1 /* origin: FreeBSD /usr/src/lib/msun/src/e_asinf.c */ 2 /* 3 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 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 #include "libm.h" 16 17 static const double 18 pio2 = 1.570796326794896558e+00; 19 20 static const float 21 /* coefficients for R(x^2) */ 22 pS0 = 1.6666586697e-01, 23 pS1 = -4.2743422091e-02, 24 pS2 = -8.6563630030e-03, 25 qS1 = -7.0662963390e-01; 26 27 static float R(float z) 28 { 29 float_t p, q; 30 p = z*(pS0+z*(pS1+z*pS2)); 31 q = 1.0f+z*qS1; 32 return p/q; 33 } 34 35 float asinf(float x) 36 { 37 double s; 38 float z; 39 uint32_t hx,ix; 40 41 GET_FLOAT_WORD(hx, x); 42 ix = hx & 0x7fffffff; 43 if (ix >= 0x3f800000) { /* |x| >= 1 */ 44 if (ix == 0x3f800000) /* |x| == 1 */ 45 return x*pio2 + 0x1p-120f; /* asin(+-1) = +-pi/2 with inexact */ 46 return 0/(x-x); /* asin(|x|>1) is NaN */ 47 } 48 if (ix < 0x3f000000) { /* |x| < 0.5 */ 49 /* if 0x1p-126 <= |x| < 0x1p-12, avoid raising underflow */ 50 if (ix < 0x39800000 && ix >= 0x00800000) 51 return x; 52 return x + x*R(x*x); 53 } 54 /* 1 > |x| >= 0.5 */ 55 z = (1 - fabsf(x))*0.5f; 56 s = sqrt(z); 57 x = pio2 - 2*(s+s*R(z)); 58 if (hx >> 31) 59 return -x; 60 return x; 61 } 62