math: tan cleanups

[musl] / src / math / tan.c

diff --git a/src/math/tan.c b/src/math/tan.c
index 2e1f3c8..9c724a4 100644 (file)
--- a/src/math/tan.c
+++ b/src/math/tan.c
@@ -43,27 +43,28 @@
 
 double tan(double x)
 {
-       double y[2], z = 0.0;
-       int32_t n, ix;
+       double y[2];
+       uint32_t ix;
+       unsigned n;
 
-       /* High word of x. */
        GET_HIGH_WORD(ix, x);
+       ix &= 0x7fffffff;
 
        /* |x| ~< pi/4 */
-       ix &= 0x7fffffff;
        if (ix <= 0x3fe921fb) {
-               if (ix < 0x3e400000) /* x < 2**-27 */
-                       /* raise inexact if x != 0 */
-                       if ((int)x == 0)
-                               return x;
-               return __tan(x, z, 1);
+               if (ix < 0x3e400000) { /* |x| < 2**-27 */
+                       /* raise inexact if x!=0 and underflow if subnormal */
+                       FORCE_EVAL(ix < 0x00100000 ? x/0x1p120f : x+0x1p120f);
+                       return x;
+               }
+               return __tan(x, 0.0, 0);
        }
 
        /* tan(Inf or NaN) is NaN */
        if (ix >= 0x7ff00000)
                return x - x;
 
-       /* argument reduction needed */
+       /* argument reduction */
        n = __rem_pio2(x, y);
-       return __tan(y[0], y[1], 1 - ((n&1)<<1)); /* n even: 1, n odd: -1 */
+       return __tan(y[0], y[1], n&1);
 }