1 /* origin: FreeBSD /usr/src/lib/msun/src/e_acosf.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 16 #include "libm.h" 17 18 static const float 19 pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */ 20 pio2_lo = 7.5497894159e-08, /* 0x33a22168 */ 21 pS0 = 1.6666586697e-01, 22 pS1 = -4.2743422091e-02, 23 pS2 = -8.6563630030e-03, 24 qS1 = -7.0662963390e-01; 25 26 static float R(float z) 27 { 28 float_t p, q; 29 p = z*(pS0+z*(pS1+z*pS2)); 30 q = 1.0f+z*qS1; 31 return p/q; 32 } 33 34 float acosf(float x) 35 { 36 float z,w,s,c,df; 37 uint32_t hx,ix; 38 39 GET_FLOAT_WORD(hx, x); 40 ix = hx & 0x7fffffff; 41 /* |x| >= 1 or nan */ 42 if (ix >= 0x3f800000) { 43 if (ix == 0x3f800000) { 44 if (hx >> 31) 45 return 2*pio2_hi + 0x1p-120f; 46 return 0; 47 } 48 return 0/(x-x); 49 } 50 /* |x| < 0.5 */ 51 if (ix < 0x3f000000) { 52 if (ix <= 0x32800000) /* |x| < 2**-26 */ 53 return pio2_hi + 0x1p-120f; 54 return pio2_hi - (x - (pio2_lo-x*R(x*x))); 55 } 56 /* x < -0.5 */ 57 if (hx >> 31) { 58 z = (1+x)*0.5f; 59 s = sqrtf(z); 60 w = R(z)*s-pio2_lo; 61 return 2*(pio2_hi - (s+w)); 62 } 63 /* x > 0.5 */ 64 z = (1-x)*0.5f; 65 s = sqrtf(z); 66 GET_FLOAT_WORD(hx,s); 67 SET_FLOAT_WORD(df,hx&0xfffff000); 68 c = (z-df*df)/(s+df); 69 w = R(z)*s+c; 70 return 2*(df+w); 71 } 72