math: use 0x1p-120f and 0x1p120f for tiny and huge values

[musl] / src / math / atan.c

diff --git a/src/math/atan.c b/src/math/atan.c
index f34551c..3c9a59f 100644 (file)
--- a/src/math/atan.c
+++ b/src/math/atan.c
@@ -60,32 +60,26 @@ static const double aT[] = {
   1.62858201153657823623e-02, /* 0x3F90AD3A, 0xE322DA11 */
 };
 
-static const double huge = 1.0e300;
-
 double atan(double x)
 {
        double w,s1,s2,z;
-       int32_t ix,hx,id;
+       uint32_t ix,sign;
+       int id;
 
-       GET_HIGH_WORD(hx, x);
-       ix = hx & 0x7fffffff;
+       GET_HIGH_WORD(ix, x);
+       sign = ix >> 31;
+       ix &= 0x7fffffff;
        if (ix >= 0x44100000) {   /* if |x| >= 2^66 */
-               uint32_t low;
-
-               GET_LOW_WORD(low, x);
-               if (ix > 0x7ff00000 ||
-                   (ix == 0x7ff00000 && low != 0))  /* NaN */
-                       return x+x;
-               if (hx > 0)
-                       return  atanhi[3] + *(volatile double *)&atanlo[3];
-               else
-                       return -atanhi[3] - *(volatile double *)&atanlo[3];
+               if (isnan(x))
+                       return x;
+               z = atanhi[3] + 0x1p-120f;
+               return sign ? -z : z;
        }
        if (ix < 0x3fdc0000) {    /* |x| < 0.4375 */
                if (ix < 0x3e400000) {  /* |x| < 2^-27 */
-                       /* raise inexact */
-                       if (huge+x > 1.0)
-                               return x;
+                       /* raise inexact if x!=0 */
+                       FORCE_EVAL(x + 0x1p120f);
+                       return x;
                }
                id = -1;
        } else {
@@ -117,5 +111,5 @@ double atan(double x)
        if (id < 0)
                return x - x*(s1+s2);
        z = atanhi[id] - (x*(s1+s2) - atanlo[id] - x);
-       return hx < 0 ? -z : z;
+       return sign ? -z : z;
 }