compiler/stdc/math/e_asinf.c

   1 /* e_asinf.c -- float version of e_asin.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #ifndef lint
  17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_asinf.c,v 1.13 2008/08/08 00:21:27 das Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 static const float
  24 one =  1.0000000000e+00, /* 0x3F800000 */
  25 huge =  1.000e+30,
  26         /* coefficient for R(x^2) */
  27 pS0 =  1.6666586697e-01,
  28 pS1 = -4.2743422091e-02,
  29 pS2 = -8.6563630030e-03,
  30 qS1 = -7.0662963390e-01;
  31
  32 static const double
  33 pio2 =  1.570796326794896558e+00;
  34
  35
  36 float
  37 __ieee754_asinf(float x)
  38 {
  39         double s;
  40         float t,w,p,q;
  41         int32_t hx,ix;
  42         GET_FLOAT_WORD(hx,x);
  43         ix = hx&0x7fffffff;
  44         if(ix>=0x3f800000) {            /* |x| >= 1 */
  45             if(ix==0x3f800000)          /* |x| == 1 */
  46                 return x*pio2;          /* asin(+-1) = +-pi/2 with inexact */
  47             return (x-x)/(x-x);         /* asin(|x|>1) is NaN */
  48         } else if (ix<0x3f000000) {     /* |x|<0.5 */
  49             if(ix<0x39800000) {         /* |x| < 2**-12 */
  50                 if(huge+x>one) return x;/* return x with inexact if x!=0*/
  51             }
  52             t = x*x;
  53             p = t*(pS0+t*(pS1+t*pS2));
  54             q = one+t*qS1;
  55             w = p/q;
  56             return x+x*w;
  57         }
  58         /* 1> |x|>= 0.5 */
  59         w = one-fabsf(x);
  60         t = w*(float)0.5;
  61         p = t*(pS0+t*(pS1+t*pS2));
  62         q = one+t*qS1;
  63         s = sqrt(t);
  64         w = p/q;
  65         t = pio2-2.0*(s+s*w);
  66         if(hx>0) return t; else return -t;
  67 }