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/atan.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'src/math/atan.c') diff --git a/src/math/atan.c b/src/math/atan.c index 5a1d33e6..63b0ab25 100644 --- a/src/math/atan.c +++ b/src/math/atan.c @@ -77,8 +77,9 @@ double atan(double x) } if (ix < 0x3fdc0000) { /* |x| < 0.4375 */ if (ix < 0x3e400000) { /* |x| < 2^-27 */ - /* raise inexact if x!=0 */ - FORCE_EVAL(x + 0x1p120f); + if (ix < 0x00100000) + /* raise underflow for subnormal x */ + FORCE_EVAL((float)x); return x; } id = -1; -- cgit v1.2.1