compiler/mlib/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 1.9 2005/12/04 13:52:46 bde 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 pio2_hi =  1.5707962513e+00, /* 0x3fc90fda */
  27 pio2_lo =  7.5497894159e-08, /* 0x33a22168 */
  28 pio4_hi =  7.8539812565e-01, /* 0x3f490fda */
  29         /* coefficient for R(x^2) */
  30 pS0 =  1.6666667163e-01, /* 0x3e2aaaab */
  31 pS1 = -3.2556581497e-01, /* 0xbea6b090 */
  32 pS2 =  2.0121252537e-01, /* 0x3e4e0aa8 */
  33 pS3 = -4.0055535734e-02, /* 0xbd241146 */
  34 pS4 =  7.9153501429e-04, /* 0x3a4f7f04 */
  35 pS5 =  3.4793309169e-05, /* 0x3811ef08 */
  36 qS1 = -2.4033949375e+00, /* 0xc019d139 */
  37 qS2 =  2.0209457874e+00, /* 0x4001572d */
  38 qS3 = -6.8828397989e-01, /* 0xbf303361 */
  39 qS4 =  7.7038154006e-02; /* 0x3d9dc62e */
  40
  41 float
  42 __ieee754_asinf(float x)
  43 {
  44         float t=0.0,w,p,q,c,r,s;
  45         int32_t hx,ix;
  46         GET_FLOAT_WORD(hx,x);
  47         ix = hx&0x7fffffff;
  48         if(ix==0x3f800000) {
  49                 /* asin(1)=+-pi/2 with inexact */
  50             return x*pio2_hi+x*pio2_lo;
  51         } else if(ix> 0x3f800000) {     /* |x|>= 1 */
  52             return (x-x)/(x-x);         /* asin(|x|>1) is NaN */
  53         } else if (ix<0x3f000000) {     /* |x|<0.5 */
  54             if(ix<0x32000000) {         /* if |x| < 2**-27 */
  55                 if(huge+x>one) return x;/* return x with inexact if x!=0*/
  56             } else
  57                 t = x*x;
  58                 p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
  59                 q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
  60                 w = p/q;
  61                 return x+x*w;
  62         }
  63         /* 1> |x|>= 0.5 */
  64         w = one-fabsf(x);
  65         t = w*(float)0.5;
  66         p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
  67         q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
  68         s = __ieee754_sqrtf(t);
  69         if(ix>=0x3F79999A) {    /* if |x| > 0.975 */
  70             w = p/q;
  71             t = pio2_hi-((float)2.0*(s+s*w)-pio2_lo);
  72         } else {
  73             int32_t iw;
  74             w  = s;
  75             GET_FLOAT_WORD(iw,w);
  76             SET_FLOAT_WORD(w,iw&0xfffff000);
  77             c  = (t-w*w)/(s+w);
  78             r  = p/q;
  79             p  = (float)2.0*s*r-(pio2_lo-(float)2.0*c);
  80             q  = pio4_hi-(float)2.0*w;
  81             t  = pio4_hi-(p-q);
  82         }
  83         if(hx>0) return t; else return -t;
  84 }