gonzui

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