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 /* coefficient for R(x^2) */ 23 pS0 = 1.6666586697e-01, 24 pS1 = -4.2743422091e-02, 25 pS2 = -8.6563630030e-03, 26 qS1 = -7.0662963390e-01; 27 28 static const double 29 pio2 = 1.570796326794896558e+00; 30 31 float 32 asinf(float x) 33 { 34 double s; 35 float t,w,p,q; 36 int32_t hx,ix; 37 GET_FLOAT_WORD(hx,x); 38 ix = hx&0x7fffffff; 39 if(ix>=0x3f800000) { /* |x| >= 1 */ 40 if(ix==0x3f800000) /* |x| == 1 */ 41 return x*pio2; /* asin(+-1) = +-pi/2 with inexact */ 42 return (x-x)/(x-x); /* asin(|x|>1) is NaN */ 43 } else if (ix<0x3f000000) { /* |x|<0.5 */ 44 if(ix<0x39800000) { /* |x| < 2**-12 */ 45 if(huge+x>one) return x;/* return x with inexact if x!=0*/ 46 } 47 t = x*x; 48 p = t*(pS0+t*(pS1+t*pS2)); 49 q = one+t*qS1; 50 w = p/q; 51 return x+x*w; 52 } 53 /* 1> |x|>= 0.5 */ 54 w = one-fabsf(x); 55 t = w*(float)0.5; 56 p = t*(pS0+t*(pS1+t*pS2)); 57 q = one+t*qS1; 58 s = sqrt(t); 59 w = p/q; 60 t = pio2-2.0*(s+s*w); 61 if(hx>0) return t; else return -t; 62 } 63