1 /* e_acosf.c -- float version of e_acos.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 "cdefs-compat.h" 17 //__FBSDID("$FreeBSD: src/lib/msun/src/e_acosf.c,v 1.11 2008/08/03 17:39:54 das Exp $"); 18 19 #include "openlibm.h" 20 #include "math_private.h" 21 22 static const float 23 one = 1.0000000000e+00, /* 0x3F800000 */ 24 pi = 3.1415925026e+00, /* 0x40490fda */ 25 pio2_hi = 1.5707962513e+00; /* 0x3fc90fda */ 26 static volatile float 27 pio2_lo = 7.5497894159e-08; /* 0x33a22168 */ 28 static const float 29 pS0 = 1.6666586697e-01, 30 pS1 = -4.2743422091e-02, 31 pS2 = -8.6563630030e-03, 32 qS1 = -7.0662963390e-01; 33 34 DLLEXPORT float 35 __ieee754_acosf(float x) 36 { 37 float z,p,q,r,w,s,c,df; 38 int32_t hx,ix; 39 GET_FLOAT_WORD(hx,x); 40 ix = hx&0x7fffffff; 41 if(ix>=0x3f800000) { /* |x| >= 1 */ 42 if(ix==0x3f800000) { /* |x| == 1 */ 43 if(hx>0) return 0.0; /* acos(1) = 0 */ 44 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ 45 } 46 return (x-x)/(x-x); /* acos(|x|>1) is NaN */ 47 } 48 if(ix<0x3f000000) { /* |x| < 0.5 */ 49 if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/ 50 z = x*x; 51 p = z*(pS0+z*(pS1+z*pS2)); 52 q = one+z*qS1; 53 r = p/q; 54 return pio2_hi - (x - (pio2_lo-x*r)); 55 } else if (hx<0) { /* x < -0.5 */ 56 z = (one+x)*(float)0.5; 57 p = z*(pS0+z*(pS1+z*pS2)); 58 q = one+z*qS1; 59 s = sqrtf(z); 60 r = p/q; 61 w = r*s-pio2_lo; 62 return pi - (float)2.0*(s+w); 63 } else { /* x > 0.5 */ 64 int32_t idf; 65 z = (one-x)*(float)0.5; 66 s = sqrtf(z); 67 df = s; 68 GET_FLOAT_WORD(idf,df); 69 SET_FLOAT_WORD(df,idf&0xfffff000); 70 c = (z-df*df)/(s+df); 71 p = z*(pS0+z*(pS1+z*pS2)); 72 q = one+z*qS1; 73 r = p/q; 74 w = r*s+c; 75 return (float)2.0*(df+w); 76 } 77 } 78