lib/libm/src/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  * $NetBSD: e_asinf.c,v 1.8 2002/05/26 22:01:48 wiz Exp $
  16  * $DragonFly: src/lib/libm/src/e_asinf.c,v 1.1 2005/07/26 21:15:20 joerg Exp $
  17  */
  18
  19 #include <math.h>
  20 #include "math_private.h"
  21
  22 static const float
  23 one =  1.0000000000e+00, /* 0x3F800000 */
  24 huge =  1.000e+30,
  25 pio2_hi =  1.5707962513e+00, /* 0x3fc90fda */
  26 pio2_lo =  7.5497894159e-08, /* 0x33a22168 */
  27 pio4_hi =  7.8539818525e-01, /* 0x3f490fdb */
  28         /* coefficient for R(x^2) */
  29 pS0 =  1.6666667163e-01, /* 0x3e2aaaab */
  30 pS1 = -3.2556581497e-01, /* 0xbea6b090 */
  31 pS2 =  2.0121252537e-01, /* 0x3e4e0aa8 */
  32 pS3 = -4.0055535734e-02, /* 0xbd241146 */
  33 pS4 =  7.9153501429e-04, /* 0x3a4f7f04 */
  34 pS5 =  3.4793309169e-05, /* 0x3811ef08 */
  35 qS1 = -2.4033949375e+00, /* 0xc019d139 */
  36 qS2 =  2.0209457874e+00, /* 0x4001572d */
  37 qS3 = -6.8828397989e-01, /* 0xbf303361 */
  38 qS4 =  7.7038154006e-02; /* 0x3d9dc62e */
  39
  40 float
  41 asinf(float x)
  42 {
  43         float t,w,p,q,c,r,s;
  44         int32_t hx,ix;
  45
  46         t = 0;
  47         GET_FLOAT_WORD(hx,x);
  48         ix = hx&0x7fffffff;
  49         if(ix==0x3f800000) {
  50                 /* asin(1)=+-pi/2 with inexact */
  51             return x*pio2_hi+x*pio2_lo;
  52         } else if(ix> 0x3f800000) {     /* |x|>= 1 */
  53             return (x-x)/(x-x);         /* asin(|x|>1) is NaN */
  54         } else if (ix<0x3f000000) {     /* |x|<0.5 */
  55             if(ix<0x32000000) {         /* if |x| < 2**-27 */
  56                 if(huge+x>one) return x;/* return x with inexact if x!=0*/
  57             } else
  58                 t = x*x;
  59                 p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
  60                 q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
  61                 w = p/q;
  62                 return x+x*w;
  63         }
  64         /* 1> |x|>= 0.5 */
  65         w = one-fabsf(x);
  66         t = w*(float)0.5;
  67         p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
  68         q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
  69         s = sqrtf(t);
  70         if(ix>=0x3F79999A) {    /* if |x| > 0.975 */
  71             w = p/q;
  72             t = pio2_hi-((float)2.0*(s+s*w)-pio2_lo);
  73         } else {
  74             int32_t iw;
  75             w  = s;
  76             GET_FLOAT_WORD(iw,w);
  77             SET_FLOAT_WORD(w,iw&0xfffff000);
  78             c  = (t-w*w)/(s+w);
  79             r  = p/q;
  80             p  = (float)2.0*s*r-(pio2_lo-(float)2.0*c);
  81             q  = pio4_hi-(float)2.0*w;
  82             t  = pio4_hi-(p-q);
  83         }
  84         if(hx>0) return t; else return -t;
  85 }