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 } 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 } 81