __expm1 (two * fabs (x)); |