math: tan cleanups

[musl] / src / math / tanf.c

diff --git a/src/math/tanf.c b/src/math/tanf.c
index 8b0dfb2..aba1977 100644 (file)
--- a/src/math/tanf.c
+++ b/src/math/tanf.c
@@ -26,37 +26,39 @@ t4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */
 float tanf(float x)
 {
        double y;
-       int32_t n, hx, ix;
+       uint32_t ix;
+       unsigned n, sign;
 
-       GET_FLOAT_WORD(hx, x);
-       ix = hx & 0x7fffffff;
+       GET_FLOAT_WORD(ix, x);
+       sign = ix >> 31;
+       ix &= 0x7fffffff;
 
        if (ix <= 0x3f490fda) {  /* |x| ~<= pi/4 */
-               if (ix < 0x39800000)  /* |x| < 2**-12 */
-                       /* return x and raise inexact if x != 0 */
-                       if ((int)x == 0)
-                               return x;
-               return __tandf(x, 1);
+               if (ix < 0x39800000) {  /* |x| < 2**-12 */
+                       /* raise inexact if x!=0 and underflow if subnormal */
+                       FORCE_EVAL(ix < 0x00800000 ? x/0x1p120f : x+0x1p120f);
+                       return x;
+               }
+               return __tandf(x, 0);
        }
        if (ix <= 0x407b53d1) {  /* |x| ~<= 5*pi/4 */
                if (ix <= 0x4016cbe3)  /* |x| ~<= 3pi/4 */
-                       return __tandf((hx > 0 ? x-t1pio2 : x+t1pio2), -1);
+                       return __tandf((sign ? x+t1pio2 : x-t1pio2), 1);
                else
-                       return __tandf((hx > 0 ? x-t2pio2 : x+t2pio2), 1);
+                       return __tandf((sign ? x+t2pio2 : x-t2pio2), 0);
        }
        if (ix <= 0x40e231d5) {  /* |x| ~<= 9*pi/4 */
                if (ix <= 0x40afeddf)  /* |x| ~<= 7*pi/4 */
-                       return __tandf((hx > 0 ? x-t3pio2 : x+t3pio2), -1);
+                       return __tandf((sign ? x+t3pio2 : x-t3pio2), 1);
                else
-                       return __tandf((hx > 0 ? x-t4pio2 : x+t4pio2), 1);
+                       return __tandf((sign ? x+t4pio2 : x-t4pio2), 0);
        }
 
        /* tan(Inf or NaN) is NaN */
        if (ix >= 0x7f800000)
                return x - x;
 
-       /* general argument reduction needed */
+       /* argument reduction */
        n = __rem_pio2f(x, &y);
-       /* integer parameter: n even: 1; n odd: -1 */
-       return __tandf(y, 1-((n&1)<<1));
+       return __tandf(y, n&1);
 }