first commit of the new libm!

[musl] / src / math / atanf.c

diff --git a/src/math/atanf.c b/src/math/atanf.c
new file mode 100644 (file)
index 0000000..8c2b46b
--- /dev/null
+++ b/src/math/atanf.c
@@ -0,0 +1,97 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_atanf.c */
+/*
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+/*
+ * ====================================================
+ * 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"
+
+static const float atanhi[] = {
+  4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
+  7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
+  9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
+  1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
+};
+
+static const float atanlo[] = {
+  5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
+  3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
+  3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
+  7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
+};
+
+static const float aT[] = {
+  3.3333328366e-01,
+ -1.9999158382e-01,
+  1.4253635705e-01,
+ -1.0648017377e-01,
+  6.1687607318e-02,
+};
+
+static const float
+one = 1.0,
+huge = 1.0e30;
+
+float atanf(float x)
+{
+       float w,s1,s2,z;
+       int32_t ix,hx,id;
+
+       GET_FLOAT_WORD(hx, x);
+       ix = hx & 0x7fffffff;
+       if (ix >= 0x4c800000) {  /* if |x| >= 2**26 */
+               if (ix > 0x7f800000)  /* NaN */
+                       return x+x;
+               if (hx > 0)
+                       return  atanhi[3] + *(volatile float *)&atanlo[3];
+               else
+                       return -atanhi[3] - *(volatile float *)&atanlo[3];
+       }
+       if (ix < 0x3ee00000) {   /* |x| < 0.4375 */
+               if (ix < 0x39800000) {  /* |x| < 2**-12 */
+                       /* raise inexact */
+                       if(huge+x>one)
+                               return x;
+               }
+               id = -1;
+       } else {
+               x = fabsf(x);
+               if (ix < 0x3f980000) {  /* |x| < 1.1875 */
+                       if (ix < 0x3f300000) {  /*  7/16 <= |x| < 11/16 */
+                               id = 0;
+                               x = ((float)2.0*x-one)/((float)2.0+x);
+                       } else {                /* 11/16 <= |x| < 19/16 */
+                               id = 1;
+                               x = (x-one)/(x+one);
+                       }
+               } else {
+                       if (ix < 0x401c0000) {  /* |x| < 2.4375 */
+                               id = 2;
+                               x = (x-(float)1.5)/(one+(float)1.5*x);
+                       } else {                /* 2.4375 <= |x| < 2**26 */
+                               id = 3;
+                               x = -(float)1.0/x;
+                       }
+               }
+       }
+       /* end of argument reduction */
+       z = x*x;
+       w = z*z;
+       /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
+       s1 = z*(aT[0]+w*(aT[2]+w*aT[4]));
+       s2 = w*(aT[1]+w*aT[3]);
+       if (id < 0)
+               return x - x*(s1+s2);
+       z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
+       return hx < 0 ? -z : z;
+}