first commit of the new libm!

[musl] / src / math / tanf.c

diff --git a/src/math/tanf.c b/src/math/tanf.c
new file mode 100644 (file)
index 0000000..8b0dfb2
--- /dev/null
+++ b/src/math/tanf.c
@@ -0,0 +1,62 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_tanf.c */
+/*
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ * Optimized by Bruce D. Evans.
+ */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+#include "libm.h"
+
+/* Small multiples of pi/2 rounded to double precision. */
+static const double
+t1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */
+t2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */
+t3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */
+t4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */
+
+float tanf(float x)
+{
+       double y;
+       int32_t n, hx, ix;
+
+       GET_FLOAT_WORD(hx, x);
+       ix = hx & 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 <= 0x407b53d1) {  /* |x| ~<= 5*pi/4 */
+               if (ix <= 0x4016cbe3)  /* |x| ~<= 3pi/4 */
+                       return __tandf((hx > 0 ? x-t1pio2 : x+t1pio2), -1);
+               else
+                       return __tandf((hx > 0 ? x-t2pio2 : x+t2pio2), 1);
+       }
+       if (ix <= 0x40e231d5) {  /* |x| ~<= 9*pi/4 */
+               if (ix <= 0x40afeddf)  /* |x| ~<= 7*pi/4 */
+                       return __tandf((hx > 0 ? x-t3pio2 : x+t3pio2), -1);
+               else
+                       return __tandf((hx > 0 ? x-t4pio2 : x+t4pio2), 1);
+       }
+
+       /* tan(Inf or NaN) is NaN */
+       if (ix >= 0x7f800000)
+               return x - x;
+
+       /* general argument reduction needed */
+       n = __rem_pio2f(x, &y);
+       /* integer parameter: n even: 1; n odd: -1 */
+       return __tandf(y, 1-((n&1)<<1));
+}