| /* ef_asin.c -- float version of e_asin.c. |
| * Conversion to float by Ian Lance Taylor, Cygnus Support, [email protected]. |
| */ |
| |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| #include "fdlibm.h" |
| |
| #ifdef __STDC__ |
| static const float |
| #else |
| static float |
| #endif |
| one = 1.0000000000e+00, /* 0x3F800000 */ |
| huge = 1.000e+30, |
| pio2_hi = 1.57079637050628662109375f, |
| pio2_lo = -4.37113900018624283e-8f, |
| pio4_hi = 0.785398185253143310546875f, |
| /* coefficient for R(x^2) */ |
| pS0 = 1.6666667163e-01, /* 0x3e2aaaab */ |
| pS1 = -3.2556581497e-01, /* 0xbea6b090 */ |
| pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */ |
| pS3 = -4.0055535734e-02, /* 0xbd241146 */ |
| pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */ |
| pS5 = 3.4793309169e-05, /* 0x3811ef08 */ |
| qS1 = -2.4033949375e+00, /* 0xc019d139 */ |
| qS2 = 2.0209457874e+00, /* 0x4001572d */ |
| qS3 = -6.8828397989e-01, /* 0xbf303361 */ |
| qS4 = 7.7038154006e-02; /* 0x3d9dc62e */ |
| |
| #ifdef __STDC__ |
| float __ieee754_asinf(float x) |
| #else |
| float __ieee754_asinf(x) |
| float x; |
| #endif |
| { |
| float t,w,p,q,c,r,s; |
| __int32_t hx,ix; |
| GET_FLOAT_WORD(hx,x); |
| ix = hx&0x7fffffff; |
| if(ix==0x3f800000) { |
| /* asin(1)=+-pi/2 with inexact */ |
| return x*pio2_hi+x*pio2_lo; |
| } else if(ix> 0x3f800000) { /* |x|>= 1 */ |
| return (x-x)/(x-x); /* asin(|x|>1) is NaN */ |
| } else if (ix<0x3f000000) { /* |x|<0.5 */ |
| if(ix<0x32000000) { /* if |x| < 2**-27 */ |
| if(huge+x>one) return x;/* return x with inexact if x!=0*/ |
| } else { |
| t = x*x; |
| p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5))))); |
| q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4))); |
| w = p/q; |
| return x+x*w; |
| } |
| } |
| /* 1> |x|>= 0.5 */ |
| w = one-fabsf(x); |
| t = w*(float)0.5; |
| p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5))))); |
| q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4))); |
| s = __ieee754_sqrtf(t); |
| if(ix>=0x3F79999A) { /* if |x| > 0.975 */ |
| w = p/q; |
| t = pio2_hi-((float)2.0*(s+s*w)-pio2_lo); |
| } else { |
| __int32_t iw; |
| w = s; |
| GET_FLOAT_WORD(iw,w); |
| SET_FLOAT_WORD(w,iw&0xfffff000); |
| c = (t-w*w)/(s+w); |
| r = p/q; |
| p = (float)2.0*s*r-(pio2_lo-(float)2.0*c); |
| q = pio4_hi-(float)2.0*w; |
| t = pio4_hi-(p-q); |
| } |
| if(hx>0) return t; else return -t; |
| } |
