From 5a608ccc2d676aa124f6b55a7b20d071e408ca31 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Fri, 15 May 2015 17:47:29 +0000 Subject: Fix tanf spurious underflows (bug 18221). The flt-32 implementation of tanf produces spurious underflow exceptions for some small arguments, through computing values on the order of x^5. This patch fixes this by adjusting the threshold for returning x (or, as applicable, +/- 1/x) to 2**-13 (the next term in the power series being x^3/3). Tested for x86_64 and x86. [BZ #18221] * sysdeps/ieee754/flt-32/k_tanf.c (__kernel_tanf): Use 2**-13 not 2**-28 as threshold for returning x or +/- 1/x. * math/auto-libm-test-in: Add more tests of tan. * math/auto-libm-test-out: Regenerated. --- sysdeps/ieee754/flt-32/k_tanf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'sysdeps/ieee754') diff --git a/sysdeps/ieee754/flt-32/k_tanf.c b/sysdeps/ieee754/flt-32/k_tanf.c index d918826338..a67f36e283 100644 --- a/sysdeps/ieee754/flt-32/k_tanf.c +++ b/sysdeps/ieee754/flt-32/k_tanf.c @@ -45,7 +45,7 @@ float __kernel_tanf(float x, float y, int iy) int32_t ix,hx; GET_FLOAT_WORD(hx,x); ix = hx&0x7fffffff; /* high word of |x| */ - if(ix<0x31800000) /* x < 2**-28 */ + if(ix<0x39000000) /* x < 2**-13 */ {if((int)x==0) { /* generate inexact */ if((ix|(iy+1))==0) return one/fabsf(x); else return (iy==1)? x: -one/x; -- cgit v1.2.3