From 0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sat, 12 Feb 2011 00:22:29 -0500
Subject: initial check-in, version 0.5.0

---
 src/math/k_tanf.c | 105 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 src/math/k_tanf.c

(limited to 'src/math/k_tanf.c')

diff --git a/src/math/k_tanf.c b/src/math/k_tanf.c
new file mode 100644
index 00000000..99ede58c
--- /dev/null
+++ b/src/math/k_tanf.c
@@ -0,0 +1,105 @@
+/* k_tanf.c -- float version of k_tan.c
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+
+/*
+ * ====================================================
+ * Copyright 2004 Sun Microsystems, Inc.  All Rights Reserved.
+ *
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+#include <math.h>
+#include "math_private.h"
+static const float
+one   =  1.0000000000e+00, /* 0x3f800000 */
+pio4  =  7.8539812565e-01, /* 0x3f490fda */
+pio4lo=  3.7748947079e-08, /* 0x33222168 */
+T[] =  {
+  3.3333334327e-01, /* 0x3eaaaaab */
+  1.3333334029e-01, /* 0x3e088889 */
+  5.3968254477e-02, /* 0x3d5d0dd1 */
+  2.1869488060e-02, /* 0x3cb327a4 */
+  8.8632395491e-03, /* 0x3c11371f */
+  3.5920790397e-03, /* 0x3b6b6916 */
+  1.4562094584e-03, /* 0x3abede48 */
+  5.8804126456e-04, /* 0x3a1a26c8 */
+  2.4646313977e-04, /* 0x398137b9 */
+  7.8179444245e-05, /* 0x38a3f445 */
+  7.1407252108e-05, /* 0x3895c07a */
+ -1.8558637748e-05, /* 0xb79bae5f */
+  2.5907305826e-05, /* 0x37d95384 */
+};
+
+float
+__kernel_tanf(float x, float y, int iy)
+{
+        float z,r,v,w,s;
+        int32_t ix,hx;
+        GET_FLOAT_WORD(hx,x);
+        ix = hx&0x7fffffff;     /* high word of |x| */
+        if(ix<0x31800000) {                     /* x < 2**-28 */
+                if ((int) x == 0) {             /* generate inexact */
+                        if ((ix | (iy + 1)) == 0)
+                                return one / fabsf(x);
+                        else {
+                                if (iy == 1)
+                                        return x;
+                                else {  /* compute -1 / (x+y) carefully */
+                                        double a, t;
+
+                                        z = w = x + y;
+                                        GET_FLOAT_WORD(ix, z);
+                                        SET_FLOAT_WORD(z, ix & 0xfffff000);
+                                        v = y - (z - x);
+                                        t = a = -one / w;
+                                        GET_FLOAT_WORD(ix, t);
+                                        SET_FLOAT_WORD(t, ix & 0xfffff000);
+                                        s = one + t * z;
+                                        return t + a * (s + t * v);
+                                }
+                        }
+                }
+        }
+        if(ix>=0x3f2ca140) {                    /* |x|>=0.6744 */
+            if(hx<0) {x = -x; y = -y;}
+            z = pio4-x;
+            w = pio4lo-y;
+            x = z+w; y = 0.0;
+        }
+        z       =  x*x;
+        w       =  z*z;
+    /* Break x^5*(T[1]+x^2*T[2]+...) into
+     *    x^5(T[1]+x^4*T[3]+...+x^20*T[11]) +
+     *    x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12]))
+     */
+        r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11]))));
+        v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12])))));
+        s = z*x;
+        r = y + z*(s*(r+v)+y);
+        r += T[0]*s;
+        w = x+r;
+        if(ix>=0x3f2ca140) {
+            v = (float)iy;
+            return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r)));
+        }
+        if(iy==1) return w;
+        else {          /* if allow error up to 2 ulp,
+                           simply return -1.0/(x+r) here */
+     /*  compute -1.0/(x+r) accurately */
+            float a,t;
+            int32_t i;
+            z  = w;
+            GET_FLOAT_WORD(i,z);
+            SET_FLOAT_WORD(z,i&0xfffff000);
+            v  = r-(z - x);     /* z+v = r+x */
+            t = a  = -(float)1.0/w;     /* a = -1.0/w */
+            GET_FLOAT_WORD(i,t);
+            SET_FLOAT_WORD(t,i&0xfffff000);
+            s  = (float)1.0+t*z;
+            return t+a*(s+t*v);
+        }
+}
-- 
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