From c599f4f4d705ba215a2672b92baa1c29d9dd0735 Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Thu, 15 Aug 2013 10:14:46 +0000 Subject: math: fix asin, atan, log1p, tanh to raise underflow on subnormal for these functions f(x)=x for small inputs, because f(0)=0 and f'(0)=1, but for subnormal values they should raise the underflow flag (required by annex F), if they are approximated by a polynomial around 0 then spurious underflow should be avoided (not required by annex F) all these functions should raise inexact flag for small x if x!=0, but it's not required by the standard and it does not seem a worthy goal, so support for it is removed in some cases. raising underflow: - x*x may not raise underflow for subnormal x if FLT_EVAL_METHOD!=0 - x*x may raise spurious underflow for normal x if FLT_EVAL_METHOD==0 - in case of double subnormal x, store x as float - in case of float subnormal x, store x*x as float --- src/math/asinf.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'src/math/asinf.c') diff --git a/src/math/asinf.c b/src/math/asinf.c index 51fe6c61..bcd304a3 100644 --- a/src/math/asinf.c +++ b/src/math/asinf.c @@ -46,10 +46,9 @@ float asinf(float x) return 0/(x-x); /* asin(|x|>1) is NaN */ } if (ix < 0x3f000000) { /* |x| < 0.5 */ - if (ix < 0x39800000) { /* |x| < 2**-12 */ - FORCE_EVAL(x + 0x1p120f); - return x; /* return x with inexact if x!=0 */ - } + /* if 0x1p-126 <= |x| < 0x1p-12, avoid raising underflow */ + if (ix < 0x39800000 && ix >= 0x00800000) + return x; return x + x*R(x*x); } /* 1 > |x| >= 0.5 */ -- cgit v1.2.1