From 37d83a089ddf7649ea0a97d4121883381e23f999 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Thu, 13 Aug 2015 16:40:39 +0000 Subject: 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 . (__tanh): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/flt-32/s_tanhf.c: Include . (__tanhf): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/ldbl-128/s_tanhl.c: Include . (__tanhl): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/ldbl-128ibm/s_tanhl.c: Include . (__tanhl): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/ldbl-96/s_tanhl.c: Include . (__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. --- sysdeps/ieee754/flt-32/s_tanhf.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'sysdeps/ieee754/flt-32') diff --git a/sysdeps/ieee754/flt-32/s_tanhf.c b/sysdeps/ieee754/flt-32/s_tanhf.c index dc96da9..5b48fb2 100644 --- a/sysdeps/ieee754/flt-32/s_tanhf.c +++ b/sysdeps/ieee754/flt-32/s_tanhf.c @@ -17,6 +17,7 @@ static char rcsid[] = "$NetBSD: s_tanhf.c,v 1.4 1995/05/10 20:48:24 jtc Exp $"; #endif +#include #include #include @@ -41,7 +42,14 @@ float __tanhf(float x) if (ix == 0) return x; /* x == +-0 */ if (ix<0x24000000) /* |x|<2**-55 */ + { + if (fabsf (x) < FLT_MIN) + { + float force_underflow = x * x; + math_force_eval (force_underflow); + } return x*(one+x); /* tanh(small) = small */ + } if (ix>=0x3f800000) { /* |x|>=1 */ t = __expm1f(two*fabsf(x)); z = one - two/(t+two); -- cgit v1.1