path: root/src/math/atanf.c
diff options
authorSzabolcs Nagy <>2013-08-15 10:14:46 +0000
committerSzabolcs Nagy <>2013-08-15 10:14:46 +0000
commitc599f4f4d705ba215a2672b92baa1c29d9dd0735 (patch)
treef9931ee00f59bae9aba69b9dbcff18a5c1613018 /src/math/atanf.c
parentcd18dc8525a275323819ac4c7826cc3404202f7b (diff)
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
Diffstat (limited to 'src/math/atanf.c')
1 files changed, 3 insertions, 2 deletions
diff --git a/src/math/atanf.c b/src/math/atanf.c
index ac8bfd06..178341b6 100644
--- a/src/math/atanf.c
+++ b/src/math/atanf.c
@@ -55,8 +55,9 @@ float atanf(float x)
if (ix < 0x3ee00000) { /* |x| < 0.4375 */
if (ix < 0x39800000) { /* |x| < 2**-12 */
- /* raise inexact if x!=0 */
- FORCE_EVAL(x + 0x1p120f);
+ if (ix < 0x00800000)
+ /* raise underflow for subnormal x */
+ FORCE_EVAL(x*x);
return x;
id = -1;